A Cheap HF Magnetic Loop Antenna - But Does It Work?
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- เผยแพร่เมื่อ 1 ม.ค. 2025
- Here we take at a relatively cheap HF Magnetic Loop Antenna. Max SSB power is rated at 20 watts, but let's test it out in the garden with the IC-705 at 10 Watts. Is this actually a magnetic loop? Answers in the comments please :-)
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Thanks!
Wow! Thanks so much!
Looks like it would make a decent receive antenna for a shortwave listener good video.
I use it for just such a purpose and it is great for that. I don't feel comfy with using it to TX with though.
@@MrToymod which sadly I don't
I home brewed a similar antenna during lockdown. It was fine at QRP but the capacitors would not take any more than 10 watts. Really sharp tuning. You probably could not make it for the money they want. It's not rubbish at all. But any user needs to be aware of the limitations.
The voltages across those crappy caps would be huge, and I doubt that the dialectic would handle it for long. a quick calculation on guessitmate dimensions from that show that at 28Mhz there would be over 1KV across the capacitor! They will get pretty hot too, so they are doubly cursed! - I have a DIY magloop with a big air spaced capacitor and it will only handle 20 watts on digital modes before I get issues, so those little beasts are not going to be too happy. IMHO
this loop is 10 watts maximum!! its qrp indeed and works great.. have bought them for our hamclub here. there fun but qrp only vhf does not work good in fact the rubber ducky is better.
I don't think capacitors will get hot. They are not resistors.
But sparks will certainly fly over the plates. The distance is very short...
@@maartenc6099 The have some kind of mica or plastic dielectric. Even so I would try to keep it down to 2.5W I don't know how many volts that would be though. This really is for QRP and narrow band modes.
i have this antenna. The built-in tuner is very variant depending on the environment and how bend the loop.. i drilled on top of the box to make another monopod attachment to hold the loop so that it wont shake during windy.
And how do you like this loop? 😊
I got one of these and it works quite well for modes like FT8 and CW where you tend to stay in a narrow part of each band and so only need to retune the antenna for a band change. Less convenient if you are scanning up and down a band, say for SSB, as the narrow bandwidth of all magloops means a retune is required if you move say 30KHz. The capacitors are ok for QRP but would break down due to the high voltage generated in a magloop if you exceed the recommended power rating. Also the caps may need their trimmers tweaking to give the full range of adjustment needed to reach from 7-28MHz- mine came not tuning all the way up to 28MHz. I like this antenna for its stealth factor. Here in Singapore the public are not familiar with ham radio and always ask me if I am a spy when I am out doing POTA! I can put one of these inside a one man tent on the beach and sit by it doing FT8 and all people see is a guy with a tent using an iPad … much more discreet.
It always amazes me that people ask operators if they are a spy... do they thing if you were a spy you would say yes...🤦🏻♀️
Yea, I'm a spy..... I'm just sitting in plain view so the government knows exactly who I am, where I am, and what I'm doing.
It's the greatest way to be a spy, getting to know the government you're spying on.
They will even give you free accommodation.
@@samcollins6394
"Are you a spy?"
"No."
"OK, carry on."
How far did you get with 10W and this antenna? Which parks are you operating from? I lived in SG for 9 years, love those beautiful parks.
I found it’s quite easy to work Japanese, Australian and Indonesian stations from Singapore on low pier with something like this but when I realised that a doublet at home was possible I switched to that and managed to work about 70 DXCCs in 9 months. But it was very slow going with QRP beyond that.
This is a variation on the “army loop” and not a magnetic loop antenna; the giveaway is the lack of either a coupling loop or a gamma match to the main loop.
This type of antenna does work pretty well for what it is.
I have the same one, these are great for QRP, just don't pump high power into them .. they take a bit of time but they work great.. no complaints here.
I wouldn't advise using that unit with the Capacitors. I have made my own loop antenna and even low power capacitors can arc across. My capacitors are good quality but air spaced. My design doesn't fold up. As today I am still experimenting with my DIY Aerial. Cheers from old George
I have a similar antenna that I use for FT8 @ 5 watts. The antenna is indoors about 5 feet away near a window. I have made contacts (confirmed with the other party) at over 5k miles away on 20M. As mentioned it's not a good antenna if you are going to run up and down the band as you need to retune the antenna all the time. but for something like FT8 or other digital modes, or calling CQ it works well.. A VNA is definitely helpful in tuning the antenna..
I may do some more tests with WSPR and this antenna, just to see how well it works on low power. cheers
_As mentioned it's not a good antenna if you are going to run up and down the band as you need to retune the antenna all the time._
Good comment. Does this mean that tuneable antennas like this aren't suitable for strictly RX? I'm not a ham but a SWL enthusiast, so I have no need for transmitting. The only magnetic loop antenna I have is a genuine MLA-30+ which is kept indoors.
@@StratmanII For receive, it is pretty much the same thing. Using the antenna, either way, it needs to be tuned for the highest noise level. So let's say I went from 17M to 20M. I would need to retune the antenna while listening for the highest noise level. If you don't retune it, and you are way off from where the antenna is resonant, it's essentially deaf.
I use it during +2 years, I use ft8 freqs for tunning, as you did it, first tune the up, then the down tune.
I did near 2000 kms contacts with voice and 5000 with ft8.
use it inside my room and it's bi-directional and it works... beleave it or not ! Works.
Is it like a dipone? NO! off course, but works fine the size, price and components.
73 to all
ea4huk
I use a 4 foot square loop made from 4 inch diameter aluminum dryer vent using a 23 inch on all sides square of 3/4 inch copper pipe as the inner loop. Capacitor changes dependent on band. These do have an upper and lower bound for what they can tune. Mine is 40 meter to 20 with efficiency at 27% near 40 m & 79% at 20 meters.
Thank you for sharing. I really want to experiment with square loops at some point.
I used the 4 inch aluminum dryer vent tubing because efficiency becomes much greater as the surface area of the main loop increases. I noticed that some vendors apply a nonvisible film on the dryer tubing and I had to sand it off where the pieces joined together or at the elbows that make the transition in direction of the sides.
I am pretty impressed by the antenna and plan on making a similar loop for 80 meters. The loop I recently made was intended for 20 meters, but does great at receiving and even transmitting on 40 meters. I also use a small fine tuning capacitor in parallel with the main tuning capacitor. This especially when gear reduced makes tuning incredibly easy.
The size of the inner loop is critical for achieving a 50 ohm impedance match. The general rule of thumb is the bigger the inner loop the lower the impedance. I found the match by trial and error but it only took two trials.
Thanks for posting. Obvioulsy not tosh on receive. Typical for "mag-loops", signal strength may be down compared to a dipole but the SNR is good. I will take a guess this is a "mag-loop" or Small Transmitting Loop to give it it's proper name. One capacitor is tuning the loop and the other is forming the series capacitor of a gamma match (that's why there is no small loop or toroid to couple to the big loop). On transmit, as for those polyvaricon capacitors? Not what I would opt to use - even at QRP power.
I've had a CHA F-Loop since 2015 and the variable caps in that are rated at a similar power. But they are a hell of a lot larger than those tiny things, I don't hold out much hope of them lasting. SWR vs Frequency you'd expect to see a lot steeper dip than shown for this one. Finally just tune for max vol/noise on your radio and you'll be in the ballpark for fine tuning using the usual built in SWR meter
I once built one for fifty kilohertz along with a homemade fixed frequency receiver. Worked quite well to receive standard time signals.
Thanks for the video. Just a couple of notes about loop antennas. First, the radiation resistance of small loops is very low, so the wire resistance in the antenna becomes a serious consideration. This is why these antennas are usually made with copper tubing or coax shields. Second is that the capacitors can see very high voltages, so that is probably why the antenna is rated for such low power. It would be interesting to replace the tuning caps with high voltage air gapped capacitors to see how it works.
The coax is FSJ-4 Commscope or a copy there of.
It is used for jumper material on Cell Phone Towers.
I've an earlier itterartion of this I think, the only difference being the common mode choke is inline with a short stretch of BNC cabling and not within an enclosure. Mine works adequately for Short Wave Listening but Ive not been brave enough to try transmitting with it. Mine is a swine to tune using a NanoVNA.
I’ve got one works with a good swr on 2m good antenna to play about with
Ps I am setting up some mesh stations and nodes soon here in jersey 73.
I am amazed that you got through on 20 . Maybe a function of the loop length ? Without an inductor coil tx will be a non starter ?
I wonder if you had a good ground(GND) would that have made it work.
Hi this loop is working verry good, i worked a station in Belgrado yesterday with 25 watt in the loop end i live in Holland. No stranges things happend. For 98 euro its a good working loop. But not the best loop, antenna i make loops my self end this loop is diong what it have to do. 73 from PD1Y.
RBN and PSK Reporter (on FT8) might be useful.
How come this does not have the second small at the top like other loops i have seen i would only use it on 10 or 20m at 5 or 10 watts
The antenna is coupled to the transceiver by means of that second variable capacitor which is connected to the loop and in series to the transceiver. In this way, you can vary the coupling for a low SWR; Army Loop config.
can we have a review of the vhf etc side of the antenna
Hi Matt! Thanks again for a great video, I love it that you test out these alternative bits of kit. Like I have mentioned in the past am not an antenna expert, but looking at around 8:49 in the video I can see that the center of the co-ax loop is not connected at all. From my limited experience a "magnetic loop" uses at a minimum two loops where one (typically the smaller one) is the driven element, driving the bigger loop via induction. In the big loop you will also find that both the co-ax braid and center are used. From what I glean from Paul OM0ET's videos (www.youtube.com/@OM0ET), mag-loop antennas will definitely work quite a bit better as transmission antennas, since the actual antenna will be much closer to quarter-wave lengths et cetera. This particular antenna seems to be more akin to the Moonraker Whizz Loop products (which I like a lot) , or the older WonderWand Wonder Loop QRP antennas for the FT-817. Cheers, Jan M7HNK
Looking at the size of the loop on 40 meters it didn't surprise me that the loops performance wasn't that good pretty inefficient for 20 meters and above it'll probably be ok, if they say it'll work on VHF and UHF be interesting to see how it works out on 6 and 4 meters.
I think the cross country willess loop was better than the one ,😁and I am going to get one for Rx only as in town I have a lot of noise
That is indeed 63.00 US in parts and a nice length of hardline. Hard to fault it on price. Not a true mag loop though.
That’s exactly what I thought, it’s more of “just a loop” with tuning. Cheers
Hm. Single loop with 2 dials vs the SignaLoop HF319's one, and the choke in a box.
What would be the take of angle if such a magloop?
I'm not 100% but I think they make a similar pattern to a dipole but just with more pronounced nulls.
So being so close to the ground on 40 and 20m would likely screw up the radiation pattern.
@@shanerorko8076 Little loops like this one generally work very well one loop diameter above the ground, possibly better a little higher. Experiment to find out. That's with the loop mounted vertically (like a bicycle wheel). Mount it horizontally and it might be better farther up.
replacing those caps with some proper air core ones (and a larger box?) would make it a decent antenna
oh what type of aircores u would use?
@dennis8019 any decent quality ones of the large type, like you seen in old radios where you actually see the capacitor plates..
They're usually rated for much higher voltages than the small rectangular type
I suspect this antenna will be very inefficient at 40m and should do a good bit better at 10m.
That's the general rule for loops of this size. Low efficiency at 40 meters/7MHz. Pretty good efficiency at 20 meters/14MHz and up. I haven't used this one, but had a couple of similar ones for years. Found it OK for digital modes, which mostly don't require frequent retuning. But: Use a small QRP loop only if no better antenna is possible. I received DX pretty well, but because most DX didn't hear me, I operated modes like FT8 and FT4 only by transmitting CQ. Even with QRP and a cheesy little loop indoors, there were always a few completed transoceanic DX QSOs in my log, though most of the comebacks were domestic.
It works better at 40 m
A good receiving loop and that's about it, but this is not a magnetic loop. Good video as always.
Defo works well for receiving that's for sure! cheers
@@TechMindsOfficial Have you had chance to do a follow up video regarding the 2e0 magnetic loop?
You actually made a contact on that thing??
Surprised myself!
Thank you for the video and double thanks for opening the box and showing inside of the same. Not looks like will last long after Txing 20W for few days.
Thx for all video.
73
VU3TBU.
Looks like the sheild is the only part that is being used on the large loop.
Yep, you’re right. I noticed that too when I took it apart.
Loops should have large surface area and very low resistance; hence using only the shield for better efficiency and bandwidth.
god job
Hi Matt great video as always, it is called 😂😂 common Mode
Dave 2E0DMB
It’s all this networking crap I’ve been doing recently, got nodes on the brain! lol cheers
Iooked good until you opened the tuning boxes
Hmmmmm
What sort of take off angle/radiation pattern would this antenna have?
Mag loops have good low take off angles with is one of their best features. There should be a bit of a null point out of the center of the loop in two directions.
@@bassmanjr100 so this isn’t going to work well in my back garden? It’s going to need to be out in the open
@@lonewolfhamradio no its not for outdoor placement.. its not waterproof and u need to tune it if u change frequenties.. get a endfed or bigger antenna.
As Mr wigglepig said its not a mag loop just another chinaloop made by trained cats.... I bet the variable caps arc's like mad at 20watts >have a look at night while TXing !
I would say under 10 watts would be just fine
Big ol' radiator loop with rinky-dink caps
Good for Rx only ans and not to water restaurant by the look of it..
u can transmit and with decent swr but horrible at vhf .. made some good contacts with it.. but its qrp only .
The right-angle 90° feed line adapter is the first sign of "run away run away run away".
Luckily its not fixed, so you could use a small patch cable instead.
Эта антенна не работает на передачу!
It's not a Magnetic Loop, There is no coupling loop
It's just a loop of what looks like Heliax type Coax,
and what looks like a Series/Parallel Tuning arrangement
I don't think this will work for very long!
I think you may be right! Maybe I will perform a test, leave WSPR running for a few days to see what happens :-) Cheers
@@TechMindsOfficial yes, I had a great deal of success using WSPR and a 40m mobile whip on a clothes dryer spike and radials! Love the channel, 73 de Andy G0VRM.
@@TechMindsOfficial What happened in the WSPR test ?
No does not work, QRP and very lossy caps. Only for fun with a toy.
That Battery seems quite a stiff price at £307.47p. at that price I would have gone for a leisure battery and saved quite a bit of money for garden use.