Loops How to optimally string a horizontal X-frame with wire for a passive loop

JELAIR

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Feb 22, 2018
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73
I got one of these things:

XframeAluminum.jpg

It's aluminum and really for drying clothes.

I have removed the plastic-wire which you can see on the image how normally sits (It was 50 meters (150 feet) long)

I was thinking of stringing some wire on to this frame, but I have doubts about which designs would make the most efficient loop-antenna.

My plan is to lead the wires up the center-pole, and then string them outwards in a spiral and back in to the center (My coax cable will then run along the ground and up the center pole to feed it at the top in the center.

But then I'm afraid this will technically be a loop with such a tiny circumference it's useless.

Would it be better to just run the wire at the edges of the 4 arms for as many turns as the wire is long? (IE not use the inner-portions of the arms)

And would it be better to feed it on the end of one arm, rather than in the center? (I could run the adjoining wires along one arm to the center)

I know it's a vague and rather un-scientific question, but I'm not really looking for a precise formula for any specific frequency here, but rather some more or less 'loose' ideas about what is the better idea to pursue (It's stiff wire I plan to use, so stringing it up on this frame will be something that isn't easy to change later. For that reason I would prefer to start of with a good design-idea so I don't have to redo it later :) )

As said; my idea is to spiral the loop so it basically looks the same as the wires seen on the image. Like a multi-turn loop, but where each turn has a smaller circumference (Like an inward spiral and then back outward, if my explanation makes any sense)
Or like a progression of different sized square-loops (Again, as it looks like on the image) but still made of just one uncut wire (So no inter-connections or short-circuit connections)

Any and all thoughts on this are welcome :)
I would just like to make good use of this rack as an antenna, without making it look too much like an antenna (HOA concerns)

Would I be better of simply laying the wire flat on the ground as a loop along the edges of the garden?

Thanks in advance.
jacob.
 

WA8ZTZ

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Feb 23, 2014
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receive only or transmit ?
btw, some neighborhood associations don't even permit clotheslines :(
 

ka3jjz

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Assuming here that you are building something just for receiving...

I am not sure, but that aluminum frame may have some detuning effects on whatever loop you build. Now if you had one that was plastic or wood, that might be a different animal.

Now if you are looking for info for a loop on the ground (LoG), there was a very extensive - and somewhat technical - discussion of this very topic some time back. There is even a website and a Facebook group for this antenna. We have all the links for this in our Loops wiki, viz.


Look in the Homebrew section, the MW/SW sub section and you'll find the first 2 links. The Facebook link is at the bottom

Mike
 

JELAIR

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Feb 22, 2018
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receive only or transmit ?
btw, some neighborhood associations don't even permit clotheslines :(
Sorry I forgot; this one is for receiving only.

I think an antenna can be beautiful, but alas I'm a minority on that.
Anyway, other people have similar contraptions set up in their gardens (Both in terms of looks and size), so as long as it at least looks like it's for drying clothes or stringing up tomato-plant stems or some play-thing for the kids like an advanced form of pole-tennis... then I don't think I will be singled out as a HOA-offender :)


I am not sure, but that aluminum frame may have some detuning effects on whatever loop you build. Now if you had one that was plastic or wood, that might be a different animal.

Now if you are looking for info for a loop on the ground (LoG), there was a very extensive - and somewhat technical - discussion of this very topic some time back. There is even a website and a Facebook group for this antenna. We have all the links for this in our Loops wiki, viz.


Look in the Homebrew section, the MW/SW sub section and you'll find the first 2 links. The Facebook link is at the bottom
I have already looked through the wiki at the top in this forum-section, and actually taken a look at the LoG.
I do find that setup interesting (Especially for its very low visual profile) but have been more or less breast-fed with the rule that an antenna must never touch the ground if you want it to work.

I do plan on trying to lay out a wire at some point along the garden-edge and see how it performs. But I do like to hear other users opinions before 'wasting' wire on a less optimal solution (If, for example, stringing up this clothes-dryer with wire might be more efficient since it will lift the wire about to meters (6 feet) above the ground)
I will look into the LoG links you provided and see what that will teach me for that later experiment :)

My understanding of loops is just not great enough for me to fully appreciate what it will mean to have 1 wire shaped into multiple size loops, as it would be if I use all the holes in the 4 arms to route wire through, vs if I only use the outer-hole on the 4 arms to make 1 single size loop (Which would then look like a fairly normal square horizontal loop)

And since the wire is stiff it's going to be somewhat of a hassle to thread the rack with it (And may break the wire if I begin to re-thread it several times in different designs)

I am under the impression that a loop's frequency is mostly determined by the physical size of the loop, and not so much by the length of the wire. So I'm worried the different loop-sizes, if I thread the arms like it is normally done when the rack is used for drying clothes, might null each other out rather than acting like a complimentary antenna-array (With each loop-size adding (Whatever range it receives best) to the overall antenna-bandwidth (IE making it more wide-band than a one-size loop))

But on the other hand; if wire-length plays a part, then maybe (Since I will only use 1 very long wire, spiralled into different sized loops (Like the sound-groove on a vinyl-record), and not multiple fully independent loops) this will increase resistance and basically make the overall antenna more efficient.

As you can hear my knowledge on this matter is still very little.
 

JELAIR

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Feb 22, 2018
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Now if you are looking for info for a loop on the ground (LoG)
Thanks again Mike :)

You mentioning the LoG had me researching it further and I fell over this page (After some google hoop-jumping in random directions)

Receiving Loop Theory - N4YWK

I will quote a small section from the bottom of that page, which I will take as being true for loops unless others contest it:

Some rules of thumb for loop sensitivity are:
  • For a fixed number of turns:
  • Sensitivity goes up as loop diameter squared, and up as wire length squared.
  • For a fixed wire length:
  • Sensitivity goes up as the loop diameter, and down inversely as the number of turns.
  • For a fixed loop diameter:
  • Sensitivity goes up as number of turns, and up as wire length.
Which shows that "Turns are good, but size is better!" and "Use as much wire as you can!"
That answers one of my questions:
Should I turn as much as possible and go for as long as the wire will let me, and apparently; yes I should :)

I'm still not sure about my idea of making the turns change in size as I go (To make it look like the image of the plastic wire on the clothes rack in the original post), but I'm guessing (Also since google searches show no such designs, which would probably have been plenty had they been any good) I should stick to the single-largest loop-diameter and forget about making different sizes and just do all the turns at that single diameter that is the largest.

And I am also not sure if it will be better to have a smaller loop 2 meters (6 feet) above the ground or the larger LoG.
Most google-searches about loops seem to mention loops placed vertically on a pole about 2 meters (6 feet) high, so I'm definitely curious which option may be best here (And if using a horizontal loop, instead of a vertical, changes which height is better)

If any of what I say here screams of being incorrect I obviously would like to get called out and set straight so I don't go chasing wild geese that don't lead to anything useful :) (No reason to repeat other people's experiments if they already are known not to work well)
 

WA8ZTZ

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Feb 23, 2014
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You may want to get a copy of Joe Carr's Loop Antenna Handbook.
Lots of interesting information although mostly dealing with vertical loops.
Otherwise, not sure about the affects of that aluminum frame. Can't recall ever
seeing a metallic loop frame (although in this case it is non-magnetic).
Loop frames are usually wood or plastic.
 

JELAIR

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Feb 22, 2018
Messages
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Thanks for the suggestion. I will look into that and see if it's for me.
EDIT: Wow, I just found it right here: Joe Carr's Loop Antenna Handbook : Joseph J. Carr : Free Download, Borrow, and Streaming : Internet Archive

I suppose I will just have to do the experiments and compare how things turn out :)

1: The LoG will have a larger circumference but be on the ground surrounded by hedge-row all the way round.

2: The Loop on the dryer-rack will have a smaller circumference, but be 2 meters (6 feet) above ground (And slightly above the hedge-row top, which in my case will give it a view of the horizon to some extent.)
 

krokus

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Possible idea: a magnetic loop, about 1.5m diameter, and suspend something decorative in the center, like a dream catcher. (Obviously, the decoration must be non-magnetoreactive.)
 

JELAIR

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Feb 22, 2018
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Short update:

I did a quick-and-dirty test of a loop on the ground vs being elevated about 1 meter (3 feet)

The LoG did pick up signals fairly well, but when being raised a meter above ground it increased its reception significantly (Giving from between 1.5 to as much as 2 times the SNR of the various stations I used for 'calibration'. So a huge increase in signal when lifted off the ground)

Possible idea: a magnetic loop, about 1.5m diameter, and suspend something decorative in the center, like a dream catcher. (Obviously, the decoration must be non-magnetoreactive.)
I hope to catch more than dreams with this antenna-setup ;)
But yes, I do want to keep the antenna as low-profile and 'invisible' as possible. I do want it to be as huge in diameter as I can get away with though, since I am also interested in the very low spectrum with this thing.
 
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