James, KF6RFX asked:

We are looking for a UHF amplifier (430-440MHz) for a transceiver to go from 10 mW to ~ 75W. Most of the amps were are funding require a much stronger input power than we can do. Note, it's a transceiver, so we want to be able to receive through the system as well. This is for half duplex satellite communication using a USRP radio.

Do you have any suggested amps?

You might want to check with some of the "custom" amateur shops like Pure RF (http://www.purepowerrf.com/), Downeast Microwave (DEMI, http://www.downeastmicrowave.com/) or DB6NT (http://www.kuhne-electronic.de/en/home.html). In particular, DB6NT has 50mw in, ~50w out amplifier (http://www.kuhne-electronic.de/en/products/power-amplifiers/mku-pa-4047-60-h...) that is close to what you ask for.

You didn't mention price constraints. Any of the "conventional" amateur "bricks" are will probably set you back $500-$750. There are some commercial alternatives you might look at. In particular check out MiniCircuits; at the $2000 level, the LZY1+ (http://www.minicircuits.com/pdfs/LZY-1+.pdf) has 39+ db gain and will produce 50 w of RF on either 2M or 70cm. Their older ZHL-50W $1400 brick (http://www.minicircuits.com/pdfs/ZHL-50W-52.pdf) is also a good unit. On the MiniCircuits units, I'd strongly advise that you get it with their BIG heatsink/fan.

You say you need fast half-duplex. I presume that the downlink will be on a different band (like 2M). If not, the selection of T/R transfer relays will not be easy, especially if you want to avoid zapping your LNA.

Good luck & 73, Tom Clark, K3IO