Magnetic loop beam?

G

guitarmaker1066

Member
Hello All,

Anyone ever heard of someone trying to build a two element beam from a couple of magnetic loops?

I got the idea for a 30 meter version the other morning, and try as I do to forget it, it won't go away! No doubt the problem with such a lash-up for most bands would be having to do synchronised remote tuning of the capacitors for the reflector and driven element.

Virtually all the 30 meter CW activity that I hear is in the lowest 25khz of the 50khz wide band. It might be possible to tune the two loops for minimum swr at 10.112 mhz, and make no attempt to re-tune the antenna for small frequency changes.

I would appreciate any input on the idea, the only suggestion so far is to treat it like a cubical quad. I would rather not re-invent the wheel if someone has had some experience with the scheme.

Cheers,

Brian Burns
 
Hiya Brian, and welcome to the forum 😊

I recall reading an article (actually more like a news snippet) in RadCom magazine many years ago, that mentioned the use of a loop beam/directional system.

It was developed my the military for tactical use. The article was very scanty with info, there was just a vague mention of the system, and the fact that it consisted of a number of collapsible loop antennas, about four or five feet square judging by the photograph, with an adjustable phasing system to feed them. Depending on the phasing you could alter the directional properties of the 'array'.

Because most military communications is satellite based these days the 'powers that be' don't seem to be overly interested in developing HF antennas these days, I just don't think that they have the money to spend on research. I myself get a number of telephone enquiries each year from various government departments trying to pick my brains for info (cheap research!).

Not so much a magnetic loop based beam, I do remember a compact beam antenna sold years ago for the 27MHz band for CB operators. It looked very much like two loops arranged face on to each other, separated by perhaps four feet or so. From what I recall though they were not two independent loops, but the ends of a half wave dipole, the centre of which formed the boom for the antenna. The other thing I recall was that one 'loop' was slightly larger in diameter than the other.

I know that the antenna was sold commercially, but I haven't a clue as to what it was called. It certainly worked though, I spoke to a guy using one and there was quite a noticeable difference between the front and back of the 'beam'.

If you get building one you will have to post a few pictures on here for us to see.

Best 73 Brian,

Mark.
 
Hello Mark,

Thanks for the reply! I posted the same question on eham and got a bunch of replies pointing out why it won't work.

Now I can stop thinking about it...whew!

Cheers,

Brian
 
Hiya Brian

You will never guess what's up for grabs on eBay... Loop Beams!

I think it's the same design I saw years ago.

Go to eBay and do a search for item number [link no longer valid]

There are two photographs of the beam, one side view and one end view. They are not the best images in the world, but they might help with your 'quest'.

I've also sent the guy an email requesting any additional information he can supply.

Best 73, Mark.
 
Hiya Brian

I had a reply back from the guy making the loop beam antennas:

I found this construction on the polish book about HAM antennas. I have made several of them for my own use and my friend's use here. Beam is made out PVC plastic pipe. Inside the pipe is wooden part that helps to keep the whole antenna steady. It's got two circles 700 mm and 770 mm. The antenna has got SWR around 1,4 - 1,5 on the whole CB Band. You can find some information here:

[link no longer valid]
Click to expand...

A quick look at the antenna tells me that it will not have massive gain (compared to a regular beam antenna), but I remember working someone using the same type of beam about thirty years ago. As they rotated the beam I noted about 4~6 S-points change, so the front to back ratio seems fair.

I've attached the image from the website he refers to...


73, Mark.
 

Attachments

  • 27mhz_loop_beam.jpg
    27mhz_loop_beam.jpg
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Hello Mark,

Thanks for your sleuthing work! I think that the CB antenna is electrically a dipole like the TAK-tenna. Here is the URL for the company:

https://www.tak-tenna.com/

They claim some directionality, but like you say this doesn't look like a real "beam" for having much gain.

I'll keep looking around, but I think that I'm going to try hanging a vertical MOXON from a rope that goes between two tall trees.

Cheers,

Brian Burns
 
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