[HBR] HBR Build Advice?

[Walt Hutchens]

Scott said:

>>>  I'm gearing up to build an HBR something over the winter after building a
>>> W7ZOI receiver last winter.
>>>  Any recommendations for "bang for the buck" and "least difficult to source
>>> or sub parts for" variety?

I've built an HBR starting with a Heath HR-10. Aside from tube
substitutions and the plug in coil stuff everything tricky comes with
the HR-10. There's significant chassis rework needed (plug in coils,
added tubes, existing parts must be moved to allow for the coils ...)
so this is a 'strip to the chassis' job -- not merely some local
tweaking of circuitry.

The HR-10 has a half-lattice crystal filter that takes care of the
selectivity issues without having to go double conversion to 85 or
100kc IFs. HOWEVER a significant number of under-the-fleamarket-table
HR-10's have bad crystals, probably as a result of not disconnecting
the receiver antenna when keying the xmtr. Don't start a project until
you've got good crystals!

There was a separate plug-in crystal calibrator; if you get that too
there's room on the chassis to build it in as part of the redesign.

Basically Heath left 'acres and acres of free parking' on that chassis
because it was a just-past-beginners project. Those who are beyond
that would have no trouble fitting a complete HBR in the space.

I discussed this several times in posts here, some years ago and there
were pictures at the time -- don't know if they're still there or not.
I never drew the  circuit and I doubt most people would want to try
to duplicate that anyhow -- the 'real' HBR circuits are easier to get
working.

(I used a plate detector and amplified AGC. While this works very
nicely, the AGC line is VERY high-Z and any gas in a controlled stage
kills it. Plus the initial set-up is tricky due to interacting
adjustments. It's not worth it as a first HBR project.)

You can track the new coils to the existing dial calibration which
makes a slick result. I could count turns on my coils for 80 and ...
40 or 20, I forget which -- and report that here if anyone's
interested. I did only two bands.

The pictures show how the front end parts are rearranged to allow for
plug-in coils. It works very well and you can't beat the easy parts
search! I made coils from PVC pipe and octal tube bases.

Walt Hutchens
I see that I'm now 'formerly KJ4KV' ... Sigh ... another
project for this winter.