Dongle, The term "dual conversion" simply means that the receiver mixes the received signal, generally down in frequency, two (2) times in the IF strip portion of the receiver. Most likely those frequeinces would be to 9MHz first and then 455KHz. This occures prior to demodulation and provides selectivity, that is to say that the receiver is more imune to adjacient signal and image interferance. If you do not understand those terms let me know and I will attempt to explain them. As an alternitive you could go to your local library and read about receivers and FM communications in the ARRL hand book. The older ones like 1960's thru 1980 will be more tecnical as the amature community newcommers have been "dummed down" just like the rest of the education establishment.

In reference to the FM signal from the transmitter, the carier is always transmitted and upon a command input to the FM modulator the output of the transmitter is shifted in frequency. For narrow band the amount of shift is 5 KHz and wide band is usually, but not always, 15 KHz. This depends on application and the amount of inteligence required to be transmitted.

As to the ability to transmit back from the receiver you could read the section on "repeater design" in the afore mentioned reference source.

I hope that some of this will be of help to you and please excuse my spelling but I am a TEXAN HI HI.

If you should have any questions that I might answer you can "e mail" me @ [email protected]

73 fly the airplane first

Lee K5MRC