[Elecraft] High SWR problem

[David A. Belsley]

>> Edward:
>> You don't give a lot of information to go on.  I gather your antenna is
>> 20 meters long.  Is it end fed or otherwise.  Supposing it is end fed,
>> does that length include the feed line? or do you have a wire coming
>> from your K2 that is 20 meters long total?  If the latter, that length
>> wire is going to present a very high impedance on 40 meters (where it is
>> a half wave) and above.  Perhaps the impedance is too high for your
>> tuner to handle.
>>
>
> It's end fed (is there anyother way to feed a longwire ?)

Sure, you can feed a wire anywhere you want.  Doing so is an effective way 
to change the input impedance.

> and it's 20m long plus it's fed by some low-loss coax (with a balun).

What are you doing with the shield side of the coax?  And how long is the 
coax? Assuming the shield is unconnected at the antenna side, and the coax 
is longish relative to the operating frequency, it is going to act somewhat 
like an extension of the length of the antenna. How effectively it is 
acting as coax is problematic, and there will likely be a good deal of 
common mode current flow in the shield as well as the center wire.

>

>
>> If you are unable to get an end fed 20 meter wire tuned, you might try
>> something that is not resonant with a high impedance at the end.  A 40'
>> or a 100' wire will often behave nicely.  Or, use the 20 meter wire with
>> a feed line whose length you can vary.
>>
> OK.
>
>> If you are using an end fed antenna, by the way, be sure to use an
>> appropriate counterpoise to get maximum effectiveness from the antenna
>> and maximum comfort in the shack -- you could otherwise end up with a
>> lot of stray RF in the shack.
>>
>
> Counterpoise == rf earth ?

Well, not really; an RF ground, perhaps, but not an earth since it has 
nothing to do with and no connection to the earth.  A counterpoise is 
anything that presents a very low impedance to the RF at the frequency of 
operation.  This is usually accomplished using a wire that is 1/4 wave 
length long at the op qrg.  Some tuners have an "artificial ground" which 
simply allows the cp to be tuned to achieve this low impedance without 
having to have separate cps for different operating frequencies.
>>
>>
>> ----------------------------------
>> David A. Belsley
>> Professor of Economics
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>



----------------------------------
David A. Belsley
Professor of Economics