Now that I have my K2 fully stuffed with goodies... DSP, NB, ATU, Battery, SSB, 60M, 160M, IO... I got busy on transverters... and have all 3 working... but...
I plan to use the K2 and transverters, portable, for the June VHF contest. I use M2 HO loops for the low gain stack to allow quick setup when we get to a hill top. By the time we've gotten "the easy ones" worked with the low gain stack, the antenna monkeys have the "real" antennas up. The 50, 144, and 222 loops are about 2 feet apart on a common mast. The plan is to use Mirage 160 watt amps on each band. Much to my dismay, I discovered that with about 150 watts output, at 144.2, into the middle loop, the PHEMT GaAs FET, in the front end of the XV-50 failed, gate to channel short. The first time, since my ESD discipline isnt the best at home, I assumed it was static damage, and the FET was wounded and failed after a couple days of operation. I was able to get several samples of this PHEMT from Agilent, and replaced the damaged part. The second time, it was obvious what had happened, the large 144 MHz signal from the nearby antenna had coupled enough energy into the 50 MHz antenna to destroy the LNA FET. This configuration has worked in the past, with other radios. My ICOM 551s receiver has survived up to 500 watts in the 2 meter loop without damage. This problem is soon to be worse; the spring antenna project will be a 6 element 6 meter yagi, on a common mast with the 2 meter and 1.25 meter yagis .. and up to 1500 Watts on 2 meters. Any suggestions about protecting the GaAs FETs from VERY LOUD out of band signals, without causing nasty intermodulation products? It would be a shame to build a killer transverter and waste its excellent performance with clipper diodes in the front end. Ive been thinking about bringing out band select signals, to switch loads onto the antenna ports of the unused transverters, but 12 volt coil coax relays are expensive. A shorted 1/4 wave stub might work, but its close to 3/4 wave at 2 meters, so it may not be enough, an open 1/2 wave stub at 6 meters is getting rather long for running around in the field, the truck already has too much clutter on contest weekends ;-) Going back to the Icom receiver is not an option, after using the fully tricked out K2, listening to the 551 all weekend would be torture. 73 DE WB7RSG -- Gregory P. Daly http://www.mitrek.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
