Good Day All,
Well, I think taht an update may well be in order here, as to the outcome of
my "...red-neck hillbilly" (apologies to all you mountain-dwelling folk
reading this) "fix" in the matter of improving the shielding of the PTO can
in my Drake T-4X transmitter...
In a word: it WORKS!!!
SO FAR it works, anyway...again to-day I've completed several CQ calls on
40-meters CW, and was engaged in a couple of lengthy rag chews---and there
was NONE of the previous intermittent tell-tale frequency jumpiness /
intermittent creeping / jiggling... NOTHING. Needless-to-say, I'm very
pleased.
Keep in mind, however, that my situation here was probably unique from most
others: I had repeatedly removed & replaced the PTO shield cover here in
efforts to track-down what turned-out to be at least one bad solder joint in
the tank circuit. No doubt this served to compromise the integrity of the
shielding of the can. Additionaly, my station is situated in a very cold
basement environment, AND I have a fan extracting air out of the final
2x6JB6A PA cage, which by default, cools the entire inside of the
transmitter...
The rig's warm-up cycle was far from normal, as a result, I'm sure...
Anyway, FWIW guys, don't neglect the critical effect that even the smallest
of gap changes in shielding seams can have upon the field of that
permeable-tuned tank coil, and by consequence, your transmit frequency. The
aluminum strip shielding technique employed here may be far from
eye-pleasing, but the benefits of its presence sure are a joy to the ear...!
Hi Hi.
Here's hoping that my travails may ultimately benefit another(s) in the
Drake community...
~73~ de Eddy VE3CUI - VE3XZ
****************************************
----- Original Message -----
From: "Diane and Edward Swynar" <deswy...@xplornet.ca>
To: <drakelist@zerobeat.net>
Sent: Tuesday, January 11, 2011 5:42 PM
Subject: Drake Twins PTO Woes...
Good Day All,
Well, I took the T-4X off-line here to-day, & set it up on the bench with
the top cover removed, exposing the PTO can...
I pondered the ways & means of "sealing" the small gaps between the base
of
the can & its metal attaching surface, with the intention of eliminating
any
consequent expansion/contraction effect(s) of the joints upon the
oscillator
frequency.
I settled upon a rather crude, but I think effective, expediency: I simply
cut a strip of aluminum cooking foil, and wrapped it around the can base,
being sure that there was overlap on the base that supports the "ears" of
the can. I then bridged the strip (on both sides) with masking tape,
ensuring good bonding along the length of the strip...
It's inelegant, for sure, but achieves its end purpose, I think...
I put the transmitter on 40-meters CW, and noted the tell tale frequency
creep one time---however, the rig had been on for only 10 minutes, barely
enough time to warm up. After about 90 minutes, I made a couple of QSOs,
and
called CQs, all-the-while monitoring myself on my R-4 receiver...
I'm happy to report that "...so far, so good." I'll need more time to
evaluate the results of all this, of course, but I'm encouraged. Perhaps
the
ultimate answer lies in operating the rigs in an environment that's warmer
than the 49F that the basement was this afternoon! Hi Hi.
Certainly, time will tell...I guess I could always place a small
incandescent bulb somewhere inside the T-4X to help speed its heating
/reaching "operating temperature"---but then that effort would be
defeated,
in large part, by the cooling fan that extracts air from the 2x6JB6A PA
cage! (that rascal keeps the whole inside of the rig cool to the touch).
~73~ de Eddy VE3CUI - VE3XZ
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