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Discussion in 'General Ham Radio Discussion' started by Andy, Mar 11, 2007.
Check out Cebik's comments:
First, none of this is from personal experience. It's just some impressions I've gotten from reading 'Cibek' and mounting 'odd' shaped antennas.
From an electrical point of view, a corner reflector type antenna can have as much gain as a fairly large yagi type antenna. That would seem to indicate that a 'reflector' would be 'better' than an average 'smaller' yagi antenna. I would also think that 'ganging' them (multiple reflector types phased) would also yield a higher gain than multiple smaller yagis. If the yagi is of a size that would yield a gain similar to the reflector type antenna, then any advantage tot he reflector antenna is sort of mute.
Then there's the 'practical' or mechanical side of things. A yagi type antenna is fairly symmetrical and can be 'ballanced' on top of that pole you mount it on. A corner reflector type antenna isn't gonna be 'symetrical' with out some fairly complicated mounting scheme, and/or balancing weights. Can't say that would be un-doable, but it would sure be different! And then there's the 'sail' area presented to wind. I would think that a reflector type even made from 'mesh'/wire screening will have at least as much 'sail' area as a pretty good sized yag. Being 'symmetrical' also plays a big part in this cuz the action of the wind on the sail is more on one side of the mounting point of the reflector antenna than the 'other'. Balancing this 'sail' area would mean adding a 'sail' on the back end of the reflector, and that would probably turn your tower/pole into a sailboat's mast, so get ready for a nice 'ride'! lol All this assumes you'd want to be able to turn the reflector like you would a yagi for the right direction. Of course, if you don't plan to turn the reflector then some of all the above can be dismissed as irrelevant, sort of.
I've never seen many (any) rotating reflector antennas, so guess somebody thinks all this might be at least 'sort of' true. The refelctor antennas I've seen have all been for a 'fixed' direction. Considering that there isn't as much signal radiation behind them as there is for a typical yagi, that's also a factor for cutting down on interference. Not a bad idea if you only wanna hit a repeater (and someone doesn't move the @#$ repeater!).
A reflector antenna for 2 meters isn't going to be exactly 'small'. Certainly smaller than the average 10/15/20 meter yagi, but still not very small for 2 meters, you know?
So, for fixed use, and above '440, they'd be almost a really good idea. From the practical stand point, below '440, they sort of get 'un-practical'.
(Not that I wouldn't like to have one, I'm just too lazy to contend with one.)
(Sorry about the length, but I do get paid by the 'word', you know. 8) )
Thanks for you help,
You can buy simple yagis for VHF for very little money. You can also use a Cubex Quad! I have a couple of Cubex's MURS prototypes and they are nice antennas!
typiclly slightly less gain then simular size boom yagi
but supposedly more reliable continuous beam
i know the arrors you are speaking of
they are good
mounting bit of a problem unless mounting 2 back to back to counter balence each other
in part they have a smaller foot print requiring far less radias to turn in and so may work easier in areas with less floor plan space
i was thinking myself of trying arrows dual 144/440 corner beam with 220 mounted behind it
let us know how you go
Here is a 2 meter, 2 el quad.
Thia is a very cheap antenna, can be built from almost nothing, and will show you just how easy it is.
It is not a antenna you would want to leave up, however it will allow you to see how the idea works, and you can build it in one afternoon.
Simple, just some wire and a few Pcs of hardware.
You can build off of this basic idea, and learn as you go
Here is a 4 El built the same way
Here are plans for a 4 el Quad, it is built to stand up to being mounted outside.
This is the same as the first 2 meter beam I built.
I ripped the boom from a 2x6 on the table saw, drilled the holes with a hand drill, and built this antenna on a Sunday. Start to on the air.
Make sure that you seal the wood with some good exterior Paint, and it will suprise you how well it will hold up!
Here is a cool deal for building your own Quads, just punch in the frequency you want, and it will crunch the numbers for you!
Building antennas is fun, not as hard as most think, and allows you to learn how they really work, Give it a try.