Increasing Icom 910H deviation on 9600 setting?
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
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@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
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James Cutler