Looking for a tube only radio or radio kit

There are lots on ebay. But what do you want? Give us a clue.

NT

Radiation hardened?

--
Adrian C

What does it matter. No transmitters will be on.

The R-390 is a pretty nice receiver, all frequencies from near zero to 30 MHz. They are snapped up by hams and collectors, so they get quite expensive. The R-392 has the same range, but is much simpler. It runs off

28 V DC, as both the filament and plate supply.

Jon

If you live near a city, there is probably an antique radio club in it. The one in Baltimore has, iirc, monthly meetings and

RADIOACTIVITY 2016 and the TUBE COLLECTOR's ASSOCIATION Annual Meet

06/23/2016 | RadioActivity 2016 Location: Timonium, MD; Type: ARRL Hamfest Sponsor: Mid-Atlantic Antique Radio Club Website: Swap Meet 8AM, Saturday Learn More

At RadioActivity there are people selling restored radios with wooden cabinets and simple tube radios from the 60's. I went one year and I think I paid $10 for one, hoping it would get a DC station maybe 35 miles away. I can never tell in advance which radios will get it. Brand name doesn't seem to matter.

RadioActivity 2016

HAMFEST/CONVENTION

06/23/2016

Start Date: 06/23/2016 End Date: 06/25/2016 Location: Holiday Inn

9615 Deereco Road Timonium, MD Website: Sponsor: Mid-Atlantic Antique Radio Club Type: ARRL Hamfest Talk-In: None Public Contact: Bruce , KA3EIE 10 Route 99 Woodstock, MD 21163 Phone: 410-461- Email: snipped-for-privacy@netzero.net

You can build a single-tube regenerative set that, if designed and constructed carefully, will have much better performance over the AM and AM shortwave bands than many commercially available superhets.

That's at odds with my own limited experience with reaction sets, and with people's experiences of commercial regen receiver ICs. They do remarkably w ell for the small number of parts, but don't compare in rf sensitivity to t ypical modern superhets. They are dramatically better at AGC though.

ISTR seeing tube circuits that were superhets with a reaction IF stage.

NT

Superregens don't have enough filtering to be good receivers nowadays--there are too many stations on the air. Their noise figures are higher than if you used the same tube as an RF amp, because they're only sensitive in the short period (a couple of regeneration time constants) after the rising edge of the quench (when the regeneration starts). The shorter sampling time leads to a larger noise bandwidth.

They're pretty remarkable though--a single tube with a gain of about 20 dB can amplify thermal noise to a level clearly audible in headphones.

An interesting thing about superregens is that although the output is at the same average frequency as the input, they don't interfere with themselves because the input is sampled at a time when the oscillator isn't oscillating.

There's a really good short book on superregens: "Super-Regenerative Receivers" by J. R. Whitehead, CUP, 1946, part of the Modern Radio Technique series.

That's better, for sure.

Cheers

Phil "rushbox fan" Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

Yes, I believe a regenerative detector following a frequency changer (aka mixer) is called "supergainer".

I have never tried a supergainer but always liked the idea of compromise best-of-both-worlds?

piglet

nd

ith people's experiences of commercial regen receiver ICs. They do remarkab ly well for the small number of parts, but don't compare in rf sensitivity to typical modern superhets. They are dramatically better at AGC though.

Because the reaction is fixed frequency, it seldom needs much adjustment. I 've not tried one either. Prewar radio is fun.

NT

I read that special forces and secret agents radios favored this technique as the emissions of the regenerative detector wouldn't leak past the front end tuned circuit so enemy DF units would have a harder time locating them. I guess it also allowed them to use quite a high i.f. so likewise local oscillator radiation would be less of a problem.

piglet

Interestingly the "super" in both "superregenerative" and "superheterodyne" comes from "supersonic", which before the 1950s meant "too high-pitched to hear", i.e. ultrasonic. You need the IF and the quench frequency to be above audio.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

The "supergainers" I heard of were not super-regenerative. Just a superhet type front end frequency changer and a regenerative ("reaction") i.f. stage, so only two frequencies in the system: signal and i.f. There was no third frequency/ultra-sonic quenching, the i.f. stage was merely steadily self oscillating like a regular plain regen receiver, so had remarkable q-multiplier type selectivity but not the extreme gain of a super-regen.

piglet

piglet

Well, if a regenerative stage doesn't oscillate, it's basically a Q-multiplier. That's more of an HF front end idea, though. If it oscillates, then either it's a superregen or it's broken.

You can make a 1-tube superregen by making the grid time constant long, so that it squegs. The squegging supplies the quench for the superregen.

Cheers

Phil Hobbs

Sorry Phil but I must query your statement "If it oscillates, then either it's a superregen or it's broken".

I would rather say that if it oscillates then it is an oscillating regenerative detector. It is super-regenerative only if that self-oscillation is itself periodic, whether by squegging or by a separate quench oscillator.

The quenching occuring at neither r.f. nor a.f. but a super-sonic rate is where the prefix super comes in.

I have built both regenerative radios and super-regenerative radios and there is a definite difference. My copy of Terman Radio Engineering 2nd ed 1937 also makes the distinction clear, see section 89 p453-456 and section 90 p456-459.

piglet

The first time I saw a circuit for one the 'ultrasonic' squegging was at 10kHz, and I don't think it was filtered out. I assume this was too high for the moving iron speaker to reproduce.

NT

I have that in my shelf, so I'll look it up when I get to the lab. Thanks!

Cheers

Phil Hobbs

Page 575 in my 1943 edition.

Ah, OK, they're running it as an oscillator with nearly unity small-signal loop gain and looking at the oscillation amplitude.

You sure couldn't do that in a TRF.

Thanks

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
Briarcliff Manor NY 10510 

hobbs at electrooptical dot net 
http://electrooptical.net

On Thursday, June 16, 2016 at 3:04:26 PM UTC-7, piglet wrote: ...

There seems to be some confusion in this thread between a "regenerative" re ceiver and a "super-regenerative" receiver.

A Super-regenerative receiver, as invented by Armstrong does oscillate at t he received frequency and is then periodically quenched - the time to build up oscillations is reduced if there is a signal present. An extremely larg e stage gain is possible. It can radiate at the received frequency.

A straight regenerative receiver is an amplifying stage with positive feedb ack and should be be adjusted so it is just below the point of oscillation

- the positive feedback increases the gain over that of a straight stage an d can improve selectivity. It should not radiate if correctly used.

kevin