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



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