Hi all,
I've been building regenerative receivers for a few years now and have been a fan of tubes for twice as long. I never thought that I would try this, but I would like to build a superheterodyne. I have a general understanding of the parts I'll need and the operation of a superhet, but there are still a few things I need to find out. I mostly have questions about the IF transformers.

I bought a Country Belle radio chassis from eBay recently for its tuning capacitor and potentially the IF transformers. Does anyone know what the IF frequency is? I would imagine it's 455khz, but I'm not sure. The radio is the battery/AC version.

Also is there that big of a difference between interstage and output IF transformers? Or that big of a difference between their input and output windings? I just want to make sure that I wire them in the right direction and in the right order.

Thanks,
Eric

Regenrodyne!

It is a regen detector with a crystal controlled oscillator. I made several. They could go from BCB up to 10 meters.

http://www.qsl.net/w/wd4nka//TEXTS/REGENf~1.HTM

Eric

Input and output IF transformers are quite often the same with 1:1 ratio windings. Either side can be used for primary or secondary.

If the original radio had miniature tubes most likely IF Frequency was 455. These transformers can be adjusted.

I built a superhet using an Arvin schematic. That was what I had and it used a min of parts. Shouldn't have a problem. Be sure polarity of the oscillator coil is correct for positive feedback.

That regenrodyne does look interesting. I may try that at some point. But for now I'd like to make a superhet for the AM broadcast band. It will be similar to an AA5.

I figured that they couldn't be very different. I had read in a couple of places that they were different in some radios. When I measured and looked at the windings of IF cans from an old parted out radio, they tested similar and were visually identical.

Thanks for the info!
Eric

The small approx 1" square IF cans often have silver migration that causes noise, may be a good idea to get the chassis operating before making a decision on the transformers...

The larger transformers with double padder adjustments in top rarely have a problem, the single adj top & bottom often have same issues as the small cans...

Building can be a lot of fun, I built a superhet almost four years ago using unloved series string TV tubes... It's in a Silvertone battery tombstone cabinet, plays great(batteries ate the orig chassis years ago)... I used a pair of transformers for AC isolation and provide voltage for the heater strings, otherwise it's basically a AA5 RF section with a pair of vertical deflection triodes for the audio and a pair of damper tubes as B+ rectifier and doubler...

If you search 11FY7, pict and schematic will be found...

Tom

I have an old console radio that has the larger IF cans. I'll take a better look at them to see how they are tuned. Other than that I have three pairs of smaller IF cans. I'll probably wire the radio first and see what works best, then I'll build it on the chassis.

I'm planning to use a 6BE6 converter, 6BA6 IF amp, 6AT6 detector/audio amp, 6AQ5 audio power amp, 6X4 rectifier, and an EM80/81 tuning indicator. I was worried at first that the EM80/81 wouldn't work with the 150 volt B+, but I tested it earlier today and it gave satisfactory illumination with the lower than normal B+.

I remember looking over that thread before. I'll check it out again though.

Thanks for the advice!
Eric

I have located some larger IF cans, but they are from an AM/FM receiver. Inside each can is a pair of larger coils in parallel with trimmer caps, and a pair of smaller coils with tuneable slugs. In each of the cans one of the small coils is in series with the larger coil and the other is completely separate. I'm not sure if this is right, but from what I have read the larger coils would be the 455khz IF coils for the AM band and the smaller coils would be for the FM band. I'm assuming that I want the larger coils with the trimmer caps and the smaller are unnecessary.

Please correct me if I'm wrong.

Thanks,
Eric

http://www.antiqueradios.com/forums/viewtopic.php?f=12&t=106846

That's just what I've been looking for ! In my very wishful queue of future projects, is an AM/FM tube radio, with completely separate AM & FM receiver sections. Only the PA is shared. I'd contemplated using separate tubes, or tube sections, for the LO & mixer. AND here it is, using a 5U8. I have a few 6GH8s, and other triode/pentode tubes, I could try. These, too, are unloved orphans from the old tube TV days. Good to see my concepts weren't out in left field. I'll make queries on the details, later.

Thank You, so very much Tom !

The ARRL Radio Amateurs Handbook and the "Radio Handbook" have many superhet construction projects from very basic to all out wild from the 30's to 60's.

Pick an era and look thru several as circuits often changed yearly.

Carl

Eric, measure the DC resistance of the windings of both transformers. If you find one winding that is lower than the other three, it is the secondary winding of the output transformer. The diode-detector/AVC circuit places a load on the transformer so some output transformers have a lower impedance secondary -- fewer turns with larger tuning cap. If all windings have the same resistance then there is no difference between the transformers as Norm said.

GL, Al