[Elecraft] Remote Antenna Tuner

Sun Sep 7 20:11:00 2003

I agree that Maxwell's "Reflections" is a great piece.  But I do not 
believe he says at all what is stated by k6xr in the message below. 
Maxwell shows quite convincingly that, as long as there is a tuned circuit 
behind the high SWR, it will re-reflect the energy (repeatedly) so that all 
the applied energy goes into the antenna ***as long as there is no feed 
line loss.***  If, however, one is using a lossy line such as coax between 
the load and the tuner with a high SWR, some energy will indeed be lost in 
the feed line (repeatedly) and will not be sent on (repeatedly) to the 
load.  That is why, if one has a goodly length of coax between the tuner 
and the load, (as would be the case if one has an internal tuner in the K2, 
coax, and then the load), there can indeed be substantial loss in the coax 
when there is a high SWR in the coax. There can be substantial SWR in the 
coax unless one is operating on a qrg for which the antenna feed point is 
the same impedance as the coax's. The only way to avoid this is to put the 
tuner at the far end of the coax, either feeding the antenna directly or 
open-wire line, so that the K2 is looking into 50 ohms all the way through 
the coax into the tuner.  The the loss will then be minimal.  A remote 
tuner achieves this goal.  If the output of the tuner is looking into 
open-wire line, any high SWR there is of minimal consequence since the loss 
of open-wire line is so low.  Maxwell's piece is a fantastic addition to 
the literature, as long as it is not misinterpreted.

best wishes,

dave belsley, w1euy

--On Sunday, September 7, 2003 1:38 PM -0700 k6xr <[email protected]> wrote:

> this discussion is handled extremely well in a book by M. Walter Maxwell,
> w2du called reflections II and is available from world radio book store.
> He makes the argument and does the math that the tuner does not need to be
> remote.
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Phil Wheeler
> Sent: Sunday, September 07, 2003 9:05 AM
> To: Elecraft
> Subject: Re: [Elecraft] Remote Antenna Tuner
>
>
> Jim Campbell wrote:
>
>> Phil,
>>
>> It would be more helpful for me, and perhaps many on the list if you
>> explained why this is not true.
>> Would it be more correct if he had said "works better" instead of
>> "needs"?
>
>
>
> Not even works better.
>
> This is an old debate, long settled.  There are many web sites with
> discussions, books, articles, etc -- some quite erudite.  Frankly I do
> not have time nor energy to rehash it.   Perhaps someone else has the
> motivation.  Or you can use antenna and transmission line analyses and
> come to your own conclusions -- as I did once many years ago.
>
> In fact the xyl wants me to get off the computer and go hiking NOW  :-)
>
> 73, Phil
>
>
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----------------------------------
David A. Belsley
Professor of Economics