I have an RF Amplifier kit that is not working. The main problem is that the input transformer presents the radio with a high, unexpected SWR. It does amplify, so something works.
The transformer is wound as a T2:T.5 turns radio. The below pictures display it. I suspect that it might have a blob of solder shorting out part of it inside or a wire is cut.
I really do not know, the circuit is a simple class ab amplifier with mosfets and feedback.
I plan to unsolder various resisters and capacitors and feed an input signal into the transformer directly and see what come out the other side.
I have an oscilloscope and cheap ebay signal generator. The signal generator I have can produce up to a 25 Mhz output into an open. Meaning, not into a 50 ohm load, like the usual signal generator. If I attach a load, it should reduce the signal generator output. Is the transformer a load, how much?
I am planning to operate this around 7.2 or 14 Mhz.
If I hook the signal generator to this transformer, will it be able to produce an output that I can measure? Should I use am op amplifier / follower circuit to increase the power/buffer between the signal generator and the primary?
The input transformer is usually directly connected to the 50 ohm output of a transceiver.
I would expect to see outputs that are 25% of the input signal 180 degree phase reversed.
I would like to do experiments to see what the swr is and how the later mosfet , class ab amplifier (with the feedback) affects it. I suppose there is a way to do this by way of loadng the secondary?
Ideally, I can gather enough information to model this in LTSPice. What this transformer is doing and its impedance is key.
Can I send my signal generator input into this transformer and get a useful measurement/learn something for ltspice? Any other advice? Thanks