[Elecraft] Remote Antenna Tuner

[David A. Belsley]

--On Sunday, September 7, 2003 8:03 PM -0700 Frank Alforo
<alforol@dslextreme.com> wrote:


> Nowhere does Maxwell say nor imply that with high SWR on a coax line, it
> does not matter where the tuner is inserted. In fact, he does say just the
> opposite, namely, the tuner is best placed at the antenna. line loss is
> minimized but, of course, not eliminated.
>
> 73,AL
>

Al:
  I'm not sure from your message whether you were intending to support my
comment or counter it.  In fact, you are saying exactly what I said.  So
I'll accept your support.

  Meanwhile, I am sending this message through the reflector since attempts 
to mail directly to Frank's address failed for reason "user does not exist".

thanks,

dave belsley, w1euy

>
> ----- Original Message -----
> From: "David A. Belsley" <belsley@bc.edu>
> To: "k6xr" <k6xr@bak.rr.com>; "Phil Wheeler" <w7ox@earthlink.net>;
> "Elecraft" <elecraft@mailman.qth.net>
> Sent: Sunday, September 07, 2003 5:05 PM
> Subject: RE: [Elecraft] Remote Antenna Tuner
>
>
>> 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,
>
>



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