Dipole counterpoise angle question.
- ghost123uk
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Dipole counterpoise angle question.
The following is just for fun really, during "lock down".
I have been experimenting (aka playing) with one of these (using it vertically) =
I have put LOADS of different mobile aerial combinations on it, including a full size 1/4 wave (both as radiator and counterpoise).
Even 2 x 2 foot "Dial-a-Match" aerials work and I did get contacts from 20 miles away even with them !!
The results in terms of SWR have been generally quite good.
I have not at this stage been noting down "real world" performance (yet).
There is of course a commercially made equivalent of this, known generally as a Boomerang =
My question is, on those, the counterpoise is always shown at a distinct angle to the radiator.
Why is this?
I have been experimenting (aka playing) with one of these (using it vertically) =
I have put LOADS of different mobile aerial combinations on it, including a full size 1/4 wave (both as radiator and counterpoise).
Even 2 x 2 foot "Dial-a-Match" aerials work and I did get contacts from 20 miles away even with them !!
The results in terms of SWR have been generally quite good.
I have not at this stage been noting down "real world" performance (yet).
There is of course a commercially made equivalent of this, known generally as a Boomerang =
My question is, on those, the counterpoise is always shown at a distinct angle to the radiator.
Why is this?
John, on the S. Cheshire / N. Shropshire border. 26TM953 / muppet handle "Grey ghost"
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
- Tigersaw
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Re: Dipole counterpoise angle question.
I know nothing about the antenna you are talking about, but one effect of angling the radiators will be to alter the feed impedance, maybe it was a crude/simple way of matching to 50 ohms?
- ch25
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Re: Dipole counterpoise angle question.
A half wave centre fed dipole antenna in free space has an impedance of 73 Ohm.
When angle between bottom part and radiating element is 135° it have 50 Ohm.
Chris
When angle between bottom part and radiating element is 135° it have 50 Ohm.
Chris
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- theEarwigger
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Re: Dipole counterpoise angle question.
As you say a 135 angle gives 50 ohms.
Local objects will alter it some but the adjustment on the boomerang allows testing. Years ago I found these -3dB down on compared to a full size half wave. Not a bad compromise for local operation.
Local objects will alter it some but the adjustment on the boomerang allows testing. Years ago I found these -3dB down on compared to a full size half wave. Not a bad compromise for local operation.
... www.M0RZF.co.uk ...
- ghost123uk
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Re: Dipole counterpoise angle question.
As I have seen so often Chris, your answer is good and straight to the point
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I added a "DV banjo" to to that "straight" dipole centre connector (pictured above) so I could experiment with angles. I can now confirm that putting the counterpoise at an angle does indeed reduce the SWR compared to having the elements inline
It currently has a full size 1/4 wave on top and a loaded 1/4 wave underneath and tunes very well. Initial tests indicate it is working reasonably well too.
However, the joke is that, in view of all this, I have now ordered a proper (full size) Boomerang
The reason being that the dipole centre I have been playing with does not look very strong (this was also mentioned elsewhere here).
It's been summat interesting to do though
John, on the S. Cheshire / N. Shropshire border. 26TM953 / muppet handle "Grey ghost"
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
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Re: Dipole counterpoise angle question.
Wow, I never knew that about the angle altering the impedance! You learn something new every day
How about a CB aerial resembling this 1950s TV aerial:
http://www.wrightsaerials.tv/aerialphot ... /048.shtml
It could be a period accessory for buildings in conservation areas
How about a CB aerial resembling this 1950s TV aerial:
http://www.wrightsaerials.tv/aerialphot ... /048.shtml
It could be a period accessory for buildings in conservation areas
- ghost123uk
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Re: Dipole counterpoise angle question.
Aye, that TV aerial is a strange one Chris
Things have moved on. I bought the Sirio Boomerang (the full size version) and it worked fine on top of my 4 Mtr telescopic fibre glass pole.
I went to a lot of trouble getting an adaptor made so that I could use std 3/8" thread mobile aerials as the vertical element. That proved fun and helped pass a day or two of lockdown, experimenting.
However, I looked at it and thought the mounting system did not really suit my application and I thought "I can do neater than that".
The result was this arrangement, which fits the pole perfectly and is neat, compact and versatile (Note = The pole is not fully extended in the pictures.)
Things have moved on. I bought the Sirio Boomerang (the full size version) and it worked fine on top of my 4 Mtr telescopic fibre glass pole.
I went to a lot of trouble getting an adaptor made so that I could use std 3/8" thread mobile aerials as the vertical element. That proved fun and helped pass a day or two of lockdown, experimenting.
However, I looked at it and thought the mounting system did not really suit my application and I thought "I can do neater than that".
The result was this arrangement, which fits the pole perfectly and is neat, compact and versatile (Note = The pole is not fully extended in the pictures.)
John, on the S. Cheshire / N. Shropshire border. 26TM953 / muppet handle "Grey ghost"
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
-
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Re: Dipole counterpoise angle question.
That looks well engineered
Tell the posh neighbours it's the new Brabantia heated outdoor ecological clothes dryer
Tell the posh neighbours it's the new Brabantia heated outdoor ecological clothes dryer
- ghost123uk
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Re: Dipole counterpoise angle question.
Nice of you to say that, but really all I did was a bit of lateral thinking, gather together the ready made bits n pieces and then drill one 3/8" hole in that mirror mount and assemble it
It has been fun testing combinations of different "twigs" top and bottom. Even 2 x 2 foot long "Dial-A-Match" ones tuned and worked (though not sure about how well they worked distance wise )
John, on the S. Cheshire / N. Shropshire border. 26TM953 / muppet handle "Grey ghost"
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!
-
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Re: Dipole counterpoise angle question.
Two 2' Dial-A-Match angled to resemble that old TV aerial, and fitted to the apex of the building, might pass as permitted development :)
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Re: Dipole counterpoise angle question.
Once the negative leg of an antenna like yours is angled it is more akin to a 1/4 wave GPA (ground plane antenna) and yes the angle alters the
feed impedance. It may be ever so slightly directional with just one ground plane. I think officially a GPA needs 2 x ground plane radials to be classed as such. The GPA is an excellent antenna when there is space available for the 3 or 4 ground plane radials.
I would love to use one but impractical for my typical garden tree / mobile static setups.
feed impedance. It may be ever so slightly directional with just one ground plane. I think officially a GPA needs 2 x ground plane radials to be classed as such. The GPA is an excellent antenna when there is space available for the 3 or 4 ground plane radials.
I would love to use one but impractical for my typical garden tree / mobile static setups.