[time-nuts] FMT

John Ackermann N8UR jra at febo.com
Wed Nov 15 21:49:07 UTC 2006


That's interesting -- from your earlier message, I thought they were
still running the Harris exciters for the test itself.  It'll be
interesting to monitor the drift during the test.

My plan is to record audio (W1AW plus my known-frequency marker) of all
three bands simultaneously for the whole test period, so if the
propagation gods are smiling upon us, I'll be able to look at the
beginning-to-end drift.

Two of the bands will use HP 3586C selective voltmeters driven from an
HP 5065A (using the internal tracking generator as the marker), while
40M will be on an Icom 746 with a PTS synthesizer hooked to the same
5065A providing the marker.  The audio from all three receivers is fed
into a 4-input Delta44 sound card and recorded as separate .wav files.

It's a shame the test wasn't a week or two later -- I just acquired two
more 3586Cs on eBay today so I would have been able to use the same
hardware for all three bands.  That'll have to wait until next year...
(I really love the 3586C as an HF measurement machine.)  I also hope
that by next year I'll have the crystal in the Delta44 slaved to the
external reference, and that will remove my last significant source of
measurement uncertainty -- though the Delta44 sample rate seems to be
very stable even on its own.

John
----

Colin Bradley said the following on 11/15/2006 04:37 PM:
> 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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