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-   -   Is This Still a Dipole? (https://www.radiobanter.com/shortwave/46498-still-dipole.html)

Volker Tonn November 27th 04 01:02 PM



Lucky schrieb:

"Volker Tonn" wrote in message
...


RHF schrieb:


You may wish to consider moving the Feed-Point from the Center of Two
Equal Arms to an Off-Center Feed-Point with a Short-Arm of 38% and a
Long-Arm of 62% of the Total Length of the Antenna. This type
'configuration' of Wire Antenna is called a "WINDOM" Antenna.


It's more likely a FD-Antenna. This is fed with a coax-cable and a 1:4
BalUn.
A real[tm] windom antenna is fed by a single wire feeding the "top of the
asymmetric T" without a BalUn. The windom Antenna is much more limited in
bandwidth compared to a FD-antenna.
The BalUn of a FD-Antenna you can feed with some more different wires of
different lenghts. Try some additional shorter wires to increase reception
on the higher bands. I feed mine with 4 wires of app. 8, 20, 45 and 120ft
paired 120 and 8 ft on one connector and 45 and 20ft on the other
connector of the BalUn with very good results from 10 to 80 meters. It
even works fine as CB-antenna with low SWR.



Hi

So you're saying add extentions to the ends of the ant not near the balun??
I'm not using coax cause the radio is right near the window on a table. The
twinlead comes in, gets hooked right up to the balun, and then 50Ohm coax
rest of the way to the to the radio. I'm using 40 FT total for that's all I
have room for but I can add the extentions. What lengths would you suggest
for each end?

I don't understand where and how I add more then 2 wires to it. At what
points do I add them to? How do you use 4 wires?


One picture explains more than 1000 words :-)
Use monospaced charctars please.
Feel free to modify the picture to explain your own setup.


8ft | / 120ft
| /
|/
0 wire connector on BalUn
coax-feed |-|-|
==============0| |
|-|-|BalUn 1:4
0
|\
| \
20ft | \ 45ft

For sure you can use a twin-lead 300 Ohm wire going off the balun and
then feeding the antenna wires of different lengths. This 300-Ohm wire
works like a ladder-line -just not a very good one though-.
Best setup is to connct the different wires directly to the BalUn. No
matter if the wires are somewhat in parallel a few feet as the wires
allways will interact some way.
Did you have the 300-Ohm wire split on the far end? This is somewhat
essential to get good signals.


Lucky November 27th 04 01:23 PM


"Volker Tonn" wrote in message
...


Lucky schrieb:

"Volker Tonn" wrote in message
...


RHF schrieb:


You may wish to consider moving the Feed-Point from the Center of Two
Equal Arms to an Off-Center Feed-Point with a Short-Arm of 38% and a
Long-Arm of 62% of the Total Length of the Antenna. This type
'configuration' of Wire Antenna is called a "WINDOM" Antenna.

It's more likely a FD-Antenna. This is fed with a coax-cable and a 1:4
BalUn.
A real[tm] windom antenna is fed by a single wire feeding the "top of the
asymmetric T" without a BalUn. The windom Antenna is much more limited in
bandwidth compared to a FD-antenna.
The BalUn of a FD-Antenna you can feed with some more different wires of
different lenghts. Try some additional shorter wires to increase
reception on the higher bands. I feed mine with 4 wires of app. 8, 20, 45
and 120ft paired 120 and 8 ft on one connector and 45 and 20ft on the
other connector of the BalUn with very good results from 10 to 80 meters.
It even works fine as CB-antenna with low SWR.



Hi

So you're saying add extentions to the ends of the ant not near the
balun?? I'm not using coax cause the radio is right near the window on a
table. The twinlead comes in, gets hooked right up to the balun, and then
50Ohm coax rest of the way to the to the radio. I'm using 40 FT total for
that's all I have room for but I can add the extentions. What lengths
would you suggest for each end?

I don't understand where and how I add more then 2 wires to it. At what
points do I add them to? How do you use 4 wires?


One picture explains more than 1000 words :-)
Use monospaced charctars please.
Feel free to modify the picture to explain your own setup.


8ft | / 120ft
| /
|/
0 wire connector on BalUn
coax-feed |-|-|
==============0| |
|-|-|BalUn 1:4
0
|\
| \
20ft | \ 45ft

For sure you can use a twin-lead 300 Ohm wire going off the balun and then
feeding the antenna wires of different lengths. This 300-Ohm wire works
like a ladder-line -just not a very good one though-.
Best setup is to connct the different wires directly to the BalUn. No
matter if the wires are somewhat in parallel a few feet as the wires
allways will interact some way.
Did you have the 300-Ohm wire split on the far end? This is somewhat
essential to get good signals.


No, it is not split on the ends at all. How much should I split them?
Wouldn't this make more like a limited dipole?

So then just add extra wires directly to the balun and run them out my
window?

Should they be running right along the other lines or should they be in
different planes?

Lucky



Volker Tonn November 27th 04 01:45 PM



Lucky schrieb:

One picture explains more than 1000 words :-)
Use monospaced charctars please.
Feel free to modify the picture to explain your own setup.


8ft | / 120ft
| /
|/
0 wire connector on BalUn
coax-feed |-|-|
==============0| |
|-|-|BalUn 1:4
0
|\
| \
20ft | \ 45ft

For sure you can use a twin-lead 300 Ohm wire going off the balun and then
feeding the antenna wires of different lengths. This 300-Ohm wire works
like a ladder-line -just not a very good one though-.
Best setup is to connct the different wires directly to the BalUn. No
matter if the wires are somewhat in parallel a few feet as the wires
allways will interact some way.
Did you have the 300-Ohm wire split on the far end? This is somewhat
essential to get good signals.



No, it is not split on the ends at all. How much should I split them?
Wouldn't this make more like a limited dipole?

So then just add extra wires directly to the balun and run them out my
window?

Should they be running right along the other lines or should they be in
different planes?


Not having split the the ends of the 300-Ohm wire you just don't have
more than a plain feeding line. To split the wire or to add some extra
"antenna" wires at the end does make it an antenna then. Bowonder you
have "low noise". You simply have "no reception" :-)
Try to put the wires as wide spread as possible. At least in a 90 degree
angle -a 180 degree angle is fine too-. Try different length of wires
and check out what works best for you. You can simply extend a wire with
a nylon cord or a nearly unvisible fishing cord to go to a fastening
point in a tree or a ielephone mast or....
Would you like to tell us what receiver you got?


Lucky November 28th 04 09:50 AM


"Volker Tonn" wrote in message
...


Lucky schrieb:

One picture explains more than 1000 words :-)
Use monospaced charctars please.
Feel free to modify the picture to explain your own setup.


8ft | / 120ft
| /
|/
0 wire connector on BalUn
coax-feed |-|-|
==============0| |
|-|-|BalUn 1:4
0
|\
| \
20ft | \ 45ft

For sure you can use a twin-lead 300 Ohm wire going off the balun and
then feeding the antenna wires of different lengths. This 300-Ohm wire
works like a ladder-line -just not a very good one though-.
Best setup is to connct the different wires directly to the BalUn. No
matter if the wires are somewhat in parallel a few feet as the wires
allways will interact some way.
Did you have the 300-Ohm wire split on the far end? This is somewhat
essential to get good signals.



No, it is not split on the ends at all. How much should I split them?
Wouldn't this make more like a limited dipole?

So then just add extra wires directly to the balun and run them out my
window?

Should they be running right along the other lines or should they be in
different planes?


Not having split the the ends of the 300-Ohm wire you just don't have more
than a plain feeding line. To split the wire or to add some extra
"antenna" wires at the end does make it an antenna then. Bowonder you have
"low noise". You simply have "no reception" :-)
Try to put the wires as wide spread as possible. At least in a 90 degree
angle -a 180 degree angle is fine too-. Try different length of wires and
check out what works best for you. You can simply extend a wire with a
nylon cord or a nearly unvisible fishing cord to go to a fastening point
in a tree or a ielephone mast or....
Would you like to tell us what receiver you got?


Yes I have several but use the Icom R-75 now. I love it. I get great
reception. I pick up everything very well. But, perhaps I am missing out on
many. I went to Home Depot on your recommendation bought 40 Ft of #22 wire.
I will try it out tomorrow.

Lucky



starman November 29th 04 08:26 AM

Lucky wrote:

On thing I should make clear is that this twinlead is NOT center fed at all.
I'm using the lead just like a long wire except the ends of the twinL are
separate and not connected and it's hooked up to a balun in the room, not
outside. Only coax from balun to beautiful radio.

Lucky


What you have is a twinlead feed line to nowhere. You need some kind of
wiring on the far end of the twinlead to have a real antenna. If you
connected a wire to each of the wires in the end of the twinlead and
extended those wires in opposite directions, you would have a
traditional dipole. However 300-ohm twinlead should be connected to a
folded dipole antenna for a proper impedance match. A simple two wire
dipole {not folded} matches to 50-ohm coax lead better than a 300-ohm
twinlead. In that case you don't need the twinlead at all.


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