[TenTec] MFJ Filter to work on TT540

[Mike Hyder -N4NT-]

I believe you are mistaken about using an audio filter external to the rig. 
The 540 and 544 derive their AGC voltage from audio.  If the filter is not 
in the circuit before the AGC sampling point, then although it may attenuate 
the volume of unwanted signals, they will still pump up the rig's AGC 
voltage.  That is not satisfactory.

73, Mike N4NT

----- Original Message ----- 
From: "Hulett, Russell" <rhulett1 at consolidated.net>
To: <tentec at contesting.com>
Sent: Friday, September 03, 2010 4:53 PM
Subject: Re: [TenTec] MFJ Filter to work on TT540


> Well, the connections used by the TT245 in the TT540 aren't like the 
> header shown in the MFJ info.  The 245 has 7 vector pins spaced about 1/4 
> inch apart.  FWIW, I built a clone of the TT245 for my 544.  You could use 
> vector board to just wire one up, but had a PCB fabricated for mine. 
> Works same as the original.
>
> BTW, the TT245 isn't in the IF, it is an audio filter.  An outboard filter 
> like the NEscaf or MFJ751B would do as well, plugged into the audio output 
> jack.