[NLRS] 5760 power amps

[Doug Reed]

I mentioned back in August that I have some power amps from old 
microwave sites. Gary W0GHZ asked for one and I'll try to bring it to 
breakfast Saturday for show-and-tell.

These amps are manufactured by Northern Telecom (Nortel) and are spec'ed 
as +32dBm output from 5.8GHz to 6.4GHz. Ray WB0EBG has been playing 
around with one at work. He said the power control circuit is holding it 
steady at +32dBm or +33dBm output from 5.2GHz to over 6.5GHz with over 
40dB of power gain. So far he has not had time to disable the power 
control and see how much it can really do....

This would make an interesting amp for a "portable" station. It requires 
+10.5 volts regulated at about 6 amps, and -15V regulated at under 100ma 
for bias. Note that this is true Class A since it is using 60W DC input 
for about 2W RF output, but it is a very "clean" 2W.  :-) I expect that 
when we kill the power control circuit, we'll probably be able to get 
5W-10W out in ham service without much trouble.

The main negative to the amp is that it comes with about 20 pounds of 
heat sink fins on the casting. This was required for continuous duty 
microwave service. We only need ICAS service unless you want to run a 
beacon. Ray did another experiment where he cut and milled off all the 
heat sink fins and cut the size and weight drastically. The amp didn't 
get warm in a couple minutes of key-down. Just be sure to shut off the 
DC when not transmitting!  :-)

The other options have to do with the TX mixer and RX mixer modules. If 
you want to make a simple mixer RX-TX system, you can modify the TX 
mixer and use it for bi-directional operation. If you want a better 
noise figure than you get with a mixer alone, then you can modify the RX 
mixer since it has an RF amp stage. I've got some small 6GHz splitters 
that were used in the RX diversity system so you can feed both mixers 
from one brick.

If you want to to recrystal a brick, you could modify and screw together 
the rest of the pieces and add a SMA relay for the antenna output..... 
If you can make use of the original brick LO frequency for high side 
injection and use an IF in the 300MHz-400MHz range, it could be very 
cheap to get on 5760MHz.

Of course, small size comes from a more modern approach, such as from 
the W1GHZ mini-transverters, Downeast, or DB6NT. You pay your money and 
make your choice.

73, Doug Reed, N0NAS.