Brian,
The 1st IF (hardware) AGC is highly dependent on the width of the
'roofing filter'. We do not have the relevant figures for the relative
dynamic range of the 8.215 kHz IF vs. the 15 kHz DSP portion of the
receiver.
When those specifics are available, your question can be answered. For
now, I only assume that a narrow filter will be the best solution for
AGC 'pumping' when operating digital modes.
The capability to demodulate PSK31 and RTTY signals and the AGC
'pumping' situation are entirely two different animals. One thing is
for certain, the AGC cannot be totally controlled by the DSP section, so
the real answer depends on the actual dynamic range that the A-D
conversion can handle - we don't have that answer yet.
73,
Don W3FPR
Brian Lloyd wrote:
In playing with PSK31 recently using a *very* suboptimal receiver (my
old Icom IC-706mkII) I realized how important it is to couple the
demodulation system with the the rest of the receiver. For example, I
can watch the AGC respond to unwanted signals and make the desired
signal uncopyable. So it seems to me that, in the process of
demodulating a signal the demodulator has information about the energy
in the desired signal that should be used to drive the AGC. That implies
to me that you really cannot effectively separate the two. The "sound
card plugged into the radio" approach is interesting as a way to start
but it is not the final solution.
One of the interesting features of the K3 is that PSK31 and RTTY
operation are part of the radio. Does that mean that the PSK31 and RTTY
demodulators in the K3 control the AGC so that the desired signal and
only the desired signal controls AGC?
As we come up with more and more interesting digital modulation schemes
for HF I can see the desire to closely couple the demodulator with the
rest of the receiving system. The K3 has some real possibility here.
Will it be incorporated?
How about an API to let other programmers add demodulators and couple
them to the rest of the receiver, controlling roofing filter selection,
AGC, etc.?
73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
