[HBR] IF Transformers for HBR from ARC

[Walt Hutchens]

John wondered:

> So am I correct in assuming that I don't need to modify them by rewiring them
> ?  Also should they be modified for 100 Kc?  Can they just be tuned up 15 Kc
> with the variable capacitors?

I can't think of any reason to modify them.   And go ahead and use them at
85 kcs -- other builders (I'm one) have done so with good results.   You
have to tweak either the 1st IF or the 2nd LO slightly to accommodate but
that's easier and less problematic than retuning the IFTs.

The variable capacitors have very limited range -- under 5 kcs, as I recall.
These were, after all, a purpose-built part, not a generic made for use in
many different radios.   So the tuning range didn't need to be greater than
would be required to accommodate slight variations in wiring and tube
capacitances.   

> I have a lot more to learn about rigs that glow... it should be a fun
> adventure.

It is every bit of that.   For some of us this is the fun-est part of ham
radio!

I'm among those who recommend completing a simpler vacuum tube project
before taking on an HBR.   These are real receivers, comparable to any of
the commercially made ham sets of the 1960 period in performance and except
that they're mechanically simpler, also in complexity.   They're 'engine
overhaul' to build, that is, not too hard at all if you know how to use a
torque wrench, separate a transmission from an engine, safely get a car up
high enough to work under, free a rusted manifold nut without ruining the
head, get a stuck head off, set valve and spark timing, and read a shop
manual easily.   But if you're back at the 'changed my oil once' level ...

This is 'do not as I did, but as I should have done' advice.   I tackled a
lot of complicated stuff over the years and very little of it ever worked.
I learned little more than I would have building things that WOULD have
worked and arguably had less fun.

The good news is that because collecting the parts for an HBR can easily
take a year or more, one or two of the simpler receivers from the mid-60's
Handbooks won't represent a significant delay.

When I can score a cheap Heath HR 10 I'm going to look at turning that into
an HBR since it would have most of the hard to find parts and if that
project were to succeed, would open a road for more potential builders.   At
the same time it would be pretty close to the ultimate silk purse from a
sow's ear project -- I have not heard of anyone receiving a signal on 15 or
10 using one of those, and they weren't great on the lower bands.

Walt Hutchens
KJ4KV