Thanks Dave,

I agree that the third solution should work well. But I will not be able =
to test it until I will be back there, and this will not be before =
several months from now.

I have verified that my Daiwa tuner has plastic tuning knobs and that =
both variable capacitors also have a plastic tuning axis, so the =
proximity of my hand should yield a limited error on the tuning point.

73

Tony, I0JX

"KC1DI" ha scritto nel messaggio =
newsp.swlf240ncdad2j@elbc-crz2m9noal...
On Sun, 04 Sep 2005 15:21:01 -0400, Antonio Vernucci =
=20
wrote:
=20
At my summer QTH, I cannot do more than using a "stealth" thin-wire =

antenna.

For operation 40 through 10 meters, I had fairly good results using =
a =20
plain 30-ft wire and a tuner. But I do not like that solution =
because, =20
in my case, access to earth (water pipe) is not convenient.

So, I decided to switch to a symmetrical antenna that does not =
require =20
an earth connection. I have then mounted a square wire loop, about =
15 ft =20
each side, fed with about 5 feet of 450-ohm ladder line. The antenna =
=20
impedance varies a lot across the desired frequency range, but it =
can be =20
easily matched by my tuner on all bands.

The antenna being symmetrical, and the tuner asymmetrical, it is =20
advisable to use a balun. Three solutions come to my mind:
1) using an off-the-shelf (e.g. MFJ, Vectronics, etc.) toroidal =
ferrite =20
balun at the tuner output. I do not like this solution because, on =
some =20
frequency bands, the antenna impedance gets very high, and I am not =
sure =20
on how the RF transformer behaves under those conditions

2) putting an RF choke at the tuner output. The choke could be built =
by =20
winding several turns of 450 ohm ladder line over a fat ferrite rod =

(obtained by glueing several small rods to each other)

3) putting an RF choke at the tuner INPUT, by winding several turns =
of =20
the RG-58 cable connecting the transceiver to the tuner on a ferrite =
=20
rod. In this way the tuner body would be "hot", but this may not be =
a =20
real problem

Any comment on the pros and cons of the three approaches would be =20
welcome.

73

Tony, I0JX

=20
Hi Tony,
=20
I used the third method you mentioned for several years with good =
sucess.
I like that option because once the tuner is match the choke balun =
sees a =20
contant impedence and is not so likely to cause problems. However =
most =20
tuners use the opposite the Balun on the output. Except the new MFJ =20
balanced line tuner.
=20
in any event let us know what you come up with
73 Dave KC1DI
=20
=20
=20
=20
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