> I do know that every SB-1000 I have tuned up on 160 meters
> has the same drift problem. I have cured that problem on several
> occasions with the Ameritron CERAMIC chip caps. With
> a single 3-500Z, voltage is not a problem in the loading
Initial parts purchases of the SB1000 were from Ameritron, so the
first 500 or so SB1000's should have no or minimal drift problems.
Some time after that, Heath purchasing selected their own vendor. I'm
not aware of who that was. It may have been ITT-Jennings or some
other manufacturer, but Ameritron stayed away from ITT-Jennings and
others.
At some time period just after HEC purchased ITT-Jennings, Ameritron
started fighting a drift problem in different capacitor batches. It
took about a year to solve the problem, so there may be some field
units with drifty loading on 160 meters. The solution was to give up
on HEC capacitors rather than sort through the incoming parts with a
temperature test, and switch to high-voltage NP0 ceramic chips.
Reasonably priced mica caps are too limited in voltage to suit the
needs, although in low- impedance systems Snubber Micas are very
good.
73, Tom W8JI
W8JI@contesting.com
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