[Elecraft] Remote Antenna Tuner

[Darrell Bellerive]

Wow, great to see some discussion on the need for a remote antenna
tuner. Like Kurt, W7QHD, I have posted this a couple of times in the
past without a single reply.

Phil, you are right, "needs to be at the feedpoint" may be a bit strong,
but there are two scenarios I would like to consider:

-------------------------

Number 1: The use of a dipole antenna as a multiband antenna.

While some hams are lucky enough to be able to route an open wire feeder
into their shacks without compromising safety, or symmetry, and not have
stray RF in the shack, most hams are not this fortunate. Using coax has
it's problems as Vic, K2VCO, points out in his message. Some, like Don,
W3FPR, have long distances between the shack and the antenna.

Mounting a tuner at the feedpoint or at a convenient point where open
wire feeder can be used for the balance of the distance to the antenna
solves these practical problems.

A dipole is an inherently balanced system, and therefor a balanced
tuning circuit will produce optimum results. The quintessential document
on this was written by Richard L. Measures, AG6K, and appears in QST for
February 1990, pages 28 to 32. Richard describes a balanced L network as
the solution. Richard also describes the use of a balun to make the
conversion from the unbalanced coaxed to the balanced input of the
tuner. This way the balun will always be at it's design impedance.

------------------------

Number 2: The use of a random length wire as a multiband antenna.

This also applies to mobile whips. A balanced tuner is not required in
this case, but the same problems occur as above. Using coax between the
transmitter and the tuner will keep the RF out of the shack, and will
allow easy and safe feedline routing.

In a mobile installation, this prevents RF from getting into the vehicle
electrical systems, and reduces noise pickup. In a portable situation,
it allows easier routing of the feedline out of the tent or camper, and
keeps the RF out of the station equipment. Since the SWR is negligible,
a short length (25 or 30 feet) of RG-174 coax could even be used where
weight is an important consideration.

--------------------------

All antenna and feed systems are a compromise of one form or another.
The case for a remote tuner is one where the ease of feedline routing
and reduction in stray RF are outweighed by the increased cost and
complexity.

I can envision an antenna tuner controller/driver taking the space now
used for the antenna tuner in the K2. This interface would provide two
coax connectors, one to connect to the remote tuner and one that could
connect to an amplifier, conventional tuner, or matched antenna. For the
remote tuner all power and control signals would flow over the coax so
no control cable would be necessary.

Wayne and Eric, what are your opinions on a remote tuner or series of
remote tuners?

Darrell   VE7CLA   K2 #1973


On Sat, 2003-09-06 at 22:58, Phil Wheeler wrote: 
> Darrell Bellerive wrote:
> 
> >I concur wholeheartedly. The antenna tuner needs to be at the feedpoint.
> >
> 
> Where did you get such a strange idea re "needs"?  It may seem 
> intuitively obvious but it is not true.
> 
> 73, Phil
> 
>