The Anatomy of a Solution

Be forewarned that this is not necessarily a classic antidote.

Wanting to get on the local two-meter side band net, I bought myself a shiny new Ukrainian transverter to use with my trusty 7300. This worked out fine but there was always just a hint, a troubling mostly um-nameable something with regards to my signal. Then a two-meter AM net was fired up and the “issue” manifested itself as full-on broke. My normally melodious baritone was distorted too nearly unintelligible. This needed to be FIX-ED!

These then are the steps to a solution and be it known that despite my 46 years as a ham that I can barely read a schematic let alone figure out where a problem might be. But I am rather good looking . . .

FIRST, verify that the thing is really broken and not just a one-time fluke. Yes, it is broken.

SECOND, discuss the issue with the highest class of ‘spert you can find; in my case a TV station chief engineer who is also an Extra.

THIRD, due diligence Lord Google. AH ha, there is reference to a similar issue and a solution!

FORTH, back and forth emails with the maker of the thing. Very helpful Ukrainian now living in Georgia (the country not the state). Insightful but not solution.

FIFTH, break out the screwdriver and the VOM and the watt meter and very, very judiciously screwdriver the thing.

At the end of the day, well, the middle of the night, I upped the bias voltage from 2.6 volts to 3.1 volts predicated upon the Google research and I lowered the AM carrier output from 13 watts to 8 watts. This reduction ‘cause I worried that I was asking more of the thing than it was comfortable with giving.

SIX, On air testing to see if, if, if. And YES the thing exhibited all signs of now working perfectly! HAPPY DANCE going on yeah!

A parting shot: note that at the end of it I changed two things at the same time. This is not good engineering practice; was it the bias change or was it the output change that made the difference?

Well, I already had the cover off . . .

Two days later, another on-air test and we are back to square ONE! Dancing shoes angerly thrown across the room! #@%!!.

Cover comes back off. Bias voltage is still 3.1 Volts BUT, carrier is back up to 13 Watts so readjusted back down to 8 watts. Did drop test from about 4” 4 times and rechecked bias and output; still where I put ‘em. So, so, so good I guess,

Called up my on-air test guy Gill and we did another round of tests. My signal is now good again on AM, USB and FM. So, I am now pensively happy again. We chatted back and forth for an hour.

I’ll try again to check in to the Wednesday night AM net and see how it goes . . .

WELL, at the end of the day, here’s the real deal!! The tiny variable resistor that controls the output was flaky. Flaky in that there was no mechanical tension between the wiper and the stationary plate. What was happening was that the inrush current at startup caused the wiper to move (no reasonable explanation here); ergo, the unit would be fine as adjusted but when switched off and then back on again the adjustment would go high. At the higher power level there was DISTORTION!

The solution came from China in the form of a new variable resistor. This new resistor measures .127” by .146”. Took some steely eyed soldering to get this puppy tacked down! But the little transverter is now working perfectly on USB, FM and AM. NOW I’m doing my happy dance!

Sometimes, one must chase one’s tail for a while . . .