Re: [Xylo-SDR] [Flexradio] Proof-of-concept successful!

[Jim Lux <James.P.Lux@jpl.nasa.gov>]

At 10:58 AM 1/31/2006, KD5NWA wrote:
> I wasn't talking about signal loss, reflections on the cable due to 
> improper impedance match can cause signal jitter.

How? If the system is stable, mechanically, then any reflections will be 
fixed, and will only manifest themselves as changes in the phase/amplitude 
seen at the load with respect to frequency.  It's unlikely that the 
frequency deviation in the source is wide enough that any sort of narrow 
band reflection phenomenon would be at work, except, perhaps in a 
pathological case.

Added jitter can only result from a modulation process, implying that some 
"second signal" is involved, be it noise that is added or multiplied, or 
some other effect.

Yes, a mismatch might make the uncertainty in a mate/remate situation 
greater, but while mated, the RF phase and amplitude through the mismatch 
will remain unchanged (although not necessarily the same as in the matched 
case).

In fact, a deliberate mismatch can make the system less sensitive to small 
changes in source or load impedance, although there are usually better ways 
to deal with this.

So.. explain a mechanism where a fixed and stable mismatch will introduce 
jitter or phase noise (other than by reducing system SNR).

Jim, W6RMK