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Re: [Xylo-SDR] [Flexradio] Proof-of-concept successful!
Since I didn't exclude any reasons I don't feel that I should
respond on a changed set of conditions.
"If", "it's unlikely", "other than by reducing
system SNR", sounds to me that getting cable that matches is far
better than guessing, assuming, and hoping.
I wonder why they bother terminating it then?
Why don't we just use a power zip cord or speaker wire, it cheap, and
close enough.
At 03:03 PM 1/31/2006, Jim Lux wrote:
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
Cecil Bayona
KD5NWA
www.qrpradio.com
I fail to see why doing the same thing over and over and getting the
same results every time is insanity: I've almost proved it isn't; only a
few more tests now and I'm sure results will differ this time ...