[HBR] So i'm gonna build an HBR-XX

[Walt Hutchens]

Bob said:
> For what it's worth, we have successfully used a tinsel wire (woven
> metalic fibers) covered with a fiberglass braid. I have no idea who
> may make it, or where that material can be obtained these days, but
> if it can be found, it would certainly be treat to homebrewers. It
> was variously called 'wire core dial cord' or 'metal core dial cord'
> ...something like that. For the hobbyist, and repair shops, (back
> then), it was marketed by Waldom and General Cement (GC). I think I
> used to buy it from Allied, in Chicago as well.

You could probably get by with a proper weight braided fishing line.
However I think Antique Electronics Supply and others sell real dial
cord.

Working with the Eddystone 898 on the current HBR project, I
discovered a minor problem with conventional dial cord. The 898 has a
logging dial graduated 0-100 over one revolution. This dial is gear
driven from the tuning knob and there's also a gear drive to the
capacitor shaft. The logging dial thus has a fixed relationship to the
capacitor setting. However the string drive to the slide rule dial
pointer is fairly long, and if the string stretches, then the SR dial
won't remain in a fixed relationship to the logging dial and
capacitor. Temperature and humidity make a difference of perhaps one
division -- roughly one KC on a band where the receiver covers 500
kcs.

The metallic core dial cord that Bob describes would solve this
problem.

This does not matter in the practical use of a receiver of this type
but it was annoying when doing the tracking of the oscillator to the
(existing) dial calibration where precise and repeatable measurements
had to be done over a period of a couple of days.  The logging scale
was more easily read, but had a slightly variable relationship to the
scale I was trying to match!

> Anyhow, good post.

Make that TWO GREAT posts!

Walt
KJ4KV