Not sure anyone asked this, and I didn't see it in your initial post,
but was the 751A already warmed up when you tested the drake?
What is the frequency reference in the 751A?
I recently used a 751 which is essentially the same frequency
determining set-up for a freq measurement test and I can tell you, it
isn't all that stable either...and, it goes up and down with small
temperature differences over a span of only several minutes. Even when
it had been running in Rx only for over 24 hours.
So..keep in mind that the data you recorded is the net difference from a
moving reference.
After warm-up, I'm not so sure that the 751A is any better than the Drake.
They are a lot better if they have the TCXO module added, but I didn't
see that mentioned.
Anyway, just curious what the reference conditions were.
Thanks
Curt
KU8L
On 11/25/2011 5:57 PM, Garey Barrell wrote:
Steve -
I think 30 minutes is a reasonable 'warm-up' time. IF the radio is in
a controlled environment.!! Take one out of the garage in winter and
plug it in, it's gonna take considerably longer before everything
reaches equilibrium. You have some sizable chunks of iron and steel
in there that can absorb quite a bit of heat. From 60 degrees to a
'nominal' 75 degree ambient on top of normal internal heating would
take a while, perhaps an hour?!? :-)
Plus as Evan said there will be a delta from transmitting as well. A
fan makes a BIG difference in this if you are into long transmissions
or TTY, etc. This is one reason why the TR-7 fan is used to exhaust
hot air from the PA right out the back rather than blow it in all over
the radio, including the PTO, with each transmission.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Steve Wedge wrote:
I always assumed it was a 30 minute warmup, because I seem to
remember the alignment procedures spec 30 minutes warmup before doing
an alignment.
Steve Wedge, W1ES/4
"I can't complain, but sometimes I still do."
- Joe Walsh
If the above message appears, it came from Steve's Son of Laptop!
----- Original Message ----- From: "Eddy Swynar" <deswy...@xplornet.ca>
To: <drakelist@zerobeat.net>
Sent: Friday, November 25, 2011 2:32 PM
Subject: [Drakelist] T-4X Stability
Hi All,
The manual for my T-4X states that stability is "LESS THAN 100
CYCLES AFTER WARM-UP". My question is simply this: how long,
exactly, is an accepted period of "....warm-up"...?
After all of the hoops that I've jumped through in stabilizing the
PTO in my rig (re-buiding it almost, actually!), I decided this
morning to actually measure its drift. I used my ICOM 751A
transceiver (in general coverage mode) as the frequency "umpire",
and tuned it directly to the Drake PTO's output frequency of
5454.0-KHz. Both rigs were in the basement overnight, where the
ambient room temperature was 59F. I measured the frequency a total
of SIX times, i.e. (1) immediately at the start of the test, (2) 3
minutes into the test, (3) 15 minutes into the test, (4) 30 minutes
into the test, (5) 1 hour into the test, and finally (6) two hours
into the test...
Here are my results:
(1) 5454.0-KHz (cold start);
(2) 5454.0-KHz (unchanged from cold start);
(3) 5453.5-KHz (downward drift of 500-Hz from cold start);
(4) 5453.0 KHz (downward drift of 1-KHz from cold start);
(5) 5452.8-KHz (downward drift of 1.2-KHz from cold start), and,
(6) 5452.8-KHz (unchanged).
So---it looks like the rascal that I have here stabilizes after a
good hour of steady warm-up, which leads me to suspect that maybe
"warm-up" to the writer of the manual was, in fact, just that, i.e.
one hour...?
No matter, it was a most interesting exercise---and I sure would be
curious if my rig's performance might match that of some of the
other T-4Xs that are out there...although I dare say, probably not
everyone has as thick a hide as I do in being able to withstand a
59F ambient room temperature...! Hi Hi.
~73~ de Eddy VE3CUI - VE3XZ
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
