RETRO RECEIVER REVIEW #16
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| Each image in this post is clickable for a close up view. |
YAESU FRG-7
by ROB WAGNER VK3BVW
Long-time shortwave listeners love remembering the halcyon days of the 60s, 70s and 80s when there were just so many stations broadcasting daily on the HF bands. And those memories are usually accompanied by recollections of the wonderful old radios they operated to tune across the dials. Hammarlund, Hallicrafters, Allied, Trio (Kenwood), Collins, Heathkit, JRC, National, Radio Shack, and so on. All were great names in shortwave radio! And, of course, in the product lines of each brand were some models that performed better than others - better sensitivity, better selectivity, better designs and ergonomics, etc. But there were just so many stations from which to choose that even a lesser quality radio would do a pretty good job of picking up a variety of international and domestic shortwave broadcasts without too much trouble.
On the many Facebook groups devoted to shortwave listening and amateur radio, there is still a core group of active and enthusiastic hobbyists who love maintaining collections of receivers from the past. They regularly post about their “finds” from local hamfests, garage clean-outs and online sales. This passion for saving grand old radios from the past and preserving them into the future is, indeed, heartening.
I don’t have a vast collection of really old receivers to show off when people visit my radio shack. But, I was always curious about the Yaesu FRG-7 receiver, colloquially known by some as the FROG-7! I didn’t know much about this model except that it used a somewhat different circuit to other run-of-the-mill receivers of the day. The literature mentioned this thing called the Wadley loop. But, back in the 70s and 80s, I didn’t explore it any further as I had other receivers that did the job for my listening purposes. Here in Australia, there were a few distributors of Yaesu gear around the time of the release of the FRG-7 between 1976 and 1980. One national distributor, Dick Smith Electronics, probably turned over more Yaesu equipment for hams and SWLs than all the other stores put together! And for a while, the FRG-7 was a large part of Yaesu sales.
Recently, I decided to look for an FRG-7 and learn a bit more about this famous rig. About three years ago, one came up for sale at a very reasonable price - $100 AUD (about $67 USD)! I was told that the receiver was working, so I figured that for such a low price, it was not a huge investment and would allow me to dip my toe in the water. If it turned out to be a dud, there would be no significant financial loss!
So, one Sunday morning, I travelled for two and a half hours across to the other side of the state of Victoria, to a farm in the middle of the wheat and cattle belt. In a barn that doubled as a workshop, with just a dirt floor and lots of dusty farming implements, sat the FRG-7. The farmer turned it on for me and twiddled across the 20m ham band to show that it worked OK. There was plenty of Sunday morning traffic on the band, and the receiver had a big full sound to it. So, I settled up the account and retraced my steps back home.
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| Top cover off - the IF/AF board is at the top left and the RF board is lower right. The white plastic containers in the lower right house the optional 8 D-cell batteries. Click on the image for a closer view. |
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| Turn it over - A nice neat layout with room to move! |
After trialling it over the next few days, I found that some bands were well down in the sensitivity department, switches required cleaning, globes needed replacing, and the rig was very dirty both inside and out. The case was knocked around and could never really be returned to its former glory. There were also some signs of rust inside the case, and the condition of the capacitors and other components remained a mystery. This rig had certainly seen better days! Summer temperatures in the 40's C, winters plunging to 0 C, and the occasional floods that frequent those broad rural plains meant that life on the farm had been hard for this old girl.
It was clear that undergoing repairs and refurbishment would demand a considerable amount of time and effort. Although I’m retired these days, spare time is not something at my fingertips. I am one of those people who seem to be just as busy in retirement as I was in full-time employment! So, what to do with this thing? The options were to pass it onto someone else or use it for parts. Currently, it still sits on the floor of the shack.
Then, just prior to last Christmas I attended a local hamfest, and there I spotted another FRG-7. This one is in much better shape. Indeed, the previous owner had looked after it very well! Cosmetically in excellent condition, clean on the inside, everything worked well and performance-wise it appeared to be somewhere near its original specifications! Given the excellent condition of this receiver, the price was realistic, so it was loaded into the car. Upon plugging it in and connecting some good antennas, this second FRG-7 really performed very well. I was delighted!
The FRG-7 is a very hands-on receiver with its band selector switch, main tuning dial, MHz and preselector dials, and the red “lock” indicator light all demanding attention, while also keeping an eye on the S-meter when peaking for maximum signal strength. This labour-intensive approach to tuning is tricky at first. Initially, when tuning around, I sometimes forgot to peak the preselector or adjust the MHz dial after swapping bands. However, once I got the hang of it, I have quite enjoyed the twiddling aspect of this machine!
The FRG-7’s old-style solid-state circuit with triple conversion superheterodyne design insures excellent selectivity and sensitivity for a receiver of this vintage. The rock-solid stability is a feature of this unit, achieved through the implementation of the Wadley loop drift cancellation circuit, designed by Dr Trevor L. Wadley (1920-1981), an electrical engineer from South Africa. The system uses a harmonic generator that is based on a 1 MHz crystal oscillator, producing a signal at 1 MHz intervals.
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| Block diagram |
Interestingly, the Yaesu FRG-7 was also sold under other brand names in different markets. Sears and Roebuck, a large U.S. department store chain, sold the exact same FRG-7 under the Sears brand and is distinguishable by its black case rather than the more traditional Yaesu grey case. And in parts of Europe, the receiver was marketed under the Sommerkamp brand name. But wherever it was sold, the FRG-7 was considered a receiver possessing good performance at an affordable price.
However, the FRG-7 was not the first receiver to use this Wadley loop design. In 1957, the British-made Racal RA-17, weighing in at a hefty 43 kg (96 pounds) for the cabinet version, was the first general coverage Wadley loop communications receiver, designed principally for military use. Then in the early 70s, the design was again used for the South African made Barlow-Wadley XCR-30, a popular portable receiver amongst some SWLs.
There is an informative YouTube video that explains the Wadley loop principle in detail using the Yaesu FRG-7 as the example circuit. Recorded by Alan Wolke W2AEW, the design principles are outlined on paper and then demonstrated using test gear in the lab. Alan has done a great job of pulling the covers off the Wadley loop design, so I encourage you to check it out below:
And Alan has a second YouTube video on how to tune the FRG-7, which will be helpful if you are not familiar with this rig. See below:
Strong Performance.....Up to a Point!
As I continue to use the FRG-7, I am amazed at just how good this receiver is for its age! Although it does not have all the fancy bells and whistles of modern rigs like the receiver section in my Yaesu FTDX3000 transceiver, it nevertheless hears many signals that the big rig hears. And having the speaker on the front panel facing the user makes so much sense, providing some great audio. The sensitivity of a well-aligned FRG-7 is very good for a radio from this era. The selectivity is generally pretty good in most situations for AM listening. However, I find the stock filter a touch too wide when trying to copy a signal next to a booming China Radio International broadcast on an adjacent channel. In SSB mode, the filter is often too wide when the ham bands are busy.
The automatic noise limiter is not much use - it just does not cope well with today’s multitude of man-made electronic interferences and hash. The rig would benefit from separate AF and RF controls instead of just a simple volume control. The analog readout is +/- 5 kHz, but later versions of this rig were manufactured with digital readout. The first-generation rigs did not include a fine-tune control, which is helpful for SSB listening. However, even for rigs with the fine-tune control, tuning in SSB can be a bit touchy at times. The Tone switch isn't much use and I just leave this on the Normal setting.
One thing I am looking forward to is taking this radio out into the great Aussie bush where noise levels drop to virtually zero, and weak signals abound! The rig can be AC mains powered, plus it has a 12v DC socket, and a battery compartment requiring eight D-cells. When out in the field, I usually take a 13.8v SLA battery, but I would be curious to see just how long eight D-cells last! It will be quite heavy with those batteries, too. Good fun!
One thing that buyers of vintage receivers need to consider is that as they age, things tend to go wrong....very much like us humans! For some rigs with older microprocessor controls and fancy-pants components, finding replacement parts can be a major headache. However, with the FRG-7 all components are still around or have suitable substitutes. This is a receiver that is still serviceable and repairable, plus there are online sources to download a clear circuit diagram that is easy to follow.
Conclusion
For a budget receiver in its day, the FRG-7 is still a strong performer in its class. Users who like to jump around the shortwave spectrum to quickly check frequencies and signals (.....like me!), the laborious method of tuning this rig will probably drive you nuts! However, for casual shortwave program listening and a very pleasant audio quality, the FRG-7 is a very enjoyable receiver. Plus, you have a unique slice of radio design history!
73 and good DX to you all,
Rob Wagner VK3BVW
(Excerpts of this article first appeared in the April 2020 issue of The Spectrum Monitor magazine: https://www.thespectrummonitor.com)
Missed the other Retro Reviews? Check them all out by clicking below:
Retro Receiver Review # 1 - The DANSK RX4000
Retro Receiver Review # 2 - The HITACHI KH-3800W
Retro Receiver Review # 3 - The SCHAUB LORENZ ITT TOURING T104A RECEIVER
Retro Receiver Review # 4 - The RACAL RA6790/GM
Retro Receiver Review # 5 - The REALISTIC (RADIO SHACK) DX160
Retro Receiver Review # 6 - The KENWOOD QR 666
Retro Receiver Review # 7 - The RODHE & SCHWARZ EK890
Retro Receiver Review # 8 - The YAESU FR101S
Retro Receiver Review # 9 - The SELENA VEGA B206
Retro Receiver Review # 10 - The DRAKE SPR-4
Retro Receiver Review # 11 - The NATIONAL RF-5000
Retro Receiver Review # 12 - The YAESU FRG-100
Retro Receiver Review # 13 - The MARC NR-82 F1
Retro Receiver Review # 14 - The MURPHY B40
Retro Receiver Review # 15 - The STROMBERG CARLSON AWP-8
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© Rob Wagner, Mount Evelyn DX Report, and contributors 2012-2023
This was an excellent receiver and got me into pretty fancy DX circles in the late 1970s. I'm sorry I don't have it now, not that there would be much to listen to.
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