Category Archives: Recordings

Midway Island Radio Terminal 1971: Digging up the past and a mystery signal…

Many thanks to SWLing Post and Shortwave Radio Audio Archive contributor, Dan Greenall, who shares the following post:

Midway Island Radio Terminal 1971 – digging up the past

It was a brief “military style” transmission on approximately 14.85 MHz shortwave, logged sometime during 1971. And I still had a recording of it!

Recording:

I wondered if there was any chance of confirming what exactly I had heard way back then, so I recently decided to try a little bit of detective work. My first contact was with Nick England, K4NYW, who runs a “hobby” website about U.S. Navy communications in the 1950’s and 1960’s. He was good enough to put me in contact with a Midway navy vet, Charles E. “Chuck” Kinzer, who writes:

“…it could be a “long count” test for one of the transmitters at the Naval Communication Unit transmitter site where I worked.

When I was there (1966-1968) they installed two log periodic fixed antennas, one pointing generally east (Washington DC) and the other generally west (toward Vietnam).

Each was connected to an AN/FRT-39 10 KW transmitter. And for the most part, always connected to the same two transmitters. (We had an antenna patch panel and could mix and match most any transmitter to most any antenna.) It is my understanding that they were used by the Security Group on Eastern Island (one of the two Midway Islands which are Sand and Eastern). They were set up for single sideband voice. (Most of the other AN/FRT-39s were set up for multiplexed TTY tones on both sidebands with suppressed carrier. 16 channels on each sideband.)

From time to time, they would tell us they wanted to do a “long count” and we would set the power level of one of the transmitters. As they did the count, we would set the power level of the peaks of the voice close to the maximum transmitter power. You could see the various meters flail up and down to near maximum along with the voice. This would be mainly the “PA Plate Current”, “PA Plate RF”, and PA Output” meters on the 10 KW final.

We couldn’t hear the voice, just see the meter activity. It would help if the person knew the frequency. If it was NOT an amateur radio frequency, it might have been one of those long count tests on one of those Navy transmitters. ….”over 50 years ago” sounds reasonable for that exercise. I assume the usage of that particular transmitter/antenna setup lasted to the end of the Vietnam war, at least.

Incidentally, when this was first set up, we had instructions to put X transmitter on Y antenna and so forth when they started testing the two new antennas. They would ask to do a “long count” test where we would set the power levels. Then shortly after they would start shouting into the microphone raising the power level too high and the transmitter would trip off. We asked them exactly what they were trying to do and, for secrecy I guess, they would not tell us. After a while, they figured out they were using the two antennas backwards. For example, they were trying to transmit east off the back side of the west facing antenna. These were VERY good antennas and very little power was wasted in the envelope going backwards.

I don’t know if this helps. Rather amazing that there is a recording existing like this. You never know what is going to pop out of the woodwork.”

Chuck later added that he might ask someone else for a little help. In the 1970’s, I used to own a guide to utility stations by Joerg Klingenfuss, that had lots of great frequency information, but sadly, I decided to part with it a number of years ago.

Please listen to the audio file of the transmission above from 1971, maybe some readers might weigh in with their thoughts on this? Please feel free to comment.

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Carlos’ Reception of NOAA Forecast via USCG Radio Station in Chesapeake

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Photo: US Coast Guard

Many thanks to SWLing Post contributor, Carlos Latuff, who shares the following video/recording and notes:

Hey Thomas, [Check out] how well the USCG signal arrives from Chesapeak in Porto Alegre, Brazil. It’s a NOAA Pacific NE forecast.

I made this video at 06h36 (09h36 UTC):

[Here is an audio ifile so you can get an idea of the quality of the reception:

That is amazing reception in Brazil, Carlos! Thank you for sharing this! I must say, you really give your XHDATA D-808 a workout! It’s a proper little DX machine!

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Carlos’ Shortwave Art and recording of the Voice of Korea (September 16, 2023)

Cuban Numbers Station HM01 Goes Cuckoo! And Other Cuban Broadcast “Shenanigans”…

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Many thanks to SWLing Post contributor, Pete Madtone, who shares the following recording of Cuban Numbers Station HM01 and notes:

Hi Thomas,

I was reading HF Underground earlier and a post on it mentioned that HM01 had gone a bit mad “10345 kHz is HM01 Cuban Lady with what sounds like a cuckoo clock“. Well I got up straight away and tuned in on VE7AV KiwiSDR and here it is in all it’s glory:

It almost sounds a bit reggaeish and even has what sounds like a little drum roll in parts.

If you’re feeling a bit down or tired today please have a listen as this’ll cheer you up!

All the best

Pete

Wow–thanks for sharing this recording with us, Pete! What a mystery behind this numbers station! Was the cuckoo intentionally or unintentionally added to the audio at the studio or transmitter level? What could that signify? Since the audio is tracking with the HM01 broadcast, it seems to be originating from the same transmitter.

Perhaps this adds more context or confusion: SWLing Post contributor Paul Walker has noted a number of audio “shenanigans” from Cuban broadcasts. Here are a few notes from his listening post in Alaska:

0320UTC Mon Aug 28 and Cuba is missing from 9700 for the 2nd time in a week, but instead of regular programming they’re broadcasting a horror movie of some kind. I can detect some kind of noise under the movie but it’s like a screech/hum, which is all I heard from 9700 last time it was on.
I should also add, after the first time i heard 9700 down on 9600, I subsequently heard it back on 9700 again…..so something’s up!
And now HM01 aka Suzie Cubana on 10345 is broadcasting……. along with Suzie counting down the numbers and the digital data bursts, theres a cuckoo bird cuckooing over the top of that audio.
In the 0500 UTC, Rebelde on 5025 kHz noted running TV audio too….some English language movie.
The domestic Radio Rebelde AM and FM web feeds appear to be running normal programming

What do you think is going on?

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Paul’s short recording of Marconi Radio International

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Many thanks to SWLing Post contributor, Paul Jamet, who writes:

Hi Thomas,

I tried in vain to pick up Radio Marconi International … And I’m not the only one! I’ve used several SDR kiwis installed in Italy, and only one has enabled me to listen to this station, which has only a very weak transmitter.

Here’s the audio file below [RMI signing on at 18hOO UTC] and a snapshot of the screen of my PC (see above):

Kind regards.

Paul JAMET
Radio Club du Perche

Thank you for sharing this recording, Paul!

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Don Moore’s Photo Album: Costa Rica (Part One)

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Radio Reloj, Costa Rica (1990)

Many thanks to SWLing Post contributor, Don Moore–noted author, traveler, and DXer–for the latest installment of his Photo Album guest post series:

Don Moore’s Photo Album: Costa Rica (part one)

by Don Moore

Costa Rica is one of the most visited countries in Latin America. I only visited there once, for three weeks in May-June 1990 when the country was just beginning to become a major international eco-tourism destination. Visitors were few and prices very affordable. Except for a short trip to the Monteverde cloud forest, we spent all our time in the central valley, staying in San José and nearby Heredia. Rather than nature, our visit focused on cultural and historical sites … and a lot of radio stations.

Since the 19th century, Costa Rica has been one of the most literate and educated countries in Latin America. That quality is reflected in its radio broadcasting industry, which has always been very professional. Curiously that’s even reflected in station verifications. Almost every Costa Rican shortwave station that I’ve verified had a professionally printed QSL card.

Despite being one of the smallest countries in Latin America, Costa Rica had a lot of shortwave radio stations. I have fifteen in my logbooks and some of the most famous ones were already off the air when I started DXing. Unfortunately, shortwave broadcasting from Costa Rica ended almost twenty years ago so there’s no more to be had. It is still possible to log Costa Rica on medium wave but it’s not as easy as it once was. When I started DXing in the early 1970s, stations in the San José were spaced twenty-five kilohertz apart. That meant that every other station, such as Radio Sonora on 675 kHz and Radio Columbia on 725 kHz, was on a split frequency that fell between the normally assigned 10 kHz channels. I logged nine Tico stations on medium wave while DXing from Pennsylvania in 1972-1981 and only one of those, Radio Reloj on 700 kHz, was on an even channel. Those split channels were eliminated in the 1980s so logging Costa Rica on medium wave is no longer a slam-dunk.

I visited a lot of radio stations and took a lot of photos on my one long-ago trip to Costa Rica. I’m going to focus on just five shortwave broadcasters in this first look at Costa Rica. The others will be featured in two or three future columns.

In the 1970s the first Costa Rican station most shortwave DXers heard was Faro del Caribe, or Lighthouse of the Caribbean. This religious station used two kilowatts on 9645 and 6175 kHz and got out surprisingly well as long as there wasn’t a more powerful international broadcaster also using the same frequency. In the late 1970s they added 5055 kHz in the sixty-meter band.

When I visited in 1990 the antennas were located right next to the studio building. The site was outside the city of San José when the station was founded but gradually a residential area built up around it.

Engineer checking one of Faro Del Caribe’s shortwave transmitters.

Fortieth Anniversary pennant from 1988. When Faro del Caribe began broadcasting on February 23, 1948, it was the first Evangelical Protestant radio station in Central America.

For DXers, Radio Reloj was one of Costa Rica’s best known radio voices for several decades. The station was founded as Radio Cristal by Roger Barahona in 1945. The shortwave frequency of 6006 kHz was added in the early 1950s. In 1958 the station was renamed to Radio Reloj when the format changed to focus on news and community announcements with very frequent time checks. (Radio Reloj means Radio Clock.) Roger’s brothers Isaac and Francisco had joined the broadcasting company and Radio Reloj was assigned the callsign TIHB for Hermanos Barahona (Barahona Brothers). Continue reading →

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Audio Plugins For Radios, Part 3 – VST Technical Setup

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Many thanks to SWLing Post contributor, TomL, who shares the following guest post. Click here to check out all of the posts in this Audio Plugin series:

Audio Plugins For Radios, Part 3 – VST Technical Setup

by TomL

Processing legacy audio still has a place in an increasingly digital world for the time being. The first article on this topic was strictly using the speaker jack output from an old Kenwood transceiver using a simple Behringer UCA-202 RCA-to-USB converter. However, my main receive radio is the SDR based AirSpy HF+. Either type of radio should work with the apps discussed below as long as the audio gets to your Windows computer unmolested. There are VST apps for Mac and Linux, too.

VST apps: VST3/VST2/DLL files

Also mentioned was how to install VST Host and the VST apps run inside it. A simple reminder is that VST Host does not really install. It just resides in any one Directory/Folder you want and you create a shortcut to run VSTHOST.EXE. All the .XML files and profiles will be stored there.

I like tinkering with many apps but you may prefer things a lot simpler. I use 64-bit versions when possible, like VST3 and x64 DLL files. Because of the myriad settings involved, I will just list the apps in order of processing with brief comments. The second icon on the top of each app opens up its control panel and the bottom left icon will Bypass the app as if it is not in the audio chain. The top-left icon Links to the Preceding app in the audio chain. Most controls inside the apps let you double-click on that control to reset to a default.

The general functional order of these apps is:

Limiting/Compressing volume – dealing with shortwave signal volume spikes plus judiciously squeezing high & low volumes for a more even sound.
High Pass & Low Pass Filters – limit the frequency range apps will need to work on.
De-noising – the biggest challenge in shortwave is to reduce static and local noise without damaging the wanted audio.
EQ adjustments – frequency tweaks.
De-essing – getting rid of screechy “sss”, “shhh”, and “squeak” noises as well as fading distortion, perhaps the second hardest thing to do.
Then a final Drive/Gain control to feed into the Windows mixer.
Special Effects apps, like adding stereo, or reverb, etc.

I would suggest not to spend any money until you get to use apps from each of these broad categories to understand how they work. It is very easy to destroy the audio with a couple of offending settings. If you need help with understanding how plugins work, there are plenty of YouTube videos available. One channel I like is “In The Mix” from a Scottish music production engineer, Michael Wynne (over 1 million subs!). He gives simple to understand instruction videos (especially EQ and Compressors), among other topics.

Check out: YouTube – In The Mix

Welcome to the world of Audio Production. Here are some plugins (most are FREE!):

Reaper ReaComp – A Compressor which I am using to limit volume spikes in the <300 Hz range.

Kotelnikov – A great dynamic Compressor that helps compress volume peaks in both Peak and RMS (average) levels. Useful for highly variable signals and highly recommended.

Reaper ReaFir – A dynamic processor, the Subtract feature is a special “negative EQ” which only reduces specified frequency “Points”. It is also used as a brick filter for low & high frequency limits.

Klevgrand Brusfri Denoiser – In Swedish, “brusfri” means “noise free”, and is a Denoiser app that functions similarly to Audacity’s Noise Reduction feature but works in real time. I move to a blank frequency on the same shortwave band, have Brusfri “Learn” for about 5 seconds, and it starts working.

Bertom Denoiser Pro – A good Denoiser app but on noisy shortwave it can have digital artifacts that get very loud. I use it sparingly immediately after Brusfri.

Bitsonic Sound Recovery – This app beings midrange more forward and can brighten up dull audio. However, it can lead to increased sibilances, accentuated fading distortion, and “boxy” sounding voices.

TDR Nova – A clean sounding parametric EQ; my settings are a work-in-progress for best settings. I am experimenting with having the Wideband setting do most of the work with a slight expansion of the audio coming from the SDR. Also used as a better Gain control for Bitsonic.

Modern Exciter – Set to MIN for shortwave, this app can enhance the extreme low and extreme high frequencies without increasing noise.

LOADES – A DeEsser from Analog Obsession, controls sibilance and squeaks (beware of wonky controls!).

Klevgrand Brusfri Denoiser & Bertom Denoiser Pro run a second time. More Denoising is needed after the processing done by Bitsound, TDR Nova, and Modern Exciter.

Klevgrand FreeAmp – A simple Drive and Gain control that was free when I purchased Brusfri. It makes sure audio is driven correctly into Voicemeeter AUX Input.

Voxengo Stereo Touch – Allows adding “stereo” to a mono signal. Various Presets are available, from narrow (Voice or Guitar) to wide soundspaces (Stage, Surround, and Wide). Very interesting!

Here are three VST Host processed .MP3 files from an IQ recording of Radio Amazonia using 5.3 kHz & 7kHz filters in SDR Console 3.2 (Noise Reduction 4 was used but only 1dB Reduction). The third one is using the Stereo Touch app using just the lowest setting (Voice). I like it! 🙂 :

VST processed 5.3k: