[HBR] another HBR

[waltah at earthlink.net]

Darrell, WA5VGO wrote:
> I've built them with the Miller transformers and the BC-453
> transformers and there is no discernable difference. The receiver
> will work VERY well with them. 

I agree -- my 'HBR-style' HBR (plug in coils, 12 tubes, dual 
conversion) works fine with BC 453 transformers.  One question for 
you Darrell; did you have the impression that I had that perhaps the 
skirt selectivity wasn't quite as good with the BC-453 transformers? 

When you look inside the cans, the 'hot' leads for both primary and 
secondary pass *very* close to the windings and the outer layer of 
the windings is hot, so there's a tiny bit of capacitive coupling 
between primary and secondary.   I don't know how much it 
matters, but you'd never let the primary and secondary hot leads 
get near each other under the chassis, so it doesn't seem like a 
good thing.  It wouldn't have mattered in the military application, but 
for top rejection of out-of passband signals this seems 'impure.'   

However, I say again that I didn't really notice any problem.

Also, the 1415 kcs 'command' transformers can be retuned to the 
standard 1st IF.   Or, you can jigger the conversion scheme slightly 
to use the 85 kcs transformers unchanged.   I set my receiver up to 
use a 1665 kcs 1st IF, 1750 kcs 1st conversion osc. (crystal), 
giving an 85 kcs 2nd IF.   There's no real disadvantage; the original 
front end coil winding instructions can be used without change as 
the range of adjustment provided by the trimmers will easily handle 
the small difference in the 1st IF.  

Ted Crosby's designs are not terribly sensitive to details and they 
remain as sound and buildable today as they were when new.   If 
carefully built, these receivers will outperform almost all of the 
contemporary designs.   The Collins sets might do better at 
measuring the frequency, but ...

And my thanks too, to Tom Dailey, WAØEAJ, for the great HBR 
story!

Walt Hutchens
KJ4KV