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

[Pete Smith <n4zr@contesting.com>]

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@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Robin Midgett
> Sent: Wednesday, September 29, 2004 3:14 PM
> To: towertalk@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.
>
> _______________________________________________
> TowerTalk mailing list
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> http://lists.contesting.com/mailman/listinfo/towertalk

_______________________________________________

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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