Category Archives: Weather Radio

Guest Post: Decoding WEFAX using an RSP SDR and SDRuno

Many thanks to SLWing Post contributor, Mike Ladd with SDRplay, who shares the following guest post:

Basics to decoding WEFAX using an RSP and SDRuno

by Mike Ladd

SDR I use:
RSPduo from SDRplay using the Hi-Z input. Any model RSP’s can tune WEFAX transmissions.

Antenna I use: Megaloop FX from Bonito. In an Inverted delta loop configuration pointed N/E-S/W. Any good antenna placed outdoors should be fine. It’s all about the SNR, not your S-meter reading.


SDRuno v1.32
SDRuno is an advanced Software Defined Radio application platform which is optimized for use with SDRplay’s range of Radio Spectrum Processing receivers.

VBcable (donationware) vPack43
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.

VAC (paid for use) v4.60
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.

Black Cat HF Weather Fax (paid for use) beta 19
Decodes and produces images from the WEFAX transmissions from the output of SDRuno using a virtual audio cable.

Use the discount link available here

Black Cat Uno UDP
UnoUDP allows you control SDRuno’s VFO frequency from within Black Cat HF Weather Fax scheduler. This is done over a virtual com port pair using a virtual com port emulator.

VSPE is a paid for use app. COM0COM is completely free. Either one of these applications will work. A virtual com port emulator allows you to create a virtual com port. The pair will internally link Black Cat Weather Fax decoder to SDRuno’s using UnoUDP as the transport protocol.




(some text taken and edited from various website)

This document is not a definitive guide to the WEFAX protocol, the process of decoding WEFAX images or reading a synoptic weather chart This is only a collection of information that I have found scatter throughout the internet and re-compiled into a document, this document. Expect typographical mistakes, inaccuracies, or omissions.

WEFAX is an analog mode for transmitting monochrome images. It was the predecessor to slow-scan television (SSTV). Prior to the advent of the commercial telephone line “fax” machine, it was known, more traditionally, by the term “radio facsimile”.

Facsimile machines were used in the 1950s to transmit weather charts across the United States via land-lines first and then internationally via HF radio. Radio transmission of weather charts provides an enormous amount of flexibility to marine and aviation users for they now have the latest weather information and forecasts at their fingertips to use in the planning of voyages.

Radio fax relies on facsimile technology where printed information is scanned line by line and encoded into an electrical signal which can then be transmitted via physical line or radio waves to remote locations. Since the amount of information transmitted per unit time is directly proportional to the bandwidth available, then the speed at which a weather chart can be transmitted will vary depending on the quality of the media used for the transmission.

Radio fax data is available from the web on sites such as the ones hosted by the National Oceanic and Atmospheric Administration (NOAA). Radio fax transmissions are also broadcasted by NOAA from multiple sites in the country at regular daily schedules Radio weather fax transmissions are particularly useful to shipping, where there are limited facilities for accessing the Internet.

Black Cat HF Weather Fax is a program that decodes WEFAX (Weatherfax, HF-FAX, Radiofax, and Weather Facsimile) transmissions sent from fixed locations around the globe.

A fax is transmitted line by line, typically at a rate of 120 lines per minute, or half a second per line. For example, to send a weather chart, you would start in the upper left corner. You would send the value of that pixel (dot), black, white, or perhaps a shade of gray. Then you would move over one pixel to the right, and send that pixel, and so on, until you reach the edge of the chart. Then you’d move all the way back to the left edge, and move down slightly, one line, and repeat the process.

Each pixel is converted into a certain audio frequency or tone. By convention, a tone of 1500 Hz represents black, 2300 Hz represents white, and frequencies in-between represent shades of gray. So if you listen to a fax transmission, you’ll hear the different tones as each pixel is present. For example, listen to a chart with mostly white background being sent. You’ll hear mostly the high pitch 2300 Hz, and some lower (1500 Hz) blips as each black pixel is sent. When a horizontal line is sent, you’ll hear a long half second burst of 1500 Hz, since the line is all black.

The transmitting station frequency modulates the carrier. That is, when a black pixel is transmitted, the carrier shifts down 400 Hz. When a white pixel is transmitted, the carrier shifts up 400 Hz. For a medium gray pixel, it stays on the assigned frequency. This is how most fax transmissions are made. Since we’re tuning it in SSB, it sounds to us as if the station is transmitting a variable frequency audio tone. The two processes are identical. This accounts for the confusion regarding what frequency to tune the radio to in order to properly decode the fax transmission. Different stations list their frequency in different ways. It is important to remember that a black pixel produces a 1500 Hz tone, and a white pixel produces a 2300 Hz tone within the AUX SP.

The setup works as follows. SDRuno demodulates the received signal. The demodulated audio is piped from SDRuno using virtual audio cable and sends it to the HF weather fax decoder. HF weather fax decoder receives this audio from the virtual audio cable that was demodulated from SDRuno and processes it, producing a picture on the screen

HF weather fax decoder can also set the VFO (tune) frequency of the RSP in SDRuno. This is done over the virtual com port pair using the UnoUDP application as the transport.

SDRuno can internally emulate a Kenwood TS-480, UnoUDP sends the Kenwood TS-480 serial commands via UDP over the virtual com port pair in order to set the frequency selected from the HF Weather Fax Scheduler option over to SDRuno.

You will need to install and configure the following applications.

1: A virtual audio cable.

2: A virtual com port emulator (If you would like HF Weather fax to communicate with SDRuno).

3: UnoUDP (If you would like HF Weather fax to communicate with SDRuno using the virtual serial emulator).

4: HF Weather Fax.

5: A simple wire antenna placed outdoors.

Virtual Audio Cable:

A virtual audio cable allows you to pipe the audio from one application (SDRuno) into another application (a decoder like HF Weather Fax) digitally. I will assume SDRuno is already installed with your device attached and functioning properly.

You can now download a virtual audio cable package.  If you already have a virtual audio cable package installed, you can skip to the next section. If you don’t have a virtual audio cable application installed, you only need to choose one and install only one of the two that are available.

Close any running apps, install the virtual audio cable and reboot your computer. When your computer boots to your desktop, your computer will now have a virtual audio cable pair installed on the system.

You can verify it the installation by going to your Control Panel and double clicking the Sound icon. VB-Cable and Virtual Audio Cable will only install a single virtual audio cable pair, one is for the input (Recording) and one is for the output (Playback). A single pair is all that is needed (as shown below).

Virtual Serial Port:

A virtual com port emulator is only needed if you would like Black Cat HF Fax decoder the ability to tune the station in SDRuno when you double click a station name in the HF Fax Decoder scheduler.

Please use the links provided (additional PDF’s and YouTube videos) on Page 2 of this document for an installation / configuration walkthrough.

You can download my WEFAX frequency bank for use in SDRuno below should you choose not to use a virtual com port emulator.

Download Black Cat HF Weather Fax and UnoUDP:

Download the latest HF Weather Fax beta package and the UnoUDP application from the link provided on Page 2 of this document. I suggest making one main folder called HFfax and two subfolders within HFfax for each of the applications. One folder is for the HF Weather Fax Decoder and the other folder is for the UNO UDP transport application.

Double click the HF Weather Fax beta ZIP file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “Black Cat Weather Fax” EXE file and send a shortcut to your Desktop.

Double click the UnoUDP zip file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “UnoUDP” EXE file and send a shortcut to your Desktop.

You should have two shortcuts on your desktop, One for the decoder and one for the transport app.

Black Cat UnoUDP:

HF Weather Fax needs a way to communicate with SDRuno, this is done via UnoUDP and the virtual com port emulator.

Launch UnoUDP with the above configuration. Set your UDP Receive port to 58084 and your UDP send port to 58083. UnoUDP must be left running in the background, this will control SDRuno. You can minimize the application or right click the shortcut and have UnoUDP auto minizine on launch.

You should see a Firewall popup prompt asking permission to allow UnoUDP to pass data within the system. You must allow this traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.

Assign 1 of the 2 com ports from the virtual com port emulator to UnoUDP (the 2nd com port will be assigned to SDRuno).  My com port pair is Com 1 and Com 2, SDRuno uses Com1 and UnoUDP uses Com 2.

Black Cat HF Weather Fax:

HF Weather Fax needs to be configured in order to communicate with UnoUDP, this is done via the UDP settings. Click “Edit” and “Preferences” Set the UDP Send port to 58084 and the UDP Receive port to 58083.

You should see a Firewall popup prompt asking permission for HF Weather Fax to pass data within your system. You must allow UDP traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.


SDRuno needs its Output assigned to the Virtual Audio Cable. The output can be changed via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

SDRuno needs a com port assigned so it can be externally controlled. The serial port is assigned via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the CAT tab.

I recommend running the RSP in LOW-IF mode, this is selected via the MAIN panel. This reduces the need to track separation between the Tuned frequency and LO (local oscillator)

LOW-IF mode also minizines the LO being placed outside of the desired preselect filter of the device in use, Remember the preselect filter is automatically enabled based on the LO frequency

I also recommend leaving the IF AGC enabled and placing the RF GAIN as high as possible without causing an ADC OVERLOAD warning within the MAIN panel. If an ADC OVERLOAD warning appears, back the RF GAIN down.

Your first WEFAX decode (Using UnoUDP)

Launch UnoUDP and minimize it.

Launch Black Cat HF Weather FAX.

Launch SDRuno. Set the mode to USB and the filter width to 2.8k
HF weather fax will not set the mode or filter width at this time.

Click the Sked button in Black Systems HF Weather Fax. A current WEFAX transmission schedule will appear. Stations listed in White are either scheduled to transmit or about to transmit based on your computers clock. Stations show in Grey at the bottom of the list are currently off the air or not transmitting.

In the Freq Offset: box enter -1.9 and hit enter (Reason for this is on Page 5).

Click any of the stations listed in the Fax Transmission Schedule and it will automatically tune SDRuno to the correct frequency.

Black Cat HF Weather Fax folder will have a file named “Black Cat HF Weather Fax Docs” Please view this file to understand some of the advanced features available.

Your first decode (Without UnoUDP)

Launch Black Cat HF Weather FAX.

Launch SDRuno.

Navigate to the Memory Panel (MAIN panel and click the MEM PAN button)

Right click the Memory panel and select “Open bank”. Navigate you C drive telling SDRuno the location of WEFAX.s1b

Double click any of the frequencies shown within the WEFAX bank and SDRuno will set the correct mode and tune that station.  My WEFAX.s1b file defaults to the Hi-Z port. If your device lacks a HI-Z input, navigate to the port section within the memory panel, double click the stations port you want to edit and change it to the correct port that’s available or in use for your device. Right click the memory panel and “Save bank” to save the changes.

To use my SDRuno WEFAX frequency bank properly. The MCTR button must be enabled within the RX CONTROL panel, enabling this option allows you to double click and tune a station that is stored within the WEFAX bank. Make sure the LO is not locked in the MAIN panel (LO LOCK).

If a decoded WEFAX image looks blocky or skewed or possibly pixeled, I recommend that the lock output fractional resampler option is enabled in SDRuno. You can enable this from the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

I hope this document helped guide you in getting started with decoding WEFAX transmissions from around the world. I am sure I missed some key features, remember this is only a primer/basics to decoding WEFAX. I do have an accompanying video located here

Warmest of 73,


SDRPlay modules use a Mirics chipset and software. The information supplied hereunder is provided to you by SDRPlay under license from Mirics. Mirics hereby grants you a perpetual, worldwide, royalty free license to use the information herein for the purpose of designing software that utilizes SDRPlay modules, under the following conditions:

There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Mirics reserves the right to make changes without further notice to any of its products. Mirics makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Mirics assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters that may be provided in Mirics data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters must be validated for each customer application by the buyer’s technical experts. SDRPlay and Mirics products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Mirics product could create a situation where personal injury or death may occur. Should Buyer purchase or use SDRPlay or Mirics products for any such unintended or unauthorized application, Buyer shall indemnify and hold both SDRPlay and Mirics and their officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that either SDRPlay or Mirics were negligent regarding the design or manufacture of the part. Mirics FlexiRFTM, Mirics FlexiTVTM and MiricsTM are trademarks of Mirics .

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Guest Post: Photo tour and history of the PPE Observatório Nacional time signal station

Many thanks to the SWLing Post contributor, Martin Butera, who shares the following guest post:


Visiting the most important time signal station in South America – PPE Observatório Nacional

by Martin Butera

Still photographs by: Mark Van Marx (Marcos Melzi)

Video by: Ligia Katze

English adaptation and correction by: Sudipto Ghose (VU2UT)

We invite you to a tour of the service division of the official time signal station of the National Observatory of Rio de Janeiro, Brazil PPE BRA OBSERVATORIO NACIONAL

Let us take you to a place for which all the readers should enjoy: the famous 10 MHz short wave transmitter of the Hour Service Division (DSHO), of the national observatory of Rio de Janeiro, Brazil.

We were invited by the engineer Mr. Ozenildo de Farias Dantas, in charge of the maintenance and flawless operation of the transmitter, to take a look at the famous transmitter.

The Hour Service Division (DSHO) broadcasts Brazil’s Official shortwave time signal on the frequency of 10 MHz.

The transmitter is located in the park, outside the main building, in a small, climate-controlled house specially designed to accommodat it.

Here are some of the transmitter’s technical notes:

Manufacturer: Redifon Telecommunications Limited, London SW.18, England
Power: 1 kW
QRG: 10 MHz
Type of modulation: A3H
Type of antenna: horizontal dipole – ½ wavelength

Here are the geocentric coordinates of the site( WGS84):

X = 4283641.45 m Length = 43 13 27.5 W
Y = – 4026026.11 m Latitude = 22 53 44.6 S
Z = – 2466098.27 m Height = 37 m

The content of the transmission: the transmission consists of the official time of Brazil (= UTC – 3 hours) announced by a female voice that begins in Portuguese with the following phrase “National Observatory” followed by the current time (hh: mm: ss) every 10 s and with a short beep every second with a modulation of 1 kHz for 5 ms and a long beep with a modulation of 1 kHz for 200 ms at 58 °, 59 ° and 60 ° seconds. [Audio sample below.]

The Hour Service Division (DSHO) also broadcasts Brazil’s official time with 2 local VHF broadcasts for the city of Rio de Janeiro on the 166.53 MHz and 171.13 MHz frequencies.
The transmission of the time signal of 10 MHz by the DSHO began in November 2008, over all these years, this signal was already picked up by radio listeners in different parts of the world, and the reports are confirmed by QSLs. Dr. Ricardo Carvalho head of that division,

Dr. Ricardo Carvalho kindly gave me one such QSL.


Engineer Ozenildo de Farias Dantas and our journalist Martin Butera, entering the house of the shortwave transmitter.
Shortwave transmitter, Redifon Telecommunications Limited, used in the Service of the official Time of the National Observatory of Rio de Janeiro. There is a ubiquitous BIRD Wattmeter on top left of the transmitter.

From another angle, the short wave transmitter, Redifon Telecommunications Limited, used in the Service of the official Time of the National Observatory of Rio de Janeiro.
Engineer Ozenildo de Farias Dantas dismantles a part of the transmitter panel, to begin with his routine of calibration and maintenance of the transmitter.
The engineer Ozenildo de Farias Dantas and our journalist Martin Butera, along with the transmitter Redifon Telecommunications Limited.

The Antenna

It is a simple but robust dipole, perfectly cut and calibrated by engineer Ozenildo de Farias Dantas for the frequency of 10 MHz, which has given excellent results to this day.

One of the sections of the dipole is supported by the historic imperial tower of the observatory. This tower is famous because many years ago a balloon was inflated at the precise moment that it was 12 noon and was launched so that this was observed in the port of Rio de Janeiro that was called the famous “half astronomical day”.

Dipole wire antenna of the National Observatory
we can see a section of the dipole, supported by the old Observatory tower
Mr. Ricardo José Carvalho (head of the division), with a history book of the National Observatory of Rio de Janeiro, where he mentions about the first tower of the observatory. Behind we can see that the tower still remains intact. Old tower of the National Observatory
Here we can see that they have a tower with different antennas to receive different world time signals
Here we can see the antennas of the VHF transmitters

Listening to the time signal frequency stations is an interesting aspect of the DXing. Many may not know that these stations are in operation in different parts of the world, and have been since the early days of the radio to the present twenties.

The purpose of these stations is to cover various branches of science, such as seismology, meteorology, astronomy, geodesy, etc.

Between the different stations a constant effort is made to coordinate their time internationally so that in the future they can all maintain and supply a world time standard without the slightest difference.

Brazil has the most important time station on the South American continent, I am very happy to present this exclusive report for SWLing Post for all of you.

This was the first time a group of DXers has be welcomed by the Service Division of the Hour (DSHO), from the National Observatory of Rio de Janeiro.

I was especially welcomed by Mr. Ricardo Carvalho, Head of the division, who kindly guided us on an extensive tour, showing all the facilities. I was also able to film a pleasant interview (in Portuguese).

Click here to view on YouTube.

Surely all of you who are now reading this report know that listening to the short wave, can become the most instructive hobby that exists.

To know about a country, its customs, its culture, its gastronomy, its geography, to follow the national or international current affairs, are the interests that define the various aspects of the hobby of radio listening.

The main purpose of listening to international short wave radio stations is to know the world better, to open up to other cultures, to other ideologies, to demystify the unknown, to have access to the many facets that make up the world.

In short, the listening to international short wave radio stations of the whole world is traveling around the globe without leaving home or even getting up from the couch.

Station History

Current entrance of the National Observatory, museum of astronomy and related sciences of Rio de Janeiro.

National Observatory of Rio de Janeriro 1827 – 2019

Now, I shall try to summarize 192 years of history, a mission that is not at all simple.
To remain as a scientific institution of recognized competence for 192 years is an almost impossible mission in Latin America.

The National Observatory (ON), established in Rio de Janeiro, is an example of determination since its foundation on October 15, 1827 by Emperor Dom Pedro I.

Since then, much has changed at the National Observatory, where the creation of the Brazilian Official Time Division with its acronym (DSHO), established by law in 1913, stands out. Nowadays, the service is generated from a set of twelve atomic clocks that also contribute to the official world time scale.

The need for an Astronomical Observatory in Brazil began in the colonial period, its creation was necessary due to the increase in commercial activities and the rapid growth of ships arriving and departing from the ports of Rio de Janeiro since the beginning of the 19th century, and this demand became more evident.

For the sake of safer sea travel, it was essential to obtain accurate knowledge of the magnetic declination, the average time and information about the length so that commanders could regulate the timers.

That is why the installation of an observatory in a fixed location could offer ships more accurate information than those obtained at sea.

The first records date from the inception to establish an observatory in the Hill of the Castle in 1730 on the initiative of the Jesuits, in the same place was established in 1780 an observatory of Portuguese astronomers where they made the first observations of astronomy and meteorology.

Hill of the Castle in 1730 (File ON)

But only in October 1827, by decree of D. Pedro I (first emperor of Brazil), the headquarters of the Imperial Observatory of Rio de Janeiro was established, this was the first institution of this genre built in Brazil.

Initially, this astronomical observatory was established in the tower of the Military School, in charge of Pedro de Alcántara Bellegarde (military, educator, astronomer and Brazilian engineer), who played a fundamental role in the area of important scientific institutions throughout the 19th century.

However, until at least the 1870s, the activities of the institution were almost exclusively related to the instruction of military school students.

Only in 1871 were its functions redefined, when it came out of the military administration, the Observatory could dedicate itself mainly to research and service activities in meteorology, astronomy, geophysics, measurement of time.

Such redefining of its sphere of activity was driven by the Administrative Commission of the Imperial Observatory, which in this period began the process to choose the new site, in a place that is considered more appropriate, where it would be transferred later.

The conclusion of several studies culminated with his transfer to the hill of “San Januário”, at the beginning of the 20th century, where it still operates today.

Panoramic view of the domes of the meridian lunettes used for the determination of time. (File ON)
Building of the National Observatory built at the beginning of the 20th century, when it was moved to Morro de São Januário. (File ON)

These fundamental changes, that took place after 1871, happened during the administration of Emmanuel Liais (he was a politician, botanist, astronomer and French explorer who stayed in Brazil for many years), who was responsible for the process of remodeling the observatory, during the two terms for which he was the director (from January to July of 1871 and again between 1874 and 1881).

The increase in the activities of the Imperial Observatory led to the publication of the first volume of the Observatory Yearbook in 1885, which gave continuity to the Astronomical Ephemerides, published between 1853 and 1870.

The aim of the Yearbook was to disseminate information obtained from astronomical and meteorological observations, constituting until today an important bibliographical reference on the annual scientific production of the institution.

In 1886, the Observatory Magazine, the country’s first scientific journal, was published in 1886 with the aim of disseminating scientific productions, which lasted for only a short time and were stopped in 1891.

With the new political winds blowing from 1889, triggered by the proclamation of the Republic, also changed the orientation of the institution, subordinating itself to the Ministry of War and receiving the name of Observatory of Rio de Janeiro.

Only in 1909 it was renamed as OBSERVATORIO NACIONAL (ON): the Ministry of Agriculture and the Directorate of Meteorology and Astronomy was created, and the Observatory was made subordinate to this.

From then on, the institution began to provide the weather forecasts for different purposes. During that time, the activities of meteorology and astronomy walked together and the calculation of time was made by astronomical methods. These two functions, however, were separated in 1917, when the National Observatory only covered studies on astronomy, geophysics, and time and frequency. With this redefinition of functions, the scientific trajectory adopted by the institution throughout the 20th century was marked.

The beginning of the 20th century also gave rise to ideas that would lead to scientific moods. The accelerated process of urban reforms and the redefinition of the state function as a promoter of national scientific activity represented a new apparatus for the diffusion of sciences, accompanied by the notions of civilisation, modernity, reason and progress that drove all actions in the scientific field.

The institutional framework of the National Observatory, in relation to these intense transformations in the Brazilian social, political and scientific plan of the beginning of the century, was evidenced in the management of Henrique Morize (considered the great introducer of experimental physics in Brazil), having assumed the post of the Director of the Observatory in 1908, was responsible for several important modifications of the institution during this period, in which Rio de Janeiro also underwent intense urban reforms.

During the twentieth century, several reforms in the political-administrative spheres changed the jurisdiction of administration to which the institution was linked; however, they changed their attributions. In this sense, In 1930, the Observatory was brought under jurisdiction of the newly created Ministry of Education and Culture; in 1976, it was transferred to the control of the National Council for Scientific and Technological Development (CNPq). In 1999, such transfer of jurisdiction took place to the Ministry of Science and Technology which is maintained till today.

Einstein’s theory of relativity

The National Observatory of Rio de Janeiro, has always been present on the world stage with many scientific contributions which were internationally recognized.

Perhaps one of the most “famous” such contribution was in the year 1919, when the National Observatory coordinated the English expedition that observed the total eclipse of the Sun, in the Brazilian city of Sobral, in the state of Ceará.

The phenomenon was also observed parallelly in the Prince Island. Such observation contributed to the confirmation of Einstein’s theory of relativity, when the deviation suffered by the light of the stars in the background of the sky caused by the gravitational field was verified due to the mass of the Sun.

Visit of Albert Einstein to the National Observatory in 1925, after having tested his Theory of Relativity thanks to the work of the National Observatory of Rio de Janeiro. (File ON)

Importance of creating a specific division of time in Brazil

To understand the importance of creating a specific division of time (DSHO), within the National Observatory of Rio de Janeiro, we list below the very relevant fact about Brazil.

Brazil has a territory of continental dimensions with an area of 8,547,403 square kilometers.
The extension of the territory, we can analyse it in the following way from north to south and from east to west, in the first case, from Monte Caburaí (Roraima) to Arroio Chuí (Rio Grande do Sul) 4,395 kilometers are recorded, in the Serra da Contamana (Acre) to Ponta do Seixas (Paraíba) results in 4,320 kilometers. As you can see in the following graphic

It is the largest country in Latin America and the fifth largest in the world. If we put all the countries of Europe ( except the Russian – European part) and there would still be space left over in Brazil.

I took the trouble to scan an old Brazilian geography book since I found the following image and it seemed very interesting, this image leads to a good reflection on the dimension of Brazil.

In case it is not clear to the valued readers, the size of Brazil and its continental dimensions, the whole United Kingdom alone, fits within the state of São Paulo.

That is why, because of the enormous size of Brazil, it has landmass in three different hemispheres at the same time: the majority in the southern hemisphere, a small part in the northern hemisphere and all its territory in the western hemisphere.

In the North It is cut by the Line of Equator and in the South by the Tropic of Capricorn, thus getting 92% of its area in the tropical zone.

Another aspect of the geographical position of Brazil is its latitudes and longitudes, that is, its geographic coordinates, which are generally measured from the equator (latitudes) and from the Greenwich meridian (longitudes). Thus, in latitudinal terms, the Brazilian territory extends from something close to 5º North to approximately 33º South. In longitudinal terms, the extension extends from 35º West to a little less than 75º West. But if we ignore some of the oceanic islands in the Atlantic, they are placed in somewhat smaller lengths.

Due to its great east-west extension, Brazil presents a great variation of time zones, totaling four different regions that we can observe in the following map.

The first time zone is two hours behind the Greenwich Meridian (-2GMT, therefore) and covers only the islands in the Atlantic Ocean, (Yellow color on the map).

The second and most important portion (-3GMT) covers most of the Brazilian states, including the Federal District and the capital, Brasilia, making it the official time of the country, (orange).

The third area (-4GMT) covers some states to the west, namely: Mato Grosso, Mato Grosso do Sul, Rondônia, Roraima and most of the Amazon, (green).

The fourth and last time zone (-5GMT) covers a small western part of the Amazon and the state of Acre, (pink).

And if you still do not understand the complexity of the Brazilian time system, we can mention this curious fact: the first day of the year never reaches all the people of the world at the same time. In Brazil it is not different, because Brazilians can celebrate the New Year four times! This is due to the four time zones that we mentioned earlier.

Brief summary of the History of the Official Time Service Division (DSHO)

The beginning of the activities of the National Observatory precedes its creation date in 1827. Since 1730, regular observations of astronomy, meteorology and terrestrial magnetism have already been carried out in Morro del Castillo, in the city of Rio de Janeiro.

With the arrival of the royal family to Brazil in 1808, the heritage with the research of the time was transferred to the Royal Military Academy. Nineteen years later, Pedro I determined the creation of the entity that would inherit his patrimony.

Since then, National Observatory has accumulated a precious history that covers the areas of Astronomy, Geophysics and Metrology in Time and Frequency.

The time and frequency metrology is the responsibility of the Services Division of the Official Time, which for more than a century and a half has been legally responsible for generating, maintaining and disseminating the Official Time of Brazil and also plays the role of Time Laboratory and Primary Frequency, denominated in its initials as (LPTF).

The Official Time Service Division inaugurated its new facilities in 2004.

The modern building is named after Carlos Lacombe, in honor of the engineer who directed that division in the period from 1963 to 1977 and participated, along with Henrique Morize and Roquete Pinto, in the creation of the first radio station in Brazil, called (Rádio Sociedade do Rio de Janeiro).

Enter the building of the official Brazilian time, it is simply fascinating, it is very large and has the most modern technologies.

To understand better how it is inside, I decided arrange the tour in the following order: Museum, Generation room, Conservation and Dissemination of time, Laboratory and we will leave the Short Wave Transmitter for the last.

Come with me !!

Martin Butera at the entrance of the modern building of the Official Time Service of the National Observatory of Rio de Janeiro.

Small Museum

When entering the modern building of the Service of the hour (DSHO), of the national observatory, the first thing we can observe is a small but very interesting museum of the first clocks and measuring instruments, kindly Mr. Ricardo José Carvalho (head of the division ), he was detailing us one by one.

Click here to view on YouTube.

These pieces are fundamental to understand the process of evolution in the measurement of time.

Different old instruments for measuring the time used by the Official Time Hour Service (DSHO), from the National Observatory of Rio de Janeiro.
Different old instruments for measuring the time used by the Official Timekeeping Service (DSHO) of the National Observatory of Rio de Janeiro.

Among the pieces stand out different models of chronographs used in the mid-1950s, from the manufacturer Édouard Belin.

Édouard Belin, was an inventor and photographer born in France in the year 1876.
Chronographs were an instrument that measured time and maintained unity. In most analog models it was up to hundredths of a second, a chronometer at that time was a high precision certificate of a watch.

Another old chronograph
Another very interesting piece of the museum is the issuer of time signals from the manufacturer James Muirhead, famous British watchmaker.
We can also observe the first spoken recording system of the hour, it was a complex system of records made in Brazil.
In the same piece of furniture at the bottom of the piece mentioned in the previous photo, we can see a classic Collins Radio Company receiver, which was used in the mid-1950s to tune in to other world shortwave time signals.
Undoubtedly a very important piece is the first cesium clock, which began to work in Brazil in 1970, it is an HP5061A
Mr. Ricardo José Carvalho (Head of the Division) and our journalist Martin Butera, editor of this report, together in Brazil’s first atomic clock.

Room of Generation, Conservation and Dissemination of the time

Leaving behind the small museum, we continue with our tour with Ricardo José Carvalho (Head of the Division) and we are about to enter the room where the Generation, Conservation and Dissemination time racks are located.

Click here to view on YouTube.

Before, we progress further it is necessary to understand briefly what is meant by generation, conservation and dissemination of time.

What is meant by generation?

The generation of time and frequency, that is, the second atomic, is done in the Official Time Division of Brazil, by means of Cesium commercial clocks and hydrogen maser clocks.
The atomic time by the International System of Units (SI) in 1967 is defined as:
“The second is the duration of 9,192,631,770 periods corresponding to the transition between two hyperfine levels of the ground state of the cesium 133 atom radiation.”

What is meant by conservation?

The conservation of the “greatness of time and frequency”, is realised through the uninterrupted operation of the atomic clocks and their evaluation of stability by means of the measurements of time and frequency difference between the clocks.

What is meant by Dissemination?

The dissemination of the “greatness of time and frequency” is carried out by the calibration of atomic clocks, frequency counters, chronometers and other different equipment. These measurements are sent to the laboratory of the division where they are checked through other standard signals and by the official time synchronization network.

In the room where the Generation, Conservation and Dissemination time equipment racks are located, we can observe 11 racks in total, with different equipment such as generators and gong distributors, top, IRIG code, synchronism signals, NP generators, secondary clocks , temperature monitors, “no-break” phase monitors, electric power phase monitors, internet talk time monitor, ZAG 500 talk time monitor, various distributors and amplifiers, cesium registers, audio and GPS distributors (time transfer system) and much more.

In the following videos, Mr. Dr. Ricardo Carvalho, Head of that division explains and details the operation of several of these teams, we invite you to see the following video links (in Portuguese language).

Click here to view on YouTube.

Racks of equipment for Generation, Conservation and Dissemination of Time, Service of the Hour (DSHO), of the national observatory Rio de Janeiro Brazil.

Racks of equipment for Generation, Conservation and Dissemination of the time, of the Service of the official hour (DSHO), of the national observatory Rio de Janeiro Brazil.
Different views of the Racks of equipment for Generation, Conservation and Dissemination of the time, of the Service of the official time (DSHO), of the national observatory Rio de Janeiro Brazil.
Different views of the Racks of equipment for Generation, Conservation and Dissemination of time, of the Service of the hour (DSHO), of the national observatory Rio de Janeiro Brazil.
Different views of the Racks of equipment for Generation, Conservation and Dissemination of time, of the Service of the hour (DSHO), of the national observatory Rio de Janeiro Brazil.
we can observe equipment, such as the monitoring of “no-break” phases.
Technician working in the room of the Racks of equipment for Generation, Conservation and Dissemination of the time, of the Service of the official hour (DSHO), of the national observatory Rio de Janeiro Brazil.


After leaving the modern room of Generation, Conservation and Dissemination of the time, we enter into another important room – the laboratory.

Here we will find various equipment for measuring, calibrating and adjusting the time, up to a faraday cage. Also in the laboratory are jealously guarded famous atomic clocks.

Currently, the service of the official Brazilian time (DSHO), has 2 atomic clocks of the Symmetricon MHM hydrogen maser (valued at approximately 250 thousand dollars each), 12 cesium standard clocks (valued at approximately 80 thousand dollars each), they are 3 three HP 5071A clocks, 3 three Agilent 5071A clocks, 4 four Symmetricon 5071A clocks, 1 a CS4000 clock, 1 a Datum 4310A, 1 a rubidio HP5065A standard clock and two GPS / glonass / galileo-TTs-4 receivers.

Having a laboratory is essential to keep exactly calibrated the national standards of time and frequency, some of these parameters are the basis of the Brazilian Metrological Traceability of Time and Frequency.

At the international level, the traceability of national standards and Brazilian official time is established with the International Bureau of Poids and Mesures (BIPM), also with Brazilian official time is compared in real time through the Inter-American Metrology System (SIM) that it is accessed through GPS Common-View.

Faraday cage

Another surprise that we are not prepared to see was to get up close and to be able to enter a famous “Faraday cage”,

On one side of the laboratory there is a famous Faraday cage, which Dr. Ricardo Carvalho explains to us, it is a fundamental requirement for the measurement of atomic clocks, since no unknown entity can be present during the calibration process, we are talking about the calibration of atomic clocks costing 250 thousand dollars.

Faraday cage in use for calibration of the official Time of the National Observatory

Faraday’s cage was an experiment conducted by Michael Faraday to demonstrate that an electrified conductive surface has a zero electric field inside it, since the charges are distributed evenly on the outermost part of the conductive surface (which is easy to try the Law of Gauss), for example we can mention the Van de Graaff generator.

In Faraday’s experiment a metal cage was used, where an insulation and a wooden chair were placed on which Faraday sat, an electric shock was given to him and nothing happened to him, which shows that a body inside the Cage could remain there, isolated as the electrons are distributed on the outer surface of the surface.

Our special correspondents Mark Van Marx (photographer), Martin Butera (journalist) and Mr. Ricardo José Carvalho (head of the division), inside the Faraday cage, together with the calibration equipment of the atomic clocks.

Racks of diverse equipment of the laboratory, of the Service of the hour (DSHO), at the national observatory Rio de Janeiro Brazil.

Racks of diverse equipments of the laboratory, of the Service of the hour (DSHO), at the national observatory Rio de Janeiro Brazil.
Our photographer Mark Van Marx, taking photograph of the various equipments of the laboratory, of the Service of the hour (DSHO), at the national observatory Rio de Janeiro Brazil.
Different signal and frequency counters, used in the calibration of watches.

Next to the famous Clock Maser of Hidrogenio Symmetricon MHM

The most accurate watch of Brazil and also of South America, is located in the basement of the Time Service Division of the National Observatory in Rio de Janeiro, the clock is kept in a special room, with constant temperature and humidity, to be able to access to watch, you have to go through three sophisticated alarm controls, we had the honor of being able to access exclusively for the ‘DX Clube Sem Fronteiras’.

This watch comes from the United States. The approximate cost is US $ 250,000.
This atomic clock “Maser Symmetricon”, which is expected to delay or advance only one second in 10 million years runs using hydrogen.

A curious fact is that from the confirmation of the order for its acquisition, the clock took six months to manufacture. The process went through the Department of Defense of the US government. To obtain an authorization of export, since it is a device that generates time with high precision.

Our special correspondents Mark Van Marx (photographer), Martin Butera (journalist) and Mr. Ricardo José Carvalho (head of the division), together with the most accurate atomic clock in Brazil as well as in South America.

From Atomic clocks to Quantum Optics

The search for the most accurate clock is an extreme challenge. Brazil does not want to be left out and like the leading countries are using “Quantum Optics”.

If you think that everything ends up in the measurement of the time produced by the atomic clock, you are wrong, in the service of the national observatory, you are already having experiences of quantum measurements through the laser system.

In another sector of the division, there is a sophisticated optical frequency measurement device. It is obtained from a company named Menlo Systems.

Menlo Systems is a German company, founded in 2001 by Professor Hänsch, Dr. Ronald Holzwarth, Dr. Michael Mei and Alex Cable as a spin-off of the renowned Max-Planck Institute for Quantum Optics.

It is a revolutionary technique for measuring the frequency of light. This invention has been called “… the greatest advance in precision electromagnetic measurements since people started measuring frequencies”

The time division of the National Observatory of Rio de Janeiro has already begun to perform experiments with optical measurements of high precision in various applications such as optical clocks, cold atoms and molecules, metrology, distance measurements, Fourier spectroscopy and Lidar measurements.

They know that the world is increasingly ultra-precise and ultra-fast and are committed to delivering measurements made in Brazil that meet the highest standards of quality and reliability worldwide.

Different lenses used for optical frequency measurements.
Our photographer Mark Van Marx, taking photographs of optical frequency measurement lenses
A top view of the Quantum Optics measuring apparatus
Our special correspondents Mark Van Marx (photographer), Martin Butera (journalist), by the side of the sophisticated equipment of measurements of optical frequencies (Menlo Systems)

By way of final conclusion

From ancient times we have designed devices that allow us to measure time and keep it for records.

In the beginning it was carried out according to the nature, like the Sundials, which use the light to indicate the time; or the movement of grains of sand inside an hourglass, or water in the case of the clepsydra.

Subsequently, more precise devices were invented, whose operation occurs thanks to the standardisation of the time units (days, hours, seconds, etc.) of the International System.
Up to now, the most accurate of the clocks invented by humanity the atomic clock, calibrated from the vibrations of the atom of Cesium.

That now is our most modern and new starting point in what we refer as time.

Special Thanks

Final thanks, once again to Dr. Ricardo Carvalho, Head of the Service Division, the Official Time (DSHO), for freely allowing the photographers who accompanied me to cover the subjects of this report.

They are: Mark Van Marx (Photographer) and Ligia Katze (Videographer), Engineer Ozenildo de Farias Dantas, Mrs. Vilma Madalena de Assis Souza (Assistant in the Service of the C & T Division of the National Observatory Time) and Miss Letícia Reitberger (journalist of the communications consultancy Target).

To my friend, the Argentine radio listener Daniel Camporini, for writing a special prologue for this report (included in the Spanish version).

To my editor in chief, dear Chrissy Brand, for giving me the opportunity to work in South America, as a journalist for the BDXC.

Chrissy brand is European DX Council Secretary-General – BDXC Communication (

To the dear friend and listener from India, Sudipta Ghose (VU2UT) for his adaptation to English and correction, member of the Indian DX club International (

To my friend Ivan Dias da Silva Júnior, director of the Regional DX – Sorocaba-Sao Paulo- Brazil, who collaborates in the Portuguese translations and publishes this material in the form of a micro book, for the club he directs (

Finally my friend Thomas Witherspoon, director “The SWLing Post”, for publishing this report and collaborating in this way to the world of radio listening.

From left to right Mark Van Marx (in photo), Martin Butera (Journalist), Ricardo Carvalho head of the Service Division of the Official Time (DSHO), Miss Letícia Reitberger (journalist of the communications consultancy Target) and the lady Ligia Katze (Videographer), in the Generation, Conservation and Dissemination room of the time.

From left to right Martin Butera (journalist), Engineer Ozenildo de Farias Dantas and Mark Van Marx (Photographer), in the Generation, Conservation and Dissemination room of the time.
From left to right, Mark Van Marx (in photo), Mr. Dr. Ricardo Carvalho, head of the Service Division, the Official Time (DSHO) and Martin Butera (Journalist), in the laboratory.


About the author

Martin is an Amateur Radio operator with more than 29 years of experience, and has participated in DXpeditions throughout South America, with the Argentine radio callsign LU9EFO and Brazilian callsign PT2ZDX.

It is to collaborate for the newsletter of the British Dx Club (United Kingdom).

Martín is the founder of the Brazilian CREW Radio Listeners’, called 15 point 61 (15.61). Martin is Argentinian, born in the city of Buenos Aires capital. He currently lives in Brasilia DF, capital of Brazil.

Martín Butera is a journalist, documentary maker and founding member of Radio Atomika 106.1 MHz (Buenos Aires, Argentina)

About the The British DX Club

Martin Butera is a contributing journalist for “Communication” magazine of the prestigious The British DX Club. We congratulate Martín Butera for this interesting report.
If you would like to be a member of the Briitish DX Club, you can find information here

Report made, visit to Rio de Janeiro Brazil, in May 2019, written completed and published in SWLing Post in the middle of September 2019.

Please contact Martin at the following email address:

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Sangean DT-800 Review: AM/FM/Weather ultra-compact radio

Two months ago, SWLing Post reader Paul Adler wrote to ask:

“Any reviews and comparisons of the Sangean DT-800?”

The Sangean DT-800? This caught my attention, as I wasn’t, at the time, familiar with this recent addition to the Sangean product family.  So I promptly began investigating the new product, and checked out the manual; I found it has a few features that really intrigue me, namely:

  • The ability to turn off soft muting
  • The ability to internally recharge NiMH AA batteries
  • Multiple bandwidth on AM and FM
  • Weather band with weather alerts
  • FM RDS
  • No telescoping antenna––rather, an included wire antenna

In my mind, these features seemed to set it apart from other similar portables.  And with the ability to defeat the soft mute, I wondered if it could make for a formidable Ultralight DX radio?

I contacted Sangean, and they kindly sent me a review sample of the DT-800. It comes in two chassis colors: standard black and and a bright fire yellow. I chose yellow, which makes it easier to spot should this handheld be lost or dropped in an outdoor setting.

Thanks for the suggestion, Paul!

Giveaway!  By the way: since this is a product sample and was sent to me free of charge, I’m going to give it away to a lucky SWLing Post Coffee Fund or Patreon supporter next week, just to say thanks!

Now, let’s get on with the review…

Initial impressions

As with almost all Sangean products, the DT-800 arrives as a complete package, with all accessories. Inside, you’ll find the radio, a full-length multi-language owner’s manual, a warranty card, an AC adapter (with in-line RF chokes, nice touch), in-ear headphones, an external wire antenna, and a belt clip.

The DT-800 fits nicely in the hand, and the matte finish on the sides and bottom of the radio make gripping it quite easy, lessening the chance of dropping or losing the unit.

The front panel is simple: five multi-function preset buttons and a Page/Menu button. All of the buttons are tactile and have a matte finish, as well; they feel of good quality and have a great response.

The right side of the radio (see side view, above) has a tuning/select up/down jog switch, a mechanical keylock button and a MicroUSB DC in port.

On the left side of the radio (see left side view, above) you’ll find the volume up/down buttons and a stereo/mono/speaker mechanical switch which you can use to switch between the internal speaker and headphones.

On top of the radio (above) you’ll find the power button, band selection button and the headphones port, which doubles as the external antenna port.

On the back of the radio you’ll find the DBB bass-boost slider switch, the battery compartment, and a belt clip.

One thing you’ll quickly notice is a lack of any telescoping whip antenna. Instead, the DT-800 ships with a wire antenna that’s almost three feet long. I suspect that this is the same type of FM antenna that shipped with the Sangean WR-7 (click here to read review).


All in all, I’m very pleased with the DT-800’s design: it fits well in the hand, the buttons and controls are easy to use, and it’s small enough––and flat enough––to easily slip in a pocket, go-bag, or carry-on. A great portable for one-hand operation. It’s also lightweight, even with the batteries inserted. Truly, this appears to be a quality little radio.

Tuning the DT-800 is a simple process: simply utilize the up/down rocker switch on the right side of the radio to increase by specified frequency steps (selectable 50/100 kHz FM or 1/9/10 kHz AM), or push and hold it in one direction to skip across the band. While the DT-800 does mute between frequencies, it’s not annoying––in fact, muting is brief and audio recovery is rapid so you can actually carry out meaningful band-scanning, actually hearing stations between the steps. If you press the rocker switch, it will initiate an auto-scan in the direction you’re tuning.

While the DT-800 lacks a keypad for frequency input (in truth, I would not expect such a thing on a walkman-style receiver)  it does make tuning to your favorite stations quite easy with 20 FM, 20 AM, and 5 WX presets. Saving a station to memory is truly a breeze: simply select the page you’d like to save it to, then press and hold the preset button to save it to one of the numbered presets. Really, it couldn’t be easier.

To change the volume on this radio, you use rocker buttons on the left side of the radio to increase or decrease volume up to 25 levels. I particularly like the fact that level 1 is very quiet and 25 is as loud as you would ever want from a small radio. I mention this because, in the past, I have reviewed radios that had coarse volume steps, and the lowest setting is louder than I prefer: not so with this little rig.

Entering menu items on the DT-800 is quite easy, too.  Some are accessed by pressing and holding the Page/Menu button and then cycling through and selecting items with the tuning up/down switch. Others are accessed by pressing and holding the Page/Menu button, then selecting one of the five buttons on the front panel (note that each menu function is listed below the numbered button).

The DT-800’s display is backlit and large, thus very easy to read at any viewing angle.

AC Adapter

I can’t think of the last time I gave an included AC adapter its own subheading in a review, but the DT-800 power supply deserves one.

Not only does the DT-800 ship with a power supply (AC adapter), but it’s a quality one: the cord jacketing is thick and feels exceptionally durable––and though I’m not going to cut it apart to find out, I expect the wiring within it is a heavier gauge, as well. This adapter also has no less than two in-line RF chokes.

In a day and age when included “wall wart” power supplies are often of the cheapest quality and spew so much radio interference that they render attached receivers useless, the DT-800 adapter is a very welcome addition to this radio’s kit.

Well played, Sangean! I hope other radio manufacturers follow your lead.


Lately, it seems most new radios are being designed to accommodate slim Lithium Ion battery packs. So, another welcome sight was opening the DT-800’s battery compartment to find slots for two AA batteries.

While Li-ion batteries have advantages in terms of weight and size, I prefer AA batteries for pocket and travel radios, as AA batteries are so ubiquitous on this planet and are available in all but the most remote regions of the world.

And better yet? You can internally recharge NiMH batteries with the DT-800. The DT-800 ships with a default setting for alkaline batteries. But to internally recharge NiMH batteries, simply open the battery compartment and change the battery type switch from “Alkaline” to “NiMH.”

This is an amazing and useful feature, but just be sure if you ever use the NiMH internal recharging function and then switch to alkaline cells, that you change the battery selection switch back to the alkaline setting. You certainly wouldn’t want the DT-800 to attempt recharging your alkaline cells!

As you can see in this photo, I’ve been using Panasonic Eneloop NiMH batteries in the DT-800. I use a special charger for Eneloops, so have kept the battery selection switch set to alkaline so the DT-800 doesn’t attempt to charge them. I might even put a small piece of colored tape on the switch to keep it in place for now.


The audio via headphones? It sounds great on the DT-800!

Indeed, the DT-800’s included in-ear style stereo earphones are a cut above most other included-with-a-product earphones, and as a result, produce more pleasant audio.

With the headphones engaged, FM offers selectable mono or stereo; mono, of course, makes marginal stations more stable since the stereo lock isn’t struggling.

Like the Walkman radios of days gone by, the DT-800 uses the headphone cord as an antenna when it’s attached. If you’re using the internal speaker, you’ll need to attach the included external wire antenna for FM and WX bands.

The DT-800 internal speaker produces decent audio for the size of the radio. The speaker is tiny, so the audio is somewhat tinny (narrow in range) when listening to music. But the DT-800 also has a DBB (Dynamic Bass Boost) switch––engaging this will increase the bass response a bit, most noticeable when using headphones.


The DT-800 has three bands: FM, AM (mediumwave), and WX (weather). Let’s take a look at each.

FM Band

The DT-800 sports a unique feature on the FM band: the ability to select between a wide or a narrow filter. Since the dawn of the DSP chip, many a portable radio has enjoyed selectable bandwidth filters, but it’s a rare portable that has FM filters. I do pretty much all of my FM listening with the wide filter engaged, but if you live in an urban area with a crowded FM band, choosing the narrow filter, even if it compromises audio fidelity a bit, will give you better selectivity. Nice touch, Sangean!

In terms of sensitivity, with the external antenna inserted, I’ve been very pleased with the DT-800. It receives all of my benchmark FM stations. With headphones inserted (used as an antenna) and stereo engaged, it has ever-so-slightly less sensitivity than several of my other DSP portables. With the headphones inserted and FM in mono, I find that it’s on par with––or surpasses––my other reference DSP portables.

Here’s a little wrinkle, though: when listening with the internal speaker, you must insert the external wire antenna to use this receiver on FM. Without the external antenna, sensitivity decreases by a good 70-80%, as you essentially have no antenna. If you live in an area with strong FM stations, you’ve nothing to fear, but if you live in a rural area, you’ll certainly want to keep that wire antenna handy.

On one hand, the wire antenna is easier and more flexible to deploy than attached telescopic antennas, which can be bent or broken. But on the other, an external wire antenna is just another item you’ll need to pack and take along with the radio if you plan to listen via the internal speaker.

If you plan to listen with headphones, however, no worries! I find the sensitivity with headphones inserted to be just as effective. In fact, instead of taking along the wire antenna you could bring the included headphones, and they’ll double as an external antenna while listening via the internal speaker. In my tests, the headphones performed about as well as the external wire antenna.

My advice? If you purchase the DT-800, either keep the small wire antenna or a pair of headphones nearby to insure you’re getting the best FM reception.

Weather Band

The same notes above about the necessity of an external wire antenna apply on the weather band as well as the FM band.

With the wire antenna or a set of headphones connected, weather radio reception is good. I was able to receive both of my local NOAA weather reference frequencies.

To be clear, the DT-800 is not as sensitive as my C. Crane CC Skywave or CC Skywave SSB––which are truly WX band benchmarks––but it will likely receive your local NOAA or Environment Canada broadcasts as well as most other weather radios.

The DT-800 also includes a Weather Alert feature, but as Sangean notes, you should only use this feature while the radio is plugged into mains power, as it will drain batteries about as effectively as if you were listening to an FM radio station.

AM/Mediumwave Band

If there’s a weak point on the DT-800, I would say it’s the AM band.

Don’t get me wrong: at first blush, the DT-800 looks like a little Ultralight DXing dream, as it’s loaded with great features, such as:

  • multiple bandwidths (wide/narrow),
  • 9/10 kHz spacing,
  • well-balanced AGC (auto gain control),
  • as well as the ability to turn off soft muting.

Yes, the DT-800 has the ability to disable soft mute. Thank you, Sangean! So far, Sangean seems to be one of the only radio manufacturers that enables this DSP chip option in their product line. Another receiver with the ability to disable soft mute was the Sangean ATS-405 (check out our ATS-405 review). I wish other radio manufacturers would do the same because soft mute is what often makes listening to weak mediumwave signals so fatiguing. With soft mute disengaged, weak signals enjoy better audio stability as they’re not fighting to stay above the muting threshold.

But, I’m sorry, DXers: unfortunately, the DT-800’s weakness on AM is the same as the ATS-405 on AM (and shortwave): a higher-than-average noise floor. Somehow, internal noise is being generated and not being contained by shielding and grounding.

I made a short comparison video to demonstrate the noises heard via the DT-800. Before you ask: yes, these noises are present regardless of radio location, or whether or not there are other radios nearby. In addition, I made this video on a folding table far away from my house or any other potential sources of noise (with the exception of my iPhone which was used to make the video). This is the same low-noise spot I use to do comparison tests of all my portable receivers:

Click here to view this video on YouTube.

As I note in the video, the noise floor isn’t consistent across the band––some parts are lower, other parts higher. One of the noise peaks is around 1600 kHz which, unfortunately for me, is where my favorite local AM station resides.

So is this a deal-breaker?  No…not necessarily.  For the casual AM radio listener––a listener primarily focused on listening to local AM stations––I think the DT-800 will please. In fact, I might not have noticed the elevated noise floor had I not: 1) listened to weaker AM stations, and 2) compared the DT-800 with other radios.

Since I’ve been using and listening to this radio for the better part of a month, I can state with confidence that most of my other portables outperform the DT-800 on mediumwave. I compared it with these rigs:

  • Sony ICF-S10MK2
  • Tecsun PL-310ET
  • CC Skywave
  • CC Skywave SSB
  • Radiwow R-108

To be clear, I believe the DT-800 has average MW sensitivity for a radio this size, but the noise floor sort of spoils any hopes of doing marginal or weak signal work, thus also making that awesome soft mute toggle less effective.

If you pair the DT-800 with a loop antenna like the AN200, which I highly recommend doing, it will help those weak signals rise above the noise. Otherwise, if your primary goal in purchasing the DT-800 is to listen to mediumwave, I regret to say, you might want to take a pass on this one.


Every radio has its pros and cons. Each time I begin a review of a radio, I take notes from the very beginning so that I don’t forget my initial impressions and observations. Here’s the DT-800’s list, from the first moments I turned it on, to the time of writing this review:


  • Great overall performance on FM
  • Quality construction and thoughtful ergonomics
  • Both clock and alarm for the traveler
  • Ability to switch between FM stereo/mono with headphones in use
  • Wide/narrow AM and FM filters
  • NiMH AA batteries can be recharged internally [make sure switch inside battery compartment is set to “NiMH”]
  • FM RDS (one mode)
  • Mechanical keylock switch
  • Ability to disable soft mute (other radio manufacturers take note!)
  • Small internal speaker providing quite decent audio
  • Comprehensive gear package includes radio, manuals, quality earphones, quality AC adapter, wire antenna
  • DC port is standard MicroUSB
  • Belt clip
  • Built-in speaker
  • Dynamic Bass Boost


  • While listening via the DT-800’s internal speaker without antenna wire or headphones inserted: FM performance is lacking, while weather radio performance is very much lacking
  • AM band: Noise floor is higher than on comparable radios


The Sangean DT-800 is a solid little radio: it’s simple to operate and feels like a quality piece of kit. It’s perfect for hiking, or any sport or task where you’d like one-hand operation.

The DT-800 also has a surprising amount of features and customization through the menu settings––much more than one would expect––which puts it firmly into what I would call the “enthusiast-grade” radio category.

It’s for this reason that it’s a bit disappointing AM reception on this Sangean isn’t better.

The DT-800 has a lot of icing on the cake, otherwise: FM RDS, the ability to internally recharge AA batteries, built-in speaker, Dynamic Bass Boost, multiple bandwidths on AM and FM, the ability to disable soft mute–all of these are essentially pro features.

So, if you’re looking for a quality portable radio primarily for FM and WX band listening and perhaps catching the odd local AM broadcast, the DT-800 is a great choice.

Sangean DT-800 retailers:

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Marine Weather Center daily weather reports on shortwave

Sail Boat Yacht On Sea

Many thanks to SWLing Post contributor, Al Holt, who writes:

Your readers may be interested in tuning in the daily (except Sunday) broadcasts of Marine Weather Center on 4045 and possibly 8173, 12,350 kHz. These broadcasts use upper sideband mode.

It’s described as, “custom weather and routing information for small vessels in the Caribbean Sea, Bahamas and United States East Coast,” and is based near Lakeland, FL.

As a subscription weather service for pleasure craft, but they provide an interesting roundup and forecast of weather in this area of the world. They do take questions and traffic from subscribing vessels at the conclusion of their broadcast.

I am usually am able to receive the omnidirectional broadcast on 4045 kHz here in northern Florida. But, their coverage at greater distances is pretty good I think.

The chart below (taken from their ‘Services’ page ) shows this broadcast starting at 1100z, but I usually hear them closer to 1200z and that may be due to atmospheric conditions. I haven’t had much success catching their later transmissions. I’m not sure how often their webpage gets updated and schedule changes are probably relayed privately to their subscribers.

Wow!  Thank you so much for sharing this information, Al.

Post Readers: I know there are a number of SWLing Post readers who sail and cruise (some on very long voyages)—I’m curious if any use the Marine Weather Service regularity. Please comment!

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WWV & WWVH marine storm warning announcements continue

Many thanks to SWLing Post contributor, Richard Langley, who notes that WWV & WWVH marine storm warning announcements continue despite a recent announcement that they would end.

Richard has been monitoring WWV/WWVH broadcasts and shared the following note earlier this month:

The weather broadcasts (storm information) were still there at 8, 9, and 10 minutes past 0:00 UTC on 1 November on WWV as monitored here in NB. Haven’t had a chance to check them since. Are they actually gone? If so, when were the last ones broadcast. The warning at the 4-minute mark hadn’t been heard for days. I’m wondering if the decision to terminate the broadcasts was reversed.

Yesterday, Richard added the following:

[…]And still there on WWV (and presumably WWVH) on 16 November at 03:08 UTC on 10 MHz. So I guess this conclusively means that the proposal to cancel the broadcasts has been rescinded at least for the time being.

Thanks for sharing this, Richard.

Your observation prompted me to check the NOAA Marine Forecast page. I discovered that it has been updated it since the notice to stop marine forecasts was first announced last month.

Before, it stated that the “end of the high seas warnings [is] scheduled for October 31, 2017.” Either NOAA made the decision to end the the forecasts in 2017 and never followed through, else the individual who posted the announcement mistakenly noted 2017 instead of 2018.

NOAA does not note edit dates on this page, so there’s no way of knowing when the page was updated. Regardless, there is no longer a firm termination date mentioned on the page. Now the National Weather Service simply states:

“the NWS is considering a proposal to discontinue this service.”

So I believe, Richard, you are correct: the NWS has at least temporarily rescinded cancellation of the service.

Thanks for following this development, Richard!

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Midland WR120 Review: Aaron says weather radios, like smoke detectors, are something we all need

Storm with lighteningMany thanks to SWLing Post contributor, Aaron Kuhn, who writes:

“Weather radio? I’ll just use my cellphone for alerts.”

If you’ve ever uttered or thought the above words – take heed.

Late last week I awoke at around 12:30 AM to the sound of some incredibly strong winds outdoors. Glancing down at my completely muted phone, I opened up my text messages to reveal a Tornado Warning. In a panic, I threw on some clothes, gathered a dog harness and leash and made my way the pantry closest for shelter.

Then I checked my phone again – and realized that tornado warning was from 30 minutes ago and already expired. Crap. That was too close for comfort. I promptly went on to Amazon and ordered the Midland WR120.

I unboxed and set the radio up yesterday and I’m quite happy with it.

The first thing I suggest doing after initial setup is turning off the button beeps which are incredibly annoying. Past that, I’ve found the radio perfect for my needs of setting it on a window sill and (hopefully) forgetting about it until it alerts me to any nearby danger.

Since SAME Alerts work on a county basis, I was very happy to discover this radio allows you to disable certain kinds of alerts that may not be relevant to you.

One thing that I think Midland should include in the box printed (instead of ads for weather apps they don’t publish anymore!) is the “Editable Events list:

By default, the radio doesn’t allow you to turn off 30 some events, including Tornado Warnings among them – this is a good thing in my opinion! However, it is a bit concerning when you first go to setup the radio and realized Tornado Warning is missing in the alert list. The reason for this is because this is one of the 30 some alerts you can’t disable.

Overall I’m happy with the radio, and hoping it’ll never fire off in the middle of the night on me any time soon – but I know it’ll be a lot more reliable than my cellphone prone to being muted.

I view weather radios like smoke alarms now, it’s stupid for you to not have one. I wasn’t expecting Tornadoes in November in Southeastern Pennsylvania, but apparently nature is one to surprise us continuously.

Thank you so much for sharing your story and your WR120 review, Aaron.

I love this quote: “I view weather radios like smoke alarms now, it’s stupid for you to not have one.” I agree completely!

A few weeks ago, there was an alert sent to every phone in the US all at the same time. I received my alert nearly 30 minutes late. Mobile phones and their networks are pretty amazing technology, but they’re not flawless.

We are so lucky to have a robust weather radio broadcasting infrastructure here in the US and Canada. An inexpensive radio like the WR120 will deliver weather alerts reliably and give you a preparedness edge.

And thank you for mentioning the number of events you can edit out of the alert system. No sense in receiving alerts you don’t need.

In addition, some weather alert radios default to receive alerts from counties and regions surrounding your own. I would suggest turning those off–limiting the alert area to your own county–else you could get a lot of alerts that don’t pertain to your location. Using the smoke detector analogy, receiving alerts from surrounding counties is much like putting a smoke detector directly over your stove! You’re just asking for false alarms. 🙂

Thanks again, Aaron, for the important PSA!

Keep in mind as the holiday season approaches: weather radios make for life-saving, affordable gifts.

Click here check out the Midland WR120 ($26.56 shipped) on (affiliate link).

Post readers: Do you have any other weather alert radio suggestions?  Please comment with your suggestions and experience.

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Weather Radio Review: Grant recommends the Reecom R-1650

Many thanks to SWLing Post contributor, Grant, who comments on our recent post about weather radios:

I’ve been pretty happy with the Reecom R-1650.

I’ve had it over 10 years and it’s been a solid performer. It has a long battery backup on 4 AA’s. It also does AM/FM, has alarm out, antenna in, audio out etc.

It’s fairly smart and doesn’t alert me when the Wednesday tests are happening but does light up during the test so it’s easy to see that it’s working and receiving alerts as it should. Getting through the programming menu is a little weird (as it is with most weather radios) but I can usually figure it out with having to hunt down the manual even though I haven’t been in the menu in years.

With the advent of the cell phone, where no one thinks they need a radio anymore for anything, the best deal in weather radios is often found at Goodwill or your local thrift shop. You can often find models with S.A.M.E for $2-3.

Thank you for the recommendation, Grant! I was not familiar with Reecom weather products. I’m especially impressed with the 185 hour backup time from a set of four AA cells! Impressive. I doubt other models can claim that amount of backup power time–a full week.

Even eHam has positive reviews of Reecom dating back to 2006.

It appears Reecom only distributes their products through, but I discovered a load of Reecom radios on eBay, many at prices well below $30 shipped. 

Grant, you also make a great point about checking out thrift stores. Many people don’t know what a weather radio is, so thrift stores sell them for $2.00 or $3.00 in their electronics pile. Just make sure you find the matching power supply.

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