[VHFcontesting] FW: ARRL Sep VHF N8RA Single Op-All Modes LP

[chetsubaccount at snet.net]

                    ARRL September VHF Contest - 2022

Call: N8RA
Class: Single Op-All Modes LP
QTH: FN31
Operating Time (hrs): GOK

Summary:
 Band  QSOs  Mults
-------------------
  222:  11      9
  432:  17     11
-------------------
Total:  28     20  Total Score = 1,120

Club: Yankee Clipper Contest Club

Comments:

The contest weekend presented a good opportunity to test a recent modification to my Elecraft XV432 transverter.

In the last contest I noticed that its frequency stability was not sufficient for dependable FT-8 operation. As it went thru transmit cycles, the received signals on the waterfall would slowly arc over on a curved trajectory. It took about 15 minutes of operation to settle down

I theorized that the high FT-8 duty cycle raised its internal temperature faster than its local oscillator crystal oven could compensate. The little fan inside simply spread the heat from the PA around to the whole unit. 

In a separate box I rigged a freq synthesizer (from Q5, having a nice TCXO)  set to produce the required LO frequency. The LO in the transverter was disabled with a jumper from its transistor’s base to ground. A BNC connector added to the side of the transverter near the internal LO circuit allowed for a small capacitor to then couple in the synthesized signal, and LO levels and alinement were similar to the original.

It worked well! Now I get quick answers to my transmissions. And, it is interesting to watch other’s signals on the waterfall- some are obviously stable with a vertical series of transmissions, but others have curving trajectories, often seen when they would first start up on the band, and those stations were often difficult or impossible to contact as their frequency moved.


My XV144 and XV222 transverters do not seem to suffer the same problem but will get a closer look.

73,
Chet, N8RA


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