[VHFcontesting] Warmup Drift Of Ukranian , UT5JCW, 222 MHz Transverters & Possible Use With FT-8

[David Olean]

You have to consider ambient temperature as well as the straight warmup 
drift. Any portable operation will make things worse as the transverter 
adjusts to a changing ambient temperature. I run into this all the time 
with a cold shack. I turn on the heat when and the room warms up along 
with the transverter. You also need to exercise the PA as it is the 
worst offender for crystal drift.

I would think you would be OK after 30 minutes, as drift is manageable 
but definitely noticeable.  I tried the same test with my rather old 
DEMI transverter built in a large diecast housing with a 20 watt hybrid 
PA on the opposite side of the chassis from the LO crystal. The drift 
was about 10 Hz per TX sequence on JT65. When you stopped transmitting, 
the crystal drifted upward during the receive cycle and would be 10-12 
Hz higher the next time you transmitted. It worked OK but people could 
see the drift.  My solution was to install a styrofoam insulator around 
the crystal to slow down any heat transfer. Then I mounted a small 12 
volt fan on the heatsink just above the heat generating hybrid amp. That 
really made a huge difference. Now my 222 transverter is very stable.  
It wanders a few hz over many sequences, and people assume that I have a 
GPS standard when they see how stable it appears. All I did to figure 
things out was to transmit with the rig on the bench and monitor drift 
with a good counter.  I ran JT65 to get a realistic drift pattern. I 
compare it to my GPS standard, so it is very accurate and does not 
drift.  Of course, then the problem becomes one of maintaining the 
ambient temperature at a constant level. That variation will cause 
additional drift. When temps are cold, I run the transverter for an hour 
or so before the sked and try to heat up the room as well.

You could try a similar test with the Ukraine unit.

Dave K1WHS

On 4/16/2021 10:30 AM, peter h via VHFcontesting wrote:
> 0715pdt 16april2021
> A number of us in SoCal have been using UT5JCW's 222MHz transverters with good success on CW/SSB/FM from home and hilltopping/roving.
> Tim, N6GP, wondered if they are suitable for use on FT-8.
> Steve, WA6EJO, 'volunteered' to plot drift data on his UT5JCW 222MHz transverter.
> His results are tabulated below.
>      Steve, WA6EJO, did some transmit frequency stability tests using a GPSDO referenced frequency counter.
>    Some of the drift may be due to the exciter, a TS2000X, but most is from the Ukranian transverter.
>    From 2 to 3 minutes after power on it moved -227 Hz 3 to 4 minutes -103 Hz 4 to 5 minutes -64 Hz 5 to 6 minutes -45 Hz 6 to 7 minutes -27 Hz 7 to 8 minutes -21 Hz 8 to 9 minutes -17 Hz 9 to 10 minutes -7 Hz 10 to 15 minutes +50 Hz 15 to 20 minutes +13 Hz 20 to 25 minutes +47 Hz 25 to 30 minutes +37 Hz
>   
>
> Do any experienced FT-8 users have any comments on possible use of the transverters with data modes?
> Thanks,
> BT73
> Pete, N6ZE
>     
>    
>     
>   
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