[Premium-Rx] real basic question on stability etc.

[John P Ceresole]

Hi Eugene

Tracking receiver is ok with input signal derived AFC whilst this works 
well with a good signal to noise ratio AND a continuous signal as you 
correctly point out FM, PM and AM signals but useless on SSB, CW (Morse) 
owing to their intermittent presence.  WJ got around that problem (I've 
only just twigged why they did this when thinking about it) by introducing 
their DAFC (Digital AFC) which holds the LO steady during the "quiet" 
periods of the received signal.

30 MHz to 1 GHz is actually a fairly interference free frequency range but 
in the presence of interference in the 1 to 30 MHz range (eg PLC and ADSL 
over aerial telephone lines) I am not sure that standard analogue AFC would 
cope with a low wanted signal to noise ratio DAFC certainly would provided 
that the digital loop was adjusted to be low sensitivity to interference.

Interesting ideas.  I have never played with either AFC or DAFC rxs but I 
have the luxury of an Rx with a long term LO accuracy better than 1 in 
10E10 and any transmitter I used would have a similar synthesiser 
performance (settable to better than 1 Hz in 100 MHz)

Best regards

John G8 BSD