Tag Archives: Yaesu FRG-7

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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Kostas’ Yaesu FRG-7 adjustment that improves opposite sideband rejection

Many thanks to SWLing Post contributor, Kostas (SV3ORA), who shares the following video and writes:

In this 7.8Mb video (attached) is my solution for “converting” the Yaesu FRG-7 for single signal reception on SSB:

Not a mod actually, no additional filters, no soldering of any kind. Just tune the BFO on USB and on LSB a bit far away from the 455KHz ceramic filter (using the transformer for LSB and the capacitor for USB, as the manual states). As the video shows, this provides the near to
carrier selectivity to cut off the unwanted sideband.

The price you pay is more high frequencies (but in the wanted sideband) and a bit attenuated low frequencies as the filter is effectively shifted to higher frequencies. Very high frequencies cut-off is helped by the tone control of the receiver to some point.

This is a cost-free mod and requiring even no soldering skills, neither any mod to the receiver. Now as you tune the bands in SSB and CW, you do not hear the same signal twice. On AM mode nothing changes, since the BFO is switched off in this mode.

Many thanks for sharing this, Kostas! This seems like a simple adjustment for one of my all-time favorite receivers!

Post readers: Check out Kostas’ website for more modifications, ideas and radio projects.

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What are your Sunday radio plans?

Icom IC-756 Pro Transceiver Dial

I had planned on today being a rather laid-back Sunday with a good book lined-up and lots of radio time. Instead, my wife has convinced me to work on a home project this afternoon. That’s okay, because it is a project I’d like to get out of the way and the weather today is ideal.

Still, this morning, I’ve been hunting a few Parks On The Air (POTA) stations with the ‘756 Pro to help park activators along with their numbers. I try to do this when I can because I’m typically the activator and I truly appreciate logging well over my ten required stations for a valid field activation.

After the project this afternoon, I also plan to hit the 31 meter band and lower, catching a few broadcast stations and soaking in the shortwaves most likely with my RSPdx and HF+ Discovery SDRs.

It won’t be all SDR, though! I’ll be busy doing band-scans with my beloved Yaesu FRG-7 (Frog 7) while my SDRs record audio and spectrum.

Post readers: What are your plans today and this week?  Please comment!


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Listener Post: Fabien’s love of radio which lead him to collecting

Fabien’s radio story below is the latest in our series called Listener Posts, where I place all of your personal radio histories.

If you would like to add your story to the mix, simply send your story by email!

In the meantime, many thanks to Fabien who writes:


I’ve been a radio listener since the age of 14. I was an SWL and a listener of local VHF free stations too.

In the beginning, my receiver was a poor radio-cassette, with a little segment of the shortwave bands. I used it for two years.

Then, for 16th birthday I received a Philips AL 990 shortwave receiver.

It was a great receiver because the sound was clear and it was easy to identify the stations when listening with my usual headphones–even those broadcasts with very weak signals and an unidentified language. The negative of this receiver was the frequency was not easy to see/read and I was at the same display for hours.

After my school period, I worked for two years and with my savings I was able to buy a JRC NRD 525 in Swizterland, where this receiver was less expensive and easier to find than in my country of France at the time.

The Japan Radio Company NRD 525 receiver. Photo: Universal Radio

The good with the NRD 525 is that it was easy to tune to a frequency, easy to read the display and easy to connect the receiver to another unit for decoding RTTY signals with an old computer monitor and a small EPSON dot printer.

I was in paradise!

But the NRD 525 has a problem with its sound. Even with my best headphones, I was not able to understand the station voices when the signal was poor and the language was not mine, so it was difficult to have sufficient details to make a good reception report for sending it proudly to the logged radio station.

My solution was strange but the only one possible : I searched for rare signals with the NRD 525 and after I found them, listened to those signals with the AL 990 and my headphones.
With this solution, I was able to send a lot a reception reports and receive some beautiful QSLs from official, pirate and clandestine stations (clandestines were my favorites).

This SWL period was until 1988. In 1988 I was obliged to move from my city to a new location where it was more difficult to be a SWL. The following years, I was more a BCL (Broadcast Listener) than an SWL.

I did BCL DX until 1999, and after 1999 most of my radio listening time was only BCL easy listening, without looking for weak signals.

Because of the Internet, online SDRs, and the closing down of a lot of broadcasters, I’m less  interested in contact stations directly, save from time to time. For me, the chase of weak signals was the most important part; now we can listen to a station via the Internet (online on a website or with a SDR online)…even the pirates stations.

My actual interest today is to have all of the receivers I was dreamed about when I was a teenager. In 2020, at 53 years old, I am now more a collector of receivers than a real BCL. I like all electronics, including many hifi systems/components and radio items.

I also love black and white film photography/laboratory too and I collect stickers from French radio stations.

Here are two pictures of part of my actual listening post. On one, you could see a model boat of the famous offshore radio station ” Radio Caroline “.

My favorite shortwave receivers are the Drake R8-E (European version of the R8), the BEARCAT DX-1000 and the Yaesu FRG-7.

My favorite receiver for synchronous detection reception is the SONY ICF-2001D (the European version of the ICF 2010).

To receive mediumwave stations, I prefer my JRC NRD 515 connected with an Australian active loop antenna.

For travel, I use a small Lowe HF 150.

For VHF FM-commercial band, I use my Grundig Satellit 500 and a Sony ICF 6800W.

Some of my best souvenirs/memories of SW reception are Radio La Voz de Alpha 66 (USA), Radio Venceremos (El Salvador), Radio Botswana, Radio Bardaï (Tchad or Libia), Radio RFO Tahiti, and Radio Bandeirantes (Brasil).

My regrets from the years 1981-1988 are not being able to receive the signal of Radio BHUTAN and the signal from The Faklands Islands.

I don’t like to travel outside my beloved country, but for the pleasure of visiting some radio stations, I made an effort and I traveled to Phnom Penh (Cambodia), La Habana (Cuba), San Salvador (El Salvador) and Ciudad Guatemala (Guatemala).

Truly Yours,
Fabien SERVE, in France


Thank you, Fabien, for sharing your story! You’ve added some truly classic receivers to your collection over the years!  I love the Radio Caroline model too! 

I encourage other SWLing Post readers and contributors to submit their own listener post! Tell us how you became interested in radio! 

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Now in the shack: A Yaesu Musen FRG-7

p5290002

Photo sent by Shawn.

In late May, as I was packing for two months of travel in Canada, I received a message from long-time SWLing Post reader, Shawn Aiken.  Shawn was seeking the right home for his Yaesu FRG-7 and Hallicrafters S-38 receivers.

p5290001

I was very interested–especially in the FRG-7. Many SWL friends (Robert Gulley and Mike Hansgen, to name just a couple) love their FRG-7s. I’d been waiting for the right opportunity to snag one at a local hamfest. I’m also a Hallicrafters fan and love the front panel design of the S-38 series: so classy.

I asked Shawn how much he’d like for the receivers–I was very much interested.

Not only would he not accept payment, but he insisted on paying the shipping as well. I felt apprehensive about accepting such a generous gift. Shawn replied:

“Although I understand your reticence, Thomas, just count this as one of the perks of the job that you’ve undertaken and, from what I can tell from a distance, taken on and done well.”

That statement made my day. Thanks, Shawn!

yaesu-frg-7

The FRG-7 now sits in my shack and I’m learning my way around its unique tuning mechanism. It’s a beauty, too: I love the utilitarian front panel and dials/controls.

Other than needing a little DeOxit on some of the pots and switches, it works beautifully!

I’ve been so busy since returning from Canada, I haven’t had the FRG-7 on the air much. That’ll all change, though, as my Fall/Winter listening season kicks in. I’m already looking forward to it.

Thanks again, Shawn! I’ll make sure both of these radios have a good home here in my shack!

Readers: Do you have a Yaesu FRG-7? Any tips/tricks? Please comment!

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Phil demonstrates the BHI NEIM1031 Noise Eliminating In-Line Module

bhi-dsp

Many thanks to SWLing Post contributor, Phil Brennan, who writes:

[Recently] one of your contributors mentioned that he purchased a BHI DSP unit at a discounted price. I purchased one (a different model to the one in the previous post) some months ago before I headed away travelling.

The post reminded me that I had made a small video demonstrating the DSP unit on my FRG7. The video shows me tuning the DSP on a broadcast of Voice of the People on 3912 khz. While QRM at my place isn’t too bad, it’s still present and the DSP does aid in clearing up a signal.

Voice of the People is usually jammed by the DPRK and the DSP also assists in reducing the roar of the jammer. Of course one can go to far with DSP and the audio can suffer from that underwater sound.

Thank you, Phil! The FRG-7 is an ideal receiver for something like the BHI module since it precedes on-board DSP. The great thing about an in-line module, of course, is that it can be used with a variety of receivers.

Click here to view the BHI NEIM1031 MKII on BHI’s website.

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eBay find: Pristine Sears 412.36380700 (Yaesu FRG-7) Shortwave Communications Receiver

Sears-Yaesu-FRG-7

This must be the day for eBay finds! This one will not be a deal (price-wise) unless you’re on the market for a NOS (New Old Stock) classic receiver.

Many thanks to SWLing Post contributor, Mario Filippi (N2HUN), who writes:

On eBay is an auction that is worth watching, just to see what the final bid will be:

Sears 412.36380700 (613638) Yaesu FRG-7 Shortwave Communications Receiver / NOS

Sears-Yaesu-FRG-7-2

This is a new old stock Sears version of the FRG-7, no different from the Yaesu except it had the Sears name on it.

Used ones have been sold on eBay but this is the first one I’ve seen that was NOS.

Amazing what people have stored away in attics, closets, basements, etc. I had one of the Sears versions years ago. Note that the older versions of the Yaesu FRG-7 did not have the fine tuning knob. This one is apparently one of the later versions.

All round excellent radio, nice big speaker, excellent sensitivity, selectivity, one of the shortwave radio hall-of-famers!

Click here to view on eBay.

Indeed, Mario! Thanks for the tip! As you say, it will be fun to see how high this listing may go befor ethe bidding ends tomorrow afternoon/evening. It’s rare to find a Sears or Yaesu so pristine. 

Here are few more photos I pulled from the listing–click to enlarge:

Sears-Yaesu-FRG-7-4Sears-Yaesu-FRG-7-6Sears-Yaesu-FRG-7-7 Sears-Yaesu-FRG-7-3

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