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Author Topic: Magnetic loop TX antennas  (Read 1376 times)

K6BRN

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Re: Magnetic loop TX antennas
« Reply #30 on: September 16, 2022, 07:21:31 PM »

Quote from: KK4GMU link=topic=137095.msg1273511#msg1273511

You're making this too much fun. ;D  You make one more erroneous assumption: You apparently believe that giving reasons  for choosing a given piece of equipment to help others understand the circumstances is disliking the answers.  Nope.  Giving reasons for choosing a given piece of equipment is NOT disliking the answers.  It is explaining the situations where use of a given piece of equipment may be most appropriate.  I understand there are those who lack an understanding of the logistical situation of some others - without assuming they are in "assisted living."  That was just a careless expression triggered by your disagreeing with my explanation.

Mmm.  Perhaps if nonsense is fun.

Seems like you already had the answers you wanted when you started the post.  Per Mark (K5LXP):

Quote
Expectation is a significant factor of your project here.  You've put a few unnecessary (in my opinion) constraints on the situation and in reading your message, there is only one possible conclusion.  That being the case, full steam ahead - get the loop, put it up and you'll decide if it works well enough for your goals.

The very attic-antenna-convenient structure of your home, open grounds and the statement that you tried laying a G5RV wire antenna directly on the roofing with less than satisfactory results pretty much says:  1. You really don't understand the opportunities you have, and/or 2. You just don't put much effort into putting up your antennas.

In that case, a magnetic loop is ideal, and I do understand.  Personal capability apparently has nothing to do with your approach - motivation vs. effort does.  And that's fine.  It's your station.  As pointed out by Mark, you get out of it what you put into it.  And experimentation is a great learning experience.

Meanwhile, my three stations are giving me great results - one of which is in an HOA with a structure not too different from yours that I operate FT8, SSB, FM and even occasionally AM from.  It uses a wire antenna.  I hope your magnetic loop solution works as well for you and that I hear you on the air.

BTW - what modes do you operate?  It does make a difference.  FT8 and CW punch through best with a compromise antenna.  But with recent very good propagation trends, you can have a great deal of fun with almost any antenna, efficient or not, on just about any mode, at the right time on the right band.

Have a good (remainder of) the day!  Mine was great.

Brian - K6BRN
« Last Edit: September 16, 2022, 07:37:51 PM by K6BRN »
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AI5BC

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Re: Magnetic loop TX antennas
« Reply #31 on: September 17, 2022, 09:44:55 AM »

Brian is like Glen must be brothers. Both are old has-beens from the QRZ peanut gallery. They like pounding their elitist chest. They remind me of Biden. They should go back to hiding in the basement.
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KK4GMU

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Re: Magnetic loop TX antennas
« Reply #32 on: September 17, 2022, 02:51:06 PM »

Brian is like Glen must be brothers. Both are old has-beens from the QRZ peanut gallery. They like pounding their elitist chest. They remind me of Biden. They should go back to hiding in the basement.
That's a fair assessment and suggestion.

Some folks are absolutely convinced that they know what they don't know about every situation while making themselves feel better by diminishing others.  In this case ignorant assumptions that a fellow ham is in assisted living, is imposing "unnecessary constraints" and "lacks motivation" are made just because someone is considering use of a different antenna design.

Amazing!  Keep such folk far away from Elmerhood.
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W1RKW

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Re: Magnetic loop TX antennas
« Reply #33 on: September 18, 2022, 04:21:44 AM »

in before the lock
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K6BRN

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Re: Magnetic loop TX antennas
« Reply #34 on: September 18, 2022, 08:18:30 AM »

Brian is like Glen must be brothers.

Hi Brad.  I got quite a chuckle over that one.  But I'll take it as a complement.  Not brothers, but both Americans.  Glenn and I have our differences, but we manage to get along nonetheless without letting politics cloud things up too much.

Both are old has-beens from the QRZ peanut gallery.

Heh!  Yep.  That's pretty much the definition of "retired", which I've done a few times.  You should try it - its a nice place to be.  BTW - aren't you about the same age as me?  I think I have more hair, though.  :)

They like pounding their elitist chest.

More like I don't like to be "gaslighted" by someone who really wants attention - any attention - by way of asking for help, any help that they don't really want or need.  Elite?  I'm elite?  Wow.  Didn't know.  I need to get some better clothes, then.  :)

They remind me of Biden.

Ah, poor Joe.  He's doing his best, and as the oldest president in history, the job is not easy (not that it ever is).  I respected Reagan, too, who drifted into a similar situation over his terms.  A good man, true to his principles from day 1 to the very end.  A lot of people forget he was governor of CA, too, and had a very big impact on the state's future.  If you're ever out in CA, the Reagan library is a "must see". REALLY.

They should go back to hiding in the basement.

I love basements.  Every home should have one.  Great place for storage and for radio stations.  Keeps the garage from filling up with junk.  Don't spend much time in them, though - just got back from a trip around the USA and Canada.  Great to do now that COVID has died down a bit.  You really should get out more and see the world.

Maybe operate more, too.  Looks like neither you nor the OP actually do that much.  You had a great start with all the old Heathkit gear on your QRZ page.  The most fun I ever had was with an HW-101.  And propagation is Up again.  So maybe time for you to get back in the hobby.  Fun.  Constructive.  Lifts the spirits.  I don't think saying that is elitest ... just being a ham. 

Have a great day!

Brian - K6BRN

« Last Edit: September 18, 2022, 08:22:36 AM by K6BRN »
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N8TGQ

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Re: Magnetic loop TX antennas
« Reply #35 on: September 19, 2022, 04:18:27 AM »

As far as you can.
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K3ZD

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Re: Magnetic loop TX antennas
« Reply #36 on: November 10, 2022, 10:49:27 AM »

I bought a second hand MFJ 935B mag loop tuner just in case I need one some day since I live in a rental house and will probably downsize some day.  I works surprisingly well, especially on FT8 since you are on one frequency.  Had no trouble working Europe with a 4 ft loop of copper tubing on 15 meters.  If you like tuning around the band forget it since you'd have to sit next to it to constantly retune.  I endorse those who say try to get up a piece of wire outdoors any way you can.  I have a 70 ft length of stealth antenna wire running from a small tree to a bigger tree end fed and it works fine.  Getting an end fed random wire to work without RFI shack problems takes some knowledge but I have no problems.  I use a coax choke to keep RF off the shield, a low pass filter, one random length counterpoise wire and an antenna tuner.  No antennas are allowed here but no one seems to notice it or care and my neighbor is on the HOA.   
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K5TED

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Re: Magnetic loop TX antennas
« Reply #37 on: December 11, 2022, 11:34:10 AM »

I ran a MFJ-1786 for years mounted to a short pole attached to a metal railing around the third floor balcony. Antenna was most efficiently tuned when perpendicular to the railing.

Worked all over the world from South Texas with 100w and that antenna. Phone and Digi.
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KF5KWO

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Re: Magnetic loop TX antennas
« Reply #38 on: December 12, 2022, 05:12:21 AM »

I have had the MFJ-1786 for about 20 years now, have run it in the attics of a 3-story townhome and my current one-story home, off a second floor balcony on a 12-foot pole laid horizontally, and my current 12-feet off the ground on that same pole (erected vertically). It is my only antenna for 20m. It does fine outside, has a remote tuner, and is easy to take apart and clean and check once a year. It’s a bit pricey now, compared to when I originally bought it new back in the day. It handles up to 150 watts. Given the HOA situation you’re in, this antenna might be a good option for you.
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KK4GMU

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Re: Magnetic loop TX antennas
« Reply #39 on: December 12, 2022, 01:05:59 PM »

I have had the MFJ-1786 for about 20 years now, have run it in the attics of a 3-story townhome and my current one-story home, off a second floor balcony on a 12-foot pole laid horizontally, and my current 12-feet off the ground on that same pole (erected vertically). It is my only antenna for 20m. It does fine outside, has a remote tuner, and is easy to take apart and clean and check once a year. It’s a bit pricey now, compared to when I originally bought it new back in the day. It handles up to 150 watts. Given the HOA situation you’re in, this antenna might be a good option for you. [bold added for emphasis]

Thank you for sharing your experiences with your 1786 loop. I expect its arrival sometime in January from HRO. 

Many here encourage trying a wire (70' more or less) or some form of home brew device based on their own experience, version of a good time, operational priorities and size/layout of their property which in my case all of which most likely differs greatly from theirs.
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N4UFO

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Re: Magnetic loop TX antennas
« Reply #40 on: December 13, 2022, 03:14:10 PM »

I got curious about mag loops (or STLs as some say they are more appropriately called - Small Transmitting Loops) a few years back and did some reading. Once I understood the theory vis-a-vis the 'golden triangle of antennas ( efficiency, small size, wide bandwidth - pick TWO) it made sense and I desired to try them out. So I first got an MFJ-935B and made some loops out of copper tubing and experimented. Not enough though, I am afraid... but what I did do showed very promising results.

When we moved cross country and into an apartment I took a certain government check sent to everyone and handed it over for an MFJ-1786 to use at the apartment we had rented. Unfortunately again, my 'play' was cut short by some very sensitive AFCI breakers. And once we were able to buy a house and move in, I found the numerous trees around to be good supports for wire antennas. One of which I built was a set of vertical wires with the feedpoint mounted at the top of a wooden fence going up to a tree limb. Each band had two radials going down the back side of the fence, spaced the same distance apart as the vertical portion. This is a very good, well tuned antenna that talks all over the world.

So... after finding a good deal on a reliable TV rotor I had used before AND being bored, I decided to get the MFJ-1786 out of storage and do some experimenting. I mounted 3' tripod on a weighted down wood pallet in the yard with a 4' mast that had the rotor and a lateral support bearing mounted to it. Then I went up with a typical 4.5' TV mast to the loop. All-in-all it was about 8 foot above ground and rotatable. Let the fun begin!

What did I discover? Well, first thing I did on the antenna was work a Malawi DXpedition on 10m FT8 that I had been unsuccessful up until then with my vertical wires. This can be attributed to other things, of course, but I did a lot of A/B testing after that. Bottom line, if I point the 'end' of the loop at a station, I would observe 2 S  units better reception over the vertical wires and a 2-3 S unit decrease when I aimed the broadside nulls at the same station. This repeated fairly consistently. BUT... the wires seemed to be much quieter than the loop, thus negating the 'advantage' when aimed at a station. This was atmospheric noise and not local noise. However, if I DID have say, some local electrical noise or RFI, aiming the loop with the null towards the noise would be a great advantage to working some stations.

My original hope was to use the 'directional advantage' of the loop to aid me in working DX stations. But the noise difference seems to make it a draw and the loop has no advantage, thus far, over the wires. What I have NOT experimented with enough is issues of take off angle... local versus distance, etc. I have a 20 ft cliff and then a metal barn just beyond the edge on top of that cliff/rise which is only about 50 feet behind my wires to the south. I would like to use the loop to work more SA on 10m and see if it helps with a higher angle due to reflection off the nearby ground.

So, there may yet be some advantages to the loop I don't yet know about. BUT, I have recently purchased a lightweight 6m yagi and may use a second slip on mast and put the yagi up in place of the loop. So, no telling if/when I will get around to experimenting more. But MAKE NOTE. I am not taking down the loop because it is not a good antenna... I am taking it down because it is NO BETTER than my vertical wire antennas. It is a GOOD antenna, in spite of what some think because of it's size.

The 'triangle' I mentioned... pick two? Obviously, it's Efficiency and Small size. The Bandwidth is VERY narrow... BUT it's remote tunable!!! So that makes up somewhat for the narrow bandwidth curve. It would not be a great 'scan the bands' antenna... but it a day & time when modes like FT8 & FT4 are popular, one can tune up on a band and sit there for hours watching/working other stations. Or occasionally QSY to another band. I seem to be able to do that to a nearby band within a cycle or two (30 seconds). Going from 30m to 10m or vice versa might take a little longer.

Enjoy your loop! I highly recommend that if you mount it horizontal, put it 20 feet or more above ground... if vertical, leave it rotatable, whether remotely with a small rotor or armstrong by hand.  :)

As always... your mileage may vary.  ;)  Wow! 6m is open... wish I had the beam up already!  :D
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KA4WJA

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Re: Magnetic loop TX antennas
« Reply #41 on: December 13, 2022, 03:28:48 PM »

Jerry,
1)  Yes, you are correct that many of your fellow hams' situations / locations / applications may be vastly different than yours....and, you desiring to try something that better "fits" your situation / application is fine.  :) 
And, I think we all wish you good luck in your choices!  :)

Many here encourage trying a wire (70' more or less) or some form of home brew device based on their own experience, version of a good time, operational priorities and size/layout of their property which in my case all of which most likely differs greatly from theirs.

But....(don't you just love it when someone says they agree with you and then they add a "but"?)


2)  But, I would like to politely point out 2 important things:

a)  that there are some hams here-about (myself included) that have many decades of experience and many years of education in these very matters / in these very same situations....so, some of the advice / recommends that you get from these folks are not only well-intentioned and/or based on those personal experiences, but also based on the "physics" of RF / Antennas, not trying to dissuade you from any particular antenna, nor steer you away from experimenting.

b)   the "physics" of RF, antennas, etc.....actually getting radio-frequency energy (RF) from your radio transmitter, efficiently out into the ether / atmosphere.....well, this is well understood (and has been for many decades), and while some salesmen might try to hype their newest / greatest antenna, etc., please remember the new ham doesn't need to understand all of the "physics" here, as long as they grasp the rather blunt (but truthful) adages of:  "you don't get something for nothing" and "there's no such thing as a free lunch", "the wheel doesn't need reinventing", etc....

c)  just about ANYTHING metallic can be used as an antenna.....it's all a matter of degree!
(if what you buy/install is good enough for you...cool....but, if you want "better", there are "better", that don't cost as much, etc.


Sure, a good understanding of the "physics" of all of this would be great....but, until then, please just accept these facts above.  :)



3)  Jerry, I truly wish I was back home (just ~ 10 miles from you), where I'd happily stop over and offer to help / experiment, etc....and especially to help you save money on boondoggle's!
(Maybe next month?)


Anyway, fair winds, good luck, and 73,
John,  KA4WJA
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K6BRN

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Re: Magnetic loop TX antennas
« Reply #42 on: December 13, 2022, 04:32:08 PM »

Hi Gerald (KK4GMU):

I see its December and you still won't have your antenna up until at least January.  Bummer!  (I love operating during the holidays). Regardless, you'll get there.  Just be persistent.  I'm sure they'll be a lot of learning along the way.  It's part of this hobby and fun by itself.

Please let us know how the MFJ loop performs when you have some time on it.

Following up on our much earlier conversation months ago, I've moved my EFHW-4010-2K into the attic of my East Coast townhome (QTH#2).  This was necessary because the tree it was run out too previously came down.  Ooops!  What to do?

Normally I don't care for attic antennas due to possible RFI/EMI issues, but I thought I'd give it a try.

The townhome has a pretty high roof peak, just like yours.  So I moved the antenna into the attic and folded it's 63-foot length into a (more or less) horizonal V, with the apex elevated to the roof apex furthest from the adjacent unit and the ends at just above ceiling height close to the adjacent unit.  The apex is pointing nearly due West.  There was a few feet left over after forming the "V" so I just bent it in the direction of forming a "delta" shape.  Then I placed a pretty hefty common mode choke about 4-6 feet from the feed-point and another at the operating station, three levels below.  To my great surprise, it works quite well with no apparent RFI/EMI issues - at least up to the 500 Watts I've pumped into the 75 feet of feedline.  And it's apparently (roughly) omnidirectional.

In the current great propagation, I've made contacts worldwide on FT8 with ease, and haven't had too much trouble talking to Europe and the West Coast on SSB (depends on the band and day).  There is some heating of the 49:1 matching transformer on 40M and some in the attic CMC as well when running QRO for extended periods, so antenna efficiency is less than perfect.  But it seems more than good enough and receives very well. too.

Your condo is single level, so I'd probably avoid placing the antenna apex directly over the operating station if I were to try the same there.

This might be one other possibility to consider during your adventures.  Which are likely to continue for some time if you stay in the hobby - they're half the fun.  You did ask for relevant personal antenna experiences in this thread a while back.  So I thought I'd contribute the results of my latest condo-living-as-a-ham-in-an-HOA experiment.

Happy Holidays!

Brian - K6BRN
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N2ZD

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Re: Magnetic loop TX antennas
« Reply #43 on: December 17, 2022, 09:36:22 PM »


  A lot of naysayers out there. I bought a Ciro Mazzoni Loop which covers 10 thru 40m.
 I figured I would give it a try since I'm now in a HOA and see how it does. Well, it works fantastic for what it is.

    I worked around the world using 100 watts with it set up on my driveway. Now here is the fun part. One day I was farting around with my FT817 and hooked it up to my Mazzoni. With 5 watts, I worked 10 countries on 10m,17m,20m. in one hour. It was set up on the Tripod, 5 feet high at the antenna base. Although this antenna is quite expensive, it does work. It tunes using a box that sends a small RF signal up the coax which returns if the swr is greater than 1.1, then antenna will adjust the size of the loop accordingly in order to couple or decouple the air capacitor on top. This is usually accomplished in under 10 seconds.

   The caveat is its expensive, its big, but in contrast,  it doesn't look like a typical antenna. But can be made to look like a SAT antenna with a gray cover or just lay it down when you're done using it.

  Anyway, one can assemble a sub-100 watt version for less than a few hundred bucks using a suitable vacuum variable capacitor. The MFJ one works, if you can find one in good shape. Is it a compromise? Yes, but a fun one. Most DX stations love to work QRP stations at 5 watts. Most rag chewers will enjoy the contact as well.

  I've also had decent luck using a 5:1 balun and rain gutters. Hidden or compromised Dipoles, and a 5BTV on a foldable mast at my previous qth. For my next trick, I'll sink a WillBurt in my yard for "Up at Night, then out of sight"

Regards Richy N2ZD

 
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KK4GMU

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Re: Magnetic loop TX antennas
« Reply #44 on: December 21, 2022, 04:10:14 PM »

Thanks John for looking out for me.

And Richy, I appreciate your sharing your successful experiences with your Mazzoni.  I'm expecting to receive my "poor man's Mazzoni", the MFJ-1786 (a bit more difficult to tune than the Mazzy) I've had on order since October and expect to receive in January.  Looking forward to the adventure.

I've installed and set up a couple of digital apps (WSJT-X and JS8Call - integrated with Win4Icom) and am familiarizing myself with them in anticipation.
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