Robert Ladden <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Hello all,
I just got my C-Line out of the closet after 25+ years of storage. They
seem to work OK. I've been playing with them with a dummy load (antenna not
up yet) and the one obvious problem I had is the carrier balance. The watt
meter showed power going out on SSB LSB with no speech. The instructions
for adjusting the carrier balance in the manual is not too good, so I
searched and found K2CU's wonderful instructions, which I pasted below for
safe keeping.
I found that I had to turn C6 completely clockwise to bring down the
carrier signal when tuned in on the receiver. But it does pass K2CU's
balance test procedure. I can eliminate the carrier completely with C6
(fully clockwise) and R21 (somewhere in the middle, it turns a lot).
C17 did not seem to do much. It may have improved the voice quality. At
first LSB sounded bad. After really turning C17 a lot, it seems to be the
same as USB.
I have yet to get the rig on the air and test with a real person. But I am
concerned that I needed to turn C6 to its extreme. I also note that the
carrier is completely gone. I also discovered that the spot signal is gone.
It is just a teeny noise on LSB and a very very weak carrier on USB. Not
really usable. It did generate a signal before I did all this.
So did I do good? Or does this rig need a lot more tweaking?
73,
Bob Ladden WA3WQB
K2CU's original message follows:
RE: [drakelist] T-4XC Carrier Balance Question
Robert Schenck
Mon, 29 Dec 2003 05:09:54 -0800
HI Mike,
Welcome to the world of the Drake equipment!
There ar ethree adjustkments that you ahev to do to correctly balance the
carrier.
They are C6, Carrier frequency trim, R21, carrier balance, and C17 Carrier
balance/phase. You should firest check that the carrier frequency trim is
correct.
the idea with this adjustment is to place the carrier on the same point of
each
sideband filter skirt. that is, to be just as far down on the lower skirt
of the USB
filter as you are on the upper skirt of the LSB filter. This is usually
done by
deliberatly unbalancing the modulator so that carrier leaks through. You
measure the
amplitude of the carrier on a test receiver and compare the level between
the USB
position of the T4X SSB switch and the LSB poisition. The carrier amplitude
should be
close to the same as posible. BY adjusting the carrier frequency trim, you
set the
carrier to the correct frequency for both modes. I would only mess with
this if there
is more than an S unit difference.....
Then you can adjust the carrier balance pot, R21 for minimum carrier. you
have to also
adjust C17 the carrier pahse. Note that you should check for balance in
both USB and
LSB modes. you will have to adjust the trimmer, C17, for optimum carrier
null for noth
sideband modes, and to has to deal with the slight difference in reactance
reflected
back from the selected filter. Now, if you only operate 20 Mtr USB, for
example, you
could just tweak it for USB. Same is true for LSB only on a l;ower band.
But, it is
best to balance it for each mode.
Hope this helps.
73's
Rob K2CU
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