ATU problem or Law of physics problem... I don't know which

[cptpatmcd]

Hmm....

I have a 66' (20m-ish) center fed dipole at 6 feet off the ground in my back yard.  The ATU in my KX1 reads P 0.3 and r9.9 at 7090 khz.  This doesn't look right to me.  Did I dork something up when I twiddled the knob?

[AC7AC]

CONTENTS DELETED

The author has deleted this message.

[cptpatmcd]

So, if I understand you right...  Sorry about getting OT here.

I can make it resonant by extending it about 1 foot on each end?

33 feet/x=7.09/7.3

x=~34

My main problem are junipers.  I can raise the antenna about 20' in the air but then the antenna is literally in the trees.  Would that create more problems that it solve?

Ron D'Eau Claire wrote

Such a low dipole will normally have, at its center, an impedance in the
general range of 4-j60 ohms at 7 MHz, so the "r" value you're seeing doesn't
seem surprising.

For all practical purposes it's "on" the ground and the earth has a very
large effect on its impedance and its resonant frequency. In that case it's
closest to resonance at about 7.3 MHz where the impedance will be close to
4.7+j0 ohms. The SWR bandwidth is very broad because of the huge resistive
losses of the earth. Even so, it should show pretty good performance as an
NVIS radiator for local contacts.

You didn't mention the type or length of feed line. Since it has a high SWR,
it will have a huge effect on the impedance the KX1 sees. For example, if
it's 50 ohm coax the SWR will be something like 33:1.

By comparison, the same antenna at 30 feet up will be self resonant at about
7.1 MHz where it will show an impedance of 70+j0 ohms, giving you an SWR of
less than 1.5:1 when fed with 50 ohm coax.

Ron AC7AC

-----Original Message-----

Hmm....

I have a 66' (20m-ish) center fed dipole at 6 feet off the ground in my back
yard.  The ATU in my KX1 reads P 0.3 and r9.9 at 7090 khz.  This doesn't
look right to me.  Did I dork something up when I twiddled the knob?
--
View this message in context:
http://www.nabble.com/ATU-problem-or-Law-of-physics-problem...-I-don%27t-kno
w-which-tp14555238p14555238.html
Sent from the Elecraft mailing list archive at Nabble.com.


_______________________________________________
Elecraft mailing list
Post to: [e-mail]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Vic K2VCO]

cptpatmcd wrote:

> My main problem are junipers.  I can raise the antenna about 20' in the air
> but then the antenna is literally in the trees.  Would that create more
> problems that it solve?

Not unless you mean mechanical problems. It will be MUCH more efficient
at 20'. Trees have very little effect on horizontal antennas. If you
have a choice, make the center the highest point.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com