Good explanation of the Wadley Loop. Dr Trevor Wadley was an amazing Engineer. The first production receiver to use the concept was the Racal RA-17. First developed in 1954. Wadley was South African and Racal was a relatively newly formed company that had originally planned to build Collins 51J's; highly stable as required for reliable RTTY reception. However, the Racal/Collins agreement fell through and Racal had to quickly come up with an alternative design. Collaborating with Trevor Wadley, the Racal RA-17 was quickly developed, put into production and remained in use by the UK Government, as far as I am aware, into the 1980s.
Despite owning an Icom IC-R75, the Yaesu FRG-7 is still my go-to receiver for most of my listening. It may be irrational, but the FRG-7 is just more fun to use and the audio seems more "organic" to my ears, even with a change to tighter IF filtering. I never cease to be amazed by the Frog's stellar performance, which is achieved with a circuit that is both relatively simple and very reliable.
Thanks for describing the loop. I took a "temporary" job in two-way radio 44 years ago. I worked six years for an RCA dealer and 4 years for a Motorola shop before starting my own business. I'm still working in my business, along with 8 employees, today. Stability in my business early on consisted of high quality crystals in ovens, followed by TCXO modules. Later phase locked loop, voltage control oscillators (VCO) and computer programming took over. My temporary job was originally based on my hastily earned FCC first class license and my ham radio experience. I didn't really start learning until I took the first two-way radio job. Ham radio stopped being an active hobby pretty quickly but today I still have a license gained in 1960 and I maintain several ham repeaters locally. I subscribed to your channel a couple of years ago and look forward to your tutorials. Everything helps and at nearly 72 I'm still learning daily.
Thanks for the video. I've worked on all sorts of electronics gear in the last 60 years, including a whole lot of RF gear, but I'd never heard of the Wadley Loop or seen a rig that was using it. Fascinating solution to drift.
Watching guys work old receivers, I had no idea what the "'spread" knob was about. Didn't have a clue I'd learn it and learn it WELL right here. Thanks.
Thanks. It's a funny thing, electronic engineering - all forms of engineering can show brilliance, but there's a particular sort of cleverness in some electronic circuits that really makes me gasp in admiration - like the Gilbert Cell you did a while ago, and this one again. What very bright men they were.
It probably wasn't more widely used because the wide bandwidth 1st and 2nd IFs present problems with adjacent signal overload. Also, the development of precise PLL based frequency synthesizers made these drift cancelling techniques unnecessary. Interestingly, there was a paper published in 2015 about using this technique for advanced coherent optical signal demodulation - everything old is new again.
Thanks for your work. Back in 86 when I first got licensed I bought one of these fairly cheap. Not knowing much about it....and not understanding how to tune it properly ....I sold it. It was only many years later....and much more knowledgeable....lol....that I have acquired my second one. All caps replaced ...and now outstanding receiver for its age and tech. I keep it next to my restored AR-88 LR. Compliment each other very nicely. And the FRG is SO much lighter...lol....the AR is 110 gut busting pounds. What a beast.
@@w2aew lol...look it up....1940's ....and built with no care about cost. They needed the best for ops.....and so it was built that way. They were used into the 60's. A mechanical marvel...14 tubes....a real beauty fully restored ready for another 70 years....if any AM still around?....lol
It’s a great video, thanks! I landed here as I was searching a possible reason why my “lock” LED is always on. Maybe my xtal oscillator has failed or the second mixer does not work anymore. Thanks again. 73, IK4QIX Mauro.
I was recently given one of these receivers, complete but slightly cosmetically challenged. My first exposure to the Wadley loop receiver was the Barlow Wadley portable radio which was made at the factory next door to where I worked. We made military radio equipment and every now and again, we would receive a batch of 10 Barlow Wadleys to evaluate. My boss was a rocket on these radios especially alignment. After he had sorted a set out, we used to take them out in the car park for a tune up around the bands. Absolutely amazing performance. Looking forward to sorting out my FRG 7 as its quite a good basic receiver for the money. Thanks for an excellent explanation of how this receiver works.
Marvellous! I've got a Barlow-Wadley XCR 30, which I think was the first consumer radio to use the Wadley Loop. Not many others did - as well as that and the FRG-7, there were a couple of Racal professional communications receivers,, a Drake and another obscure one I forget the name of. Performance is remarkably good for a circuit that, although it looks complex, can be implemented in a very small number of transistors considering its capabilities. On mine, I can get the tuning bang-on by eye from the dial of a station before turning the radio on, which for an analogue set more than 40 years old is uncanny. Frobbing the preselector is an essential skill, though.
Nice comments, thanks. I think the Radio Shack Realistic DX-300 was a Wadley Loop receiver (although I think the preselector and 1MHz band select are ganged together, which I don't particularly like).
No, if you look at a picture of the DX-300 there is a ring around the main tuning knob that is the 1MHz tuning, the band selector is to the left. Yes, I have one :) Once owned a RA17 too, but it was just taking up too much space.
This was an excellent receiver. I got one in 1977 from Gilfer in NJ for 300-something dollars. I didn't know it was a Wadley Loop receiver--I thought only the XCR-30 was that way.
Excellent video (as usual). Very interesting solution demonstrated in an excellent way. Sir, you have a gift in the way you explain things to others. Thank you for sharing your knowledge. Vy 73 de CT7AFR, Emmanuel.
My FRG-7 is on the back burner, I bought it in unknown condition and was/is "deaf". I have cleaned the switches and even went on to re cap it, with winter coming on I'll have more time to work on it. Thanks for this presentation video
Me too, I have a good buddy that wants to help with the trouble shooting, he has the test equipment that I don't. I have a hard time understanding how the 4 pin front end transistors are tested. Other than the work I have done this unit looks to be un molested.
Thanks for sharing. Very interesting circuit. Apologies to W.A. Mozart, I assume... At 12:30ish you say that it uses a second VFO that is controlled by a crystal oscillator, but you point to the second tuning knob. The LO controlled by that knob is not crystal controlled, right? Just the comb generator? Or is LO(3) also crystal controlled? I thought at that time in history crystals were pretty much fixed.
Thank you for your description of the Wadley Loop. I really learned a lot. I would like to have seen a circuit diagram of the harmonic comb generator circuit. Of course, I could always "Google it"! -- 73, DE WE3P
It's a pretty simple circuit - feed the output of the oscillator through a small capacitor into a grounded diode. This is followed by a low pass filter to limit the comb tones to
Honestly speaking...For me this was the First time I heard of such " Waldo ckt..".. am not into r.f. nor own any rf gear..etc..great ingenuity applied in it back then..is it still used today? Back 2003-2008 something was going on about the " Motorola SYMPHONY CHIPSET " whats happened ????
Hello sir i want to build a music syncd led circuit which runs 12 v led strips at full brightness And input power supply of circuit is not dual polerity Please give suggestion
Radio Shack made receivers similar to this in the 70's. Pros were they were pretty good shortwave receivers. Cons were they we not good on the broadcast band, and had really tinny audio. Nice video!
Interesting principle. But I'm desperately missing a teardown or a brief look at the interior of the receiver...ancient components & technology are really fascinating.
There's nothing very remarkable about the interior. This receiver is from the mid 1970s, so it's far from ancient. A couple of interior pics are shown here: www.rigpix.com/yaesu/frg7.htm
It could be a number of factors, from layout related parasitics, to loading effects, etc. It is a fairly simple oscillator circuit. Bottom line, the amplitude was sufficient to drive the inputs of the Gilbert cell double balanced pre-mix mixer.
Does the LED light up at all when adjusting the MHz knob? If not, then the PLL has a problem. If it does, then poor sensitivity could mean a problem with the preselector or IF stages/filters.
w2aew Big thank you for your video. I traced everything with a CRO and thanks to your video everything looked the same. Found a blown LED driver transistor. Sensitivity was fixed by AC power. Seems the batteries I was using were not delivering enough voltage. Around 7.8v.
LO1 is only used to select which harmonic of the crystal oscillator is used for LO2. That selects a particular 1MHz frequency range with the drift canceled. The main station tuning is then done with LO3 over the the selected 1MHz frequency band.
Interesting after I saw how consistent the amplitude of the harmonics where I knew it couldn't use a simple square wave since the harmonics would go down in amplitude really quckly with a square wave.
This Soviet transmitter used the same technique - museum.radioscanner.ru/r_140/peredatchik_r_140.html. Not sure they called it a Wadley circuit though. Thanks for the nice video!
Yes, Sommerkamp was (is?) a Swiss firm that imported Yaesu equipment and sold it under their brand name. I also have the same FRG-7 with the Sears brand. Sears was a large consumer chain in the US.
Why did you upload your last couple of videos with just 15 fps? That's somehow annoying to watch. Please switch back to 25 or 30 fps.Nevertheless a good video, as always.
I didn't. It's a RU-vid problem. These videos are all done at 30fps. For some reason, RU-vid is rendering them at 15fps. I haven't changed anything on my side with respect to how I capture and process the videos, so it has to be on their end. I'm working with them to try to figure out what's happening.
It's a RU-vid problem. Nothing has changed with my video settings here, and the file plays fine/smooth here. Properties show 29fps, just like all my other videos. Not sure what I have to do to make RU-vid play it at the higher framerate like my other videos.
Hm, RU-vids player shows it is running at 15fps. screenshot.tbspace.de/fybxeckundw.png Could you set the framerate to 30 fps instead of 29.97fps as a test/for a short test video clip?
All of my videos for the last 2+ years have been recorded and edited exactly the same. It's only been the last few videos that YT is now playing differently. I don't know if I have an option to increase the framerate of my camera.
