[TenTec] Model 238C Tuner Questions

Steve Hunt steve at karinya.net
Tue Oct 16 16:27:03 EDT 2012

It might or might not be a high impedance load for the tuner, depending 
on the length of the ladderline. For example, an 80m half-wave dipole 
used on 40m will have a feedpoint impedance of 4000 Ohms or so; feed 
that through an electrical quarter-wave (or odd multiple) of ladderline, 
and the tuner will see a load of about 40 Ohms. With careful choice of 
feedline length you can usually avoid impedances that are either outside 
its matching range, produce high losses, or create excessively high 

After some tests on losses and current balance, I now feed my 
doublet/ladderline combination from my 238 tuner using an external 1:1 
current balun rather than the internal 4:1 voltage balun.

Steve G3TXQ

On 16/10/2012 20:56, Rick - DJ0IP / NJ0IP wrote:
> Bob,
> I agree with you but let me play devil's advocate...
> There are those who say a center-fed dipole, say for 80m, fed with openwire,
> with have a high impedance on its even harmonic - a couple thousand Ohms.
> Doesn't this result in excessive power loss in the matchbox?

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