Hi Tony,
Your comments about Drake PTO frequency stability are certainly timely here...
I've resolved to get "into" the PTO of my T-4X transmitter yet again here---and
I mean RIGHT inside the thing, as I did before, with the circuit board
completely removed from its "moorings" in the rig, & on my work bench.
The reason...?
Well, you may recall awhile back that I had cold solder joints with the
3000-pfd. silver mica capacitor in mine. I replaced this capacitor lock, stock,
& barrel, & the sudden intermittent jumpiness of the signal---& its associated
raspiness---was gone...but there would still be a wee bit of residual signal
drift of a few Hertz in the transmitted signal, again, intermittently.
This condition disappeared if I warmed-up the rig for at least 1.5 hours, so I
figured I could probably live with it. At the very most, I was half-seriously
planning on installing a bypassed small pilot lamp inside the PTO enclosure, to
act as a "pre-heater", stabilizing (hopefully) the 50 year old temperature
compensating capacitors therein, and hastening the warm-up time.
Anyway, to cut to the chase, to-day I was in QSO with a fellow on 40 CW, when
the sudden intermittent drift reared its ugly head yet again, even AFTER a
warm-up of some 3 hours---and the drift this time was far more than the usual
several Hertz!
I think I might just wholesale replace the other fixed frequency determining
caps that I might find in there---there are three others---and see if that
might help. Unfortunately, the Drake schematic indicates the value of two of
these caps as being simply "*", or, "selected at time of production"!
I really do NOT want to delve this deeply into that PTO can again like this,
but the alternative of having to constantly apologize for the poor quality of
my signal simply is NOT acceptable...it's either this, or set the Drake T-4X
aside & simply look at it.
Wish me luck!
~73~ de Eddy VE3CUI - VE3XZ
***************************************************************
----- Original Message -----
From: "Richard A. (Tony) Stalls" <rasta...@verizon.net>
To: <drakelist@zerobeat.net>
Sent: Saturday, January 01, 2011 1:49 PM
Subject: [Drakelist] TR7 Drift
> My TR7 drifts around 100-150 Hz PTO during the first hour. After
> that it calms down a bit, but it still drifts. I've come up with a
> couple of potential solutions, but to be truthful, I don't know
> enough to competently decide if they're what I want.
>
> The Swan guys tell me the Cumbria Designs X-Lock huff-puff type
> frequency stabilizer (http://www.cumbriadesigns.co.uk/x-lock.htm)
> guarantees < 10 Hz stability, but it's apparently better than
> that. One person I know installed them in a Heathkit SB transceiver
> (I forget which) and a Swan 270B Cygnet and measured the drift at about 3 Hz.
>
> I've also looked at the DL1SDQ "Digital Automatic Frequency Control"
> (DAFC) huff-puff stabilizer (http://www.conny-dl1sdq.de) that he says
> is intended for the TR7, although it appears it's not adaptable for
> RV7. It's about $114 as compared to the X-Lock for about $30, as of
> yesterday's Euro and Pound exchange rates.
>
> Does anybody have any experience with either of these huff-puff
> stabilizers, or is there a better way? How about for the RV7?
>
> Thanks and Happy New Year!
>
> 73,
> Tony
> K4KYO
>
>
>
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