Tuned Magnetic Loop Antenna - ENMU - EET 490 Capstone - Update 2
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- Опубликовано: 3 мар 2019
- I have some stupid b-roll footage and comments in this video that will drive radio folks crazy. Such as a demo of the antenna at the wrong frequency with respect to its design. I later demonstrate operating the antenna at 5.935MHz towards the end of the video. ~55:57
3D Prints files can be found here (4" Dia Rigid Duct Clamps & Couplers): www.thingiverse.com/thing:370...
The Objectives
• Need #1: Design a Magnetic Loop Antenna to operate in the 80m to 20m bands or wider.
• Need #2: Implement the Antenna with an overall budget of $100 or less (not including the transceiver).
• Need #3: Leave room in the design for improvements such as automated tuning or directional rotation.
The Solution
• Recommendation #1: Use semi-rigid aluminum ducting instead of copper.
• Recommendation #2: Use dimensioned lumber to support the structure of the antenna.
• Recommendation #3: Use a 3D printer to ensure piece parts fit together and provide durability.
A loop antenna is defined by the ARRL Handbook as “a closed-circuit antenna that is, one in which a conductor is formed into one or more turns so its two ends are close together [1]”. In the case of this antenna, a tuned loop antenna is the same thing except a capacitor is designed and added to the loop across the antenna’s terminals.
The use of semi-rigid aluminum ducting will have a much lower price point than copper, especially when considering larger diameter such as 4 inches or greater. Additionally, the aluminum semi-rigid duct is lightweight. A larger diameter for the primary loop directly contributes to the antenna’s efficiency. Dimensioned lumber and 3D printed components are hard wearing enough to support the light-weight structure of the antenna. The rationale for the selected materials is straight forward. But why choose a tuned magnetic loop antenna and not some other design?
The tuned magnetic loop antenna used in amateur radio technology and other HF radio applications today have a few particular advantages. Because a tuned loop antenna puts high selectivity up at the “front” of a receiving system it can significantly help factors such as dynamic range with loaded Q values of 100 or higher easy to obtain assuming proper construction of the loop antenna [1]. Additionally, because of the versatility of the design which utilizes a variable capacitor, multiple ham radio bands may be effectively accessible through a single antenna without the overall design being too large or costly to construct.
• Result #1: The semi-rigid duct (aluminum) was far less expensive than copper for an equivalent diameter.
• Result #2: The dimensioned frame and rotating mechanism were locally purchased, without requiring shipping.
• Result #3: The overall antenna cost excluding the vacuum variable capacitor, was under $70 USD.
• Result #4: The 4” semi-rigid duct allows for an increased efficiency of +40% compared to 0.5in copper.
• Result #5: The antenna is highly directional resulting in the ability to null out undesired interference.
• Result #6: The inclusion of a tuning capacitor allowed a variable resonant-frequency design.
Given the appropriate band selection and antenna tuning, voice, text, data and even images can be transmitted and received using this antenna. The only equipment required in between the radio (transceiver) itself and the antenna is coaxial cable. Since both a radio and coaxial cable was readily available in addition to the materials required to construct the antenna, this project was feasible to accomplish in 8 weeks’ time.
The antenna worked as designed and was able to operate at frequencies in the 80m to 20m wavelength bands. There are many additional uses which the antenna can be applied to and the project here has only scratched the surface.
REFERENCES
[1] The ARRL Handbook, United States: The National Association for Amateur Radio, 2018
[2] “Magnetic Loop Antenna,” nmwilliam.tripod.com/mla.html Accessed Jan. 21 2019
[3] “Factors Affecting Capacitance,” www.allaboutcircuits.com/text... Accessed Jan. 21 2019
[4] “Small Loop Antennas,” Steve Yates, www.aa5tb.com/loop.html Accessed Mar. 3 2019
[5] “Loop Antenna Radiation,” Heyno Garbe, www.researchgate.net Accessed Mar. 3 2019 
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Nice build Daniel. Enjoyed the technical presentation. Keep up the great work.
Fascinating... Ingenious application you’ve put to the MagLoop... Well Done, Sir! Well Done!
Very well done video and antenna build. I have built quite a few magnetic loops for my shortwave radios using various materials and now you have added the AL flex tubing to my next build.
Very enjoyable video. Thanks for the presentation!
I loved your video, especially since you're new to listening to the bands and figuring out what the signals actually are. I've been learning quite a bit about magnetic loop antennas myself in the past few weeks, mainly because I want an efficient, low noise antenna for my apartment amateur station.
Excellent choice on the capacitor and what a great deal on it. DSDPlus and SDRSharp is free software and will decode the NXDN, P25, DMR, C4FM etc. digital signals you will find. I'm putting a commercially made mag loop in use on my amateur radio station but your video is inspiring me to homebrew one. Great job on the build and video editing!
add virtual cables and ya set.
you worked hard to make this antenna. If I were you, my mother would have thrown me out of the house with the antenna, or she would have set me outside so that I could be the antenna itself. Greetings to the respected mother who participated with you in helping to complete the work and salute for your efforts
Great idea.....I love it...The loop is big and has a Flash Gordon retro look.....Love to see this thing mounted on my balcony, as it would drive my neighbors bananas.
Now that's an idea I hadn't thought of. Unfortunately both my neighbors are engineers. They'd probably come over and detail everything wrong with the design. Hahaha
Very nicely done!
Beautiful job!
Nice work!
Love your work...your my hero.. beautiful work
"Nulling" refers to turning the antenna to minimize the interfering noise source, not maximizing the receive signal. Good job. You would make a good ham.
Thanks! I did notice the interfering noise peaks reduce directionally, but I also noticed the signal strength peaks directionally as well. Thanks for the pointer, sorry for any confusion.
I can feel your frustration with that coax shield! Aluminum can be really difficult to solder. I've resorted to wire nuts, crimp connectors, nuts and bolts ... all kinds of alternatives. People talk about galvanic corrosion, but it's not easy to get copper and aluminum together!
Nice construction job!
Thank you. You can see it operated on the correct band towards the end of the video
Amazing man!
An interesting mag loop antenna, although as others have said, using flat copper strip or flat braided straps instead of wire around the capacitor (used for bonding metal panels and for heavy duty earth cables) will help the performance. RF travels on the outside of conductors so the surface area is the important issue - this is also the reason your large diameter ducting is good. You probably know this but it's important for the viewers to understand what is meant when you talk about pointing the antenna at something. The mag loop transmits and receives co-planar with the loop itself, in other words if you extend an imaginary line from one side of the loop to the other that is the plane the loop is most efficient in and pointing this imaginary line at where you want your signal to go or where you want to receive from will maximise performance. Pointing the broadside of the loop will have the opposite effect and one of the main advantages of magnetic loops is there ability to null out unwanted signals. Another advantage of mag loops is that they transmit and receive a high percentage of what hams call "high angle signals" when used in the HF frequencies. This means that they are very efficient for long range communications and that they do not have to be mounted high off the ground to operate very efficiently .
I would strongly suggest you look at becoming a ham and assuming you are in the US join the ARRL. Regards Sarah G7TXR
Sarah, I've actually been learning a lot from comments from the community - including yours! I'm glad I posted the video because the feedback has been awesome. The skin effect on the copper does make since. Not sure why I didn't think of that during the build. I'm moving right now and almost done relocating. I'll do a follow-up video to address all the good feedback topics and modify the antenna a little. My coax (RG-6) is actually 75ohm, so I have to correct that as well. In my follow up video I may see if a Smith chart will be useful for tuning the antenna for impedance matching with the line.
@@TookBurrow Good luck with your move, the great thing about home made antenna's is that they are never really finished, in the life of the antenna you will get them to the point you think they are finished, then learn something new enabling you to revisit it and improve it further. "Home Brew" ham gear of all types is like this and a small amount of money and a lot of ingenuity will get your signal a long long way :-) Regards Sarah
Thanks for this video. Very nice construction project. However, I am baffled as to why you chose to make sure a large loop to use for UHF/VHF listening? The size of this loop would seem to be more suitable for 40 meters and lower frequencies.
It is used at 50m at the end of the video. This is one of those videos I love to leave unedited to remove b-roll footage. All the UHF drives radio operators crazy and keeps the comments coming in. I really should move the 50m clips to beginning of video somewhere 😅
Thanks for showing your work, like the alu ducting idea ! Given the dimensions of the loop I was expecting a demo with signals in the HF band, say around 4 to 8 MHz, did you opt for the VHF/UHF signals as they were constantly transmitting ?
So I did recieve at ~5Mhz towards the end of the video. You are correct on expectations on which bands given loop size.
U just blew my mind :)
Joe Faz.
Where did it go? I hope that you get it back!
Massive loop. that's one hell of a receiver antenna.
Very well done, your presentation is very fine , I had a Stroke 2004 but friends of mine will help me to copy your specifications. G6RFL ...Rico ..
Only came across your video now. nice build indeed, what is the bandwidth of the loop? i know most loops are very narrow.
Very good job Daniel. RG-6 is 75 ohm cable TV coax. You can also use it for transmitting but just be aware that you will have a slight impedance mismatch.
Thank you. I was wondering why they didn't print the impedance of the RG-6 on the package. But I realized the typical user will not need to know that. Do you know if the impedance varies much from one manufacturer to another?
@@TookBurrow The impedance will not vary. However the velocity factor can vary. The VF is a function of the coaxial dielectric and it's physical size. The VF is significant in determining the power loss in decibels/100' at a particular frequency.
Hi yes, good principle of design since RF currents migrate to the skin of the loop conductor (its almost all 'skin'). What would really show whats happening here is to use an antenna analyser, which when swept would show the resonance being in the HF bands for the dimensions used here. Im interested enough to try one this way myself, so thanks for the stimulating video, even it shows some more research needed to get it singing on the right bands.
Where did you find a vacuum variable capacitor for less than $100?
thank you ! 👍
Awesome build. Bravo!
Nice job with the loop. The 4" rigid duct, while it is a very good inexpensive alternative, may some losses which can be reduced. As a suggestion you could also use a piece of 1-5/8" or larger Heliax like AVA7-50. The corrugated outer conductor is copper.
Very interesting. I'm going to give the AVA7-50 a good look
Moving from the duct diameter to AVA7-50 would roughly halve the efficiency (from c 39% down to 21% or thereabouts)...you always need the absolute maximum conductivity on the loop skin you can acheive.
Bit puzzled... Have I missed something here?
That superbly built loop and the vac. capacitor described,. would resonate somewhere near MF... 3.5 /7 Mhz ish.
Why is the video describing reception at 139.00 Mhz?
A great video...one thing that intrigues me is that you are receiving UHF frequencies with mega loop. The resonant frequency you receive depends on the length of the primary loop.with this big loop you should be in the range of the HF wavelengths.Its a combined effect of tuning the LC circuit. you definitely dont need such big lengths to receive uhf with the principle of Magloop.I reckon your coupling loop itself is acting as a folded dipole for the uhf frequencies...well these are all my assumptions...Anyway good luck with your future projects...And ofcourse great job with 3D printing.
Yes, towards the end of the video I was receiving at aprox 5MHz. I think the UHF was b-roll footage. I've been planning on successfully recording that and showing the antenna operating at resonant frequency earlier on in the video.
The dryer aluminum tube is interesting, but the figure of merit is the loops Q that can be seen tuning across a noisy band as the width of the Mag Loop's resonance.
If you want to impress, show the BW of the mag loop and the freq being scanned.
Do that in the lower HF band with mag loop at resonance.
First - Awesome build! Very cool idea & it seems like it works quite well! Great job!
Second (and most important) - Your cat is adorable ;-)
Thank you! Yes the Cat named Finn helps on all our projects. He wants to be in the center of all household activities :)
Awesome idea and it is great that you include the time lapse videos of the process. Thanks! I am sure that , as others have said below, you would benefit immensely by getting an FCC Amateur Radio License(s). I studied intensely and passed all 3 in one morning. I am sure that you can do the same and it is very worthwhile to have no restrictions on transmitting. It would be fascinating to see how this antenna behaves on transmit and to see what kind of power it can handle. Careful with the Voltage/Current and RF! Do you have some idea based on your calculations? (Perhaps it was stated in the video. I was pressed for time and skipped through, but will watch in its entirety later.) Thanks, Jason / KY9I
I will have to do that. My father in law is a licensed amatuer radio operator, so I may see if he wants to try transmitting with it. I've been very busy with work, so my favorite project hasn't seen much of me. Fortunately people keep commenting here and I'm learning so much for the next video. Thank you!
Dan, the 3 - 1 tone pulses is SE in morse.
Good video and nice build. Kinda surprised the upper frequencies we so high, I wonder if the coupling loop was working by itself up there. I would think zero chance of transmitting in the VHF range. That ducting should be great for dealing with the skin effect issues since it's mostly surface area. I've thought about using ribbon for the same effect. Any thoughts on that? Also back to the skin effect issue. Seems like all designs have a huge issue there with the connection to the capacitor. Any thoughts on losses there? Obviously you intend to put real power into it with the 15kV vacuum capacitor. Also wondering what kind of Q you are getting at the down in the longer wavelengths. Also I was more under the assumption that mag loops have a very strong null, but not vary directional otherwise. Thanks.
There were quite a few problems with it along the way and left an appetite to try again some day. I don’t professionally work with really anything related to radio and probably a good thing as I’d need to brush back up on the finer points. What antenna would you build if you could build any kind?
Have you tried combining the loop's RF with the signal from a simple dipole or vertical antenna? You can get very nice notches on specific signals.
That would be "signal peaking" when the antenna is directed at the desired signal and nulling when the antenna is directed such that an interfering signal is minimised.
That's a great Idea. I will experiment with that this summer.
I'm a little surprised that you didnt print the divider in the prmary loop. Wood can absorb humidity and change the performance.
Interesting design choices. The thing certainly looks impressive. If it is meant for receiving only, the loop size and capacitor type would allow for simplification. If it was meant for receiving and transmitting, the aluminum material might be too lossy. The first signal might be an ATIS, the second is a beacon transmitting "SE". Looking at the frequency it might be a VOR, not an NDB (which would be at LF frequencies). The spectrum is very broad which is unusual for a working magloop. At this size, it should be tuning at much lower frequencies (like 80 meter). If it works as designed, you should see a dedicated peak that moves when turning the capacitor.
Yeah it’s lossy, i haven’t used it for transmitting. It was a fun project though.
I haven’t done any further testing with this. It is disassembled, but I certainly kept a few parts from this build. I believe at the end of this video I recorded receiving around 50meter? Not sure if you watched till the end since the video is lengthy
Thank You. Well Done. VE7WD
If you would reshape the small loop into an elipsoid and if you would match the long part of the elipsoid to the large loop then you would have better transfer between the 2 loops and that would increase the performance of the antenna .
Have you put the antenna on a Antenna Analyser to see were the antenna is resonant at.
Wow awesome, thumbs up !
Not sure though, is there a good contact at top of the loop? (as the copper wires are just tightened to the aluminium with brackets) ?
Yeah, I didnt like that part either. Not a great way to do it, bit it didn't seem to effect it much. Of course, I don't have an good point of reference for the resistive losses either. I've got to say though, this video has been wildly popular on RUclips and I've learned so much from everyone's constructive comments. The amatuer radio community is awesome. Thank you!
@@TookBurrow I am too thankful you built this antenna, i have been learning at the same time ; has to withstand several hundreds of watts on HF the way you engineered it (the key here is the Vacuum Cap). With the digital FT8 mode, you'd be amazed how far (actually to other continents) this antenna can reach. And with not even several hundreds of watts.
Oh and I wanted to say how great idea it has been to engineer the loop bracket and have it 3D printed.
So yes, amateur radio is a great community, if you ever have your ticket, you'll be more than welcome among us.
So you definitely have a follower here, Daniel.
Just keep on doing what you are doing !
Chris ha7wx
@@W-733_KWX Thank You!
Chrisophe Barbe
Can't be all that awesome if he gets it wrong!
At the top of the loop, the quality of contact is unimportant.. At that point, here is a very high RF voltage but no current flows.
@@TookBurrow " I don't have an good point of reference for the resistive losses either." Well, measure it! Use a milli-ohmmeter. Efficiency = radiation resistance/(ohmic loss*radiation resistance)
thx from dl.
flex tube is a genious idea!
for rx only a cheap varicap will do.
but for tx a vacuum cap is the way to go...exept for qrp;)
verry well done!
i will try this with a buterfly and a plastic tube inside the alu tube for stabilsation (for outddor). you are an Inspiration!
best 73, a
sorry for my poor english!!
hello ! you just now made me very enthousiast for making my own antenna ! you mentionned the use of a Varicap ( diode) if the antenna is for reception only , wich is my case ! the variable capacitor was a big brake for my project . thank you and have a good day from France.
I know this is a few years old but was wondering.. If I only wanted to receive on my sdrplay rspdx , what could I leave off if anything to do that? Yes, I don't know squat about this but thought since you said you are going to transmit also , maybe if I only want to listen, I could save by leaving off some of this.
Thanks for the video, what antioxidant paste brand you used ? Thank you
What was the center frequency you were aiming for? The null is on the narrow sides. The broad sides are the lobes. So you would have two null sides and two sensitive. I believe when you showed the field it was showing the antenna you built if it were horizontal.
269.9 MHz is the MIL frequency for the Automatic Terminal Information Service (ATIS) at Cannon AFB (KCVS). You can see it on a chart at SkyVector.com by entering "KCVS" and hitting [Go].
AFAICT The beacon at 138.925 is outside of the civilian navigational radio bands, so it's probably something military. Whatever it is, I'd interpret that transmission as being the two digit identifier "SE" or "ES", depending on which order you pick. ;)
That's an awesome HF antenna! I might have to build one.
Thanks for the tip on that cool website. The ES/SE was another persons guess as well
Magnetic loops are normally designed to cover one octave of frequency, this meaning the high frequency end will be twice the lower frequency of the range. The loop circumference should be about 1/8 of WL at the lowest frequency and 1/4 of WL at the higher one, it shouldn't be no longer than 1/3 WL tops, because it will not work anymore as a small magnetic loop and will start radiating bidirectionally and perpendicular to the plane containing the loop (like big loops do), instead of radiating bidirectionally along the plane containing the loop with a kind of a figure 8 broad pattern (which is not very directional) and deep sharp nulls centered on the plane perpendicular to the loop's.
You can work it at lower frequencies than where it is 1/8 WL but it will reduce the already low efficiency and increase the voltage across the capacitor. By the size of your loop it should be good for around 5 to 10 MHz and a bit beyond these limits. The current density of these loops is huge, with power levels of 100 W and more there will be a lot of amperes on it. Keep all living things away from it when transmitting, that includes you! A 100 W excitation can put 5 kV across that capacitor. I would put an RF choke near the feed point to make sure that the coax is not contributing to the radiation pattern.
Nice built, thou.
You missed that he's only using the antenna for receiving.
Nice job!
Thanks, it was fun. I learned a lot from everyone's comments too! I'm loaded with great suggestions for the next build now.
That is a very well built loop. However, i believe you used the wrong measurements if you plan on listening to VHF and UHF frequencies. The only element listening on VHF and UHF is the coupling loop. Im will to bet that if you remove the coupling loop from the outer bigger loop you will still receive the VHF/UHF freqs. The antenna you built is more efficient on the lower frequencies such as 3.8mhz thru 14mhz. You also mentioned that it is 20mhz wide in regards to receive. Which also leads me to believe that the only element that is doing the work on VHF/UHF is the coupling loop. Magnetic loops by nature are extremely narrow banded and will need to retune the variable capacitor every 50 to 70 kilohertz and have a super HI-Q. Not bad though.
Regarding the 20 MHz, I should clarify - I meant the SDR reciever (Hack RF) was capable of receiving with up to a 2O MHz bandwidth. I confused a lot of people by using some B-Roll footage of me learning how to use the software. I need to do a new video using the loop at its resonant frequency spectrum and tune through it with the cap 50 Khz or so.
Daniel Tooker yes would love to see how that bad boy performs on the low bands.
Daniel your radio knowledge is all confused sir - your antenna dimensions suit 5MHz NOT 100 - 400Mhz Try talking to some Radio Hams, don't brush all of them off as numbskulls, or Google the topic, there's lots of info out there ;-)
N2SAL RADIO
Good point except I can't get even 50Khz band width with mine!
Try flattening your coupling loop into a D shape to produce much better coupling. Flat of the D toward the main loop.
Great work. Have you tried to tune in to hf? Like 7 or 14 MHz?
I tuned into ~5MHz. It can be witnessed at the end of the video
To be honest, vacum capacitors are useful when you want to transmit at a reasonable amount of power. As for reception, an air capacitor would do the exact same job without any difference.
Air capacitors can cover from a real zero pF to 3 or 4 hundreds pF with no problem. If you want more capacitance, you can add a switchable fixed 100 or 200 pF capacitor in parallel.
I'm certain you are correct. I had an air gap butterfly capacitor, but it was 500pF to 1500pF and very jumpy/sensitive to the slightest rotation. But my vacuum cap was ~0pF to 300pF so I used it instead. Was much easier to tune since nearly a full revolution was a 10pF Delta
Nice for remote tuning.
I wonder what the basic resonance frequency of this huge loop is. Certainly not 139MHz or 239MHz. At first I thought this is a loop for frequencies below 100kHz. But very interesting, thanks for the video!
Check out WSPR, Weak Signal Propagation Reporter. It is an automated, digital mode used by hams to test antennas and HF propagation. The nice thing is that it uses only a fixed 200 Hz window in each HF ham band. Usually there is at least something to receive there. So if you need some signal to receive to test your setup, WSPR is a valuable tool.
Once you got a ham license you can also transmit. WSPR is effective even at very low power. I am in Germany. Often I receive a station from Japan 9350 km away that is sending at 5 W and a station located in Saudi-Arabia, 4150 km away, transmitting a mighty 0.2 W. I receive 5 W signals from the US / Canadian east cost on a regular base.
Very cool!! Well definately check that out. I've been getting such good advice from the community here that I will have to upload a follow up video here on RUclips
Hi Daniel... Good stuff.
I may have missed a point here, but are you receiving these VHF stations on that large loop?
I wouldn't have thought that it would tune so high.
Maybe I should start at the beginning and run through it again?
G3NBY
Some of the frequencies you see me tuning to in the video was me just having fun with the SDR program. Towards the end I tune into a frequency at which the antenna nominally operates, I think it was around 4-6 MHz
Hi, nice build. Would you like to share you're 3D printed parts on thingniverse or somewhere else. I would like to try it myself. I have an ham radio licence, so i'll give a try transmitting with it.
Look up DanTTT on thingiverse, or better yet use 3D Geeks app to browse Thingiverse. It's a better way to use their website.
Thanks for this video, where did you get the radio unit and what does it consist of? I am kinda of old school, all my radios are still tube type except for the aircraft units. N5UEB
Hi. In my video I was using a software defined radio that connects to the computer through USB. It's called a Hack RF
Thanks Daniel. I found one on Ebay for about 160.00 but did not say if software was included. Sure seems like a good way to go and I like that kind of bandwidth. Can you tell me if software is included or separate. Thanks Tom Turner N5UEB
@@hokepoke3540 I Downloaded a free software called SDR console.
Thank you for giving me allot of ideas. What are you using for a video monitor? I really like the large size.
It's a 65" TV. I've always done that. Its 4K @ 3840x2160. So lots of usuable screen real estate.
How do you overcome the higher losses of aluminum and at the connection made between the two pieces?
It's the outer diameter of the rigid ducting. Its large enough that the losses are offset. I think the DC resistance of main loop was under 0.5 ohms.
@@TookBurrow 0.5 ohms? Got to be waaaaay less than that for any reasonable efficiency.
Why is there no balun at the feeding point of the small loop?
Nice looking antenna. Do you have copies of .stl files for the 3D parts available. Thanks
I need to upload those. I'll do so on Wednesday morning
@@TookBurrow Many thanks. I will build one for my IC-7300.
I have uploaded the STL files for 3D printing here: www.thingiverse.com/thing:3705271
So what is the circumference of the primary loop?
Good video, problem is in the UK, a vacuum variable capacitor is upwards of £90. If I just want to receive, the capacitor costs more than the sdr, ham it up, cable etc.
I saw your name and thought you might be the Mr. Pickering of PXI Chassis. You are right though. The vac-variable caps are only worth it if you plan to transmit and generate multiple kV across the loop. I think a ham fest or radio garage sale might beat ebay for used caps in terms of price points and being able to see before you buy.
Sadly not me, I work for a VERY large organization in a telecommunications specialist role. Ham and RXL is a hobby I have very little time to do. At the moment I am grounded in isolation because of Covid-19, RXL is a great thing to do or I'll be RUclips surfing!
that vacuum cap is so sexy!
I see multi turn loops now and then, so at what point does a multi turn loop become a circular polarized yagi?
I'm not sure. That's a good research topic, or perhaps someone in the amatuer radio community has already done a good write up on it.
Nice. A little bit of Gene Scott on 5.935.
Hi,
Nice job! I like your 4 inch tubing because it lessens resistance which allows the antenna to be more efficient when one is transmitting.
I have 3 of this type antenna at the moment where my largest is 4 foot square but I use a spiral wound method for the large inductor portion of the antenna that is connected to the capacitor.
I am not surprised that you recieve in the 400 MHz portion of the spectrum but I suspect your inductor is probably around, what do you think, 25 or 30 micro henries so the capacitor's ability to tune the circuit is probably 1.5 mhz to 4.5 mhz. I was wondering if you put this to a test? Also, one of mine was built for the AM broadcast band. It would be neat if yours should tune that low because broadcast DX ing is a bit fun. I once picked up Hanoi Vietnamn at around 800 kHz.
The other thing that would be interesting would be to place it on an antenna analyzer. I believe they are called vector analyzers today and can be bought fairly cheaply like the Sark 100 out of China.
I have the Sark and its quite nice to have for a lot of different reasons. My big question that I have that the Sark could answer is what is the input impedance at your sense or coupling loop? All three of my mag loop antennas have a rather high input impedance but since I don't transmit with them and use them on receivers or SDRplay its not too much of an issue.
My final thought of interest is how narrow is the tuned section, think it may be called pass-band, of the antenna when the capacitor and inductor is tuned to resonance with the frequency being recieved. Mine are very narrow. I am guessing maybe 30 to 50 kHz to left and right of carrier or center. With your huge tube I am wondering if yours is a bit wider?
Enjoy, nice job......mike
I'm going to use your comments as a guide for an update video, once I get the free time. I'll borrow an ESR meter and check the inducatance of the loop and input impedance of the coupling loop.
I wanted to see more of the cat. But the design and construction had merit too.
The voice on the radio station is Judge Joe Brown. Nice build video and explanation.
I wondered who that was Judge Joe Brown. Good to know. Cheers
I was thinking,how can I get that aluminium pipe, suddenly it clicked that cooking gas stove outer pipe (though it has low diameter) can be available.i think , in fixing kitchen chimney,this type of pipe use as exaust.
It is flexible dryer vent pipe
So did you ever actually get the antenna to resonate on HF? WWCR seemed pretty weak and I didn't see much of a noise peak on the SDR.
RG6 is 75 ohms, but very nice job.
Scott K5RSB
Great video but RG6 coax has always been 75 ohm... RG58 would be the 50 ohm version that's the same outer diameter and RG55 is the mil spec version which is 53 ohm.
Try flat copper strips around capacitor . Wires are not the best choice for RF . 👍
I have read people suggesting that. What I've seen is that whatever you can do reduce the overall resistance in the loop, especially contact resistance where connections are made helps. Soldering is best for that of course, versus just compression or clamping. I'll see if copper strips make a tangible difference when I get another chance to play.
@John Cliff Thank you for the notes on silver plated copper strips (skin effect). That is a very cool and practical change I could make, not sure about how much silver plating would cost, but I imagine it would help overcome some of the losses from the material I used for the loop itself.
@@TookBurrow In uhf/vhf a few db gain may be the difference in deciding digital signals. Or not. This is a mv/hf antenna but digital signals are increasingly found within that spectrum.
I would love to see this transmit on HF.
you will not
For RX you don't need vaccum capacitor, just a simple spica radio capacitor.
verry nice antenne 73, jürgen DD5JK
Thank you!
if you can still find it there is/was a program called "dsd plus" that useing virtual cableing you can decode most digital signals but not ones that are encrypted i used it a cpl of years back so not sure if its still available and another one called "dump1080" for tracking and decodeing aircraft messages
Thank you. Is DSD plus a plugin for another program or a standalone program?
@@TookBurrow both are stand alone but you do have to have an sdr program running then the virtual cable to connect the two together im sur if you search on YT there should be one or two vloggs showing how too
I see no reference to you having a call sign or doing any transmitting, Is this a recieve only ntenna or can it be used to transmit also?
Nice job
Good construction approach I’ve used myself but little confused. Based on loop size and capacitor value, would expect a frequency range of approximately 7 MHz to maybe 21 MHz. You were listening to frequencies in 269 and 138 MHz area, At those VHF frequencies, this loop would be nothing more that a large diameter piece of wire and would demonstrate absolutely none of a magnetic loops characteristics. Try it in HF range and think you’ll be pleasantly surprised. .
I built it for HF, the demo in this video was b-roll footage I had to use since I'm in the middle moving. Cant wait to play with it more after the dust settles. I want to use it at resonant frequencies tuned to HF bands. I'm working on a stepper motor to tune the cap from the PC. I've got a video on my channel about. Got almost everything working, but running short on time.
138.925 is usually USAF. The tones appear to be morecode and translates to the letter "V". Location beacon?
Or...S E
I'd hate to see the Fedex box that comes in. Hows it working for you ? 73 de kg0tr
Sorry. I'll have to watch it again. I got distracted by your cat. :)
Bravo!!!
20:46 - Pussy-cat: "Get ma dinner, or I'll key this mutha and fry you!"
Very good job thank you
7:00 - ATIS (Automated terminal Information Service)
Michael Doran thanks!
Btw: I'd expect ATIS is in the air band - so you may have received a harmonic of 134.950MHz there
Dude, you can get some copper stripes and use them, it would be much better. I learned the hard way that losses negatively impact SNR and you will have less efficient on TX too.
Thanks! I'll include that suggestion for an upgrade or project on this antenna or perhaps a new build...
That size loop is for 40 or even 80 meters not vhf uhf
50Hz is normal for single-tone signals like CW or beacons. That's one of the reasons morse code is still quite popular for long-distance, low-power communication.
Obviously another step would be to automatically tune the antenna with a stepper motor, to match whatever frequency you're trying to listen to on the hackRF... Might need a network analyzer to know what frequency it is resonant at...
Neat! Thanks for sharing
It's a star gate!
That religious stuff is what steered me away from short wave radio, it got old. But stupid me did not look into the ham bands because my radio didn't have the ability to receive them. Getting back in the saddle soon.
😂
I bet he's working for L3Harris now... ;-)
RG6=75 Ohm normally. But cool build.
trying to solder aluminum shield
The Police might be using DMR Digital Mobile Radio
ahah funny see you trying to solder the coax braid
Yep, that was definately not solderable braid! The more expensive coax braid will accept solder at about 500-700°F
invert your antenna with the coupling loop at the top and your tuning capacitor at the bottom....
There are those who have said the opposite.
How much for that vacuum variable capacitor?
I think I scored it for 50. Was worried about a compromised seal at that price point, but I got lucky. Checked it's full range with an LCR meter and die pen chamber. No leaks! They usually go for $100-300
@@TookBurrow You did mention the cost in your video. I hadn't seen the whole thing yet. Great video, by the way.
Most of the traffic you were seeing in the 225 - 400 MHz band was military aircraft related.
That variable cap was a freakin' steal. I have 2 similar ones I have not even used yet. I bought them simply because they were cheap ($70/each).
Keep up the good work. Beats the hell out of watching TV.