[TowerTalk] 160M DIPOLE USIGN COAX
ersmar at comcast.net
Fri Nov 11 12:06:24 EST 2005
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.
Gene Smar AD3F
> 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.
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