[Amps] Ten-Tec Titan 10 Meter Input SWR

[donroden at hiwaay.net]

"True SWR" doesn't change, but *WHERE* it is measured will vary widely.

exception :  perfect Z load for perfect Z line where Zload=Zcoax

You are measuring VOLTAGE inside the coaxial line and the voltage  
varies along the length of the line like a sine wave.

Some distances from the wrong Z load = peak voltage
Some distances from the wrong Z load = minimum voltage
Some distances make for a close-to-perfect input match.
1/4 wave away from the above perfect match is a point that
your transmitter probably won't like.

In other words, changing the coaxial length *COULD* improve
your situation, but it could also make it worse.

The Smith Chart is your friend, or just make five jumpers of  
1,2,4,8,16 feet with a handful of couplers and start substituting  
jumpers between the meter and the load.   One combination will *MATCH*  
or make a length that the transmitter likes.   Others will make it  
worse.

This is why it's important to measure the Z *AT* the load and not  
through an arbitrary length of coax.

Don W4DNR



>> ##  On a related note,  why is it, when I increase the length of 50  
>> ohm coax  from my drake amps to the xcvr, that the
>> input swr rises ??   Its flat  with  4 ft or less.... but rises  
>> when say 5-8 ft is used.  Thats on all bands.
>
> <REPLY My understanding is that's a false reading caused by current flowing
> on the outside of the coax braid. The true SWR does not change.