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The Quad Debate

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Webmaster

Wed Aug 13 2008, 07:28AM
By now you have probably read Kerry's (G0LCS) call for a discussion on Quads in SN96 "Whats on Six". Have you used one? are you still using one? what do you think of them? Why do you think Quads don't appear popular at the moment. Please lets have your thoughts, comments and experiences here please or via email to Kerry. A Photo of your Quad would also be nice and can be posted here.
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Dai, G8FXM
Wed Aug 13 2008, 03:02PM
Webmaster

Registered Member #2
Joined: Mon Mar 17 2008, 06:10PM

Posts: 204
Here's something from our Archives to get the debate rolling
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Ken, GI7UIP
Wed Aug 13 2008, 03:06PM
Ken, GI7UIP
Registered Member #676
Joined: Wed Aug 13 2008, 03:06AM

Posts: 3
Around my QTH there are simply no big antennas for any bands going up. Whether this is planning, lack of money, lack of interest or what I do not know but I definitely get the feeling that 6m is treated by a lot as the band between 2m and HF on the rig, a sort of freebie band that nobody uses. o use for local and no good for DX most the time is the impression I get.

Maybe it has something to do with the influx of new blood to the hobby from the CB arena. It's a lot easier to make that move now than when i did and HF offers instant gratification to the DX calling M3 even on 10 watts, not something that 6m can do.

Either way i think it says it all that when I said that plans were to run an IC-746 as a 6m radio and put up a co-phased, 4 beam array for 2m and another for 70cms that most the locals here basically thought I had lost my sanity......

For info - dipole on 6m now, 3ele yagi in shed still to go up at new QTH and plans for a homebrew 5 ele quad afoot.
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Kerry, G8VR
Thu Aug 14 2008, 06:20PM
Kerry, G8VR
Registered Member #107
Joined: Mon Mar 31 2008, 07:00PM

Posts: 28
Hi Ken
I'd be really interested to see how you get on with that. My 3-ele on a 6ft boom was used here to good effect. Rather than a 5 on a 12ft boom, how about 2 stacked 3's (bayed better) 10ft apart for a start?
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Justin, G0KSC
Wed Oct 29 2008, 12:10AM
Justin, G0KSC
Registered Member #64
Joined: Thu Mar 20 2008, 04:10PM

Posts: 49
I think there are a couple of reasons for there not being so many quads about and some of these overlap. There are not a great deal of commercial quads available for six and not too many designs around the Internet. I am a fan of quads and decided I wanted to have a look at designing some. However, most commercial design software has problems with loops. In fact, the problem is with angles within elements of 90degress or less. Therefore, trial and error is the only real surefire way of knowing if something works. With the Yagi desgins, the antenna model software is very accurate and includes (in most cases) Yagi optimisers in order to hone the antenna for best effect.

This said I have 3 antenna modelling packages one of which I purchased because it claims to have 'corrective algorithyms' which ensure accuracy with loop antennas. I have had good results with single quads and deltas and will be building some 2 and 3 element Deltas to test against my Yagis so watch this space!!

Justin G0KSC
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Trev, EA5ISZ
Wed Oct 29 2008, 09:11AM
Trev, EA5ISZ

Registered Member #13
Joined: Tue Mar 18 2008, 01:43PM

Posts: 143
There is further information on quad construction in our archives Here . Brian G3HBR used these to great effect on 6m and was often the first to detect an opening.

[ Edited Wed Oct 29 2008, 09:18AM ]
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Justin, G0KSC
Fri Dec 05 2008, 10:33AM
Justin, G0KSC
Registered Member #64
Joined: Thu Mar 20 2008, 04:10PM

Posts: 49
Guys,

I have been playing with quads and wanted to make something a little different but worthwhile. Below are the details of a 3 el quad for 50Mhz with a short boom of just 1.38 Metres long.

The antenna is 50 Ohms so requires direct connection with 50 Ohm coax, no matching required. Forward gain is a respectable 7.56dBi and an impressive Front to back figure of 26.27dB (both figures at 50.150Mhz).


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[ Edited Fri Dec 05 2008, 10:40AM ]
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Justin, G0KSC
Fri Dec 05 2008, 10:39AM
Justin, G0KSC
Registered Member #64
Joined: Thu Mar 20 2008, 04:10PM

Posts: 49
Dimensions are as follows:

12 gauge uninsulated hard drawn copper wire

Boom spacing:

Ref to Driven - 1.195 Metres
Driven to Director - 0.185 Metres

Loop sizes:

Reflector - 0.809 Metres per side (X4)
Driven - 0.779 Metres per side (X4)
Director - 0.724 Metres per side (x4)

Enjoy!

73
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Martin, DK7ZB
Sun Dec 14 2008, 07:16AM
Martin, DK7ZB
Registered Member #788
Joined: Thu Dec 11 2008, 05:01PM

Posts: 7
An important statement first: I have used, built and designed several quads in the past and compared with yagis.

The myths and fairy tales about this antenna type has a simple reason. It was the first multiband directional antenna amateurs could build and trim with good effort. There were only two steps to do that. The radiator loop was cut for a good SWR and the reflector loop for best forward gain or best f/b ratio. The advantage of a directional antenna with 5 dBd gain and a good f/b was evident. This fact is still a good reason for using a quad.

A quad does not have a lower radiation angle than a Yagi when mounted in lower heights and the gain is between a 2-El.- and 3-El.-Yagi. The bandwidth is not greater and depends only on the gain and the radiation resistance. For quads 110 Ohm is a high impedance with greater bandwidth and 50 Ohm is a low impedance with small bandwidth.

For a jugdement of the effectivity of a monoband Quad we must distinguish the mechanical and the electrical attributes. If built with low cost parts (wood, bamboo) and wires the Quad is still a good choice. With high-tec materials (glassfibre) the construction of a Quad is more expensive in relation to a Yagi.

The gain of a multielement directional antenna is influenced by the length of the travelling wave zone and not by the shape of the elements. That has pointed out DL6WU already thirty years ago and this is so still today. A 5-el.-quad with a given boomlength has the same gain and F/B as a 5-6-element-yagi which is much easier to construct. The gain is only influenced by the radiation angles (azimuth and elevation) of the forward pattern and these are identical for the two antenna types. The quad needs twice as much halfwave elements for the same gain and the advantage of the stacked single element in a multielement Quad goes to zero.

I see absolutely no reason to build and use multielement monoband quads....

73 de Martin, DK7ZB
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Justin, G0KSC
Sun Dec 14 2008, 04:17PM
Justin, G0KSC
Registered Member #64
Joined: Thu Mar 20 2008, 04:10PM

Posts: 49
But isn't it fun just playing with stuff? The thing is, you have done all of these experiments. For some of us we are just starting out! for me, a lot of the fun in this stuff is playing, experimenting and comparing results.

Funnily enough, I have been trying larger arrays and not getting much better results than I could with the Yagis of the same boom length. You comments in another post about the first director being a matching unit is very much the case in the above antenna and due to how close it is, not much of an increase in boom length is seen.

Since this posts, I have been playing with short boom yagis and have had good results with a 3 element 1mtr and 1.3 mtrs boom(s) both showing higher forward gain than the above although F/B was compromised.

J
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