Ham Radio - 80 160 meter magnetic loop transmitting antenna
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- čas přidán 9. 05. 2015
- This is my 6 foot diameter magloop for 80 and 160 meters. I create a two turn outer loop to get down to 160 and it works very well. I checked in to a local 160 meter net and 4 out of 5 stations could hear me. Pretty neat for a 6ft antenna!
There have been a few questions about the capacitor I used. Measured on my old Heathkit RLC bridge, it looks to be around 20-700pf with about 1mm plate spacing. I've pushed it to 40 watts without an arc.
I also built a mini loop out of junkbox parts for fun. It's 1 foot square and works really well.
• Ham Radio - Junk Box M...
Also, check out my quick and easy field day vertical:
• Ham Radio - Quick and ... - Věda a technologie
You're a better ham than most I know, including myself. Most of us buy stuff like this from MFJ, cross our fingers and hope it works out of the box. You, on the other hand, are the Homebrew KING!
That is a sweet setup ! Love homemade antenna designs ....
Great Job! That is a smart design you have made.
Nice job, Kevin!
That is a nice design, i think thats the nicest homebrew i’ve seen. Very nice job
Thanks. Search for Jeri Ellsworth on you tube. She's recently started building a very similar loop, partially inspired by mine. Her's is a much higher quality build though.
Yeah i saw that. There's only been one instalment so far, but yeah i'm itching to see more
Big upgrade for the loop since then
A loop like that is perhaps 2 to 3 percent efficient at most for 1.9 MHz at that diameter, also, that small of copper pipe has high IR losses, the diameter needs to be much larger, one recommendation I've seen is greater than 1/24 diameter of the loop itself which is at least 3 inches and as a double loop, double that diameter of pipe. I mention this so others can know these loops need much larger diameter conductors due to high IR losses from skin effect.
Nice work.
Good job Kevin.
Cool. Jeri (ki6tk) keeps the loops parallel and crosses at the bottom. Just beginning my studies of the Mag Loop. Thanks.
great! well done!
Totally incredible
Good job Kevin, hadnt found this one yet , i built one similar to your for 40m , couldnt get it to work , strange ! made a 10 pc of CU in a circle and a split rotor cap , tried various feeds , Notta ! Congrats om ! Good luck K. 73 Jerry K9UT
amazing!
You say "...not very efficient" and I'm imagining you're referring to TXing thru the loop, but I know many 160 lovers who swear by a loop like this for
- RX ONLY -
to help eliminate local QRN, then TX thru a large Inverted-L, dipole or T-pole, etc.
Great Video, and all you needed to say was "the two loops are now in series" (4:21) most will track with you.
Thumbs UP!
Nice great job
Great video. How did you figure out how much space you need between both loops?
I like it!
A point to consider, If you use a butterfly capacitor you won't have the resistive wiping contacts thereby improving the Q of the system. I'll be making a magnetic loop later this summer. I'm in the process of designing a split cylinder rotary variable capacitor rated at several kV. (Remotely operated I hasten to add!)
nice one
Have you ever tried to tune up the 160m configuration on 80m? Thanks.
Kevin UR brilliant. Tnx for video. I was building a 6 ft loop for 80m and decided to watch UR video. I like how you think. Gud DX
VE3LYX Don
Hi Don! I like how you think as well. Nothing long homebrewing.
Harbor Freight has a fairly inexpensive tubing bender... I made my magloop with that tool and it's a nice perfect circle.
@Überleben I heard the feed loop couples with the main loop better when egg shaped, but I haven't heard about the entire antenna reacting that way.. I'll have to try it. Thanks!
What tubing did you use? Why not just buy like 0 gauge copper wire? Then you could bend by hand no?
@@Justin-bd2dg The larger diameter the loop conductor, the more efficient (higher Q) it is. And the more broadbanded it is. Ideally you'd want a donut shaped loop (that looks like an actual donut or bagel) but doing that in copper or silver is impossible for most people.
Q is a function of resistance. Accounting for surface effect, then the smaller diameter the loop conductor, the lower the Q and the more narrow your parameters will be.
The more resistance in your loop, no matter the dimensions, the worse the performance. So if you were to try and make a donut shaped loop of massive proportions but built it poorly, although the shape was ideal, the resistances of the shape would remove all your gains.
Thinking of this further, if you were to fabricate a giant donut of some material that was conductive and smooth, and then electroplated it with copper or silver, then you'd be golden!
BONUS: If the cross section of said donut was large enough, then you'd just need to manipulate the gap between the separated ends with precision for your capacitor, provided the ends were terminated with conductive circles, perhaps separated by glass or other suitable dielectric.
@@patrickp4827 I saw a guy build one of these with aluminum clothes drier ducting.
Nice 👍🏼
Capacitor looks to be about zero to 400 Pico Farad Variable....I like those
Neat! Good job. Glen, N0QFT
Kevin that is an amazing idea!! 73 N9RAN
Perfect,super
Could you do the same with PVC as the shape and braided ground strap inside?
Kevin, great job. Can you point me to the theory behind the "crossed loops"? I have looked. Lots of theory on mag loops but not concerning the way that you crossed them.
I don't know that there is any. It was just an experiment that worked.
Kevin. I love your design for this 80 / 160 m loops. I already have a mag loop that covers 40, 30 and 20 m and have been looking for designs to cover 80 and 160 and yours is the best one I have found. I have an FT-817ND too, but also a Kenwood TS-850S, and want to build the new loop for higher power levels, so have bought a Russian KP1-8 15-750 pF vacuum variable capacitor to use with it that is rated at 5 kV and 35 A. I may also try to use larger diameter pipe than you have too (I aim to make it handle up to 100 W).
I would be grateful if you can tell me how your loop performs on 80 m when configured for 160 m, compared with configuring it specifically for 80 m?
I will be extremely limited for space for antennas as my new location which is a second floor 2 bedroom apartment (fortunately with a nice size loft). If 80 m performance is too poor when configured for 160 m, then I might consider using some form of remote switch to cut out the second loop. I already have a 3000:1 gearbox motor of the type I use for my existing loop for remote tuning.
I am also unsure of the plumping aspects as I have not worked with copper pipe. I have seen simple designs for pipe benders which could be made to make a pure circle, rather than a 12 sided one, but would like to know how you fitted the threaded unions, what did you use to solder them on?
Thank you so much for publishing your design and hope that you get some great contacts with it! 73
loop like that is perhaps 2 to 3 percent efficient at most for 1.9 MHz at that diameter, also, that small of copper pipe has high IR losses, the diameter needs to be much larger, one recommendation I've seen is greater than 1/24 diameter of the loop itself which is at least 3 inches and as a double loop, double that diameter of pipe. I mention this so others can know these loops need much larger diameter conductors due to high IR losses from skin effect.
I'm geeting the license, soon (beginning of the new year). So I'm looking for a simple antenna for 80m. I think a copper loop should be a goal...
Kevin: I know this video was made quite a while back, but I made a 2-turn loop recently, and found it would tune across a 2:1 frequency range without having to change from 1 turn to 2 turns. Did you investigate the possibility of using the 2 turn configuration for both bands?
de WB2VUO here near Buffalo, NY
I like this antenna. Is it possible to use a crucifix frame and two turns of standard antenna wire?
Yes and no. Efficiency is dependent on electrical resistance of the outer loop. Thinner wire would lower the efficiency quite a bit.
Hi, Im a new ham (general) KM6IEV as of 2/7/17. I just got a FT-817 radio package that was a steal. it came with the LDG Z817 tuner, a mini buddipole antenna with an 18' mast and tripod. It also has the MFJ- 1899T multiband antenna and the Arrow II satellite handheld antenna along with a wolpilink for computer control and digital modes. needless to say i basically got a portable QRP station in a box. I love the idea of QRP and bouncing DX on low power. anyway i figure with a mag loop in my attic i could get some pretty good distance since its about 18 foot above ground.
I have been looking at the mag loop antennas because i live in a condo with an HOA. I dont want to have to put up and take down an antenna every time i want to get on the air. I would like to build one that would cover from 160 to 6 meter. I know this may not be possible because of the physics. however if in not wrong in the way this looks the small loop is the real antenna and the larger loop is the coil that works with the capacitor as the antenna tuner. in this case why couldnt you build a radiator thats about 1 foot diameter and then a single turn larger loop of say 4 feet and then add an inductor in series with the larger loop to add in the inductance needed to tune the various bands. if im not wrong this is basically the way the antenna tuners work anyway so why wouldnt this work for the mag loop antenna to make it multiband????
Thanks.
A magnetic loop is basically a tuned circuit by itself. So if you nested loops, they would interact with each other and throw everything off. If you have multiple magloops for different band ranges, they'd have to be well away from each other, like 20 feet or so, to prevent them from affecting each other.
Height doesn't matter much with them either, they work about as well an inch off the ground as they do 5 feet off the ground.
If you have an attic, you might do better with a dipole the full length of the attic, at the peak of the roof, and use the tuner. If your house is at least 40 feet long, you'll do well on 40 through 10 meters that way.
160-80 meters really needs space. My loop worked on 160, but not as well as a longer wire antenna. Some people get away with an end fed wire running from the house up into a tree. If you use small gauge wire, it will be hard to see from any distance.
Unfortunately my attic is only 20 feet long and about 28 feet wide with the peek along the 20 foot length. i guess i could try and do some kind of Z shape with a trapped dipole but still it would be an odd shape and not so efficient. If i had more then one mag loop ad there was only a few feet between them how would they effect each other if only one of them was powered up at any given time??
I could use the MFJ-1899T but to really make it work properly for the lower bands you really need a counterpoise and that again is a problem since my station is on the second floor. I cant really drill holes in the walls. I have thought about making a narrow strip of aluminum with connectors in it that can sit in the window and connect to outside wires but being on the second floor its still a bit of a problem. Also i dont have any trees i can use for an end feed antenna. I possibly could route a wire around the garage roof so it couldnt be seen but i would still need to run the coax to it. It would be long enough to get a 160 foot length and with traps could work multiband but its only 10 feet off the ground and would be a U shape.
Its a frustrating situation but i will figure out some way to get this rig set up with a good antenna without breaking the bank doing it. I have even thought about setting up the buddipole so the mast goes thru the access door into the attic but then i have to worry about the heating ducts blocking half the antenna not to mention the impossibility of changing bands.
Thanks for the info, its given me a couple more things to think about.
If you can put a radial system in your attic, you can get a remotely tuned mobile antenna. Yaesu makes the ATAS-120 that tunes down to 40 meters that your radio will easily work with. A step up would be a High-Q antenna. They make several antennas that go lower. You must accept that short antennas are very inefficient but they still work. If you have a patio, and you can lay out radials, you can use several single band mobile whip antennas that only run about $20 each. Low bands will have a narrow bandwidth. You can get quick disconnect mounts for those if you wish.
You can always use a combination of antennas too. A magnetic loop antenna vertically is directional and that can be an advantage but you have to be able to turn it. Can't do that in an attic. If you have a patio, no problem.
Good luck!
Nice build. Can you possible use a motorized tuner instead so you can put that antenna in your attic and tune it from your shack?
+John Athanassion Sure. See my other video on my smaller loop. I have a really nice remote tuning system with feedback at the control box. The video is here:
czcams.com/video/J2QBQ45C0b0/video.html
question ? how did you arrive at 6ft for the 80 loop ....also will the 80m loop work on 40m/20m ? ... if i build a 12 foot loop would this work on 160m using the same 20- 700pf cap ? curious
My answer may disappoint you. I had good results down to 40M with a 3ft loop, so I simply doubled it hoping for a linear relationship between size and frequency. It worked out precisely so. However, the range of frequency shrunk with the size increase. I was not able to get the 6 foot loop up to 7Mhz with the lowest capacitance.
I think the scaling up of size of the loop would also need larger gauge conductors in order to maintain efficiency and band spread. But that's just a guess, without building one to test.
I have no idea how a 12ft loop would behave. If you build such a monster, I'd love to hear how it behaves.
hi Kevin, thanks for the reply ... i may at some point build the 12footer my concern was about the capacitor needed to tune im guessing that if your tuning the 6ft at half the total of your 20-700pf then at 12ft there maybe a double up effect or even slightly less .but i will certainly let you know if i start a 12ft loop 73
there are other antennas that do multiple loops in series like this but its usually avoided because it makes them alot less effecient and they are VERY narrow banded compared to a single loop. BUT great job getting on 80&160 on such a small footprint. My motto is if it works good it is good.....73 kc9zhr
It's interesting that you still get a good match with the 2 turn tuned loop as that would provide a different ratio to the coupling loop. The two turns would be less efficient than a single turn and for this reason I would've just tried more capacitance to get it to 160m as its simper and the efficiency goes down in either case anyway.
+Dazzwidd The ratio difference is exactly why it works. Think of the loop as an air core transformer with a primary and secondary winding. Yes, the efficiency goes down, but it works. Having a QSO with an indoor 160 meter antenna was a thrill. Although the other guy didn't believe me when I told him.
I'm not questioning that it still works but am contemplating that instead of having a 1 to 1/5 ratio, you now have a 2 turns to 1/5 ratio of circumferences. It's interesting and makes me curious why you don't need a 2 turn loop on the coupling coil for best operation.
Dazzwidd 2 turns, but still the same diameter. The ratio in diameter is unchanged in the two turn version, the coupling loop is still 1/5th the diameter of the outer two turn loop.
The only change is in the ratio of inductance between the two loops.
I wonder that as your inductance loop will induce "two" loops simultaneously if converting into a figure of * so that it only induces one that you might have better performance. It would double your foot print to do so though...
lukeoid153 I would wonder about the phasing in a figure 8. It would probably cancel itself out that way. I have a 98 foot end fed wire, and the loop performs just as well in testing.
Where is a good place to buy or get varable capacitor and how far can you change the frenqency before the SWR gets to high?
I get caps at hamfests. The bandwidth is around 5kHz from 2:1 to 2:1 on either side of the resonant point.
Do you happen to remember what your SWR & Q was for that on 160M ?
I was able to get the SWR right down to nearly 1:1 and the bandwidth was ridiculously narrow. Just over 3Khz.
Can you explain your impedances & impedance matching & balanced vs unbalanced. Am I wrong in seeing you solder an unbalanced-system coax to a balanced (by nature) loop? Did you need a balun?
As far as I'm aware, nobody has used one with these loops. It's an interesting thought though. I'll have to go look around and see if there's any discussion anywhere.
xyz abc A current balun 1:1 is what I use. When you use alot of power its possible to experience rf down the sheilding. However these antennas usually work fine without.
Without a balun though touching the coax or the placement of the coax will cause a very small drift in the tuning. In both cases its best to make sure the coax is not parallel to any part of the coil or touching it as this will throw off your swr. I tend to use like a string or rope to hold the coax near the center and out of the plane. Usually I have a nema box and just run the coax through a duct tape mounting system to keep it from wandering.
nice setup. can you give what is the value of the capacitor and up to what wattage wwre you able to run without arcing? and are you able to work all the 160 and 80 meter band or just a part of it?
+Kevin Loughin exactly. will work on a project like this, will give you back news, that of course if I find a good vacuum varable capacitor.
+Pierre Martel Great! Would love to see what you come up with. Hey, did you see my quick and easy field antenna video? Setup time is 2 minutes and you're on the air for 20, 17, and 15 meters without a tuner.
+Kevin Loughin nope! will take a look!
+Pierre Martel I've just measured the cap. It's 20-700pf and I'm hitting the middle of each band around to 250-370pf range. Plate spacing is about 1mm, and I've hit 40W without arc.
It is pretty large
How about making the plans for building this online some where ?
It's the same mechanical construction as any other magnetic loop. I give the dimensions in the video. You should have all the information you need.
Was wondering how much power were you running during he contacts you made?
That was a long time ago, but I think I remember that it wasn't much. 20-30 watts most likely.
As I understand Small Magnetic Loops, they are fed at the point opposite of the capacitor; 1/2 way around the loop. When you switch from 80M to 160M, by leaving the feed point where you have it, aren't you feeding the 160M loop at the 1/4 and 3/4 points rather than 1/2 point around from the capacitor? Would also enjoy seeing your field strength device implemented on this one. Thanks, Ron, AE5WW
It's the physical layout that matters on the cap and coupling loop. Related to the physical magnetic fields.
I've thought the same thing. Seems like you'd couple the drive loop at the electrical center of the radiating loop, so the magnetic peak of the drive loop would match the magnetic peak of the radiating loop. In the two loop configuration that would put the drive loop at the bottom, coupled to the loop section at the back of this configuration where it's passing by the capacitor on the bottom.
I have experimented with moving the coupling loop closer to center. The weird thing I observed was although I could still tune to a point of resonance, the radiated field strength dropped off tremendously.
I've seen another video illustrating the voltage vs current peaks on a magloop. Like with a dipole, they are 90 degrees out. There was a voltage peak on the loop at the capacitor, but a current peak at the coupling loop side.
I think with the coupling loop centered, you don't get that relationship and it just doesn't radiate. But I'm not a math guy, more of a gut instinct experimenter.
I"m not sure we're saying the same thing. I don't mean centered within the big loop, as in concentric, circles with a common center. The drive loop has to be quite near the radiating loop for the magnetic fields to couple. This is hard to describe, it seems. I mean the drive loop inverted from how it is now up top, and placed "on" or very near the bottom of your back-side loop. It would magnetically close-couple from the small drive loop to the large radiating loop. My thought is that would happen best at the point of maximum current, the *electrical* center of the radiating loop. As if the center of dipole that happens to be coiled into a loop. Maximum magnetic field occurs at the point of maximum current, the center of the "dipole" if you will.
Some people build them with the coupling loop at the bottom and the capacitor at the top. I've built them both ways and don't see any difference in performance. I usually put the capacitor at the bottom only because it's easier to mount it there on the base.
Do you have design specs to follow so we can make one?
+Daniel Looper The outer loop(s) are 6 feet in diameter, the driven loop is 1/5th that, so 6/.2 will give diameter. The tuning capacitor was not measured, but any cap with wide spacing should work, your frequency range may vary a little.
How many watts are you putting through that antenna on transmit??
ABikerLife I have pushed 40W through it without any arcing on the cap. Worked a guy three states away on 160 with the antenna indoors.
specs on the length of the pipe used to make the inner loop and both outer loops would be greatly helpful to new hams in building this. if you don't have a patient and don't plan to use it as such, please share
Here's one of those times where high school math that you never thought you'd need proves it'self to be useful. ;-)
The circumference of a circle is equal to it's diameter times Pi. The outer loop is 6ft in diameter.
6 * 3.14159 = 18.84 feet total length. Subtract the length of the connector pieces to get the length of each pipe. One pipe has to be about 2 inches shorter so it can cross under one of the others.
The driven loop is 1/5th the diameter of the outer loop, so 6 * .2 = 1.2 feet in diameter. 1.2 * 3.14159 = 3.76 feet of pipe for the inner loop.
To clarify further, the outer loop is 18.84 feet in length per turn. If the connectors are 4 inches in length, that's 8 total, so the outer loops length of pipe would be 18 feet. Since it's in halves, 3 pipes that are 9 feet and one that's 8 feet 10 inches.
Thank you. Most include such measures in their presentation. Not all of us have a 140+ IQ as I and yourself. We include such things to help those who don't and it save them a lot of embrassment or never asking the "stupid " question.
Chill James. No need for the mild sarcasm. Notice I put a wink in there, " ;-) ". The wordy explanation was not meant to be condescending, only informative.
There are no stupid questions.
Hi Kevin, nice job mate. Can I ask what was the veriable cacitor you used please?
What is the capacitor?
Great job, what's the specs on the capacitor?...
Bud...
budleyca1 I think it was marked 500pf, but it could be smaller. I find both bands near the middle of the range and I've pushed this one to 50W without arcover.
Great, tnx...
Kevin Loughin but you burned your wooden pole a bit ¿ :) Nice construction im gonna undertake a loop but am playing with a motor and vacuum capacitor at the moment.. Have you tried putting it a loop diameter above the ground believe this is the reccomended to lower radiation angle and tested versus on the ground ?
Yep, the burn was from soldering with a needle torch.
I need a loop for 6m & 10 m. What would the measurements be? For 50 watts.
+Richard Girou Antennas for those bands are already extremely small. Are you sure you need to go for a magnetic loop?
I live in a small apartment. No antennas allowed on outside
If you have a room that's 16' across diagonally you can actually put a dipole up, and it's going to be much more efficient! My first HF antenna was a 10m folded dipole strung across my bedroom.
just for reference I also put up a dipole antenna across my apartment on the ceiling. It works fine for 20M on JT65, but would not work at all for anything else. likely too much shielding from the wire cage effect inside my building. The loop antenna might work better for this circumstance, as it filters out all the other frequency interference.
I'm flummoxed. First try at a mag loop and the SWR is 9+ below about 12 MHz. The loop is double (10m) of RG6 approx 3 metres dia.. The coupling loop is about 30cm diameter tuned with a 500pF variable. No short circuit. Sumpin ain't right.
The coupling loop is placed near the"centre" of the double loop (ie down at the bottom)
VK4AKH
You don't tune the coupling loop with the capacitor. It needs to be connected to the outer loop. The coupling loop needs to be physically at the side opposite the tuning cap.
Again , Very Nice Video..de K4ARD/ Brian
Been done
Yep that's kind of what I said when I finished the project.
antena loop de 80 y 160 mts muy simple. ok
How come we NEVER hear you guys with the loops on the airwaves? In particular, on 160 meters!!!!
I make contacts on my loops quite often. Those guys hear me. So maybe change "we" to "I". ;-) I've also made many contacts with other guys running loops. They're out there.
Probably because mag loops are not very efficient when transmitting on those bands. How efficient is this antenna?
@@loughkb re: "I make contacts on my loops quite often. Those guys hear me. "
When I say "hear" I mean literally HEAR, as in, not running digital modes but operating VOICE. I have never had a voice contact with a station running an STLon 160 ... I run a 1/4 lambda circumference loop myself - the ONLY one in Texas to do so.
VK4AMZ has details on an 11ft some odd inch diameter loop that works quite well on 160, 80 and 40 meters according to his website describing said loop ... in particular, he mentions the various nets he checks into down under in Aussie-land ... BTW, I'm getting spots in VK-land on 160m WSPR again as the seasons have shifted a bit to favor the MW frequencies ...
Guys. Is very simple to bend a pipe. CZcams make everything. And don’t existing nothing more pleaseant to make the homemade your own antenna. And then look to how work. My recomendation ??? This is the matther of the radio amateur
Great job you have done there.When you tuned 160 i could hear PLT interference it seems the world is suffering from this technology we have a website here in the UK www.ban-plt.org.uk its killing the HF spectrum and making ham radio almost impossible in urban environments .I pick it up on my old cap.co loop i have for 3.7.10mhz fitted with a vacuum capacitor good for QRO operation .Sorry to go on a little about PLT but its something the Amateur radio operators emporiums society's need to address when its gone we will never get it back.!!
Watch that union word. The boss don't like it. It's a 3 piece coupling.
I'll buy that for a dollar
Nice work.