Re: 20dB VHF amplifier
The 20dB gain amplifier you refer to is basically a pre-amplifier the maximum output power that it can give is about 0.001W. It is intended for the input to a receiver, not the output of a transmitter.
Assuming the 20V you measured is across 50 ohms then your transmitter is already giving about 1Watt output. If you add a 20dB gain amplifier after this, it will have to give 100Watts.
The amplifiers performance is not just about gain it is also about a number of other requirements, output power being just one of them.