Have any of you tried using a tower as a J pole antenna for 20 or 40
meters?

According to calculations, it looks like a 50-foot tower would be about
right for 14.1 MHz with a 16.6-foot matching section that could be made
out of aluminum tubing and spaced out about 1.5 feet.

This should make a decent low-angle radiator without needing any buried
ground wires (which would be difficult to put in around here).

Then I thought maybe a taller tower, perhaps 80 feet, with a triband beam
on top, could perhaps be made into a J-pole for 40 meters with the beam
acting as a hat.

Obviously I haven't thought this through very much but I was just
wondering if any of you had tried any of this or knew of any articles or
websites that describe such a project.

I like people who think big.
Go for it!

If you actually do this, a report back to this NG would be appreciated.
Dan
AI8O

"Eric" wrote in message
news

Have any of you tried using a tower as a J pole antenna for 20 or 40
meters?

According to calculations, it looks like a 50-foot tower would be about
right for 14.1 MHz with a 16.6-foot matching section that could be made
out of aluminum tubing and spaced out about 1.5 feet.

This should make a decent low-angle radiator without needing any buried
ground wires (which would be difficult to put in around here).

Then I thought maybe a taller tower, perhaps 80 feet, with a triband beam
on top, could perhaps be made into a J-pole for 40 meters with the beam
acting as a hat.

Obviously I haven't thought this through very much but I was just
wondering if any of you had tried any of this or knew of any articles or
websites that describe such a project.

"Eric" a écrit dans le message de news:
...

Have any of you tried using a tower as a J pole antenna for 20 or 40
meters?



hello,

I tried it, but it was not a great success
I used a tower with a TH6 as a capacitive hat
matched with a gamma match system
and 16 radials

It was working first on 80 as a quarter wave, then on 40 as a half wave, and
I tried it too on 160

In fact, it was good, but not better than a dipole at the top of the mast; I
suppose due to the very poor ground here.


pse excuse my english

73

André
http://f5ad.free.fr/QSP_Antennes/F5A...r%20Google.kmz

"André" a écrit dans le message news:
...


Wow! André
http://f5ad.free.fr/QSP_Antennes/F5A...r%20Google.kmz
peux tu nous décrire les antennes que l'on voit sur Google earth?

could you describe the antennas ?

"Alain.11" a écrit dans le message de news:
...


Wow! André
http://f5ad.free.fr/QSP_Antennes/F5A...r%20Google.kmz
peux tu nous décrire les antennes que l'on voit sur Google earth?

could you describe the antennas ?



Oui, bien sûr,

At the top you can see a parabolic dish (diameter 3.2 meters)

underneath a TH6, stacked with a Create DB18-24

underneath it's not a 4 elements yagi but 4 VHF antennas:
two phased 9 el yagi 144
and two phased 19 el yagi 435
rotatable site and az for sat tracking

On the right, you can see 6 whites points
the first 3 points are offset dishes (30 and 60 cm) for links on ATV 10 GHz
FM (transmitting)
the other 3 points are offset dishes (50 and 80 cm) for links on ATV 10 GHz
FM (receiving)

The links a
with a repeater on Mont Aigoual (70 km)
with a repeater on Mont Ventoux (80 km) and montagne de Lure (120 km)
with a repeater in Marseille town (100 km)

underneath, near the shack, you can see a 5 elements yagi on 50 MHz and 2
small offsets on 10 Ghz for a link with F6BES 6 km away.


73
André

On Mar 7, 4:05 pm, Eric wrote:
Have any of you tried using a tower as a J pole antenna for 20 or 40
meters?

According to calculations, it looks like a 50-foot tower would be about
right for 14.1 MHz with a 16.6-foot matching section that could be made
out of aluminum tubing and spaced out about 1.5 feet.

This should make a decent low-angle radiator without needing any buried
ground wires (which would be difficult to put in around here).

Then I thought maybe a taller tower, perhaps 80 feet, with a triband beam
on top, could perhaps be made into a J-pole for 40 meters with the beam
acting as a hat.

Obviously I haven't thought this through very much but I was just
wondering if any of you had tried any of this or knew of any articles or
websites that describe such a project.

I tried it making mine(20M) out of conduit. Tweaking it up was a lot
more trouble than I thought it would be. Try building one for say 6
meters with only approximate deminsions, note how much tweaking it
takes to get it right them multiply this by 100. It can be a real
PITA. You are going to be fiddling with the length of the tower, the
length of the stub.

I turned my 65 foot rohn 25 into multiple antennas. #1 160 meter shunt fed, #2 80 meter shunt fed, #3 160 meter inverted L. #4 20 meter J-pole, soon to be fixed up with a 10 meter version. The 20 meter J seems do do quite well on the whole band, and the autotuner on the Kenwood 2000 will tune it from roughly 13.2mhz, to somewhere in the 15.5 mhz. SWR is flat "as a fritter" in the targeted middle of the band. At 100 watts iv'e worked Russia and Japan, and the occasional asiatic islands on Psk 31. USA local is a breeze. I simply measured the tower the appropriate distance (3/4 wave) and bolted the 1/4 wave section to the tower, approx one foot out. But be carefull of the top of the 1/4 wave swinging in the wind, it will de-tune the antenna in a hurry. Also, I have all my guys insulated from the tower.I have also thought about loading a 40 meter 1/4 wave at the very bottom , and using a "top hat" as well, to get that needed 100 foot or so for a match on 40. I shunt fed the tower once for 40 , but had a cruddy ground plane at the time, results were quirky. New attempt is coming in a few days...good luck...Dave KC5UTA

Yes i like people who think different form others and every trend can be changed if some new ways and trends can be set then it is possible to get the good results.

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