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5

SSB phone requires good frequency stability to be intelligible. Anything over 10Hz of frequency difference between transmitter and receiver and the signal starts to sound funny; beyond 50-70 Hz of error, intelligibility starts to drop. Hitting that target is more difficult at higher frequencies than at low frequencies. In the HF bands, getting within 10Hz ...


2

It looks like no one is going to answer this question and in the mean time i've found out was what wrong anyway so i am posting my own answer. Firstly after some more thinking it became obvious to me that the local oscillator has nothing to do with what the S meter reads, as the BFO injection is done in the product detector which outputs an audio signal and ...


5

It seems that FreeDV encodes the input audio signal in both the frequency and time domains, which means that the output signal amplitude doesn't follow the input signal amplitude, but rather the output level from FreeDV is always high, even with no input audio. Nah, that's not really the case. FreeDV uses a multicarrier scheme with 14 orthogonal carriers. ...


1

If you rely on detecting RF output to activate the T/R relay, you will be switching it while there is already RF output (obvious, I know...) this leads to two problems: the switching can cause a transient high SWR that may damage the exciter, and switching under power can cause arcing which damages the T/R relay itself. Even if it doesn't cause an immediate ...


0

As I understand you, your amplifier looks for a certain level of RF power at the input. If it is there, then the amplifier switches to active mode; if the RF power isn't at the input, then the amplifier switches to standby/bypass mode. The advantage of using that switching method must be that no secondary connection for a switching signal between the ...


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