[TenTec] 238 Tuner Mod

[pfizenmayer]

Guess there must be 238's, 238A's  and 238B's - I have one I bought new 
circa Feb 2005 called 238B SN 09C10104 where the padders on the Schematic 
are shown as 2 each 220 pfd in parallel in each location.

The parts list says they are 180 pfd and my unit has 150 pfd. The variable 
cap is shown as 40 - 500 pfd.  I suspect the reason they kept sneaking the 
value of the paralleled caps lower and lower is that the stray inductance 
and the little network inserted to tune out the residual SWR makes the 
paralleled values look larger than the actual capacitance. And even at 150 
pfd paralleled in each section I have many cases where for instance LOZ-1 
will not quite match at max variable capacitance even on 80 meters and LOZ-2 
is too much capacitance.(var cap at minimum is too much )  No huge deal as 
the final SWR is less than 1.3 :1 but often thats as close as you can get.

Anyhow - I also suspect the paralleled caps instead of single caps helps the 
"drift" substantially . I have never noticed any drift with the settings I 
have to use with my dipoles at a kw. Usually in LOZ1 or 2.  On 160 the 
configuration I have makes me have to add another  CM45 2000 pfd  externally 
and using that I still notice no drift at a kw.

73 de Hank K7HP


----- Original Message ----- 
From: "Ron Castro" <ronc at sonic.net>
To: "Ten Tec List" <tentec at contesting.com>
Sent: Monday, March 03, 2008 4:28 PM
Subject: [TenTec] 238 Tuner Mod


>I few months back, I modified my TT 238 tuner by changing out the disc 
>ceramic caps with surplus Soviet military doorknob caps, which dramatically 
>improves the power handling capability on 160 and 80 meters.  Heating used 
>to cause the SWR to 'drift', even at 100 Watts in some situations on 160. 
>The mod worked well, and if anyone is interested, I have all the details 
>and pictures on my website at www.n6ie.com.
>
> 73,
>         Ron N6IE
>      www.N6IE.com
>
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