So how does one measure performance? Is it weak signal performance and the ability to hear signals from afar under less than ideal band conditions. Is it the ability to separate stations in a pile up? How good are the AGC characteristics? Is it the number of QSO's made or the percentage of responses to the usual CQ? Is the ability to stay on frequency? Is it the signal reports relative to signal strength and signal quality? Does it have a noise blanker?
In sum it is probably all of these and in reality an affirmative to all of these would probably mark a high end receiver and something beyond this project. The receiver hears well and most of the weak stations are heard. The radio does not have a noise blanker and there is no AGC. (Albeit the audio gain control does a pretty fair job and having the Receiver RF AMP switch selected does help --a lot!) The radio has been run driving my 3CPX1500A7 amp for 1 KW out and thus hearing the radio is not a problem. Signal reports typically comment on the FB audio although there is a tendency to favor highs. That is probably a result of the Heil DX Microphone Cartridge and the circuit parameters of the microphone amplifier.
Many contacts including stations in Spain, Australia and Japan were worked using 30 to 40 Watts. The audio reports were very good. In fact I broke a pile up on an EA station using only 35 watts. One day while running the the KW amp I was inundated with calls and about 15 stations in a row were worked. Imagine my surprise. Running 60 Watts with the 20M MMIC transceiver driving my 3CPX1500A7 Linear Amplifier I have worked stations in Ireland, Austria, Wales and England.
The original design objective was a shirt pocket sized transceiver. We didn't make that objective but we are getting closer. As of about three weeks ago I have been exclusively using the Drake TR-7 PTO and now have a digital display-- which is a must. The Drake PTO outshines the VTO in so far as stability and frequency coverage (full band).
I have also been using the radio on 75 Meters. For operation on this band I have a separate transmitter board complete with Receiver RF Amplifier and band pass and low pass filters.With this board two watts output are available. I have made several contacts with the radio using the outboard amplifier and again excellent signal reports. The difference from the 20M board is that there is no intermediate bi-lateral amplifier stage. None is needed!
I have rebuilt the 20M Transmit Power Amplifier stage at least five times and seem to be at a 1 watt plateau. Any more power and there is unwanted oscillation. I suspect that the board layout is a major factor. Using the outboard amplifier to drive the 3CPX1500A7 amp easily produces 1 KW --so that may not exactly be a problem from the home station.
But what about contacts at 1 watt? Well I think in total there have been about 5 contacts mostly out at 2000 to 3000 miles and typically they were an honest S5 signal report. So 1 watt at shirt pocket size is probably OK.
Given that the transmit board is a stand alone there is a good opportunity to build another transmit board the same size as the receiver board and see what happens. I am certain the RF chain could produce 3 or more watts without oscillation with attention paid to the layout.
How about smaller. I think the radio can be made smaller with the inclusion or more surface mount parts and using the mini-mill. For a really smaller radio that would mean a professionally made circuit board. Perhaps the whole radio on one single 3X4 board. The crystal filter would need to be a homebrew 4 pole to conserve space.