[R-390] building new components (PTO)

[Dave Maples]

Conard is talking about Bill Hoehl, WB4MUZ, and he did indeed build a PTO
replacement using a 10-turn pot and a diode linearizer.  There's an article
published in the 1983-84 timeframe (QEX?  Not sure).

Today I'd do it with a DDS and either two encoders (one fast to handle
fractional kHz and another one to handle the higher steps with suitable
gearing) or else revert to something simpler and just ADC the 10-turn pot
and use it to drive a lookup table for the DDS.  The only thing I didn't
like about the 10-turn pot is that if you forgot and turned past 000 going
low or 999 going high you were going to break the pot.  A 15-turn pot would
be the cat's meow.

Dave WB4FUR

PS.  Bill died of colon cancer in 1986.  He didn't take good enough care of
himself, so by the time he actually DID something about the fact that he
couldn't eat, it was too far gone.  If you aren't taking care of your
health, PLEASE remember that even if it seems inconvenient there's someone
somewhere who really, really needs you to be healthy.



-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of Conard Murray
Sent: Thursday, December 15, 2005 2:53 PM
To: r-390 at mailman.qth.net
Subject: RE: [R-390] building new components (PTO)


Back when I was a young whippersnapper, my elmer was given a '390A from
a batch that MARS was distributing without PTOs. This guy was a
build-it-yourself sort of ham and since PTOs weren't as available in
1978 as they are now, he built up a solid state VFO for it using a 10
turn pot as the tuning element.
I especially remember this because we went through what seemed like
thousands of 10 turn pots at hamfests looking for a non-wirewound one
for the tuning element.
This lashup actually worked out with fairly decent tracking, so it can
be done.
Conard, WS4S


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