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 Which antenna would you choose and why? 
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Post Which antenna would you choose and why?
Ok what would be the main difference between:

http://www.sandpiperaerials.co.uk/index ... ucts_id=85
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and

http://www.sandpiperaerials.co.uk/index ... ucts_id=86
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Mon Apr 19, 2010 8:05 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Well first off i wouldn't pay that money anyway. considering say 2 years back that mini beam was around Ā£50 tops at blackpool rally..


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Mon Apr 19, 2010 9:01 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
But are they 'beams' or are they just folded dipoles (aka cobwebb)?


Mon Apr 19, 2010 9:06 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
both beams if not mistaken. The bottom one looks a bit like a cobwebb but the web is made different ..

Steve G3TXQ has a cob on his sight which to me is far superior to the original one as far as homebrewing goes..IMO

billy

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Mon Apr 19, 2010 9:19 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Yeah, just don't understand how they can be beams as there's only one element per band, surely making them dipoles? I'm confoosed


Mon Apr 19, 2010 9:24 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
they are both "dipoles" ... im sure the way the top one its constructed gives it the characteristics of a beam ( i could be wrong on the top one but im just going off what i read way back when they first hit the market)

.. the bottom one is 2 elements per band .. they are seperated halfway round with little insulators.. but all the driven elements are dipoles whether they are bent or not..



the driven element of a beam is just a dipole anyway ..

maybe someone will come and give a solid answer , sorry i couldnt be more help but the above is my understanding

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Last edited by m0jha on Mon Apr 19, 2010 10:01 am, edited 1 time in total.



Mon Apr 19, 2010 9:54 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Ahh yes I see the insulators now. So the lower pic is a 2 ele beam in effect.... Gotcha. The top one just looks like a cobwebb folded in a delta shape rather than a square.

I think the lower would give 'some' f/b and maybe even a little more gain over a dipole?


Mon Apr 19, 2010 9:56 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
just looked at it again on a web site and it looks like the top one is constructed as a folded dipole .. look up GM3VLB and it gives some info on the antenna..

http://www.g3ejs.com/files/antennas/gm3vlbdelta.pdf

billy

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Mon Apr 19, 2010 10:00 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
The top picture is a "triangular" version of the Cobweb - a 4 band "bent dipole". When GM3VLB wrote an article on it, he wrongly labelled it a beam; it's not - it has about 1dB less gain than a dipole because it's more omnidirectional.

The bottom picture is a 3-band 2-element parasitic beam - very similar to the VK2ABQ. Grossly inflated Gain figure, by the way.

Big difference in turn radius.

I think you are asking us to choose between apples and bananas, not varieties of apple :)

73,
Steve G3TXQ


Mon Apr 19, 2010 11:06 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Steve, thanks for that. I think I can fit both (just) above my house. Used to have a TGM HQ1 mini beam up there so the VK2ABQ shouldn't be a problem.

In your opinion, if you 'had' to chose one or the other which would it be Steve?

Many thanks for your help, it is appreciated.


Mon Apr 19, 2010 11:37 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
M6AXL wrote:
In your opinion, if you 'had' to chose one or the other which would it be Steve?


Judging purely on performance, probably the VK2ABQ if I had the room for it (it's bigger than my hexbeam).

But you should also think about:

* The quality of construction - why is the beam so much cheaper than the dipole?
* How important to you are the 17m and 12m bands which the beam doesn't cover?
* The cost of a rotator for the beam
* Could you get the dipole significantly higher than the beam+rotator? If so it probably negates the gain advantage of the beam, although you would still benefit from the beam's F/B

73,
Steve G3TXQ


Mon Apr 19, 2010 12:08 pm
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
I think I'll go for the beam :) I'd love to have 17m but I suppose I could make a dipole or vertical for that band as and when I wish to use it.

Thanks for your help, I'll order the beam now :)


Mon Apr 19, 2010 12:17 pm
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
if going for a beam i would go for another TGM or MA5B or a hexbeam
my tgm 36r works really well for it's compact size :D :D

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Mon Apr 19, 2010 1:25 pm
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Hi Rob,

The only similarity to a Cobwebb is that it has fibreglass spreaders, a Cobwebb is
an array of folded dipoles, the Moxon is a take on a 2ele Beam. As has been mentioned earlier
in the thread a Cobwebb has slightly less gain than a dipole due to the omnidirectional
radiation pattern. The quoted 7dBi gain of the Moxon results in just over 3dB gain advantage
over a dipole, when you factor in the cost of a rotator and control cable the extra 1/2 s-point
seems a little expensive. The quoted 300Watt power handling is limiting compared to the
near 2kW power handling of a Cobwebb, I know one op who could peak up nearly 1.5kW
through a Cobwebb and nothing caught fire :-) If you are intending to use the Moxon
for portable work then the price differential swings in its favour as most folk would use
the Armstrong method to rotate and very few would go anywhere near the 300Watt limit.

As you've probably guessed my preference is for a Cobwebb (Not the Lamwebb / GM3VLB
mini-delta as pictured above ), probably because I have one myself. Sure it's not the cheapest
of antennae but it works out of the bubblewrap first time and has opened up parts of the
world that on other, more expensive, antennae have not even detected.

Adam, I'd be very cautious when contemplating the Lamwebb / GM3VLB Mini-Delta. I was
involved in the purchase and erection of one of these for a Ripon Club member. One of the
fibreglass supports started to fail during construction when the support was being tensioned.
The materials used suggested to me that it would not fair well in a harsh enviroment. In fact
the one we constructed for a club member folded in on itself during a period of strong winds.

Regards


Wed Apr 21, 2010 5:09 am
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 Which antenna would you choose and why? 
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Post Re: Which antenna would you choose and why?
Cheers for that Nidge, I had a cobwebb up at this qth for about a year and loved every minute of using it (worked K5D on it with 10w).

Hoping for a little front to back with the 2ele sandpiper wire beam, should be ariving today, not exactly sure how I'm going to get it in the air, should be 'interesting' to say the least!

I know what you mean about the build quality, I've been warned by a couple of people, but then other people have sung sandpipers praises....

Only time will tell, I'll take some pics during construction and let you know how I get on.

Hope you are well Nidge, will have to pop over your way sometime for a catch up.

Adam


Wed Apr 21, 2010 7:04 am
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