[time-nuts] FMT
Didier Juges
didier at cox.net
Wed Nov 15 23:23:23 EST 2006
Recent radios of that grade all have TCXOs, and that level of
performance is really not that hard to achieve today at constant
temperature.
My Yaesu FT-1000 Mk5 Field (with TCXO) drifts much less than 0.5 Hz at
14 MHz between 30 minutes and one hour after being turned on (in
receive), but a couple of Hz during the 1st 1/2 hour (from memory, I did
not record the data). I have not tried after continuous, prolonged
transmission. I need to retake this data now that I have much better
equipment. With regard to accuracy, the rig is about 0.82 Hz low at 14
MHz after warm-up (original factory adjustment, the rig is about 2.5
years old), measured in AM transmit mode, using a 40dB power attenuator
on the output driving an HP 5370A counter with 1 sec gate time, with a
Thunderbolt GPSDO as external reference.
My older Kenwood TS-440S/AT radio (no TCXO, bought new in 1991), drifts
about 100 Hz (at 14 MHz) during the 1st 30 minutes of operation
(receive) but is quite stable after that ( I did not measure how much,
but absolutely no noticeable drift in normal operation, for instance
using WWV's zero beat as a reference), regardless of Tx or Rx operation.
Didier KO4BB
Colin Bradley wrote:
> I received the following email from the station manager of W1AW.
>
> Hi Colin,
>
> I didn't want to answer your question too soon.
>
> On the days prior to the FMT, I conduct measurements at 1 hour, 3 and 6 hours after initial warm-up. (And of course, this time frame includes the normal broadcast schedule.)
>
> >From what I can see, the drift on the Orion and Pro IIs is minimal. For example, from the 3 to 6 hour time period (today), the "40-meter" Orion drifted 0.12 Hz. The "80-meter" Pro II drifted about 0.11 Hz and the "160-meter" Pro II drifted about 0.04 Hz. (You have to understand that these three radios are here for evaluation only, and went through their respective Service Departments before we received them.)
>
> And just now, I conducted a quick test to see what the "real short-term" drift would be (given the time frame of the FMT). I didn't notice any significant difference.
>
> I'm a little surprised at these numbers. But I have to go on what my counter is telling me. Oddly enough, when we used to run the Harris exciters (during past FMTs), it was not uncommon for me to see at least a 2-4 Hz difference in the 3 to 6 hour time period.
>
> So we'll see...
>
> Good luck!
>
> 73,
>
> Joseph Carcia, NJ1Q
> W1AW Station Manager
>
> Interesting...I would not have thought these transceivers were that stable.
> Colin
>
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