[Antennas] Fw: QUADS & BEAMS ??

[Alex Eban]

If talking about simple antennas, I would like to mention the Moxon
Rectangle.
Moxon and later Cebic experimented quite a lot with this folded antenna and
Cebic came out with a simple design procedure with very good practical
results.
This antenna needs only 4 spreaders, not 8 like the Quad. It is built on a
two dimensional X frame and elements for a number of bands can be
interleaved on the same spreaders.
It has a moderate gain of 6-7 dB, but an incredible front to back ratio of
about 30dB! At least, the EZNEC analysis confirms this claim.
Being two dimensional, it should be easier to build and install than the
Quad.
Alex	4Z5KS
 

-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of JK
Sent: Wednesday, October 07, 2009 4:26 PM
To: ANTENNA Reflector
Subject: [Antennas] Fw: QUADS & BEAMS ??


> Quads have virtually no problem with rain or snow static because of 
> the closed loop driven element. I have been unable to operate with my 
> 20M 5el yagi because of 20 db over 9 rain or snow static while my 
> nearby friend with a quad had no static at all.
>
> I really can't think of too many advantages of a 2 el yagi over a 2 el 
> quad other than the durability and the yagi is in one plane while the 
> quad is 3 dimensional. My first directional antenna was a homebrew 2 
> el 20M quad with the center of it at 35' up. Worked all over the 
> world. I still have 7 of the original 8 fiberglass wrapped bamboo 
> spreader arms. Now they are about 47 years old.
>
> The Gem Quad (boomless) out of Canada was a great performer. I think 
> they are out of production. My friend has his up over 20 years. Sprays 
> Blue Rustoleum on the fiberglass arms about every 4 years. They look like
new.
> If you don't coat the fiberglass from time to time, the arms will 
> deteriorate from UV as years go by and they will eventually break.
>
> An excellent way to feed a quad is with balanced transmission line and 
> use of a tuner. You can tie all of the driven elements together except 
> for the 10M driven. (See older ARRL Handbooks for details) That should 
> be fed separately as tests have shown interaction when the 20M driven 
> element and the 10M driven element were tied together. That 
> interaction resulted in degraded performance on 10M.
>
> Then all you have to do is adjust each reflector for minimum signal 
> off the back at the freq U do most of your operating. Always tune the 
> lowest band first, then go up the bands. 14 Mhz, 18, 21, 28, 52.

Max F/B will occur over a very narrow part of each band. Maybe only 5-10 khz
wide. Then it will taper off
> rapidly as U move away from the point of max.
>
> Other than a dead band, there is nothing that quiets a receiver more 
> than about 30 db back rejection of signals near
your operating freq.
> >
> It is possible to make remote tunable reflector stubs that can be 
> adjusted for max F/B while the antenna is at full height and the 
> person doing the adjusting stands safely on the ground pulling a 
> string! The remote stub will get longer or shorter depending on which 
> of 2 strings is pulled downwards. Once Max F/B is attained, you can 
> lower the antenna and fix the tunable stubs in position permanently. I 
> have photos of these adjustable stubs if
interested.
>
> Jay NE2Q
>
>
>
>
> ----- Original Message -----
> From: <SECOPSYS at aol.com>
> To: <w5jv at hotmail.com>; <>
> Sent: Saturday, October 03, 2009 10:38 PM
> Subject: Re: [Antennas] QUADS & BEAMS ??
>
>
>> Quads are quieter..many times I can copy weak signals on my quad 100% 
>> when they are "there but not copiable" on my yagi.
>>
>> Quads are much more broadbanded.  Great SWR across entire band.
>>
>> Quads are much more forgiving..spacing 2 elements 10 thru 13 feet (on
>> 20mtrs) and  it'll still works very well..perhaps not optimized but 
>> works very well.
>>
>> A little patience, a slingshot, a roll of #14 THHN wire, and a  
>> decent tree will give you 2 diamond shaped 20 meter elements (fed at 
>> botton of
>> diamond)
>> in a fixed favored direction for very little money.
>>
>> 73,
>> Richard
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