I did manage to adjust T7 in the 2B to get the BFO harmonics at 100khz and 150khz as close as I could discern using a receiver that tunes in 100hz steps, switching between usb and lsb and splitting the difference. Then I tried to do the same on my 2A but I found there wasn't enough adjustment in the slugs, top or bottom to get closer than about 500 hz high at the 100khz harmonic. My question is, does this mean that the capacitor inside the can has changed in value? What other components would cause this?
-DS

Doc,

The permeability of the core can also change but in any case the easiest way to adjust is the capacitor value.

Did you check your test receiver against a broadcast station to make sure that its BFO and master oscillator are dead on first?

Rodger WQ9E

Thanks, Rodger. Yes, I did check the Satellit 800 for its accuracy and found it to be accurate - at least as close as can be determined when tuning is in 100 hz steps. (I have another way I could check and it would be good practice: putting my "new" HP606A to use for the first time.) I have not taken apart one of these transformers before and I'm not sure how to go about it. I also do not understand how the top and bottom slug adjustments relate. I would guess that one is a fine adjustment and one is a coarse adjustment. I recently saw someone asking about the same issue on the NC183D thread, but my questions remain.
-John

I just re-checked the BFO frequency using the 606A and got results consistent with what I was seeing using the receiver method. The BFO is oscillating at 50.265 khz and won't go lower unless some interaction of the top and bottom adjustment screws such as backing one out farther so the other can go in farther or some such is possible. As it is I think they are both in as far as they can go without stripping. Of course, now someone will ask how certain I am that my 606A is accurate. I'm checking it against a frequency counter (Fluke 1900A) and then disconnecting the frequency counter in order to connect the RF probe to the radio. And, of course i'm assuming that the 1900A is accurate just to avoid an infinite regress, and because the measurements I've made all seem pretty consistent.
-John

John,

Now you have to have something calibrated traceable to NIST Seriously, I think your test setup is sufficiently accurate.

I can't remember adjusting the BFO in my 2B but it seems odd that there are two slugs for the BFO coil. Any chance you have a single slug on a single rod that comes out of both ends? Watch one end while turning the opposite to see if it moves.

According to the schematic representation the frequency determining capacitor, C51, is external to the BFO coil. Even if it is internal you could still tack a mica cap across the end coil connections of T7 (not the cathode tap) which would place it in parallel with the existing capacitor, try around 47 pf and see where that gets you.

Rodger WQ9E

This is the 2A, not the 2B. (I did a sly switch a few posts back after I got the BFO on the 2B to adjust properly.) Here, then, is a difference between the 2A and the 2B; On the 2A diagram C50 and C51 are inside the can. On the 2B they are outside! C50 is in series with the tank circuit and is inside the can on the 2A, so if I want to make this work to spec, I'll need to go into the can. You were right about the two adjustment screws: turning one turns the other an equal amount.
-John

John,

I missed the switch between receivers.

With it only being off a bit over 200 hertz I think I would leave well enough alone. The bandpass filter in the 2A is sufficiently broad that it will still work fine. With the later R-4 series receivers and the "improved" pass band tuner setup is more critical but with the 2-A lower Q tuner taking the risk of perhaps damaging the BFO coil isn't worth it.

Rodger WQ9E

Hi Rodger
We often pass on AMPHONE.Net.

I wonder about your statement. If it is true, there would be no pre 1930 EBay section on radios, and a lot of those go for pretty high bucks. I think nostalgia gets replaced by appreciation for the technology of the day.....
AM radios are going for far more than they did in the 70s. What will the future bring?
Hope we live to find out

Hi Carl,

I think the scarce items will always be desired and I should have been more specific because I was thinking about the common gear, especially that of the 50s though the 70s era. Transceivers like the HW-101 and TS-520 are everywhere as are S-40 and HQ-110 receivers. But the early gear and the less common stuff of the more modern era will continue to be desirable due to the limited amount. It is amazing to me how much gear did survive from the 30s and early 40s. I am finishing up a Sargent 10-CA now and then I am going to jump into the cosmetic restoration of a RCA ACR-111 which will need an added hole in the front panel filled and painted but it is worthwhile because there aren't that many of this model around. I have the transmitter, receiver, dynamotor, and coil sets from the command set predecessor and I plan to get this setup on the air soon although I expect the bandwidth of this TRF with straight detector setup is going to be tough to use with current QRM as will the low power suppressor modulated transmitter.

I do think there will be a much smaller number of people in the not so distant future who have the interest and ability to work on tube type high voltage gear but the number certainly won't be zero. There are some who have developed an interest in classic communications gear who completely grew up in the solid state era but I imagine most of us started when tube type gear was at least commonly used if not the norm.

I got my novice ticket in 1975 at the age of 14 and my first setup was a Johnson Valiant and Hallicrafters SX-101 but even then most ham gear was at least hybrid and the all solid state rigs (like the Heathkit SB-104 and the little Atlas rigs) were getting a lot of attention. Later in 1975 I upgraded my ticket to advanced and gear to a Heathkit SB-102 and after college graduated to an all solid state Yaesu FT-980. After several more SS rigs I became bored with contesting and recreated my novice setup and also started collecting a lot of the gear I had read about in old radio magazines while I was studying for my novice. For me it was more of being reintroduced to vintage gear instead of being introduced for the first time and that is probably true of most of us on here and on AMfone. Certainly there are exceptions and for close to a year I have been exchanging much email with a younger ham who has really become interested in vintage gear and although it is sometimes frustrating to help someone repair equipment via email I also find it more enjoyable than much of the university lecturing that I do in my "real life". I have also recently spent several hours on the phone helping a senior citizen ham learn about repairing a much abused DX-40 and although I could have repaired the rig in an hour if I had my hands on it he is learning a lot and I only wish more of my senior business students were so motivated to learn as this elderly gentleman.

Rodger WQ9E