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Old 04-18-2017, 2:44 PM
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Default Mag Loop / horizontal vs vertical

I am studying the very basics of magnetic loop antennas, I do not have one. I am trying to learn about proper location and mounting. In the most generic terms, it appears a horizontal mounting of a magnetic loop should produce a general omnidirectional antenna, and a vertical mounting of a magnetic loop should produce a directional antenna. In the most basic terms, is this correct??
I have found from reading that there are countless numbers of homemade loops, and plenty of commercially produced loops. And because of the wide variety, there are no set answers for exact placement and setting on any particular angle. I am simply trying to make sure I understand the fundamental concept of horizontal = omnidirectional vertical = dual directional, that's all. Thank you all for your time and help, take care.
I would like to save the discussion regarding a proper height of a horizontally mounted antenna for another day, I have read those, and even I know that can get lengthy, thanks..
Also, I realize FM is line of sight, so the term 'omnidirectional' in horizontal position isn't 100 % accurate, but I just want to make sure I grasp the concept. My interest would be more toward MW and SW, so FM isn't a large factor.
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Last edited by AlphaFive; 04-18-2017 at 2:54 PM.. Reason: add fm information
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Old 04-19-2017, 8:30 AM
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Quote:
Originally Posted by AlphaFive View Post
I am studying the very basics of magnetic loop antennas, I do not have one. I am trying to learn about proper location and mounting. In the most generic terms, it appears a horizontal mounting of a magnetic loop should produce a general omnidirectional antenna, and a vertical mounting of a magnetic loop should produce a directional antenna. In the most basic terms, is this correct??
I have found from reading that there are countless numbers of homemade loops, and plenty of commercially produced loops. And because of the wide variety, there are no set answers for exact placement and setting on any particular angle. I am simply trying to make sure I understand the fundamental concept of horizontal = omnidirectional vertical = dual directional, that's all. Thank you all for your time and help, take care.
Yes, at the most basic level, without talking about E vs H and polarity (and how that will impact efficiency), a horizontally mounted mag loop will exhibit an omnidirectional pattern compared to a vertically mounted mag loop.

What has really happened is the loop is still bidirectional, however now you have pointed the nulls straight up and down, at zenith and at the ground.

Also keep in mind that a mag loop is not very directional with regards to skywave signals. The higher the arrival angle the less well defined the pattern is. For direct path and groundwave signals a loop can have extremely deep nulls. Typically the main beams are not very sharp, they are wide and flat, but the nulls can be very sharp and deep.

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I would like to save the discussion regarding a proper height of a horizontally mounted antenna for another day, I have read those, and even I know that can get lengthy, thanks..
Also, I realize FM is line of sight, so the term 'omnidirectional' in horizontal position isn't 100 % accurate, but I just want to make sure I grasp the concept. My interest would be more toward MW and SW, so FM isn't a large factor.
You really cannot separate out height from the rest of the discussion, a vertically mounted mag loop might be very directional (to groundwave and direct path signals) when low, but become less directional to some of those signals when mounted above a certain height.

I am not sure what you are saying about FM and line of sight I assume you mean the VHF FM broadcast band, which of course would be primarily LOS by virtue of the frequency. However a mag loop for MW/SW would not be usable the same way on VHF, so not sure why you are including that. A mag loop is physically small, less than 1/10 wavelength. A 1 meter loop may be good for MW/SW, but would be too large for use on VHF. At those VHF freqs it would not function as a mag loop, but rather more as a folded dipole or sky loop, with different properties from a mag loop.

T!
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Old 04-19-2017, 9:04 AM
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Default Mag Loop antenna

Thank you very much for your reply, it was informative. I am starting to see that just because a mag loop may be in a vertical mount, that does not mean a large portion of the available area is simply not accessible. Apparently the non accessible area would exist out from the center point of the vertical antenna body on each side. I find many articles that do not even consider a horizontal mount worth discussing or mentioning. I just looked at a Monitoring Times review of the LA 400 and LA 800. The review covered vertical mounting. It must not be completely evil....
I did not discuss the height issue because my soon to be purchase of a mag loop will be for an attic mount. Still trying to wrap my mind around the accessibility issue for tuning / turning the unit, haven't figured that one out yet.
As far as the FM mention, I left this out, but I have been eyeing an LA 400. The claim is for up to 500 Mhz. I see many references that indicate yes, it will go that high, but no, the quality will not remain heading up into UHF, to put it simply again. I was picturing a horizontal mount, in my mind, seeing the antenna focusing on anything above it, and anything below the unit. Knowing FM is sent out "line of sight", my limited knowledge pictured the signal being ignored coming in at a perpendicular angle to the antenna. Again, thank you for your help, it appreciated. I'm going to read over the post again, and make sure I comprehend what you were trying pass on to me. Take care
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Old 04-19-2017, 10:01 AM
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While MT isn't evil, the prices on those loops are (way overpriced). You might want to consider the W6LVP mag loop, which is a whole lot less expensive than the overpriced and overcharged AORs. It is, in fact, among the least expensive of the loops currently out there. Here's the link, and also a link from eHam using the antenna with the T/R switch (which really won't affect receive performance)...

https://www.w6lvp.com/product/amplif...ower-inserter/

W6LVP Receiving Amplified Loop with transmit/receive switchbox Product Reviews

If I still had an attic, this would be the way I would go. Of course, outside and away from the home is best, but if you can't, then the attic is the next best choice...

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Old 04-19-2017, 10:33 AM
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Default Mag Loop

Haaaa, sorry about the confusion, M.T. is great. I way talking about vertical mounting. When I began reading about horizontal mounting, I started to think that (horizontal) was then only way to go for MW and SW, and that vertical was extremely restrictive in areas of reception. I am starting to see that is not the case. I will look over these links and take in what they have to say. Thanks for your help, it's always appreciated.
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Old 04-19-2017, 2:07 PM
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If you are serious about attic mounting, you will definitely want a remotely tunable magnetic loop, or at least one which will allow you to cobble together some form of remote capacitor tuning.

I'd like to give you my experiences with the MFJ-1786, but mine is still on "back-order" so I've had six weeks to simply stare at my shiny KX3 and PX3 and dream...
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Old 04-19-2017, 2:38 PM
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Default Mag Loop

Thanks for that Bill. I went to the website, watched an 18 minute video of the unit in use. A good video, makes the system look fantastic. Again, I see that the user in the video felt no need to go horizontal, just vertical. He had a temporary set up in his back yard, with basic coax, he was making it from Florida to Missouri.
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Old 04-19-2017, 8:15 PM
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I understand that W6LVP is very receptive to questions, so I would encourage talking to him about his product.

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Old 04-19-2017, 8:24 PM
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Quote:
Originally Posted by N4GIX View Post
If you are serious about attic mounting, you will definitely want a remotely tunable magnetic loop, or at least one which will allow you to cobble together some form of remote capacitor tuning.

I'd like to give you my experiences with the MFJ-1786, but mine is still on "back-order" so I've had six weeks to simply stare at my shiny KX3 and PX3 and dream...
While this is a receive only forum - we have another forum for ham antennas - there are a couple of other alternatives that are, in some cases, far less expensive than the Mighty Fine Junk model - but not to worry, these would work just fine for receive apps too..

Magnetic Loop Antennas

https://www.dxengineering.com/parts/...FYaPswodwQkCoA

There's likely several others I don't know about, and any additional links are welcome

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Old 04-20-2017, 9:41 AM
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Quote:
Originally Posted by ka3jjz View Post
While this is a receive only forum - we have another forum for ham antennas - there are a couple of other alternatives that are, in some cases, far less expensive than the Mighty Fine Junk model - but not to worry, these would work just fine for receive apps too..

Magnetic Loop Antennas

https://www.dxengineering.com/parts/...FYaPswodwQkCoA
With respect Mike, it matters not. Regardless of intended use, all mag/loop antennas require manual or automatic tuning for good reception. Mag/loop antennas are very narrow around their resonant frequency.

In fact "coarse tuning" is best accomplished by adjusting the tuning capacitor for maximum "noise" in the speaker...

...a task that would be massively inconvenient with an attic mounted mag/loop.
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Old 04-21-2017, 7:22 AM
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Quote:
Originally Posted by N4GIX View Post
With respect Mike, it matters not. Regardless of intended use, all mag/loop antennas require manual or automatic tuning for good reception. Mag/loop antennas are very narrow around their resonant frequency.
Active mag loop antennas, like the Wellbrook or Pixel Pro, do not require tuning. Of course, traditional passive mag loops do.

Quote:
Originally Posted by N4GIX View Post
In fact "coarse tuning" is best accomplished by adjusting the tuning capacitor for maximum "noise" in the speaker...

...a task that would be massively inconvenient with an attic mounted mag/loop.
I have built remotely tuned mag loops before. A simple radio control servo driving the tuning cap works fine. Some servos make RFI, so it can be a tune, listen, tune, listen operation, depending on the servo. When combine with something like an Arduino or similar controller you can build a table of frequencies and servo settings, so that you input the freq with push buttons and an LCD screen, and the Arduino drives the servo to the right point. Although I have not yet done it, you could even have the Arduino poll the receiver (assuming the receiver can be computer linked) and automatically drive the cap tuning servo position based on tuned frequency.

By the same token, another servo can be used to adjust taps, to allow wider bandwidth with multi turn loops.

Also, a TV antenna rotor with the loop makes for a very complete setup. You can turn the loop to maximize desired stations, or to minimize noise or unwanted stations.

T!
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Old 04-21-2017, 8:40 AM
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Default Mag Loop

So,,, if I chose not to attempt manually (remotely) tuning a magnetic loop, which having very limited knowledge of the subject seems right. Then I will want to chose active, not passive, correct?? This has been very helpful, I started this with very little of the knowledge necessary to install a correct system, now I am starting to see a little light...haaa. Thank you all for your help. I hope someone else in my position is reading this and learning a little too

I believe you are both correct, just on an adjusted scale, at least from my limited point of view.. If for example I look at an LA 400 active antenna. It does come equipped with a "remote tuner", that simply works from a dial. So yes it does have to be tuned, but the procedure is so simplified that I can do it. I watched the video of the remote tuner on the backyard system. There would appear to be a learning curve. So yes, it would appear active antennas ( LA 400 ) do need to be tuned, but,, the procedure appears to be simplified for ease of use, somewhat different from a passive unit. That's the way I see it so far. Thank you both.. your time is appreciated.
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Last edited by AlphaFive; 04-21-2017 at 9:06 AM.. Reason: add clarification
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Old 04-21-2017, 10:48 AM
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It would appear that the active loops (including the W6LVP model) don't require tuning, so I would say yes. The tuned (passive) ones would be great for N4GIX's lo power applications, as long as he wasn't needing remote tuning (and they're a heckuva lot less expensive than the MFJ model that's been backordered).

If it were me, I'd look at the W6LVP model - it's a lot cheaper than the Pixel...Mike
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