[ICOM] IC-706MKII low FM audio adjustment

[gfiber at comcast.net]

Dana,

Generally you have to change the mic amplifier circuit to boost the mig gain. The Max deviation adjustment limits the deviation to 5 KHz. 

Without seeing the service manual I think the 3.5 KHz deviation pot may be for the narrow FM mode which generally limits the narrow FM deviation to 2.5 - 3 KHz.

In the past some of Icom's 2 meter transceivers had 2 deivation adjustments like the 706MKIIG, one appeared to be a mic gain. I think the IC-27 was that way. If I were to pick on one to try I would pick the 3.5 KHz diviation control. 

Gary K8IZ
 -------------- Original message ----------------------
From: "Dana Luke" <danaluke at maine.rr.com>
> 3/24/2006
> 
> QST to anyone who might know how to adjust the FM audio level on an 
> IC-706MKII,
> 
> I have an IC-706MKII (not the G model) which seems to have low audio when on 
> FM using the stock HM-103 hand mike.  I've had the rig 6 years now but never 
> used it much on FM so it wasn't a problem but now I'd like to use it on FM 
> more.
> 
> When I have the mic gain set to 10 the audio is just barely acceptable if I 
> speak loudly into the mic.  On SSB I can run the unit at a mic gain of 6 or 
> so and it's OK.  I tried a different HM-103 mic with the same results so 
> it's not the mic.
> 
> Inside the unit there are two adjustment points, labeled FM MAX DEVIATION 
> (R274) and FM 3.5 kHz DEVIATION (R260).  I have a feeling that adjusting one 
> of these will fix the problem.  I don't want the rig to deviate more than 5 
> kHz and go out of the passband of the repeater receiver, and I'm not clear 
> as to which one of these adjustments will bring up the audio gain without 
> making my signal more than 5 kHz wide.
> 
> Can somebody please advise me as to which one to turn?  Thanks!
> 
> 73 de Dana KA1PK
> 
> 
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