[TenTec] [QRP-L] ARGOSY 525 PTO DRIFT?

[Upton, Shawn]

Not sure.  I'm not sure I'd trust it that much for any of the digital modes,
as it will be somewhat drifty, at least whenever compared to any decent PLL
rig.

But I'm not aware of a PTO issue on this radio.  You could try to change the
compensation capacitor in the PTO for lower drift.  IIRC, the inductor has a
positive tempco, and so a negative tempco capacitor (N1500, etc) is used to
try to balance that out.  I'm sure someone has done this kind of fixing
before, but I believe the procedure is along the lines of, remove the tempco
cap (replacing with same size cap), measure the PTO temp before and after
starting the rig, measure the drift from initial startup to end of drift,
and then determine what level of compensation capacitor to use.  Then
retest.

That, or put a 10W resistor in there, dissapating a few watts.  Preferably
with a temperature sensor of some sort--in an attempt to keep it (the PTO
area) at a constant temp.  Or perhaps a light bulb, as they have a bit of
thermal compensation in them (resistance--and power dissaption--varies as a
function of temperature--as they heat up, the resistance goes up, a rough
form of temperature compensation in this case).

Did you notice the drift after transmitting for a while?  Radio was probably
heating up a bit.  You could try a small fan on the backside of the radio,
using lower power (and an amp if necessary), or the like, to try to keep the
radio at a constant temperature.

Shawn Upton, KB1CKT

-----Original Message-----
From: qrp-l-bounces at mailman.qth.net
[mailto:qrp-l-bounces at mailman.qth.net]
Sent: Sunday, October 02, 2005 11:53 PM
To: QRP-L; TenTec Contesting; TenTec List
Subject: [QRP-L] ARGOSY 525 PTO DRIFT?


I tried my Argosy 525 on MFSK tonight, and had to turn switch rigs because
of the PTO drift.  Is there a known problem with PTO drift on this rig?  If
there is, what's the fix?

Thanks,
ed - k9ew

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