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Thanks Steve - WA1QIX

PostPosted: Tue Mar 07, 2006 12:49 am
by Brent
I had fallen into a state of depression after rebuilding the 75 meter 20 Fet PDM rig and not be able to get the damn thing to resonate. I called the guru for some help and Steve took a ride to Derry to help me out.

It turns out my dyslexia got the better of me. Steve stared at the rig and we couldn't get the beast to load; mind you I replaced the Cardwell air variable series tuning cap with a new 10kv ceramic Jennings variable 25-1000pf cap. I also removed a turn off the tank to bring the series inductance to about 6 uh's to lower the Q. To make a long story short, I hooked up the leads to the gate transformers all in phase and all the modules were bucking each other....ARRGH!

Such a basic mistake....after it was all said and done the PDM monster was putting out a full kilowatt. By running a lower Q I picked up about another 100 watts of power and the rig has been stable YAY!!

Thanks again Steve!!

Brent W1IA Class-E for (E)veryone...STRAP!!!!!

PostPosted: Tue Mar 07, 2006 1:33 pm
by frank carcia
Very good Brent! Keep an eye on the drain. I had to add more shunt C to keep it happy. As the shunt caps heat up the value goes down.
Check your coil temperature after a buzzard TX.
If you want to run at 1 KW is should be stable at 1200 watts.