Category Archives: Articles

How to install a mechanical SSB filter on the Yaesu FRG-7

Many thanks to SWLing Post contributor, Kostas (SV3ORA), for sharing the following guest post which originally appeared on his radio website:

How to install a mechanical SSB filter on the Yaesu FRG-7

by Kostas (SV3ORA)

The Yaesu FRG-7 is a general coverage MW/SW receiver that uses the Wadley Loop system for stabilizing the frequency tuning. The receiver has a good sound on AM mode, that reminds me the tube receivers sound. However, on sideband mode, it is pretty much useless. The IF ceramic filter that is used, does not have enough selectivity to reject the opposite sideband. No matter if the front panel mode selector switch states USB/CW and LSB, these just shift the BFO, nothing more. The receiver is a DSB set not SSB. A cheap way you can accomplish single signal sideband reception with the FRG-7 is described in this link. Whereas it works, it increases the audio bandwidth of the signals to the high pitch.

A better approach is to install an additional mechanical filter to the receiver. This of course requires expensive 455KHz mechanical filters, but if you have one in hand or if you are willing to pay for the improvement in performance, then this is the recommended option. But you can’t just desolder the ceramic filter of the receiver and solder a mechanical filter in place. On AM mode, you need wider bandwidth, but on SSB mode you need narrower. So both filters must be in place and a selection must be done in each mode. Thankfully, this modification is pretty easy on the FRG-7 and it does not require any modification of the external appearance of the radio.

The schematic of the FRG-7 is shown above. Everything with red color, are part of the modification. The modification is pretty straight forward. You have to desolder the original ceramic filter from the FRG-7 PCB and install it on a separate PCB along with the new 455KHz mechanical filter. To select between the two filters, a 9-12v DPDT relay can be used and it must be connected as shown in the schematic. The power for the relay coil is derived from one section of the mode switch (S3d). On USB or LSB modes, the BFO is energized and this power is also used to energize the relay, which in turn switches to the narrow mechanical filter on these modes.

A good place for the new PCB that accommodates the filters, is just below the main tuning dial of the receiver. There is a hole there and three screws, which can be used to also hold this PCB in place. I needed to replace these screws in mine with longer ones, because I used spacers to prevent the PCB from touching the chassis. But this is optional.

Two small pieces of coaxial cables are used to connect the new PCB to the pads of the ceramic filter, that has been now removed from the original PCB of the receiver. Ground these cables on both ends.

The power cables for the relay coil (shown with red and black in the picture above), are passed below the PCB to the chassis opening and through a hole to the bottom of the original PCB of the receiver. The ground wire is soldered to the filter ground point and the red wire is soldered to the mode selector switch S3d. S3d is the outer wafer onto the switch. Use a multimeter to find the contact of the switch that has VCC when the mode is switched to USB or LSB. This is the point where you want to connect the red wire.

After installing everything, you should perform an alignment of the TC404 and the T406 in the BFO section as described in the manual. This requires a frequency counter, but I did my alignment by simply adjusting the two controls by ear, until I got roughly the same pitch on LSB and SSB audio bandpass. These controls interact, so you have to do a bit of back and forth in both of them. It is very easy.

After installing the modification and aligning the receiver, the result is pretty obvious. No more DSB reception, SSB signals are received just once in the dial and their bandwidth is limited as it should on SSB. The mechanical filter I had, was a bit narrow (2.1KHz) so I can also hear a bit os “seashell” sound on SSB, but SSB voice signals are perfectly understood. It is interesting that the audio volume between the ceramic filter and the mechanical filter was just about the same, which indicates that there is no additional loss in the newly installed filter. Another interesting thing is that there was no need for any impedance matching using active devices or transformers on the mechanical filter. It worked just by directly connecting it. Neither it’s loss, not it’s response seems to be affected by any possible impedance mismatches.

Note that Collins produced both symmetrical and asymmetrical mechanical filters (yes they used two filters, one for USB and one for SSB in some of their gear). My filter is a symmetrical one (same roll-off response curve on both sides of the filter passband). If you use an asymmetrical filter, expect a bit different pitch when switching from LSB to USB and vice versa. Not a huge problem, but just a note.

By performing this simple modification, you will end up with an FRG-7 receiver that is trully selective, allowing for real SSB reception. Most importantly you do not ruin the appearance of your precious FRG-7, but just improving it’s performance. This modification would probably be appreciated much when deciding to sell your FRG-7 to someone else.

Thank you for sharing this practical and affordable project with us, Kostas!

Post Readers: Check out this project and numerous others on Kostas’ excellent website.

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Andy builds a genius companion control display for the Yaesu FT-817 transceiver

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Many thanks to SWLing Post contributor, Andy Webster (G7UHN), who kindly shares the following guest post:

Yaesu FT-817 companion display

by Andy Webster (G7UHN)

Like so many I love getting out portable with my FT-817 but I do seem to spend so much of my operating time fiddling through the soft-keys because my most used functions (CW narrow filter, power and keyer settings to tune an ATU, A/B, A=B, etc.) are spread across different “pages” of the A,B,C assignments. Compared to the sublime experience of using my Elecraft K2 the FT-817 can be a little frustrating!

Last month, inspiration struck and I thought I could cobble together a small microcontroller and a little OLED display with some buttons to provide some extra soft-keys for the radio using the CAT serial port. Nothing particularly original here (I’ve seen articles of people using PICs for this purpose) but it seemed like a nice sized project for me to play with and build some experience doing PCBs (I’ve only done this once before at home). A little bit of discussion with Michael G0POT (FT-817 and SOTA guru), some Google searching and we were looking over KA7OEI’s excellent reference page (http://www.ka7oei.com/ft817_meow.html) and thinking about our favourite FT-817 commands…

As it happened I was lucky to have the right bits (Arduino Nano, small OLED display, buttons, prototype board and an 8-pin mini DIN cable) lying around the house to see “first light” from my FT-817’s serial port that evening. The Arduino Nano is a good place to start because it works at 5V so can work directly with the FT-817 levels on the ACC port. What followed next was some late nights of hacking on Arduino code to send and receive the data for my favourite commands and more experimentation on prototype board.

I tried a couple of cheap OLED displays and they look great indoors but weren’t quite up to the job in full sunlight which is fairly typical in my portable operations.

Daytime readability issues with an OLED display

By this point I had also realised the utility of having an auxiliary display on top of the radio as a much easier thing to view than the 817’s own display on the front panel. I’d also experienced some interference from the unshielded prototype board coming through as clicking sounds on the radio’s receiver so it looked as though some isolation between radio and my circuit might be necessary. Guided by many Internet tutorials, I switched to using a Nokia 5110-style LCD for better daylight readability and lower power consumption. Adding an ADUM1201 digital isolator and a B0505S-1W isolated DC-DC converter to the prototype board (modules acquired very quickly from eBay suppliers) gave me some isolation and lowered the interference which I guessed would disappear when I made the design on PCB with good ground planes around the signal lines.

Screen capture showing the schematic (click to enlarge)

With a (mostly) working prototype it was time to hammer the Internet tutorials again, this time to learn how to use KiCad, a free open-source PCB design tool available on Linux, Windows and Mac. I’ve done one PCB for home projects before using Autodesk EAGLE and I found learning Eagle pretty hard going, it seems like it carries 20 years worth of baggage and dogma in the user interface. In fact I started using EAGLE on this project but spent 3 hours on the first evening just trying to change the labels on the ADUM1201 chip that I couldn’t find in an EAGLE library… so I gave up and thought I’d try KiCad which I’d seen some recent good reports on. I’m happy to say after finding an excellent tutorial on KiCad I had drawn the schematic and my PCB layout in about 15 hours working time spread over a few evenings.

I should add that the 15 hours of KiCad time did include several hours of agonising over the choice of slide switch so a PCB can be done much quicker than that once you’ve got your favourite parts sorted!

That’s pretty impressive for my first go with KiCad as a near-beginner to PCBs, I heartily recommend it, it was so much easier than EAGLE and quite an enjoyable tool. Right, PCB design done and uploaded to JLCPCB for manufacture. 5 PCBs with DHL shipping cost me less than £20 and arrived from China within 5 calendar days. Other PCB fabs are available… 🙂

Click to enlarge

So that brings us to today, pretty much. The PCB was assembled very quickly (!) and there is no sign of noise from the serial data lines creeping into the 817’s receiver now it’s on PCB. Some lessons have been learned through the construction (e.g. brown 6mm push buttons are less “clicky” than the black ones and that’s a good thing!) and I now have my companion FT-817 display/buttons in field trials. I’ve no plans to sell this, it’s a trivially simple design, but it does make a great home project to polish your skills in microcontrollers, PCBs and construction. I’ll post a write-up on my website in due course.

In use, the device works just as I’d hoped, I can do everything I want to on my FT-817 without having to fiddle through the awkward button presses. The frequency display is also in a much better position for me now (as most FT-817 owners will know as they jealously eye the KX2, KX3, etc…!) and I think I used it for the whole session when I took it to the field on Saturday. If only my CW had been so slick!

Next steps are to work on the Arduino code. My code is pretty rubbish (my coding style involves a lot of Stack Overflow and copy/paste!) and not safe for public consumption. There are also some health warnings to be noted in manipulating the FT-817’s EEPROM (required for some of the functions I wanted), explained on KA7OEI’s page but there have been a few volunteers on Twitter to help with the software which is great. Also I may do a “Rev 2” board with an Arduino Pro Mini to lower the drain on the FT-817 battery before sharing the PCB files. Other than that it’s now time to get back outdoors and enjoy the new improved interface to my smallest radio! 😀

73
Andy G7UHN

Andy, I absolutely love this project! A wonderful addition to the FT-817/818 and I’d hardly call it a “trivial” design–!

I purchased the original FT-817 shortly after it was introduced. At the time, I was living in the UK and travelled extensively throughout Europe. I loved the ability to simply throw this little rig into my carryon and play radio pretty much anywhere my work travels took me. In the end, I did less ham radio work with the FT-817 and more SWLing.

Still, I eventually sold my FT-817 for the very same reason that motivated you to build a companion display: the front panel is too small and my most used functions require too much menu digging.

Your companion board is an elegant homebrew solution. I love the Nokia LCD screen–superb readability in the field.

Thank you again and once you do a write-up on for your website, we’ll be sure to link to it on the SWLing Post!

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Deke Duncan of Radio 77: Broadcasting to an audience of one

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Photo by Ben Koorengevel

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who writes:

I’ve just finished reading “Sealand’s Caretakers”. Very fascinating.

In the article, they give a link to an article “This excerpt describes the fallout that came from a gang of international scam artists bootlegging Sealand passports.”

This article is titled: “The Plot Against the Principality of Sealand” and is hosted on narratively.com.

It’s another fascinating article about Sealand and well worth the read.

Narratively.com is a very interesting site with lots of well written articles. In perusing the site, I came across an article about Deke Duncan who ran Radio 77 from a backyard shed for an audience of one.

At the end of the article, you can listen to the “Radio 77” episode of Snap Judgement by Jeff Maysh.

BBC did a piece on it in 1974:

It’s a great story about someone’s love of radio.

For even more detail about Deke, check out this article.

Thank you so much for sharing this, Bill!

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Radio Waves: Deep ABC Cuts, Ham Radio Saves a Life, SDR Academy Updates, and a new free e-magazine from RASA

Radio Waves: Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers. To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Michael Bird, Alexander von Obert, and the Southgate ARC for the following tips:

Up to 250 ABC jobs to go, ABC Life brand scrapped, flagship radio news bulletin dumped to tackle $84 million budget cut (ABC News)

The ABC will axe up to 250 jobs and cut programming as it deals with budget cuts of $84 million.

Managing director David Anderson said a flagship radio news bulletin would go, the ABC Life lifestyle portal would be rebranded, and programs would be reviewed as part of a major overhaul of the national broadcaster.

There will also be cuts to travel and to spending on television productions, as the organisation moves to become more relevant to more Australians and better reflect community diversity, he said.

Mr Anderson said the redundancies and savings would affect every division across the ABC.

“We anticipate we may farewell as many as 250 colleagues through this process,” he told staff in a briefing.

The News division is set to lose about 70 staff, the Entertainment and Specialist division 53 staff and the Regional and Local division 19.

Mr Anderson said there would be changes to executive staffing, but did not offer any details.

And he said the organisation would aim to have 75 per cent of its content-makers based outside its Sydney headquarters by 2025.

The ABC had already flagged that it would shed about 250 jobs due to a three-year funding indexation pause announced by the Federal Government in 2018.

Mr Anderson said the flagship 7:45am radio news bulletins would end, and be replaced by a five-minute bulletin at 8:00am. A 10-minute bulletin at 7:00am will remain.

The changes include:

ABC Life will become ABC Local and have a “broader editorial direction”

The travel budget will be cut by 25 per cent

Spending on external and independent television productions will be cut by $5 million a year

The ABC Comedy television channel will be rebranded to cater for a broader array of programs and content

Leasing of space at the ABC’s Sydney headquarters will be explored

TV and radio broadcast channels will remain, but transmission cuts have been flagged for future years[…]

Ham Radio Saving A Life Locally! (Western Massachusetts ARRL)

On Tuesday, June 15, Alden Sumner Jones IV, KC1JWR, was hiking on the southern part of the Appalachian trail in Vermont (it’s also been reported as being on the Long Trail) with his cousins at around 12:30 PM. Alden started feeling light headed, his pulse was racing and the next thing he remembers is waking up with an EMT named Dave, from AMR out of Springfield, MA, who was hiking and saw Alden go down. Alden had suffered seizures. It was later determined that this was caused by low blood sugar. Dave attempted to call 911 on his cell phone. He could connect, but the 911 operator couldn’t understand him. At this point, Alden pulled out his HT ham radio, a BaoFeng.

He made contact through the K1FFK repeater. This repeater is located on Mt. Greylock on 146.91. The repeater is owned and maintained by the Northern Berkshire Amateur Radio Club. The initial call went out just before the Cycle 1 of the Western Massachusetts Traffic Net. Ron Wonderlick, AG1W, took the call. Alden initially asked if the 911 call went through. Ron began an eight hour process of acting as a relay between Alden, the emergency crews and various others.

The Traffic Net was truncated and the frequency was cleared by Peter Mattice, KD2JKV, who also stood by as a backup for Ron. KC1JPU, Matthew Sacco, was also monitoring and after a short consultation with Ron & Peter, proceeded to head to the staging area where the Fire and EMS crews were going to come from.[…]

Software Defined Radio Academy 2020 Update (Markus Heller)

Dear ARRL recipients,

this year’s Software Defined Radio Academy is going to take place during the next weekend on June 27 / 28. We have now finalized the programme.

Since we decided very early in March that we’d organize an online strategy, we were not grounded by Corona. Using YouTube and our video conferencing system, we were able to organize a rich SDRA conference with speakers from all over the world.

Since this year’s European GNURadio Days conference in Besancon, France, could not take place either, we were asked to give their speakers a stage. This is the reason why we have a specially strong GNURadio focus.

With such a rich programme, we decided to span the talks over two days and start in the European afternoon, so that we could give our overseas audience a chance to participate live.

The mode is this: Even though all the talks are pre-recorded, the speakers will attend in the video conferencing system and respond to questions that come in through the YouTube channel. This way we can maintain a certain degree of interaction, which is important for any kind of scientific conference.

Here is the programme:
https://2020.sdra.io/pages/programme.html
and here is our YouTube stream URL:
https://youtube.sdra.io

We will start on Saturday 27 at 12:30 UTC+2
and on Sunday June 28 at 13:00 UTC+2.

For those of you who understand German, please note that this year’s HAMRADIO conference will also go online. We have worked hard in the past two months to record 65 hours of talks and discussions. Here is the HAMRADIO programme, which the SDRA is part of:

https://www.darc.de/fileadmin/filemounts/gs/oeffentlichskeitsarbeit/Veranstaltungen/HAMRADIOnline/HAMOnline_Sendeplan.pdf

QTC e-magazine (RASA via the Southgate ARC)

RASA is pleased to announce the release of a new E-magazine for Amateur Radio in Australia. The magazine, QTC, named after the Q-code “I have a message for you” will be published every two months.

We’ll be renaming our regular email bulletins QTC-Lite and they’ll be aligned with the release of our fortnightly Podcast.

In this first issue of QTC, we have news and updates about regulations, and information on our 60m submission in response to the ACMA’s Consultation paper. There’s a “Getting started” regular column, with this issue covering HF DX-ing. There’s also a regular column on how you can deal with QRM and RFI in your shack. This month we have a feature technical article on 3-Phase Power Converters.

Click here to download the first issue of QTC.

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Christoph’s homebrew custom hotkey pad for SDR applications

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Last week, I saw a fascinating post by Christoph Jahn on the SDRplay Facebook page.

Christoph created a custom hotkey pad for use with SDRuno. The project is actually quite simple and his finished product looks amazing:

The steps involve downloading “LuaMacros” a freeware macros utility that allows you to map macros to an external USB device like a cheap numeric keypad. Christoph then designed the key templates and printed them on a strong adhesive vinyl foil.

I asked Christoph if I could post his project on the SWLing Post and he kindly sent me the followed PDF with step-by-step instructions.

Click here to download the instructions as a PDF (6.71MB).

Christoph also shared the macros file he used for his project (download .XML file 8.77 KB).

Thank you so much for sharing this, Christoph! Your finished product is so professional, I would have thought it was produced by SDRplay!

This could be a useful tool for a radio friend who is visually-impaired and, of course, could be compatible with a wide range of SDR apps and rig control software that allow keyboard shortcuts.

Readers: Have you done a similar project? Please comment with your experience and any details–especially noting applications and programs you find are compatible with keyboard shortcut mapping. This could be very beneficial for radio enthusiasts with disabilities!

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Beating the Quarantine Blues: Readers build homebrew NCPL antennas

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My homebrew version of the NCPL antenna.

Recently, I published a step-by-step guide on building a Noise-Cancelling Passive Loop (NCPL) antenna. Evidently, this antenna project really resonated with readers! [See what I did there? If so, my apologies!]

I think this passive loop antenna project has been so appealing because (1.) most of us around the world are sheltering at home due to the Covid-19 pandemic and (2.) this project is simple and you likely have all of the components in your tool shed or junk box at this very moment.

A number you have written to tell me about your antenna builds and some of you have agreed to allow me to share your projects with the SWLing Post community.

Below, you’ll find three fine homebrew examples of the NCPL antenna–all of which were made with what these fine radio enthusiasts had on-hand:

Jerome van der Linden

Jerome’s NCPL antenna

Jerome writes:

Hello Thomas,

Well, I took up the challenge and built a NCPL antenna pretty close to your instructions.

Unfortunately, the coax I had available used (had aluminium shielding, and too late into the project I discovered solder would not take to it. My solution was to cannibalize a coax cable joiner (see photos attached), where – normally – the centre conductors are joined / held by a plastic centre piece and screw fittings.

The braid / shield for the two bits of coax is clamped / squeezed by an outer metal piece. My cannibalising effort involved removing the plastic centre bit which joins the two centre cores, and keeping just the outer metal component which I used (after completely cutting through the coax) to clamp the two metal braid sections, while the two centre copper bits were far enough apart for me to solder the leads for the ferrite balun.

Of course, I could not do the same at the top of the loop where the internal and external conductors need to swap over. I soldered some quite thick copper wire (perhaps 2mm in diameter) to each center core, pushed the center core into the opposing coax and coiled the 2mm thick copper tightly around each end of the coax.

Once it was all taped up it looks no worse than yours, and it does indeed WORK! [see photo above]

Here in Oz, I could not source the identical ferrite, but I think it’s pretty close. Best performance for me is on 11MHz, where the Radio New Zealand signal on 11725 is markedly better using the loop than the internal whip on my Tecsun PL-880. Other bands not quite so significant, but the Noise level is definitely lower.

As you say, Jerome, once all packaged up, it looks great! Sure, the mixture of materials you had on hand wasn’t ideal (aluminium shielding, etc.) but you found a way to make it work from the resources you had in your home. And I love the fact it’s lowed your RFI level! Thanks for sharing!

Giuseppe Morlè (IZ0GZW)

Dear Thomas,

I’m Giuseppe Morlè (IZ0GZW), from Formia, central Italy, on the Tyrrhenian Sea.

I wanted to build your noise canceling loop seen on SWLing Post …
seems to work well especially from 40 meters. upward…
the diameter is 50 cm.
I will do other tests soon.
You can see the initial test on my YouTube channel via this link:

Thanks for the nice idea and a greetings from Italy.
73. Giuseppe IZ0GZW

Thank you, Giuseppe! What an amazing view you have there from your balcony! I’m quite impressed your PL-660 can take advantage of this design so well. We look forward to your other tests! Grazie mille!

John Mills

Hi Thomas,

My idea was to use a fitness hoop 75cm diameter bought off eBay. I removed the flashy striping to reveal a plastic like hoop that was joined in one spot with a plastic insert.

I have wrapped the whole hoop in tin-clad copper foil tape that has a conductive adhesive backing, but to be sure I have soldered all the overlapping seams. I drilled two holes opposite each other for the upper foil connections and the lower exit to the Balun.

Hopefully the three pictures will be helpful, I did the 4 turn design on Airspys website and it works really well connected to my RSPdx.

73

John

Thank you, John. What a fantastic way to build the NCPL antenna without using a coax for the loop. Indeed, since your plastic hoop has a small insert in the middle, you’ve an ideal spot to make the shield to center conductor cross-over. Very clever! I also like how you mounted the 1:1 Balun (or Unun) on a small board. Thanks for sharing this.

Got Loops?

Post readers: If you have your own unique NCPL antenna design, please consider sharing it with us! Contact me with details and photos. I’ll plan to publish at least one more post with examples here in the near future.

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Site shares story of the BBC’s wartime reporting

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Many thanks to SWLing Post contributor, Kris Partridge, who shares the following note following our recent series of posts about WWII radio:

The, nearly, full story of the BBC’s wartime reporting can be found here. Yes, I hope another interesting read both for your good self and the readers of The SWLing Post:

http://www.orbem.co.uk/repwar/wr_action.htm

What an excellent read! Thank you for sharing this link, Kris!

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