SR-III HOT-ROD Project
Professional AM Broadcast
The Final Version of this New Model
The GE SR-III is a $49.00 radio. It is a great performing AM/FM analog radio, either as a tag-along
portable, a table top receiver, or a bedside listener.
There is nothing REAL special about it, except that it is a good clean design, very sensitive with a nice
quiet noise floor, and decent, effective IF filtering with selectable narrow/wide passbands.
That's it ... nothing more, except that in today's world, it's value is probably underrated and could
realistically retail for twice its current price.
I suppose it could be said for just about any radio, but this particular device has potential far and above
what its marketing people allowed its engineers to create. At the target retail price, there ain't a lot of
budget room for many more bells and whistles.
Interestingly, two of the radio's better-known qualities, and selling features are of little or no concern in
1. The SR-III is touted as having outstanding audio. Well, for the price and size, that's true. It uses a 5-inch high-compliance woofer
and a 2 inch cone tweeter. In the audio-design field, this is known as "faux-fidelity." The engineers take advantage of particular
acoustical characteristics that impart a full-bodied, apparently , high quality sound. They are the same techniques that make little,
tiny computer speakers sound fairly decent. All that aside, it is executed quite well in the SR-III. But that has nothing to do with this
project since its primary purpose as the SSR-III involves much more significant capabilities of this little radio's basic design.
2. Likewise, the radio incorporates an 8-inch ferrite rod antenna. That certainly is an anomaly in an AM radio of any size or price.
Again, that really doesn't apply to this project, although some ancillary utility of that loopstick antenna will be available in the
|Here is the basic layout of the 5th iteration of the radio's front panel which is 5 1/4" x 19"
A closeup of the panel's left side.
A closeup of the panel's right side.
The controls' labels and nomenclature should be fairly self-explanatory.
Several months and several hundred hours later, I have pretty much satisfied myself that the performance of all
the indicated functions are doable. Everything has been bread boarded, to some degree, in order to (at least)
prove their utility and determine their potential and limits.
This project will take several months, as opposed to some of the preselector projects that also appear on this site.
The actual first working prototype will become the test platform for further developments and refinements.
Other panel designs and layouts reflect some compromises in this, the most complete version.
This will be a real "knob turner's" delight. But when you are chasing the "tough ones" and trying to dig-out the
last dB of signal - that's what's necessary - lots of knob twisting.
I have been asked, "...are you crazy?" Well, I guess that depends on who you ask, or which project I
am currently working on. Why all this design engineering effort, time, cost and bother for the SR-III?
Why not? No, it's not a triple conversion receiver. No, it's not DSP or the latest offering from JRC,
Icom, Harris, TenTec, or watkins Johnson. But what it is, is a good performer with potential far and
above its natural self. With the mods that i have added, this radio should suit any AM broadcast SWLer.
Imagine if you bought an SR-III and had a digital display added. That would be pretty cool, huh? Then a
tuner to match various antenna impedances, then a preselector to single out your desired frequency,
then selectable IF bandwidths with adjustable gain, then a preamp, an antenna switch, a calibrated
attenuator, and of course, a tunable AGC section. What about audio contouring and some basic DSB.
Well, that's what you have here, and more ... but it's all in one package.