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

[James Cutler]

All, for anyone interested, we figured out how to increase the FM deviation
of the Icom 910H.  It takes a fairly simple single resistor change to the
rig.  A brief overview is online.  Thanks to all those who offered comments.

http://exploration.engin.umich.edu/blog/?page_id=668

--James, KF6RFX



On Fri, Dec 23, 2011 at 11:21 PM, James Cutler <jwcutler at gmail.com> wrote:

> 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
>
>