You need this
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On 12/4/2011 11:57 AM, k4...@fastmail.fm wrote:
Here's a good one. I have been having trouble with some rfi on a couple
of my wire antennas causing a slight echo in my ssb audio transmission.
I have no doubt it was the rfi causing it because as soon as I added a
coax rf choke right below the balun on the first antenna the echo went
away when using that antenna, but remained on the other two antennas.
The echo only showed up when I was using my MultiSwitcher which must
have been where the rf was causing the problem because if I plugged the
mic directly into the Flex, no echo. In addition, I could see the
unselected leds on my remote antenna switch control flicker when I
talked. All of these effects went away on antenna 1 as soon as the rf
choke was added.
So I was on a net on 40M the other night testing antenna number 3 (no rf
choke there yet at that time) and a station who checked in after me
proceeded to inform me that the echo on my signal was not caused by rfi,
but it was due to the latency/delay in my computer running the sdr. I'm
currently running the Flex on a Neal super computer and the average
latency is around 10 microseconds with some peaks up to a little under
50 microseconds - not too shabby. When I informed him that plugging the
mic directly into the radio eliminated the problem, he launched into
some highly technically suspect explanation about the lack of delay in
the MultiSwitcher offsetting the latency in the computer so the echo
disappeared. Nothing I said could change his mind. Now I'm wondering
which school he got his Phd from so I'll be sure none of my
grandchildren go there.
The good news is that after I added coax chokes to the other wire
antennas the echo and the flickering leds disappeared when using them
too.
The bad news is that there are still some technically inept hams out
there when it comes to sdr who may convince others of their erroneous
point of view.
73
Wayne
k4ELO
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