Posted by
w4ish on
Mar 09, 2009; 11:09pm
URL: http://elecraft.85.s1.nabble.com/Curious-about-the-whooshing-tp2452198.html
Hello fellow Elecrafters.
I have a question about which my curiosity is just getting the best of
me. When I have the Sub Receiver on, linked, and all parameters the
same between the two receivers, and I have the Balance control set in
the middle, and then tune quickly across the band, sometimes it has a
"whooshing" sound which makes it difficult to tune and listen. As I
slow down, the whoosh gets much less noticeable, but it is still there
as the tonal quality seems to slowly shift from bass to treble.
I have 2.8kHz roofers in both receivers as well as AM filters in both.
All filter frequency shifts are set to 0.0, but I'm guessing that
there is a slight phase difference between the two receivers and when
they are tuned, the time differential in both VCOs settling down
varies enough to make a noticeable difference. If I go to CONFIG:FLx
FRQ and change the setting from 0.00 to 0.01, I can get the same
effect without having to tune the two linked receivers. Of if I
simply listen in either LSB or USB for a long time on one frequency, I
can hear the background hiss tone going from bass to treble and back
again at a very slow rate (This is most noticeable when no signal is
within the passband, but who, in their right mind would use a Ham
Transceiver to monitor an empty frequency!-- ooops, I guess that would
be me!)
Anyway, is my assumption about the phase difference between receivers
a reasonable explanation, and/or is there anything I could do to
eliminate the effect? BTW, without an antenna (or the wrong antenna,
e.g. an 80 Mtr Dipole on 20 Mtrs), I cannot perceive it, but with a
resonate antenna, the phenomena appears. I am using the same antenna
on both receivers.
Am I far off base on my assumptions, or is there a simple explanation
which I have not thought of yet?
Just Curious
W4ISH
Bill
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