[amsat-bb] Increasing Icom 910H deviation on 9600 setting?

James Cutler jwcutler at gmail.com
Fri Dec 23 20:21:00 PST 2011


Dear AMSAT,

Has anyone successfully increased the maximum FM deviation of the 910H when
using the 9600 setting on the radio?  We have not been able to.  We have
two units, and one is maxed at 2.5 KHz and the other at 3.2 KHz deviation.

We've used the service manual to adjust the deviation to max higher values
(>7KHz).  But, this doesn't affect the 9600 input path.  Looking through
the service manual, on  page 10-1 lower left corner, it shows that the gain
control we just set doesn't affect the 9600 path.

So, I'm thinking of modifying the over modulation detection circuitry to
allow for a larger peak to peak voltage signal to be input.  The components
that see that voltage appear to be able to handle it.

Has anyone tried this, or know of another way to increase the deviation?

73,

--James


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