Strange behavior when tuning around with SUB receiver LINKED

[w4ish]

James,
I, too, have noticed what I believe you are noticing.  It seems to me  
that the jumps in the tracking of VFO A and VFO B occur at the  
transitions of the bandpass filters.  It is as if when the bandpass  
relays switch, the VFOs lose their synchronization. (Of course, I  
could be wrong, but it seems that way to me)  I tried to discover the  
repeatable conditions for its occurrence, but other than quickly  
tuning the main VFO knob over large excursions of frequency with  
linked VFOs, I could not discover any real reason for the occurrence.

Concerning the motorboat zipper noise, I have 8 pole filters in both  
the main and sub receivers, but they are evidently not exactly  
matched.  When I tune quickly, the phase difference between the two  
receivers, due to the tuning delays in the VCOs kicks in and causes  
the motorboating.  As soon as I stop tuning, the phase differences  
come back into sync (or nearly so) and I do not have the  
motorboating.  Now if there is a tutorial which describes how to find  
the actual offset of the 8 pole filters out there, we could find the  
offsets and adjust them accordingly, and be rid of that problem.

That is my diagnosis, and I'm sticking to it (at least until the true  
reasons are discovered.)

Bill
W4ISH -- With my call, you only have to know half the Morse Code --  
Just the Dits.
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[w4ish]

Looks like I may not be sticking to my explanation after all.  Try  
this and see what you get:
WITHOUT the SUB Receiver linked, tune the main receiver to 6.000.000  
MHz.  Be sure you can see the frequency of the Sub Receiver on VFO B  
area and the tuning rate is FINE.
Push A>B twice to synchronize the two VFOs.
Now tune the main receiver to 5.999.999 MHz.  You should hear a slight  
click.
Look at the frequency of VFO B.
Mine read 5.346.50 while the main receiver still read 5.999.999
Now tune back to 6.000000 on the Main Receiver.
Both VFOs on my K3 read 6.000.000
mmmmm...... something fishy here!

Any explanations, anyone?

Bill
W4ISH

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[K2QI]

Hi Bill,

Tried your experiment, and my main VFO jumped to 5.069.029 while the sub VFO
stayed at 5.999.99.  This was with both receivers linked.

Trying the experiment again, this time with both VFO's unlinked as you had
requested, when I tune to 5.999.999 on the main, the sub also goes to
5.999.999.  However, tuning back up to 6.000.000, the sub VFO readout now
jumps to 6.056.95.  I could hear the relay clicking during both experiments.

As for my motorboating issue, this is not something that you hear if you
just let the receiver sit at 5.000.000.  Instead, the noise only appears
when you turn any VFO or filter knob... if you turn the VFO knob quickly
enough, then it sounds like a motorboat.

This happens from approximately 4.899.91 to 5.102.35

What's really weird though is that if I happen to come across a broadcast
station anywhere between those frequencies, then the motorboating noise will
stop until I pass the station.  After that noise picks up again... it's as
if the receivers don't know what to do with themselves when there's no
signal received between those frequencies, and they decide to inject noise
until another station pops up, or you reach the end of this particular
frequency area.  Now if I stop turning the VFO, then no noise... just band
static.

I uploaded a video that will need VLC to play back.  I hope you can view it
and give me your thoughts.

73,
James KC2UEE

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of William Evans
Sent: Sunday, February 22, 2009 7:54 PM
To: William Evans
Cc: [hidden email]
Subject: Re: [Elecraft] Strange behavior when tuning around with SUBreceiver
LINKED

Looks like I may not be sticking to my explanation after all.  Try  
this and see what you get:
WITHOUT the SUB Receiver linked, tune the main receiver to 6.000.000  
MHz.  Be sure you can see the frequency of the Sub Receiver on VFO B  
area and the tuning rate is FINE.
Push A>B twice to synchronize the two VFOs.
Now tune the main receiver to 5.999.999 MHz.  You should hear a slight  
click.
Look at the frequency of VFO B.
Mine read 5.346.50 while the main receiver still read 5.999.999
Now tune back to 6.000000 on the Main Receiver.
Both VFOs on my K3 read 6.000.000
mmmmm...... something fishy here!

Any explanations, anyone?

Bill
W4ISH

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