For what it is worth. The 70Mhz enabled radios (C2) do not work well without modification.? Approx 12 watts output for 15 amperes current draw, and a very deaf receiver. Add spectral purity on the output signal that includes a signal at 48Mhz only about 4dB down.? The problems appear to be the wrong value of components fiited in filters on the TX side, and the requirement for a pre-amp make it an expensive way to get on 4. A friend of mine weighed it all up, and decided on a transverter from 10 metres, which works considerably better, and easier to implement.
Andy Bosworth