[TowerTalk] 160M DIPOLE USIGN COAX

Fri Nov 11 12:40:15 EST 2005

Hasan:

     My tower has a moderate ground field underneath it as I also use the tower with a shunt-feed gamma wire on 160M.  I have about 135 feet of #2 copper wire and a dozen copper ground rods in the earth for lightning grounds.  Perhaps that's why I've been lucky with the sloper wire on 80M.

     But I've read the results of modeling from others here on TT.  Their models  show minimal current flowing in the tower below the connection point for the shield and nearly equal currents flowing in the slant wire.  (Check Tom N4KG's  posting that I've cited several times recently:  http://lists.contesting.com/archives//html/Towertalk/2002-01/msg00186.html .)  

     Irregardless, the sloper works for me and it allows me to operate on 80M  from a relatively small property.  And its cheap!

73 de
Gene Smar AD3F
P.S.  I wrote irregardless just to cause a stir among language purists.  

> When I have used and modeled this antenna I found that the wire is not such 
> much a radial, as a "slant wire feed" for the tower. The tower/beam/etc are 
> in fact doing the radiating and the wire is just the feed method. If you 
> look at the currents, you will see very little current in the wire, and a 
> LOT of current in the tower. Makes for a very good antenna, actually.
> 
> However....one needs to put a full radial field down at the base of the 
> tower, just like for any 1/4 wave vertical.
> 
> 73,
> 
> ...hasan, N0AN
> ----- Original Message ----- 
> From: <ersmar at comcast.net>
> To: "J. Hector Garcia XE2K" <hector at telecom1.net>; 
> <towertalk at contesting.com>
> Sent: Friday, November 11, 2005 11:06 AM
> Subject: Re: [TowerTalk] 160M DIPOLE USIGN COAX
> 
> 
> > Hector:
> >
> >     Many folks have asked on TowerTalk in the past about using coax for 
> > shortened ground radials, using the VF to shorten the required length. 
> > That doesn't work.  The VF is important only when using the coax as a 
> > transmission line, NOT when you want to use one conductor as a single 
> > wire.
> >
> >     If you do not have enough room for a full size dipole on 160M off your 
> > tower, try a half-sloper wire.  That is one half of a dipole (for 160M a 
> > wire about 125 feet long) hung off the tower near the top and connected at 
> > the ground end to a tree, etc away from the tower, not folded back to the 
> > tower.  Then connect the center of your 50 Ohm coaxial feedline to this 
> > wire (use an insulator at the tower top to hold the wire and connect the 
> > coax to a short piece of the wire coming out of the insulator.)
> >
> >     Then connect the coax shield to the tower somewhere below your HF 
> > Yagi, etc..  This is the tricky part.  You will have to try several times 
> > to get a good match for 50 Ohm cable but you should be able to find a good 
> > spot on the tower.
> >
> >     I understand that this arrangement uses the tower and antennas above 
> > the tap point as a vertical radiator; the sloper wire is one radial for a 
> > ground-pane.
> >
> >     I did this with my 64 foot tower on 80M.  My tap point is at 50 feet 
> > above ground.  I have a Bencher Skyhawk antenna and D40 dipole on the mast 
> > above the tower.  This sloper wire works very well for me on 80M with only 
> > 100W.  Maybe you can first try connecting the coax shield to your tower at 
> > 100 feet.
> >
> >     Please ask if you want more information.
> >
> > 73 de
> > Gene Smar  AD3F
> >
> >
> >
> >> TT's:
> >>
> >> I read the last NCJ, where K3LR 160m Dipole as sloper appears, i will 
> >> like to
> >> try something like this here, but i have only 140 ft  of tower, is 
> >> possible to
> >> reduce the full size of the 160m dipole to a 66-70%  using only the RG-58 
> >> COAX
> >> as antena not like feed,  in other words use the Vel Factor from the 
> >> cable that
> >> is around the 66-70 to reduce the phisical length and make posible that
> >> configuration ?
> >>
> >> the antenna is like this   I>     where   I tower   > dipole
> >>
> >> i try to find something abouth this but nothin show up , jus the moxon 
> >> antenna
> >> using coax to reduce size, looks that work,   really work ?  and i can 
> >> use legal
> >> power ?
> >>
> >> i will like to hear if someone before try  and the result, before buy the 
> >> coax
> >> spool  and just loose my time.
> >>
> >> Hector XE2K/XF1K
> >> _______________________________________________
> >>
> >> 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
> >> TowerTalk at contesting.com
> >> 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.
> >
> > _______________________________________________
> > TowerTalk mailing list
> > TowerTalk at contesting.com
> > http://lists.contesting.com/mailman/listinfo/towertalk
> >
> >
> > -- 
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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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