[ICOM] Inrad filter mod for IC-765

[paul at w8aef.com]

1 KHz seems to be a little far off for not completeing the alignment when 
replacing ssb filters.  I would expect maybe 100 or 200 Hz would be closer 
to normal.

I believe the purpose of Inrad's alignment is to center the audio passband 
into the filter passband.

I don't remember the exact frequencies but as a for instance let's say they 
are 300 Hz and 2.5 KHz for a 2.2 KHz ssb filter.

You generate an audio tone at 300 Hz that would produce 50 watts out of the 
radio (rf output control and maximum and into a dummy load).

Then you generate a 2.5 KHz tone at the same level and observe the output 
power.  If it is 50 watts you are done.  But if it is not then you adjust 
the carrier oscillaor frequency such that the power output from the radio is 
equal when you generate the 300 Hz and 2.5 KHz tones.

And then do the same for the opposite sideband.

The reason for using the audio generator and the 50 watts output is so that 
receiver agc and transmitter alc will not mess you up.

Then when you switch between sidebands the receiving station will (should) 
hear the same audio response.

And your dial frequency may or may not indicate your actual carrier 
frequency.

It's been 12 or 13 years since I did this so be sure and refer to the 
instructions that came with your filter.

My experience with the original Icom filters in my 765 was not good, but the 
Inrad filters worked fine.

de Paul, W8AEF

----- Original Message ----- 
From: <dmeitzen at comcast.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Sunday, January 08, 2006 10:09 PM
Subject: Re: [ICOM] Inrad filter mod for IC-765


Thanks for the answer. The question is if you do not do the alignment will 
the unit seem to be off frequency to the receiving station? I have been 
getting complaints that I am about 1Khz low?
Thanks
Dave

-------------- Original message -------------- 
From: <paul at w8aef.com>

> Not sure which filter mod you are talking about, but could it be 
> installing
> Infrad filters and the subsequent alignment using an audio generator?
>
> I did that about 10 years ago to a 765 and it is a rather involved
> procedure.
>
> de Paul, W8AEF