HR-10/B

[Bill Coleman]

On 11/28/01 10:50 PM, Richard H. Arland at rarland at EARTHLINK.NET wrote:

>I am sure there are other things you can do to this fine example of a
>Novice receiver of the 1960s. Check out Mike Bryce's Heathkit Shop web
>site for further details.

There was a great article in a 1972 issue of 73 Magazine. I think it was
the November or the February issue. It had several design improvements
for the HR-10.

* First was to get rid of the 6X4 rectifier and use modern silicon
rectifiers.

* Second was to get rid of the (can't remember the tube) diode tube, and
use modern small-signal diodes for the detector, and AGC detector. (I
think there's three diodes here)

* Third was to install a OB2 regulator tube (the vacated 6X4 socket was
handy) and use this regulated voltage to run the BFO, and VFO. This
greatly increased stability.

* Seems like there was another mod in this article that required you to
install another tube. I think it was an AGC amplifier or something. If I
recall correctly, these mods made for a much getter AGC -- fast-attack,
slow decay.

When I build my HR-10B in 1975, I made these mods. It turned the HR-10B
into a much better receiver.

My biggest complaint about the HR-10B was the lack of selectivity. The
two-crystal filter is very wide. The receiver was really designed for AM
reception more than SSB or CW.

Since my brother also had an HR-10B, I did make some attempt to improve
selectivity. I tried replacing one of the IF crystals with one of the
same frequency as the remaining crystal. Unfortunately, this caused the
IF amplifier to oscillate uncontrollably.

I think two closer-spaced crystals might have made a passibly narrow
filter for CW receiption, as Heath did in the HW-16 receiver.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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