Tag Archives: Guest Posts

Guest Post: 13dka Explores the International Beacon Project

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


In search of benchmark signals: The International Beacon Project

by 13dka

If you – like yours truly – like to tinker with antennas and radios to get the most out of them, you likely have your own set of reference stations. If this is a new concept for you – reference stations are whatever stations you deem apt to check propagation, the general function of your radio, when trying to improve reception or comparing radios… They are ideally always on when you need them and come in various strengths and distances on several bands from all over the world. Traditional sources for that are of course time signals and VOLMET stations on HF, even though the latter are giving you only two 5-minute slots per hour for testing reception from a specific region and the former have their own specialities here in Europe:

A typical scene on 10 MHz, captured at home 30 minutes after the full hour: BPM voice ID from China mixed with something else, then Italcable Italy kicks in on top of some faint murmur possibly from Ft. Collins, in winter some South American time stations may stack up on that together with splatter from RWM 4 kHz lower…

A reliable source of grassroots weak signals is particularly desirable for me because I enjoy proving and comparing the practical performance of radios at “the dike”, a QRM-free place on the German North Sea coast. In the absence of manmade noise and the presence of an ocean adding 10dB of antenna gain, finding benchmark stations with “grassroots” signal levels turned out to be a different challenge than it used to be: With somewhat sizeable antennas the stations tend to be (too) loud there, even with the baseline ionospheric conditions under a spotless sun in its activity minimum. In short, my old benchmark stations didn’t work so well anymore and I had to find something new. Continue reading

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Bob’s Updated Passive, Resonant, Transformer-Coupled Loop Antenna for Shortwave

Figure 1. A Passive, Resonant, Transformer?Coupled Loop Antenna for Shortwave

Many thanks to SWLing Post contributor, Bob Colegrove, for the following guest post:


A Passive, Resonant, Transformer?Coupled Loop Antenna for Shortwave

By Bob Colegrove

Over the years I have resisted the level?of?effort necessary to construct and maintain outdoor antennas. Rather, I have focused on squeezing out all of the microvolts I could get inside the house. Many years ago I had access to a well?stocked engineering library, and used my advantage to gather information about the theory and development of loop antennas – a daunting undertaking for an English major. Ultimately, by adhering to a few basic rules, some of them dating back 100 years, I found quite acceptable performance can be had with an indoor passive antenna intersecting just a few square feet of electromagnetic energy.

Theory

There are a couple of advantages of resonant loops as opposed to non?resonant ones. The first is the fact that the signal dramatically increases when you reach the point of resonance. The second follows from the first in that resonance provides a natural bandpass which suppresses higher and lower frequencies. This gives the receiver a head start reducing intermodulation or other spurious responses. The downside of all this is that the resonant loop is, by design, a narrow?band antenna, which must be retuned every time the receiver frequency is changed by a few kHz. On the other hand, there is nothing quite as rewarding as the sight (S?meter) and sound you get when you peak up one of these antennas – you know when you are tuned in.

There is nothing new about the loop antenna described here. It’s just the distillation of the information I was able to collect and apply. There are a number of recurring points throughout the literature, one of which is the equation for “effective height” of a loop antenna. It basically comes down to the “NA product,” where N is the number of turns in the loop and A is the area they bound. In other words, provide the coil with as much inductance as possible.

Unfortunately, for resonant loops, the maximum coil size diminishes with frequency.
With this limitation on inductance, the challenge becomes minimizing unusable capacitance in the resonant frequency formula in order to get the highest inductance?to?capacitance (L/C) ratio possible. Some of the unusable capacitance is built into the coil itself in the form of distributed capacitance, or self?capacitance between the coil turns. This cannot be totally eliminated, but can be minimized by winding the coil as a flat spiral rather than a solenoid, and keeping the turns well separated.

The second trick is with the variable capacitor. Even with the plates fully open, there is residual capacitance on the order of 10 to 20 picofarads which can’t be used for tuning purposes. A simple solution is to insert a capacitor in series, about 1?4 the maximum value of the variable capacitor. This effectively decreases the minimum capacity and extends the upper frequency range. In order to restore the full operating range of the variable capacitor, the fixed capacitor can be bypassed with a ‘band switch.’ With the series capacitor shorted, the variable capacitor operates at its normal range and extends coverage to the lower frequencies. Continue reading

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Guest Post: Simple Android Database Part 2

Many thanks to SWLing Post contributor, Bill Hemphill, who shares the following guest post:


Simple Android Database-PART 2

by Billy Hemphill, WD9EQD

In the first part, I showed how you could easily take a spreadsheet and create a simple database for viewing on an Android phone/tablet. The examples used in that article was two spreadsheets of radio schedules – one for Shortwave and one for FM Radio Programs. See the following link to the original article: https://swling.com/blog/2021/10/guest-post-radio-schedules-in-a-simple-android-database/

There are many lists on the internet of various radio databases. If the database can be downloaded as either a CVS file or a spreadsheet, then it is possible to load it into the PortoDB app on the phone tablet. I’ll show how this can be done with two popular databases that I reference all the time.

EIBI Data Base

Most of you are probably familiar with the EIBI database of shortwave schedules. Many of the Shortwave Schedule apps on the Phones reference this database. For example, I use the Skywave Schedules on my phone. While it does allow for me to search by many parameters, I thought it might be fun to have it in a PortoDB database. Plus it would be interesting to see how PortoDB performs with a large data set. Continue reading

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Guest Post: Jock explores the Tecsun PL-880’s ATS system

Many thanks to SWLing Post contributor, Jock Elliott, who shares the following guest post:


Oh, no, it’s broken – NOT! And other observations on the PL-880

by Jock Elliott, KB2GOM

 

Okay, okay, I’ll admit it: I’m an oldster, currently enjoying well over 70 trips around that Big Orange Ball in the sky. Further, I’ve been out of SWLing for a while.

Coming back into the hobby after more than a decade’s absence, has been eye-opening. Back when I wrote for Passport To World Band Radio, my main interest, equipment-wise, was tabletop communications receivers hooked to serious outdoor antennas.

Today, however, tabletop communications receivers are hard to come by (there are few new offerings), and, in my situation, serious outdoor antennas present a series of logistical problems that aren’t going to get solved quickly.

So that has brought me to today’s crop of portable shortwave receivers, and – bottom line – they are pretty darn cool, offering worthy performance on a number of levels. My latest acquisition is the Tecsun PL-880.

Like many of the current SW portables, it offers a system for scanning the SW bands and automatically storing the stations it finds into memory. On the PL-880, it’s called ATS (for Auto Tuning Storage.) Oh, you knew that. Yeah, but did you know that the PL-880 has, essentially, two ATS systems?

The down arrow activates ATS Mode A, and the up arrow activates ATS Mode B.

Check it out: If you press the DOWN arrow button (in the SW-METER BAND rectangle), the ATS Mode A system searches the band you are in (FM, MW/LW or SW, including ALL the SW meter bands), automatically stores stations it finds, and “previously stored radio stations will be replaced automatically by the newly found stations.” Each band has its own set of memories, so that SW stations will be stored in SW memories, FM stations will be stored in FM memories, and so forth.

ATS Mode B, however, behaves differently. You can activate it by pressing the UP arrow (in the SW-METER BAND rectangle). If you are in SW frequencies, ATS Mode B will search and store stations only within the current SW meter band. Further, it will NOT overwrite memories, but will start storing stations it finds, starting with the first available unused memory. Pretty neat.

You can, however, fool yourself. I ran ATS Mode A on SW frequencies one night and found a station that was broadcasting unusual stuff (Kennedy assassination, UFOs, and the like). A couple of nights later, I wanted to see what the night’s topic was on that station, so I punched the button to access memories and found . . . nothing! Oh, no, it’s broken!

Then I realized I was in SSB mode, and, it turns out, the PL-880 has a separate set of memories for SSB. (And the manual says that explicitly.) I switched off the SSB mode, and – tah-dah! – the SW memories reappeared. Sometimes it really does pay handsome dividends to read the manual.

One of the slick things about the PL-880’s memory setup is that, when you are in memory mode for a particular band, you can easily scroll through the memories simply by turning the tuning knob.

Wire antenna reels come in different styles. PL-880 (left) and CCrane Skywave SSB. But both improve performance for their respective radios.

The PL-880 has a nice long whip antenna (nearly twice as long as the CCrane Skywave SSB’s antenna), and it seems to be quite sensitive operating off the whip. But if you take the time to deploy the external wire antenna that comes with the PL-880, there is a considerable gain in sensitivity. Tuning around the 40-meter ham band, with the external wire antenna plugged into its socket, I could hear two stations in conversation, one louder than the other, but both copyable. When I tried to listen to the same pair of stations with just the PL-880’s whip antenna, the fainter station disappeared entirely, and the louder station was “down in the mud” but copyable. So the external wire antenna is clearly worth using.

So far, I am well pleased with the PL-880.

PS: Here’s a link to a really good article on extending the wire length of the reel-up antenna that came with the PL-880: https://www.hamuniverse.com/shortwavereelantenna.html

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Guest Post: Radio Schedules in a Simple Android Database

Many thanks to SWLing Post contributor, Bill Hemphill, who shares the following guest post:


Radio Schedules in a Simple Android Database

by Bill Hemphill

I am a program listener. I really enjoy listening to various radio stations direct and by internet streaming. Over time, I have come up with a couple of spread sheets that lists the program, station, time, date, etc. For example, following is the spreadsheet for the shortwave radio programs/stations that I enjoy:

As the program schedules change, I update the spreadsheet. This has worked quite well for me. I usually sort on the weekday and then print out the spreadsheet as a list by time and frequency for each day.

While this method works, it does mean that I have these multiple page printouts that I have to refer to. This got me thinking that it would be great to have this on my Android phone/tablet. Then I could refer to it no matter where I was located.

At first, I tried to use Google Sheets, but found that using a spreadsheet on the phone or even a tablet to be a pain. I then tried entering it into a calendar program, but also found that very cumbersome. Continue reading

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Guest Post: Citizens Band FM mode is long overdue

Many thanks to SWLing Post contributor, Peter Laws, who shares the following guest post:


Adding FM as an allowable mode on CB seems long overdue

by Peter Laws

The FCC’s recent action to add FM as an allowable mode on CB seems long overdue.  See the final rule as published in the Federal Register on September 28, 2021: https://www.federalregister.gov/documents/2021/09/28/2021-19399/review-of-the-commissions-personal-radio-services-rules

Looking through old CB and amateur radio magazines from the 1970s it appears that the FCC considered allowing FM around the time that the service expanded to 40 channels.  The FCC being the FCC took their usual “what’s the least we can do to make this issue go away?” path and just added 17 new channels starting at the beginning of 1977.  Other than that expansion, they didn’t really change anything.  There were incumbents on the spectrum re-allocated to CB, too, and licensees were given a 2-year grace period to vacate what was to become channels 24, 25, and 26 and up.

Personally, your humble reporter is happy that the Commission has finally allowed FM on CB.  This should be a big improvement for people who are actually trying to communicate.  The reduction of static alone will be welcome.  There are claims that AM has better range than FM at the same power levels.  I suspect that people who make that claim are confusing AM broadcast (on MF) to FM broadcast (on VHF) but the proof will be in the pudding once we start to see new FM CBs hit the market.

And what about that?  When will we see new radios?  It should happen pretty quickly, almost certainly by the end of the year “Christmas” rush assuming no supply chain delays.  If you are unfamiliar with CB outside of North America, you may be surprised to find that radios that will meet the new FCC rules already exist.  I don’t mean those quasi-legal “Export” radios that many are fond of, but main-stream consumer radios from vendors like Midland, Cobra (the petitioner that got FM approved), Uniden, and President.

If you are an amateur licensee, you may be familiar with CEPT, the Conférence européenne des administrations des postes et des télécommunications.  That’s an association of the various FCC equivalents (and USPS equivalents) in each of the European nations.  In the amateur world, CEPT has a simple reciprocal licensing regime that allows US amateurs to operate in CEPT countries and amateurs from CEPT countries to operate in the US without any extra paperwork.  CEPT also works to harmonize radio and other telecommunication rules regimes between the different nations to make it easier for vendors to build equipment acceptable to all and making the market bigger.

For the most part — there are exceptions — CEPT nations have all adopted the same CB radio band plan and rules.  Here’s the surprise: they are nearly identical to the FCC rules!  Same 40 channels, even with the weirdness between channels 22 and 25 and the skipped channels for radio control, the 4 W power output, etc.  The only big difference is that CEPT allows FM in addition to AM and SSB.

So a CEPT-spec radio will meet the new FCC rules today.  A vendor will simply need to make certain that their product’s firmware and other components really do match US requirements, get it tested by a contract certification facility (those facilities will also need to update their FCC CB test procedures for the addition of FM), and file the paperwork with the Commission.  This is far simpler than actually having to engineer the addition of FM to an existing AM-only product.

One jurisdiction that has their own rules, in addition to allowing CEPT rules, is the United Kingdom.  When CB was legalized in the UK in 1981, the government allowed FM (only) on 40 channels that start at 27.60125 MHz and go up every 10 kHz to 27.99125 MHz.  A decade or two after that, the UK also made operation of CEPT-spec CB radios legal with the result being the UK CBers have 80 legal channels available – 40 CEPT channels with all three modes and an additional 40 with FM only.

Don’t expect to see “multi-norm” radios in the US like those marketed in Europe.  Multi-norm units allow for switching between CEPT, UK, and other national channel/power/mode layouts, often with only a few simple button presses.  Historically, the FCC has been reluctant to allow radios that have user-adjustable operating parameters outside of the Amateur Radio Service so watch for firmware on US versions to be locked down.

Undoubtedly, some will claim that this is all being done so that Cobra (the petitioner in this case) can sell more radios.  What is the problem with this?  The new rules do not change anything with regard to the current rules.  If you have a legal AM or AM/SSB radio now, you will still have a legal AM or AM/SSB radio after October 28, 2021.  And after that, it will be legal to sell an FCC-approved radio that includes FM in addition to AM or AM and SSB.  That’s right – radios may include FM but must have AM.

Generally speaking, I am one that is not in favor of deregulation.  But if you look through old FCC regulations, either in Part 97 (Amateur) or Part 95 (CB, GMRS, et al), there really were a lot of silly regulations.  But only silly by the time they went away; at the time they were created they were, or were at least thought to be, vital.  Time showed that some of those rules really weren’t vital and many have been removed.  One of those rules was the 250-km limit on CB communications.  It’s likely that at the time the rule was promulgated it was intended to reinforce that Class D CB (as it was known then) was intended as a short-range communications system.  The ionosphere made sure that the “DX rule” was nearly impossible to enforce as even regular, law-abiding citizens could and did answer a “breaker” who ended up being 1000 miles away!  In Cobra’s initial 2017 petition to the FCC, they requested abolition of the distance limit and the Commission agreed but in that same Report and Order, they declined to add FM.  Cobra petitioned for reconsideration of that point (FM) and here we are.

While there are still allocations for other services between channel 40 and the start of the 10-m amateur band, and while there are still licensees there, it is hard to imagine that those licensees are actually using that spectrum.  Free-banders, yes, licensed stations, unlikely.  A quick tour of the Commission’s Universal Licensing System shows a number of licensees in the spectrum between channel 40 (27.405 MHz) and the start of the amateur allocation at 28.0 MHz.  Most, however, appear to be dealers, consultants, and manufacturers in the communications business that are required to have blanket licenses for any band that they intend to use.  As a result, there are many licenses that cover 25-50 MHz (and many other bands) inclusive for demonstration purposes.

So where is this story going?  Why not petition the FCC to allow UK-spec radios to be used in the US?  Literally, almost no one is using this spectrum aside from freebanders that may already be there.  The reason that the Congress reserved to itself the ability to regulate the radio spectrum, later delegated to the FCC, was to ensure that the spectrum was used in the most efficient manner possible and to prevent interference.  Since almost no one uses this patch of spectrum at 27 MHz, why not let it become an expanded “national park” for hobbyists?

If you are thinking, “well, if the FCC does that for 27 MHz, why not new bands in other, largely-abandoned spectrum?”  This reporter’s answer is “sure, why not?”  This is, after all, how amateurs got bands at 630 and 2200 meters – the spectrum was largely abandoned.  WL2XUP is an Part 5 experimental station that is transmitting various digital modes between 40.66 and 40.7 MHz.  This roughly aligns with 8-meter amateur allocations that are popping up in other jurisdictions.  Maybe this 8-meter experiment, too, will pave the way to a new allocation like the Part 5 operations did on the new MF and LF bands mentioned above.

It’s a brave new world in CB.

Peter Laws has been licensed as a ham since 1991 (after a false start c.1978), has listened to scanners since 1982, was on CB in the late 1970s, and started DXing on MW and SW in the mid-1970s.  He edits columns in both LWCA’s Lowdown and IRCA’s DX Monitor.  He lives in Norman, Oklahoma, with his wife, several small doggoes, and many radios and antennas.

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Guest Post: A synchronous detector crash course!

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


Revisiting the Belka’s “pseudo-sync detector”: A sync detector crash course!

by 13dka

“It’s usually hard to assess whether or not a sync detector helped with a particular dip in the signal or not, unless you have 2 samples of the same radio to record their output simultaneously and compare.”*

That’s what I wrote about the “pseudo sync detector” in my review of the Belka DSP last year.

Since I was recently upgrading to the Belka DX in order to pass on the Belka DSP to a friend, I had briefly two examples of almost the same radio on the table at the dike. I tuned them to the same stations and recorded some audio clips with one radio on sync detector, the other in regular AM mode, to answer the question whether or not sync has “helped with a particular dip in the signal”. Then I thought that demonstration would be an opportunity to try an explanation on what exactly (I think) sync detectors are all about anyway, hoping to find a middle ground between “technical” and “dumbed down beyond recognition”.

The trouble with sync detectors

Perhaps no component of a shortwave receiver is surrounded by so much misconception and confusion as sync detectors. Full disclosure: Until quite recently, I had an, at best, vague concept on what they do myself. It seems it’s not so much that people don’t know how they work, what they actually do when they work is where the ideas often diverge. Continue reading

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