[TowerTalk] 80m Newbie...Help w/ Inverted V Please

[Pete Smith]

I'm more inclined to think maybe there's an AM radio station somewhere 
nearby that is responsible.  I found that my 80 and 160 antennas are quite 
difficult to tune (160's impossible) with the MFJ-259 because of 
interfering RF.  I wound up carting a rig out to the base of the tower, and 
then everything went fine.

73, Pete N4ZR

At 04:51 PM 9/29/2004, Keith Dutson wrote:

>I have the Alpha-Delta 80 meter dipole as inverted V on my 150 foot Rohn 45
>tower.  It is suspended from 90 feet, and hangs off a short piece (about 4
>or five feet) of 1 inch PVC tie wrapped/taped through the tower (sticking
>out about 2 feet).  The legs are tied off at about 200 feet from base of
>tower.  It is direct fed with LMR400 coax.  VSWR is close to 1:1.  This
>antenna was installed several years back when guys were 1/4 EHS.  All have
>been replaced with Phillystran, but this change did not affect VSWR to any
>extent.  VSWR measurements were made with MFJ259, and later with MFJ269 that
>replaced it when it went south.
>
>I am wondering if your aluminum stand off is causing the problem.
>
>Keith NM5G
>
>
>-----Original Message-----
>From: towertalk-bounces at contesting.com
>[mailto:towertalk-bounces at contesting.com] On Behalf Of Robin Midgett
>Sent: Wednesday, September 29, 2004 3:14 PM
>To: towertalk at contesting.com
>Subject: [TowerTalk] 80m Newbie...Help w/ Inverted V Please
>
>Hi,
>My attempts to make an inverted V resonate on 80m are not meeting with great
>success. I've put up inverted V antennas before (10m & 40m) and they worked
>very well...not so in this case; 2.8:1 (feed point fully up) is the best
>match I've seen yet. I'm hoping some of you more experienced will have some
>constructive input.
>Here's the configuration:
>130' of Rohn 45G, on fairly flat, level ground with a 24" (out from the
>tower) aluminum stand off bracket at the 60' level. A rope and pulley rig is
>used at the end of the stand off to haul the feed point of the V up to the
>60' level.  Each leg of the V is ~62' long, and there is ~ 80-90 degrees
>between them. The ends of the wire (14 ga. stranded) are formed into a loop,
>which is where a small piece of rope attaches and anchors to a stake in the
>ground. Pretty typical stuff, from all I've seen before.
>The tower is guyed at 30' intervals to posts 85' from the tower base, so guy
>wire lengths (all 1/4" EHS) are 90', 104', 124' & 127', no insulators on any
>of them.
>With the feed point pulled up all the way, ~3:1 is the best match I get. If
>I lower the feed point to ~50', and the ends of the wires are drooped onto
>the lawn, the match improves to ~1.8-2:1.
>I'm using a MFJ-269 to make the measurements. I find really good matches
>(~1.5:1 or better) at 12 MHz, and odd multiples up the bands.
>I've changed the coax, no help. Removed the coiled coax choke; no help.
>Checked continuity from shield to end of one wire, OK; from center pin to
>end of the other wire, OK; no shorts, either.
>Is this possibly a case of guy wire coupling/interaction? Might raising the
>feed point to a higher level help the match? Should I extend the distance
>from the side of the tower to the feed point?
>Thanks,
>Lost in H.F....going back to VHF+....Robin KB4IDC
>
>"Success is the ability to go from failure to failure with no loss of
>enthusiasm." -Winston Churchill
>
>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
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>_______________________________________________
>
>See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless 
>Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with 
>any questions and ask for Sherman, W2FLA.
>
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