[TenTec] RF loss in antenna tuner

[Dr. Gerald N. Johnson]

On Sat, 2007-03-03 at 17:26 -0700, David Humelsine wrote:
> Greetings and such  I want to get back on HF so my plan is to call Ten Tec 
> Monday morning and order a Argonaut. For domestic and money reasons I plan 
> to keep the operation small (for now) so I need to decide on an antenna. 
> After a lot of though and study I have two ideas.  A steppIR smaller (10 
> thru 20 meter ) vertical mounted on the shack roof or one of those fiber 
> glass push up poles clamped to the back yard fence and about 25 feet of wire 
> over to the roof of the shack and one of the new MFJ 926 tuners or an SGC 
> 230. That should give me 10 thru 40 meters.  But I am concerned with power 
> loss in the tuner.  My main interest are PSK31, CW and Rtty. With only 20 
> watts to start with how much can I expect to loose in the tuner?  Please 
> reply to
> n5wmqmail at comcast.net
> 
> thank you
> David 
> 
I prefer a center fed wire to the vertical or inverted L. It cuts down
on RF received from the shack computer and the home TV set.

I've run several Field Days with a bare 8' whip on the top of my little
Airstream with a L match tuner inside the trailer. And I've worked many
contacts during FD with the rig turned down to 25 watts output. 40
through 10.

Tuner loss is least when the impedance transformation is closest to 1:1.
And highest when the tuner is dragging something obnoxious into
resonance. Tuner loss is greater when the tuner is compact, least when
the tuner coil is large.

Your SteppIR or SGC tuner options are not low cost. A wire from front to
back with that fiberglass support fed with a manual tuner and some
ladder line is least expensive and effective. You do have to develop a
little skill in tuning, but that's not hard to learn. Use something in
the 300 watt MFJ tuners, but look for enough SWR meter sensitivity to
work at 20 watts, some may not be that sensitive. I build all my own
tuners but have used some of the MFJ on occasion at club FD stations and
they did work decently.
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer