[VHFcontesting] Elecraft xvtrs

[MICHAEL SAPP]

>I plan to acquire Elecraft transverters for 144, 222, & 
>432. and the required 100-150w bricks. I currently have a yagi and a 
>loop for each band. Any pitfalls I should avoid?

>Dave NT9E

  Part of this comment is second hand info from K3JRD  who built an elecraft 222xvtr for another ham in our area as well
as my comments. Jim found some instability in the transmit side of the elecaft 222xvtr upon kit completion and talking to
the repair tech at elecraft it seems that he spends considerable time improving the grounding on the chassis of that kit by removing
paint at assembly contact points and the like. They are not as squirrely as the old LMW 23 and 13 cm xvtrs where "everything"
changes when the cover is off, but there is some of that enclosure-capacity effect to contend with---at least that was Jim's experience.
We put the finished kit on my HP141T and it was clean on transmit at the recommended drive levels with 2nd and 3rd harmonics within
FCC requirements. The preamp of the front end hears well. It has an adjustable gate bias so you can tweak it for best noise figure. We used
the lots of 50 ohm attenuation in front of the Elecraft Noise Gen which I modified with a 555timer switched at 500Hz  to gate the DC to the zener noise diode and tweaked it for best relative
NF (tune input cap for best gain, adjust bias for lowest noise: repeat:repeat:repeat). The trick was to attenuate the gated tone to about 10db above the background noise when tweaking (with the attenuators connected to the gated Noise Gen source) . You can use Spectran to monitor the gated tone level from the receiver audio and get decent relative NF results, but there is some averaging time lag with Spectran, so be patient with the adjustment process.  After tweaking with the gated source I used my Wavetek signal generator to output a -70dbm signal and added another 50~60db attenuation to check for weak signal performance in the AM mode (the Wavetek is not stable enough for narrowband critical measurement use) and minimum discernable signal was in the low -130 to-133 dbm range from what my 25 year old surplus test equipment could measure---which is not bad for a 6KHz rx bandwidth. Our conclusion was the transverter could use a better enclosure and improved grounding but otherwise it works well enough. It is easier to improve enclosure grounding during initial building versus reworking everything later, so keep that in mind if you go the kit route.  Mike WA3TTS