Hi Eddy:
Excellent! Now, you might also learn something worthwhile by doing the
same test, but measuring the drift of actual output after mixing at say
7 or 14Mhz. If the crystal Osc goes the other direction, it might get
somewhat better...then again if it goes the other way...well...! :)
I'll see if I can measure my B twins here but will not guarantee my
room temp to start at 59.. It is usually about 62 upstairs in the AM now.
Curt
KU8L
On 11/29/2011 8:30 AM, Eddy Swynar wrote:
Hi All,
Well, this morning I essentially duplicated my previous stability tests with the Drake
T-4X here, only with a minor change: as was suggested to me earlier, this time I let the
"umpire" rig---my ICOM 751A transceiver---warm-up, alone, for a full hour...
Before getting to the results, I should add here that the T-4X has a small
cooling fan mounted above the amplifier cage, extracting air from inside it to
the outside: it ran continuously whenever the rig was on during the course of
both evaluations. Ambient room temperature in my basement was 59F, as before.
Again, 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. The actual PTO frequency itself was monitored with the
751A in general coverage mode...
Here are the results this time:
(1) 5455.0-KHz (cold start);
(2) 5454.8-KHz (downward drift of 200-Hz from cold start);
(3) 5454..4-KHz (downward drift of 600-Hz from cold start);
(4) 5454.0 KHz (downward drift of 1-KHz from cold start);
(5) 5453.7-KHz (downward drift of 1.3-KHz from cold start), and,
(6) 5453.7-KHz (unchanged).
The end result in terms of drift was actually 100-Hz MORE than was observed the
first time, i.e. 1.2-KHz with both rigs running from cold starts, to 1.3-KHz
with the ICOM warmed-up for an hour!
No matter---after an hour's warm-up the signal remains essentially unchanged,
and I'm happy with that. I'm especially pleased to note that the warbble effect
/ jumpiness previously afflicting my PTO has apparently disappeared, in the
aftermath of all of my resistor swapping in it...and the dial correction that I
have to do on the T-4X after the resistor swaps is pretty much in line with
what I had to do before the re-build.
My conclusions after all this stuff? Well, #1, it was most interesting& gratifying, both...and #2,
if I take the quoted manual "warm-up" period time to be, in fact, one full hour minimum, then
my transmitter actually EXCEEDS the quoted Drake specs for drift of ":...less than 100 cycles
after warm up" considerably: in fact, mine doesn't drift at all after that time...!
And THAT, as Martha Stewart is wont to say, "...Is a GOOD thing." Hi Hi
Now---how about all those other T-4X rigs that are out there in general
circulation...? Are the results of YOUR stability tests similar to mine here...?
~73~ de Eddy VE3CUI - VE3XZ
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