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I am repairing an IC-761 for a friend and I noticed something odd.? Does anyone know why the frequency changes when switching modes?
For example, here is what I get when switching modes:
LSB? 7.260MHz
USB? 7.257MHz
CW? 7.2594MHz
RTTY? 7.2594MHz
AM? 7.260MHz

I ran into something similar with a radio about 25 years ago.

I think it was a Kenwood, I think the issue had to do with RIT/XIT not being zeroed or set to track properly, essentially adding an offset of a few kHz. I only ran into the issue once, and the recollection is vague at this point.

It could be a place to look.

Kurt

I believe these are set so that the SSB modes use the passband of the crystal
filters since there is a 3 KHz difference on SSB (the nominal passband is 3 KHz
on many radios, tighter for SSB-Narrow, often 2.7 KHz. For CW, it's probably
arranged so that the received code has a certain note to it (this can be changed
if you have a RIT control).

RTTY is probably where it is for a similar reason and AM so that the lower side
fits in the LSB crystal filter passband.

That's my guess, based on seeing similar discussions in other brand radio
groups. In other words, I think this is all normal. I believe that in normal
operation, the operator is not going to see any problems.

Is this one of the Icom models that require a backup battery to be changed every
several years? If so, consider adding two clip-in battery holders in parallel
and removing the original one. That way, you can have one battery in a removable
holder. When it's time to replace, put a fresh one in the other holder and
remove the old one. You can put a date on the coin cell where it can be seen
when it was changed, or a tag on the back of the radio telling when the next
battery replacement is due. Just a thought. Some of those, when the battery
dies, the programming for the main board dies with it. I believe those can be
reflashed, but Piexx makes a replacement board with ROM instead RAM backed up by
a battery.


Donald KX8K


On Sat, 08 Mar 2025 19:50:47 -0800, "Greg Miller via groups.io"
<gtmiller76@...> wrote:

Hello all,

I am repairing an IC-761 for a friend and I noticed something odd.? Does anyone know why the frequency changes when switching modes?

For example, here is what I get when switching modes:
LSB? 7.260MHz
USB? 7.257MHz
CW? 7.2594MHz
RTTY? 7.2594MHz
AM? 7.260MHz

I've gone through and done all of the alignments and everything is set correctly.? I would think that the radio would just stay on the frequency it's set to like most radios do?

Thanks and 73,
Greg K2GTM

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