You will loose more then 20db on your 150 feet run.
Even with 600 ohm true open wire 15db are gone.
Tuner losses will add up on that.
With single section W8JK antennas the use of folded dipoles is recommended
to bring the impedance up.
73
Peter, DJ7WW
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Gary Slagel
Sent: Dienstag, 28. Februar 2012 16:11
To: Paul Christensen; TowerTalk
Subject: Re: [TowerTalk] balanced line loss on a mismatched antenna
Thanks Paul,
I've attached the Source Data output below. This, I believe, is showing me
SWR and impedance at the feedpoint of each element. I'm not sure if EZNEC
gives me a way to see the SWR at the single feedpoint that I'll use to feed
these two feedpoints but I assume it will be equally as bad.
I'm using the standard ARRL W8JK model that comes with the demo version of
EZNEC in the ARRL antenna book. I modify that model to look like what I
want to build and as long as I don't save it the software performs like the
full version of EZNEC. I'm over my head with antenna modeling as soon as I
move past modeling a dipole but I forge ahead and try and get as much useful
information as I can from it.
The question still is, if I get the antenna working properly how much loss
will I see on the feedline. Thanks much for your help.
EZNEC ARRL ver. 4.0
2/28/2012 7:53:59 AM
--------------- SOURCE DATA ---------------
Frequency = 7.05 MHz
Source 1 Voltage = 397.6 V. at -89.63 deg.
Current = 1 A. at 0.0 deg.
Impedance = 2.597 - J 397.6 ohms
Power = 2.597 watts
SWR (50 ohm system) > 100 (75 ohm system) > 100
Source 2 Voltage = 397.6 V. at 90.37 deg.
Current = 1 A. at 180.0 deg.
Impedance = 2.597 - J 397.6 ohms
Power = 2.597 watts
SWR (50 ohm system) > 100 (75 ohm system) > 100
Total applied power = 5.193 watts
Gary Slagel
KT0A
________________________________
From: Paul Christensen <w9ac@arrl.net>
To: Gary Slagel <gdslagel@yahoo.com>; TowerTalk <towertalk@contesting.com>
Sent: Monday, February 27, 2012 4:48 PM
Subject: Re: [TowerTalk] balanced line loss on a mismatched antenna
> "I think I can tune the antenna with the feedline and get it down to a
more reasonable level, maybe 10 to 1, at the tuner end. Then the tuner will
tune it to resonance so the xmttr can put its full load into.
> Question is, since the swr is 10 to 1 at the radio end of the feedline but
100 to 1 at the antenna end of the feedline, am I going to see the 3.5 db
loss from a 100 to 1 swr or the .5 dbi that a 10 to 1 swr would give me."
Gary, you can vary the impedance at the input end of the line, but not the
SWR. The SWR on the 450-ohm section will remain nearly constant over your
150 ft run, even with length trimming.
In EZNEC, what is the Z of the antenna you're modeling at the operating
frequency in an R+j format?
Paul, W9AC
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