vertical di pole
 

At 20 meters, the overall length would be about 65 feet, and the two halves
of the dipole would be about 32 feet. Perhaps one of the Hams here can help
you out with the coil specifications.

I am wondering if making that a sloper might be easier to erect in a
confined space, and whether maybe a half-wave would be more convenient ? In
other words, with a suitable base and vertical pole, you could set some
stakes away from the base a suitable distance, and use insulated hook up
wire from an insulator on the pole to insulator on stake. You could still
use the coil, and I think you might have an advantage of less noise from the
antenna as well. I used a similar arrangment once when I had an upstairs
apartment and had access to the roof. I was using it for receiving only, and
had a lot of wire in the air in a small space by looping the wire several
times. It worked quite well. Hope your project works out well.

wrote in message
om...
HI
I am a SWL trying to construct a portable 20mtr Di pole from a 14ft x
1inch length of ali tube to use at my holiday trailer park can
someone tell me how many turns I need to put on the centr loading coil
and what diamiter the coil should be I can not find a suitable Article
on the net any help would be apreciated

Barry

On Sun, 10 Aug 2003 15:47:04 GMT, "Warpcore"
wrote:

At 20 meters, the overall length would be about 65 feet, and the two halves
of the dipole would be about 32 feet. Perhaps one of the Hams here can help
you out with the coil specifications.

The dipole would need to be (10 metres * velocity factor of material)
long to be resonant on 20m band, roughly 16'6" per leg.

Warpcore wrote:

At 20 meters, the overall length would be about 65 feet, and the two halves
of the dipole would be about 32 feet. Perhaps one of the Hams here can help
you out with the coil specifications.


Yikes! A half wave at 14 MHz is 33'- a 1/4 wave then is 16.5'
Why not end feed it with an appropriate Z matchbox at the base as in:
http://www.parelectronics.com/end_fedz.htm


You could still
use the coil, and I think you might have an advantage of less noise from the
antenna as well.

What is the explaination for this?

Dale W4OP

20 meters is 3.28*20 isn't it : 65.6 ft a full wavelenghth, so a dipole of
two lengths would need to be half the total length no s ?

"N8KDV" wrote in message
...


wrote:

On Sun, 10 Aug 2003 15:47:04 GMT, "Warpcore"
wrote:

At 20 meters, the overall length would be about 65 feet, and the two
halves
of the dipole would be about 32 feet. Perhaps one of the Hams here can
help
you out with the coil specifications.

The dipole would need to be (10 metres * velocity factor of material)
long to be resonant on 20m band, roughly 16'6" per leg.

That is correct, certainly not 65 feet in total length.

Warpcore wrote:

20 meters is 3.28*20 isn't it : 65.6 ft a full wavelenghth, so a dipole of
two lengths would need to be half the total length no s ?

A full 1 wavelength dipole presents a center feed impedance of 1K Ohm and
higher- hardly a good match for coaxial cable.

Dale W4OP

Since you said you were a SWL, then you're not going to be transmitting ...
so i wouldn't worry about trying to be too
exact on the dimensions. An few inches more or less really wont make much
of a difference when receiving.

wrote in message
om...
wrote in message
. com...
HI
I am a SWL trying to construct a portable 20mtr Di pole from a 14ft x
1inch length of ali tube to use at my holiday trailer park can
someone tell me how many turns I need to put on the centr loading coil
and what diamiter the coil should be I can not find a suitable Article
on the net any help would be apreciated

Barry

Hi
I gather it will be easier to telliscope another peice of tube inside
the 14ft length so as to ajust the length to 16.5ft or there abouts
aprox Quarter wave at 20 mtrs so if I use a tuner I could use the same
pole for 40 and 10
It is not possible to have any sort of wires due to restrictions on
the park so I would have to use a ground stake or try the water main