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Topband: Newbie question

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Subject: Topband: Newbie question
From: "Mark Lunday" <>
Date: Sun, 22 Aug 2010 21:07:14 -0400
List-post: <">>
OK, Topbanders, I have a mystery I am trying to solve with my inverted L

Last December, I put up ¼ inverted L (vertical was 80 feet, horiz was 52
feet).  Remote coupler at the base (CG-3000 Pi-L).  It was cold outside and
I was travelling a lot, so I only put down three radials?each 130 feet.  I
wanted to see what would happen, establish a baseline from which I knew I
could improve with more radials.

I have 200 foot of low-loss coax from the shack, but I still don?t want to
give up any of my 100 watts to SWR losses in the coax?so I use the remote

Well, the results were astounding on 160 for my first attempt?45 countries
with 100 watts, including lots of EU and a 4X at his sunrise.  I also heard
and worked some excellent DX on 80 with it.

In March, we had a horrific windstorm and the wire broke.  So I restrung it.

Since putting it back up, I was unable to get the remote coupler to tune the
inverted L on 160.  I tried changing the length of the wire to vary the
resistance/capacitance to see if that would be more coupler-friendly.  I
used lengths from 114 feet, 132 feet, and 174 feet.  No success.  I added
four additional radials.  Still no tune with the remote coupler.

So I decided to start a serious investigation.  Using an MFJ-259 tonight at
the base of the antenna, I see 1 ohm of resistance and 400 ohms of reactance
at 1.8 MHz, for a length of 174 feet of wire.   At 3.5 MHz, I see 25 ohms
resistance and 85 ohms reactance.

>From the readings, I have the following thoughts.  
*       I would expect a higher resistance with the longer wire above ¼
wavelength on 160, say around 100 ohms, because an end-fed ½ wavelength wire
should be seeing 5000 ohms.  Why the low resistance?
*       I would expect a much higher resistance with the wire on 80 meters,
maybe 500 ohms.  Not 5000, because it is NOT a half wavelength end-fed, but
certainly higher than 25 ohms
*       Even with just 6 radials, I should see 10 or 20 ohms of resistance
on 160

Any assistance/guidance appreciated.  I have time before 160 season starts,
but I want to be READY!  Thanks in advance

Mark Lunday


UR RST IS ... ... ..9 QSB QSB - hw? BK

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