[Moon] DL4MEA's first JA on 13cm (2424MHz)

[Koellner, Guenter (NSN - DE/Muenich)]

Hello,

happy to tell you that this weekend I managed to work JA4BLC on 13cm, my 1st station in JA, my first QSO with 2320/2424MHz crossband. Signals were 439/539 on  both sides.

I am now QRV on 2320/2304MHz if somebody wants to try.

I had a little bit of troubles, because yesterday I blew the two LDMOS of my feed-mounted PA. I then took the older outside equipment into the shack, re-aligned it, and had to re-install in the morning. Just in time for the sked I was ready on 2424MHz.

I am mixing 2424MHz down to 2324MHz using a cut out mixer from a GSM exciter, probably used for the local RF loop. In front of it there is a 5pole finger filter. Sun noise on 2424MHz is ok. The mixer is inserted into the RX using a transfer relay, so I am able to switch quite quickly.

Who knows clearly (no guesses necessary!) Each of the two blown MRF6S221140 LDMOS is showing a funny behaviour: While in original the gate is high-impedance, and fed with bias using a high value resistor, the gate now became low impedance. If I feed bias using a regulated power supply, the gate draws about 1A at 3.5V, and the devices starts amplifying, I went up to 15A at 28V on the drain-source! Somehow like a bipolar NPN transistor. Knowledge about the effect that might have happend would help me in order to avoid it for a future try. I can supply some more facts if required.

73, Günter (dl4mea)
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