Category Archives: How To

Giuseppe’s Homemade “Magic Tablet” Antenna System

Many thanks to SWLing Post contributor, Giuseppe Morlè, who writes:

Dear Thomas,

This is Giuseppe Morlè, from Formia central Italy on the Tyrrhenian Sea,

I built this “Magic Tablet. during a rainy afternoon to test various portables I have.

The tablet is composed of 2 separate circuits: one for the short waves, a single coil along the entire perimeter of the tablet, and another with 2 ferrites wrapped around 36 turns of telephone cable for the medium waves.

The heart of the system is a 1050 pf variable capacitor with its old wheel.

To listen to medium wave I have to exclude the short wave loop with a switch on the loop.

I also added another small switch to connect it to a capacitor for more or less capacity, but this I will do later.

I can test my portables like this because the tablet tunes very well from 500 kHz to 18 MHz. I spent very little to make all this as it is all recycled stuff.

You can see the first tests on the balcony of my house with a Tecsun H-501 via my YouTube channel:

Note: this video is in Italian, but you can turn on closed captions and have it translate into the language of your choice.

As I always say, I am not a technician and I have little manual skills in building things, not having a proper laboratory. When I get an idea, I put it on paper and I start to find all the materials and then see if they work. Not all of us are of the experts in electronics–what drives me is a passion for radio listening. Now being retired, I have more time to devote to it.

Thanks to you and hello to the whole SWLing Post community …

73. Giuseppe Morlè (IZ0GZW)

I love this, Giuseppe! What a clever all-in-one portable antenna system for your shortwave radios. I especially love the fact you were able to create all of this from parts you have at your home. You’ve got a winning attitude, too: build and experiment! Thank you for sharing.

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Jock explores “The Essential Listening Post”

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

The Essential Listening Post

By Jock Elliott, KB2GOM

Listening to shortwave radio (or any radio, for that matter) is just plain fun.

So what do you need to get in on the fun?

A radio. With today’s crop of portable SW radios, many of which have search and store capabilities, a newbie SWL can get started quickly without a lot fuss and bother and no extra stuff. Just hit the search and store function (it has different names on different radios), let the search function do its thing, and step through the memories to see what’s out there. If your radio doesn’t have search and store, you can just tune around to see what’s currently broadcasting or, if you have a computer or smart phone, use it to explore one of the online directories like https://shortwaveschedule.com/

What follow next are some things that I’ve found increase my enjoyment of SWLing. Continue reading →

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Radio Mods: Unblocking the YAESU FRG-8800 Frequency Coverage Limitations

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Many thanks to SWLing Post contributor, Paolo Viappiani (SWL I1-11437), who shares the following guest post. Note that, as with any radio modification, perform this operation at your own risk. This is a very simple mod, but if you feel it might be beyond your skill level, consider hiring a radio technician to perform it on your behalf:

Unblocking the YAESU FRG-8800 Frequency Coverage Limitations

by Paolo Viappiani

Figure I: An unblocked FRG-8800 receiver tuned to 29.999.9 MHz.

Introduction

It is well known that some receivers produced in the last decades of the last century suffered from a limited frequency coverage due to legislative restrictions in force in some countries (Germany, Australia, etc.).

In particular, in Germany it was forbidden to listen to HF frequencies higher than 26.1 MHz, while in other Countries shortwave were not allowed to receive frequencies below 2 MHz.
These restrictions led most radio manufacturers to produce “blocked” versions of their HF receivers in order to satisfy the various national requirements; almost classical examples are the world renowned SONY ICF-2001D and the PHILIPS D-2935/D-2999 portables.

The blocking/unblocking procedure of some frequency bands was quite simple in microprocessor-governed synthesized radios: usually it was sufficient to add (or remove) proper jumpers in the vicinity of the microprocessor to perform the task, and the correct procedure was often covered in the Service Manuals or in specific Technical Bulletins; in any case plenty of information can be found on the Internet. Continue reading →

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Ham Radio Workbench episode explores Diversity Reception

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The SDRplay RSPduo

I just finished listening to the most recent episode of the Ham Radio Workbench with John Fallows (VE6EY) as a guest.

John is an SWL and Ham Radio operator and speaks at length about how he uses diversity reception to mitigate persistent local RFI (radio frequency interference).

If you have persistent issues with radio interference or if you’ve been curious about using diversity reception for mediumwave and shortwave DXing, I highly recommend listening to this episode. John has been known to frequent the SWLing Post and actually comes into the discussion primarily from an SWL’s perspective.

If you’ve tried diversity reception or a noise-cancelling system like the Timewave ANC-4+ in the past with mixed results, you’ll definitely benefit from listening to John’s best practices.

In addition, John points out that the excellent SDRplay RSPduo is a very affordable way to explore proper diversity reception.

How effectively can you mitigate RFI with diversity reception? Check out this video on YouTube queued up to the point where John does a live demo with his Anan SDR and loop antennas: https://youtu.be/vu8D87aVUTQ?t=2011 (I also recommend watching to full video presentation for even more detail.)

I’ve embedded the audio for the Ham Radio Workbench podcast below, but you can also find it along with show notes on the Ham Radio Workbench website.

Ham Radio Workbench is one of my favorite podcasts; if you like exploring a wide variety of technical topics, I highly recommend checking it out. It’s available on all podcasting platforms.

Also, check out John VE6EY’s YouTube channel and web site/blog.

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Guest Post: 13dka Explores the International Beacon Project

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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

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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

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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