Trevol, the portion of the coil between the tap and the base of the vertical
determines resonance and needs to be variable unless you were lucky and found
the correct value. The shunt portion of the coil affects the feed impedance.
This shunt portion is like the hairpin match for a yagi. You select the series
inductance to make the antenna slightly capacitive and adjust the shunt
inductance to raise the feed impedance. Both these moves interact. Use a clip
lead to vary the inductance of the series coil.
Cheers,
Ron N9AU
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of MR TREVOR
DUNNE
Sent: Wednesday, November 01, 2017 12:12 PM
To: Wes Attaway (N5WA)
Cc: topband List
Subject: Re: Topband: 160m Vertical matching Help
Hi Wes
Thanks for the reply I can move the point of lowest SWR by moving the tap on
the coil, I need to lower the SWR I thought using the coil across the feed
point would do this but its not working for me??
Thanks
Trevor
EI2GLB
----- Original Message -----
From: "Wes Attaway (N5WA)" <wesattaway@bellsouth.net>
To: "MR TREVOR DUNNE" <ei2glb@eircom.net>, "topband List"
<topband@contesting.com>
Sent: Wednesday, 1 November, 2017 17:02:55
Subject: RE: Topband: 160m Vertical matching Help
Without doing any modeling, an off the top of the head idea, one option would
be to drop a wire down from the end of each of the T wires you have at the top.
You might be able to move the point of lowest SWR down to 1.8 with 2x 15' +/-
drop wires.
-------------------
Wes Attaway (N5WA)
(318) 393-3289 - Shreveport, LA
Computer/Cellphone Forensics
AttawayForensics.com
-------------------
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of MR TREVOR
DUNNE
Sent: Wednesday, November 01, 2017 11:54 AM
To: topband List
Subject: Topband: 160m Vertical matching Help
Hi All
I finally got the vertical up and running, problem I have now is I can't find a
low SWR on the coil, the best I can get is about 2.8:1 no matter where I tap
the coil that's the best SWR, I can move that point up and down the band by
moving the tap but the SWR stays the same,
My current set up is about 55ft vertical I have 2 loading wires in a T shape,
wires are 50ft either side of the vertical and the are pretty level and in line,
I have 38 radials averaging about 45-60ft long, I will add more when time
allows but don't the make the SWR worse ??
With no coil I get resonance at 2.12mhz with R=16 X=2 on my MFJ269,
The coil is 25ft of 5mm copper brake pipe in a 4" diameter, the coil is
attached to base of the vertical and the other end is grounded,
Any pointers on what I can do to get a better match,
Thanks
Trevor
EI2GLB
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