----- Original Message -----
From: "Diane and Edward Swynar" <[email protected]>
To: <[email protected]>
Sent: Thursday, December 30, 2010 10:10 AM
Subject: [Drakelist] Drake R-4 PTO Heater Regulation
Hi Guys,
Per chance, does anyone reading this have any recollection
as to the QST / "Hints & Kinks" edition which made reference
to regulating the 6.3 heater volts of the 6AU6 VFO tube in
the Heathkit SB-300/301 receiver...?
I have the very same malady, I'm sure, plaguing my R-4
receiver.
The station with the Drake Twins is located right between
the sump room & the forced air electric furnace of the
basement: whenever either (A) the furnace, or (B) the sump
pump, or (C) the well water pump kicks in, the CW station
I'm listening to will slowly start to drift a second, or
two, after said device starts. Once the unit kicks off, the
CW signal will return to "normal", again, after the
prescribed second, or two.
I suspect that unregulated heater voltage is affecting the
PTO frequency, just as it did in the referenced Heath
receivers...
The "cure" in that instance (per that now-forgotten "Hints &
Kinks" piece) was the incorporation of rectifier, small
electrolytic capacitor, & a zener diode at the filament
supply of the VFO tube...
Ring any bells with anybody...?
~73~ de Eddy VE3CUI - VE3XZ
I just checked my R4XB on a variac. There was very
little change in frequency for a line input change from
around 110V to 130V. Some change below 110 volts. Most of
the change was intantaneous. I listened for a slower change
that would come from the filaments changing temperature but
there really was none. FWIW, I also checked my R-388, that
remains almost perfectly stable with input voltage from
perhaps 100volts up to 130volts. Both receivers work down to
around 90V. I don't think filament regulation is justified.
If you have a really badly regulated line voltage perhaps
using a line regulator like a Sola transformer would be a
better solution than modifying the receiver.
--
Richard Knoppow
Los Angeles
WB6KBL
[email protected]
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