[NLRS] WSPR on Tuesday

[Chris Cox, N0UK]

If you didn’t have the OCXO option installed in your IC-746, then it was most probably the transmit fan coming on that caused the rapid and significant drift, rather than the PA heating up.

I wrote up a short doc many years ago right around the time of the first WSJT release that I think is still somewhere on www.chris.org <http://www.chris.org/> and copied elsewhere for a CWXO fix (Cotton-Wool XO!).  The PA fan blows directly across the 60MHz reference crystal and the cotton wool provides enough insulation to virtually eliminate the drift.

Chris Cox, N0UK
chrisc at chris.org
https://www.credly.com/go/IR77aRbH2rFDdOiymuxu2w



> On Jun 10, 2025, at 14:34, Chris Elmquist <chrise at pobox.com> wrote:
> 
> There is an old discussion of "drift" on the WSJT mailing list here,
> 
> https://wsjtx.groups.io/g/main/topic/how_does_wsjt_x_calculate/78207034
> 
> When WSPR was a new thing, a very long time ago, I played on HF quite
> a bit with it and my IC-746PRO which I had at the time.
> 
> What I discovered was that whenever the rig went into transmit, there
> would be subtle but noticable heating of the entire radio, even at
> low power levels like 1, 5 or 10W.  This heating drove the reference
> oscillator off frequency a little which manifested as a "slant" in my
> TX frequency.  After it unkeyed, you could then see it slew back to the
> correct receive frequency as the radio cooled back down, with another
> slant in the received signals.
> 
> This drove me to build a PLL to lock the 32 MHz reference oscillator in
> that radio to 10 MHz GPSDO which eliminated all of this drifting.
> 
> I did the same with this FT-736 for VHF+ use.
> 
> My IC-7610 for HF accepts 10 MHz external reference out of the box,
> so I definitely use that.
> 
> Chris NØJCF
> 
> On Tuesday (06/10/2025 at 02:07PM -0500), Chris Elmquist wrote:
>> On Tuesday (06/10/2025 at 01:53PM -0500), Dave Fugleberg wrote:
>>> for those of you with an IC-9700...how stable to you find it to be?  I'm
>>> seeing a lot of traces in the waterfall with significant drift (like 30-50
>>> Hz) over the course of the 2 minute WSPR window on 70cm.  Not nearly as
>>> pronounced on 2m.   I have yet to copy anyone on 70cm - maybe that's why.
>>> Has anyone added that ref lock board from Leo Bodnar to their 9700?
>> 
>> I'll let Jon respond on his own situation but I think his -9700 is
>> externally referenced-- as is my FT-736.  And between Jon and I, we
>> are always exactly on the same frequency.
>> 
>> I am transmitting with offset 1480 Hz (per the WSJT setting) and Jon
>> reports all of my spots on 144.49080 +/- 1 Hz and 432.301480 +/- 1 Hz.
>> 
>> Similarly, I spot him at 144.490500 +/- 2 Hz.  I have not seen Jon on
>> 432 yet today but I conclude his TX offset is 1500 Hz, the default.
>> 
>> Yesterday when we were playing on 1296, we were both on 1296.501500
>> exactly for each of us, on each spot-- no drift.
>> 
>> You can look in the WSPRNet database here,
>> 
>> https://www.wsprnet.org/drupal/wsprnet/spots
>> 
>> and set up the query to show what others are seeing from you and vise-versa
>> as a good way to check this sort of thing.   This of course assumes those
>> spotting are uploading their spots.
>> 
>> Chris NØJCF
>> 
>> -- 
>> Chris Elmquist
>> 
> 
> -- 
> Chris Elmquist
> 
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