Excellent video. I am just getting into ham. My Technician's license is only 2 weeks old. Been watching videos on how to create this type of antenna. Most were good, but were showing the "ideal" way to do it. This one, showing things at their most basic and crude methods _really_ helped my understanding of the building of it. And inspires me to start playing. Obviously until I get my General I'll be stuck on 10m and 6m, but it's a start!
I would keep a fire extinguisher near! over 3KV @ 100 W on a loop that size. Make a series capacitor from 3 sections of coax, 1KV across each coax would be far safer. That size loop is also down about 10 dB, you are only ~1/2 S-unit over a QRP with a proper dipole but when and where space is limited it is a great solution. If you built it with a 5-meter section it would be 3X as efficient or only down less than one S-Unit from a dipole on a 100W rig. But the voltage will go up to over 4KV across the coax capacitor. It is great to see someone showing homebrew crafty solutions to get on the air. It seems that so many hams today think you must have the newest most expensive 4 digit rig, a KW+ amp and a branded antenna on a massive tower to enjoy the hobby.
Hi Peter, I've kept tabs on all of your videos for some time, as I too am into everything electronic. Repair, communications, modifications, and of course home brew construction of really cool stuff for 40 years now. I took a break from Radio for a while and out of all the cool videos here online, it's your abstract, but most interesting videos that have literally made me go through all my stuff- looking forward to getting back on the air very soon. Thanks for that & happy holidays to you.
I run an indoor loop about the same size as that, roughly 3 foot diameter / 115 inch circumference, and it works decent despite my less than ideal tubing diameter. I have a large air variable to tune mine anywhere on 40/30/20 and the furthest contact I've made was from NE USA to Slovenia using 50W on 20m USB a couple weeks ago. The efficiency on 40m is quite low, but I have made some contacts into the SW parts of the USA with it on 40m using the full 100W. Interestingly enough, I'm also driving mine with an IC-751. Not a bad older rig, I like mine. 73s
I made one out of RG6 Coax for 10,11,12 and 15m I made a second that is quite efficient out of two RG6 coax runs in parallel. I do have problems with flashover on the RG6 cable. I might give the RG213 a go if I can find some. Look up trombone capacitors made from copper pipe they work well They work a treat. Watch for flashover on the capacitor. You’ll want to have a look at 66 pacific dot com for some loop calculations
Peter, I just finished building a qrp version using coax as the loop. I could not get the vSWR any lower than 2.5:1. I then used the copper tubing as the loop and was slightly better but still cannot drop it down any further. When I tested it with a smaller loop I was able to get the vSWR flat. I think my inner loop is not close enough to the outer loop or not exactly in the same plane. Going to play with it some tomorrow. Thanks for the Video and best 73
Hi Peter, Brilliant idea for the capacitor, Peter! I like the variable cap idea. I've built a QRP portable loop which covers 10m - 20m using RG-213, shorting the braid and inner conductor together at the SO-239 connectors in the box which houses the variable cap. I think I need to revisit the idea of a QRP loop but taking out the cost of the vacuum cap. I'd be really interested in it's DX performance over your wire antenna :) Thanks for posting the video's I always enjoy watching them. 73 de M0SNR
EXCELLANT idea to use RG213 and PCB MATERIAL as variable cap in place of a expensive HV vacuum or air variable cap. Could you possibly provide the dimensions of the outer loop and inner coupling loop to get people in the ball park . ??? ..... Built mine with flexible 1/2" LDF 4 solid copper shield feedline "hardline" therefor no couplers required like rigid copper pipe ... im still tweeking the loop lengths, tuning cap and mounting issues ... Your cap idea to be part or all or used in next revision . YOUR audio level / quality in this video is also nicely done. Thanks a Meg ... JF
Thanks. Inner loop is about 1/5 the diameter of the outer loop. Dimensions not very critical provided you can bring the loop to resonance, though bigger is better for more efficiency (to a point where it ceases to be a mag loop).
I am glad that a ran across this. I know this was published over a year ago and I hope you'll get an email with my question here. What is the dimension of your fine tuning section? Other than that, I have done the dimension conversions for the pipe and now ready to build this thing. Thanks
This is very interesting and impressive. How did you acquire all this great knowledge of RF design? I've taught myself many math and technology related subjects, but RF design somehow has never clicked in my mind. To me it is far more mysterious than most branches of electronics.
Ralph Dratman Get confident with (linear) electrical circuit theory, where you will apply algebra and complex numbers in cases where electrical voltages and currents oscillate sinusoidally. Next take a simple textbook intro to electromagnetism to begin with.
Nice! I built a magnetic loop antenna, Is there any recommended minimum gauge for inner loop wire or can I just use something that keeps the shape? Thanks.
Try several shorter coax lengths in parallel. It'll have the same capacitance but lower current per leg so perhaps slightly more efficient and more compact.
Hi Peter, whilst I have little interest in transmitters these days, I did find your video very interesting. It's amazing what you can do with a few bits if pipe and sticky tape. Reminds me of Blue Peter (a UK kids TV programme of many years ago!) P.S No connection with your name!!
I tried to build this loop too. Result: sparks in the coax, temperature increase in the PCB-capacitor, which results in variation of the resonance frequency and finally holes around the edges of the PCB. The coax capacitance is lossy, I think. I used good coax, but even silver core and shield and low-loss dielectricum are not good enough for a high-Q loop. I can recommend TEFLON tube with alumin rods as capacitor. The rods can move in and out and allow tuning. No sparks, no burning holes and stable capacitance at 100 watts. 73 PA0FSB
vk3ye I’m playing with some similar designs. Only I have a heap of RG6 from a strip out that I have been using as loop and capacitance materials. If I want less resistance. I can simply double or triple up the coax in parallel As for remotely tuning the capacitor, there is a motor from Jaycar that does one turn every two seconds. I am using that to drive some threaded rod to slide a block with some copper tape over some copper strips. I also purchased some 3/4” and 1/2” lengths of copper to play with some trombone capacitor ideas using the same motorised thread drive Currently I use an almost 10m length of RG6 in a kite shaped loop with sone fixed 6KV ceramics that are consistently tuning the CW portion of 7MHz and give me around 80KHz between 2:1 points. It copes with up to 40-50W however I need a few caps in series to run 100W without having a _Nichola Tesla_ moment.
Wouldn't it very be dangerous to fine tune the loop (during transmission), with the pcb capacitor? That's needed in my experience with mag loops, in addition to the "noise maximization" step.
you are the only one shooting radiation pattern upward. all the others shoot it into the dirt and complain hiw little effective it is. 😂 way to go man.
Ok I’ll go do that. I’m waiting for the shops to open :D Why is a HF antenna ok so low to the ground? I was hoping using a magnetic loop for rx might help with noise.
It should be pointed out if you intend to use this antenna indoors or in an apartment or condo setting it is best to use low power to avoid dangerous RF exposure and reduce interference to your neighbor's electronic devices.
@@vk3ye Sorry to trouble you again, and believe you me this will be the last! I have a variable capacitor from a tuning tank of a old valved transceiver which is 370pf. If your RG213 has a total capacity of 185pf and your copper board capacitor adds to it, would my single 370pf be ok?
Nice video Peter, thanks for the fun down at the Bay today. One question which I forgot to ask is what is the rough dimensions of your variable part of the capacitor? Do the plate sizes vary the capacitance efficiency a great deal? Some further clarification on that point would be appreciated. 73 :)
How would a double coil on the outer loop compare? It would be smaller. Would the inner loop also need to be smaller ? Also, how much spacing would be optimal between the two coils of the outer loop? As always, your videos are the best.
Very interesting. Which antenna you recommend? Long Wire + Balun or Magnetic Loop? (listens to a larger spectrum of Short Wave with the best signal x noise). Thanks You.
Are there any easy step by step instructions for a magnetic loop antenna like this? I want a to build a loop but don't want to buy a capacitor. But I don't want to start until I get dimensions for the sliding capacitor on this video.
+vk3ye I have been searching google for months. Just found what you are talking about. www.iw5edi.com/wp-content/uploads/2015/02/w2bri-loop.pdf. Thank you! Also, thanks to your video I built a 40m mag loop antenna. I can hear so much stuff! But, I have trouble transmitting being in the middle of the pacific, in Hawaii. Nonetheless so much fun!
I noticed the antenna switch on top of the radio. is yours using a common coax ground (metal case) or do you isolate the coax grounds as well when you switch from one antenna coax to another? It would seem logical that having a di-pole and a vertical on a switch could affect the antennas if the coaxes were still joined in a switch box...wouldn't it?.
Depends on the capacitance needed. Which depends on the size of the loop which governs inductance. If using the same loop size as one for 7 MHz I'd say roughly 1/4 the length for 1/4 the capacitance.
+Jihad khalil When the loop is tuned, all the energy is induced from the small loop to the bigger loop, like a transformer. Note that the key element here is TUNING. This is why the use the capacitor. The cap and the loop form a resonant tank circuit. The proper way to tune it is to set the frequency in the transceiver and adjust the capacitor for maximum received noise. Then, using low power, adjust for minimum SWR. then you are set and switch to high power.
I have found the measurements for sliding variable capacitor. Now I would like to ask about the coupling loop. Do I just use the inner conductor of the RG-58 and solder that to one end of the 60cm loop and insulate the outer braid ?
what info do you know of that can educate me to build variable caps. I have an idea to make a normal air dielectric cap into a extreme votage variable cap. 30,000 volts or better. but not knowing what that dielectric does to the capacitance. has me in quandary. but it would offer a cheaper alternative to vacuum variables.
He is using 3 meters, 19mm copper tubing for the large copper loop (See 1:24). The coupling loop is made from ordinary mains flex with all three cores connected together. The size is not mentioned, but it's usually 1/5 of the main loop, so it would be 0.6m.
sir, could i get you to calculate the copper square tuner for 14 to 30 mhz. i would like to build this antenna. at the end of the RG-213 coax. i dont want to use a high priced tuner. this is in affordable range, your help would be appreciated. Tommy
All my Magloops tune to 1.1 SWR still after so many built from small 6M Magloops up to my current 2 element in series. Gastite Pexal tube from Bunnings - magic in 16mm and 20mm. Capacitors are RG-213 inner slid into one end. s12.postimg.org/jj6ocra99/TWO_TURN_PEXAL_MAGLOOP.jpg Have fun Peter. Myles VK6ZRY
hello vk3ye excellent project for apartment is possible for CB 27mhz I have very limited space and would put it on the porch and by my accounts is 2.63 meters copper tube and 52.6 the smallest circonferencia and I will leave a length of coaxial cable RG213 about 1.85 meters ok do not know if that's my doubts is like tuning the stationary excuse my English is poor ok ..73
+MultiJorgecardoso cardoso El largo total del tubo, tiene que ser un poco menos que 1/4 de onda. En tu caso andaría bien un caño de 2,5 metros, formando un círculo de algo más de 80 cm. Para sintonizarlo en 11 metros, vas a necesitar muy poca capacidad. Creo que con 30 cm de coaxial, ya tienes suficiente. Muchos le sacan la vainja de PVC y suben y bajan la malla hasta encontrar la sintonía. En esa freciencia, el ancho de bnd va a ser de unos 300 Kc, de modo que tampoco necesitarás un ajuste dentro de la banda. El aro interior, tiene que ser de unos 20 cm de diámetro y hay que retorcerlo hasta bajar la ROE. Que tengas éxito en tu proyecto. Un abrazo desde Argentina. LU1AR.
+Edgardo Maffía Buenas tardes Edgardo, veo que tienes buenos conocimientos del tema, me podrías indicar cual sería la longitud del aro para una antena que funciones en 7 MHz y si es posible usar esa misma antena para los 14 MHZ? Cuanto coaxial necesitaría para formar el capacitor? tengo necesidad de construir una antena loop para poder ubicarla en mi unidad residencial ya que no dispongo de mucho espacio para instalarla. 73 Cordiales HK6PAN hk6pan@gmail.com.
La banda de 14 Mhz te limita el perímetro del aro a 4,5 metros es decir 1,5 metros de diámetro. El aro puede ser un cable coaxil viejo, ya que solo se aprovecha la malla debajo del PVC que equivale a un caño de 10mm. En este artículo hay una antena para 7 Mhz que te va a interesar: www.carc.org.uk/downloads/A%20Coaxial%20Magnetic%20Loop%20%20for%207MHz.pdf Y esta nota es lo mejor que vi, en español: lu6etj.host-argentina.com.ar/lu6etj/tecnicos/loop/antena_de_cuadro.htm Saludos. LU1AR
Peter I love your videos but this one in particular worries me a little bit... Encouraging people to touch a "high power loop" without specifying (in capital letters) that doing so during TX might result in injuries or even death is a bit dangerous, don't you think? Moreover, the design of your variable capacitor is a clear invitation to touch the plates during tuning. I think its dangerous... We are talking about 4KV in this case. You should specify that the loop might spark fires at the coax capacitor (happened to me) and WILL KILL if you are not careful enough. Putting aside the other safety considerations about magnetic loops, I would say: NEVER EVER TOUCH MAGNETIC LOOPS - ESPECIALLY IF YOU ARE NOT QRP. 73's Alain
I wish I still had access to tubular copper bus for substations. I worked at a small foundry that used tubular bus. They stuff could easily do 1000 watts. Bending it would take a hydraulic bender and special shoes, & follow bars. I like the 40 meter band. (7MHz). I want to make some loops for listening, and probably just use dipoles, bazookas (single double) or verticals for transmitting, and have TX RX relays. My high power amp is 1500 watts and I just made one that will even do 1500 watts AM. It was a headache, as I went with valves, and used SIX 4-125A tubes. With 80 watts drive, it will do about 2000 watts out FM, and less than that on 2 meters, but I am still at about 1 KW. I have become totally disgusted with the quality of the products MFJ makes. If not for fixing brand new MFJ, Ameritron, Cushman, and other junk made under the MFJ company names, I'd have probably never renewed my license. Most of their stuff is cheaply made, but serviceable, but the poor quality of assembly makes these products prone to catastrophic failures. I just bought one of the best antenna tuners Heathkit ever sold. I went though it, cleaned all the silver, wrapped all the straps in high voltage silicone, & rubber slicing tape, carefully measured and bent all the blades on the variable caps to center, adjusted the counter, reflowed the solder, cleaned polished & lightly greased the contacts on the coil, hi potted it at 3000 volt AC, and buttoned it back up. Running the Heathkit 2060A feels like driving a Cadillac, whereas the MFJ 3K legal limit tuner feels like driving a worn out Yugo. You can go in and tighten things up, clean this and that up, replace the cheap connectors, and it feels like driving a well cared for Yugo. It's still cheap feeling, but not quite as bad. 73s KI7AQJ
Bello ma non consiglio di usarlo in un appartamento con potenze dell'ordine dei 100 watt, personalmente non andrei oltre i 10 watt per non rischiare, potrebbe creare danni alla salute dato l'elevato campo magnetico e le tensioni particolarmente elevate che vengono generate dal loop magnetico.
Super simple solution. I like it. I also use a capacitor made from a piece of coaxial cable with my 11m CB MagLoop. However, this can be adjusted wirelessly via 433 MHz to the exact CB channel required, see the text below my video: ua-cam.com/video/eKzy6q4C9Zg/v-deo.html
Most of your signal is warming the Earth. It's up side down matey. No, its not an antipodean joke ;) Current should be at the top or facing your fave direction.
Great work. I am interested in the length of these antennas versus transmitting effectiveness at different frequency bands. I've been experimenting with a much longer 40 meter loop using multiple windings as shown here: ua-cam.com/video/07yP5ToA-ao/v-deo.html 73s. K7NXT
I've watched 2 of your videos now and you seem to miss the point and challenge of QRP. My antenna will be indoors as will my 500 mW to 1W radio. And that is the point. What can I accomplish with those limitations. If I wanted a heavy antenna and 100W I'd simply go commercial and not home brew.
Why? Ham radio is all about experimenting. Most of Peter's videos are of him using 5W or less and often with home brew equipment. He's allowed by the class of his license to use 100w if he chooses so doing experiments with that from time to time is no sin. Go and watch some more of his videos then comment again
+Dazzwidd Dazzwidd you are spot on. People forget about experimenting which is a shame. Ham radio or even CB 27MHz is really like fishing in my way of thinking. How much fun would fishing be if you used an explosive or a huge net and just went there for 5 minutes got a huge load of fish and went home. The fun is using less easier way of getting the fish. Its more fun using home brew antennas and smaller wattage's to see what you can drag in. But if a person wants hi power and huge antennas to guarantee range then why not just use the internet or a phone? Peter brings back to life the old way of radio to me.
looks like you missed the point THE POINT IS A HOMEBREW ANTENNA THAT CAN DO 100 WATTS FOR SOMEONE WHO HAS LIMITATIONS ON THE SIZE OF ANTENNA OR PLANNING RESTRICTIONS
I think he has done enough videos not to be nervous about it, and I like his style. No silly background music and just the technical details. Many of his viewers won’t speak English as a first language.
Great audio - thanks for taking the time to make the audio crisp and clear.
I cant believe this is the first time I ever saw this video. I will be reviewing this many times.
you sir, are a legend! been looking for capacitor alternative
Peter, thank you for making this video, it's incredibly informative and has helped more than any text can.
Excellent video. I am just getting into ham. My Technician's license is only 2 weeks old. Been watching videos on how to create this type of antenna. Most were good, but were showing the "ideal" way to do it. This one, showing things at their most basic and crude methods _really_ helped my understanding of the building of it. And inspires me to start playing. Obviously until I get my General I'll be stuck on 10m and 6m, but it's a start!
I would keep a fire extinguisher near! over 3KV @ 100 W on a loop that size. Make a series capacitor from 3 sections of coax, 1KV across each coax would be far safer. That size loop is also down about 10 dB, you are only ~1/2 S-unit over a QRP with a proper dipole but when and where space is limited it is a great solution. If you built it with a 5-meter section it would be 3X as efficient or only down less than one S-Unit from a dipole on a 100W rig. But the voltage will go up to over 4KV across the coax capacitor. It is great to see someone showing homebrew crafty solutions to get on the air. It seems that so many hams today think you must have the newest most expensive 4 digit rig, a KW+ amp and a branded antenna on a massive tower to enjoy the hobby.
Interesting video, I see magnetic loop antennas are more costly than what I want to spend. This gave me good insight on building my own!
Hi Peter, I've kept tabs on all of your videos for some time, as I too am into everything electronic. Repair, communications, modifications, and of course home brew construction of really cool stuff for 40 years now. I took a break from Radio for a while and out of all the cool videos here online, it's your abstract, but most interesting videos that have literally made me go through all my stuff- looking forward to getting back on the air very soon. Thanks for that & happy holidays to you.
Nice video. The antenna looks / sounds surprisingly effective!
That's what "home made" should be. Very sharp and well done (and, I just subscribed)!
Great video with the live resonance demo. No one does this. Thank you.
Well done! Perfect audio! Thanks
GL 73's sp6ml
Beautiful work......
Very thought provoking, thank you for making the video.
+David Lisney ¡Very good sound too!. Remote mic, is the key.
Clever way to avoid the expensive variable cap :-)
I run an indoor loop about the same size as that, roughly 3 foot diameter / 115 inch circumference, and it works decent despite my less than ideal tubing diameter. I have a large air variable to tune mine anywhere on 40/30/20 and the furthest contact I've made was from NE USA to Slovenia using 50W on 20m USB a couple weeks ago. The efficiency on 40m is quite low, but I have made some contacts into the SW parts of the USA with it on 40m using the full 100W. Interestingly enough, I'm also driving mine with an IC-751. Not a bad older rig, I like mine.
73s
Thanks for sharing, I’ll get one built when I’m stuck home in the rain.
Great work Peter will have to make one and use it on the 27mhz cb band and see ho well it can perform there
I made one out of RG6 Coax for 10,11,12 and 15m
I made a second that is quite efficient out of two RG6 coax runs in parallel. I do have problems with flashover on the RG6 cable. I might give the RG213 a go if I can find some.
Look up trombone capacitors made from copper pipe they work well
They work a treat. Watch for flashover on the capacitor.
You’ll want to have a look at 66 pacific dot com for some loop calculations
¡Thaks for sharing all your experiences, Peter!. LU1AR
Awesome home brew antenna bro cheers for the video 🇦🇺✌️
Peter, I just finished building a qrp version using coax as the loop. I could not get the vSWR any lower than 2.5:1. I then used the copper tubing as the loop and was slightly better but still cannot drop it down any further. When I tested it with a smaller loop I was able to get the vSWR flat. I think my inner loop is not close enough to the outer loop or not exactly in the same plane. Going to play with it some tomorrow.
Thanks for the Video and best 73
Great audio in this video
Hi Peter,
Brilliant idea for the capacitor, Peter! I like the variable cap idea.
I've built a QRP portable loop which covers 10m - 20m using RG-213, shorting the braid and inner conductor together at the SO-239 connectors in the box which houses the variable cap. I think I need to revisit the idea of a QRP loop but taking out the cost of the vacuum cap.
I'd be really interested in it's DX performance over your wire antenna :)
Thanks for posting the video's I always enjoy watching them.
73 de M0SNR
Wery good antenna! Good design of the condenser. Only I did not realize you've been working on it for TX?
EXCELLANT idea to use RG213 and PCB MATERIAL as variable cap in place of a expensive HV vacuum or air variable cap.
Could you possibly provide the dimensions of the outer loop and inner coupling loop to get people in the ball park . ??? .....
Built mine with flexible 1/2" LDF 4 solid copper shield feedline "hardline" therefor no couplers required like rigid copper pipe ... im
still tweeking the loop lengths, tuning cap and mounting issues ...
Your cap idea to be part or all or used in next revision .
YOUR audio level / quality in this video is also nicely done.
Thanks a Meg ...
JF
Thanks. Inner loop is about 1/5 the diameter of the outer loop. Dimensions not very critical provided you can bring the loop to resonance, though bigger is better for more efficiency (to a point where it ceases to be a mag loop).
I am glad that a ran across this. I know this was published over a year ago and I hope you'll get an email with my question here. What is the dimension of your fine tuning section? Other than that, I have done the dimension conversions for the pipe and now ready to build this thing. Thanks
+Harold Kinchelow (K7ILO) Did you ever get an answer?
This is very interesting and impressive. How did you acquire all this great knowledge of RF design? I've taught myself many math and technology related subjects, but RF design somehow has never clicked in my mind. To me it is far more mysterious than most branches of electronics.
I think the same thing about algebra, calculus, imaginery numbers and programming!
I learned algebra, calculus, imaginary numbers and programming, but RF seems out of reach to me. How did you learn all that?
Ralph Dratman Get confident with (linear) electrical circuit theory, where you will apply algebra and complex numbers in cases where electrical voltages and currents oscillate sinusoidally. Next take a simple textbook intro to electromagnetism to begin with.
Best alminium antena ,stronk propogasient, gold ? Tank'd
I love this video....
Nice! I built a magnetic loop antenna, Is there any recommended minimum gauge for inner loop wire or can I just use something that keeps the shape? Thanks.
Try several shorter coax lengths in parallel. It'll have the same capacitance but lower current per leg so perhaps slightly more efficient and more compact.
Hi Peter, whilst I have little interest in transmitters these days, I did find your video very interesting. It's amazing what you can do with a few bits if pipe and sticky tape. Reminds me of Blue Peter (a UK kids TV programme of many years ago!) P.S No connection with your name!!
Brilliant idea to use coax as the capacitor (:
I tried to build this loop too. Result: sparks in the coax, temperature increase in the PCB-capacitor, which results in variation of the resonance frequency and finally holes around the edges of the PCB. The coax capacitance is lossy, I think. I used good coax, but even silver core and shield and low-loss dielectricum are not good enough for a high-Q loop. I can recommend TEFLON tube with alumin rods as capacitor. The rods can move in and out and allow tuning. No sparks, no burning holes and stable capacitance at 100 watts. 73 PA0FSB
Great video! I have a Russian vacuum variable capacitor; now, on to the construction phase!
thanks for you video nice
Excellent loop... try to feed it with a gammamatch.. it wil have a lot less losses..:-)
I see you have asked the same question. Seems a gamma match would be far better.
Nice! I want to build one for 80 meters!! :)
What dimensions are your pcb boards? Single-sided? non-copper sides facing each other? Thx! SV0SGS
About 8 x 10 cm. Yes and Yes.
vk3ye I’m playing with some similar designs. Only I have a heap of RG6 from a strip out that I have been using as loop and capacitance materials. If I want less resistance. I can simply double or triple up the coax in parallel
As for remotely tuning the capacitor, there is a motor from Jaycar that does one turn every two seconds. I am using that to drive some threaded rod to slide a block with some copper tape over some copper strips.
I also purchased some 3/4” and 1/2” lengths of copper to play with some trombone capacitor ideas using the same motorised thread drive
Currently I use an almost 10m length of RG6 in a kite shaped loop with sone fixed 6KV ceramics that are consistently tuning the CW portion of 7MHz and give me around 80KHz between 2:1 points.
It copes with up to 40-50W however I need a few caps in series to run 100W without having a _Nichola Tesla_ moment.
good project, i want to build one for the 20m band. how well will it work, will i get alot of DX contacts on 20m with that magnetic loop ?
20m is a tough band for DX. But especially on digital modes, and especially with the improving conditions it should do OK.
Using a wired microphone from the stone age just matches that loop antenna! LOL!
I think you will find that just adjusting the capacitor matches the antenna. LOL
Wouldn't it very be dangerous to fine tune the loop (during transmission), with the pcb capacitor? That's needed in my experience with mag loops, in addition to the "noise maximization" step.
Un saludo buen video donde va conectado el bunkle no entiendo muy bien
Y si es una chapa de cobre
you are the only one shooting radiation pattern upward. all the others shoot it into the dirt and complain hiw little effective it is. 😂
way to go man.
suppose an inefficient loop on 40 meters would beat a too-low dipole?
Ok I’ll go do that. I’m waiting for the shops to open :D Why is a HF antenna ok so low to the ground? I was hoping using a magnetic loop for rx might help with noise.
It should be pointed out if you intend to use this antenna indoors or in an apartment or condo setting it is best to use low power to avoid dangerous RF exposure and reduce interference to your neighbor's electronic devices.
In Germany we actually have limits on how close people can be to your antenna based on field strength.
I need to know where to get the lime colored shorts.
Thanks Peter! I only seem to be able to get 15mm copper pipe here in UK. What difference does this make, please?
Not much. Thicker slightly better though.
@@vk3ye Sorry to trouble you again, and believe you me this will be the last! I have a variable capacitor from a tuning tank of a old valved transceiver which is 370pf. If your RG213 has a total capacity of 185pf and your copper board capacitor adds to it, would my single 370pf be ok?
@@control5835 Should be fine.
Where can I get the plans? I have difficult time understanding specifics. How can I get copy of full article? Is there a pdf available? Thank You
Notes at home.alphalink.com.au/~parkerp/projects/projloop.htm
Hi from Garth Close ZS6ANO
Nice video Peter, thanks for the fun down at the Bay today. One question which I forgot to ask is what is the rough dimensions of your variable part of the capacitor? Do the plate sizes vary the capacitance efficiency a great deal? Some further clarification on that point would be appreciated. 73 :)
is that a icom ic-751? would love to build 40m mag loop. this is all i need for now.. lols
Yes.
@@vk3ye tnx 73
If you could only have four outdoor ham antennas what would you choose
Depends on how much room you've got and your frequencies/interests.
@@vk3ye say 18m wide by 25m long, 80-10
@@PatAutrey See my website vk3ye . com for ideas but basic end-fed or dipole will get you started.
How would a double coil on the outer loop compare? It would be smaller. Would the inner loop also need to be smaller ? Also, how much spacing would be optimal between the two coils of the outer loop?
As always, your videos are the best.
Thanks EM - I haven't tried a double coil but I believe others have had varying results.
Peter.. a great training video with points clearly made. Really helpful for newbies like me. Thank you!! ZL2JED
What formula did you use to determine the length needed for the coax capacitor.
Very interesting. Which antenna you recommend? Long Wire + Balun or Magnetic Loop? (listens to a larger spectrum of Short Wave with the best signal x noise). Thanks You.
Y de que material es lo que se mueve con la goma
Do you have a rough drawing of this Loop Build? I would like to try it. thanks
Are there any easy step by step instructions for a magnetic loop antenna like this? I want a to build a loop but don't want to buy a capacitor. But I don't want to start until I get dimensions for the sliding capacitor on this video.
+Gordon Freeman On many websites. W2BRI springs to mind.
+vk3ye I have been searching google for months. Just found what you are talking about.
www.iw5edi.com/wp-content/uploads/2015/02/w2bri-loop.pdf.
Thank you!
Also, thanks to your video I built a 40m mag loop antenna. I can hear so much stuff! But, I have trouble transmitting being in the middle of the pacific, in Hawaii. Nonetheless so much fun!
Well done Video. Motivates anyone to build one. - 4S7AB Sri Lanka
I noticed the antenna switch on top of the radio. is yours using a common coax ground (metal case) or do you isolate the coax grounds as well when you switch from one antenna coax to another? It would seem logical that having a di-pole and a vertical on a switch could affect the antennas if the coaxes were still joined in a switch box...wouldn't it?.
3m circumference I think you mean.
So if 40 m required 185 cm of coax. How much coax do you think a 20 m frequency would require
Depends on the capacitance needed. Which depends on the size of the loop which governs inductance. If using the same loop size as one for 7 MHz I'd say roughly 1/4 the length for 1/4 the capacitance.
@@vk3ye thanks, Good place to start
What size cable are you using from the small loop to the transceiver ?
RG58. It doesn't matter as the length is not long.
vk3ye Tks. Am using 20m RG58. Mainly for receive for now.
I don't understand the loop antenna for transmitter you short 100w out put power with a circule ?
+Jihad khalil When the loop is tuned, all the energy is induced from the small loop to the bigger loop, like a transformer. Note that the key element here is TUNING. This is why the use the capacitor. The cap and the loop form a resonant tank circuit. The proper way to tune it is to set the frequency in the transceiver and adjust the capacitor for maximum received noise. Then, using low power, adjust for minimum SWR. then you are set and switch to high power.
+Gabriel Sierra ok thanx. man
u have mentioned out loop legth is 3 Meter- Can say inner loop length
It's about 1/5 the diameter of the main loop
If the copper tube is not available, could I use an aluminum tube? :)
Yes. Hardest thing is getting a good electrical connection at the top.
@@vk3ye Hey, thanks for that reply! I just found out that I have 7 meter length 3mm outer diameter copper tube. Will it work?
@@jharwinbarrozo A bit thin but it could work.
will this work with QRP?
Yes.
I like this
Very interesting design. Excellent video and thanks. de KM2U
I have found the measurements for sliding variable capacitor. Now I would like to ask about the coupling loop. Do I just use the inner conductor of the RG-58 and solder that to one end of the 60cm loop and insulate the outer braid ?
Steven CARR So what are the dimensions you found? Share....
+Steven CARR For the coupling loop both inner and outer conductors are soldered together. Feedline inner goes to one side, braid to other.
+Harold Kinchelow (K7ILO) There are online calculators for loops that can give a reasonable starting point for dimensions and capacitances.
Nice video ! Love loops for QRP operation 73's SA5LKC
How did you estimate the length for the coax capacitor?
Can you use two pop cans as slider ("trombone") capacitor instead of the circuit board?
Potentially. Key issue is providing a high quality low resistance electrical connection.
very nice tks 7351.
What is the size of the printed circuit used for the tuning capacitor ?
+Steven CARR About 6 x 8 cm or so
I could not quite understand in the video what you said your 2:1 bandwidth is on 40M. Can you tell me?
Thank you.
So what would be the ideal size of a square loop for 6.5-7.3 MHz?
+Michael Fearnley 1 to 1.5m in diameter would work but bigger - eg 3m diameter - would be more efficient but is a bit of a monster.
what info do you know of that can educate me to build variable caps. I have an idea to make a normal air dielectric cap into a extreme votage variable cap. 30,000 volts or better. but not knowing what that dielectric does to the capacitance. has me in quandary. but it would offer a cheaper alternative to vacuum variables.
What is te size of the 2 loops, to 40m band, please?
He is using 3 meters, 19mm copper tubing for the large copper loop (See 1:24). The coupling loop is made from ordinary mains flex with all three cores connected together. The size is not mentioned, but it's usually 1/5 of the main loop, so it would be 0.6m.
sir, could i get you to calculate the copper square tuner for 14 to 30 mhz. i would like to build this antenna. at the end of the RG-213 coax. i dont want to use a high priced tuner. this is in affordable range, your help would be appreciated. Tommy
+Tommy Schales This method is only good for a single band. For a wider range use a variable capacitor. Say air spaced or vacuum variable.
why such a high capacitancw? i used online calculator and got 37pF for 7.1Mhz.
The capacitance I used was consistent with all other magnetic loops I've built. Roughly 2 to 3 pF per metre of wavelength.
vk3ye thx for your reply. i did find a mla calculator. should have looked more thoroughly before asking. my bad.
Gut 73!
Hi all, I've tried to build this antenna, but I get extremely high SWR no matter what position the loop is. Any suggestions?
Probably too much/too little capacitance, or the loop is detuned by surroundings.
+Carsten Bauer Maybe your Faraday loop is wrong? You need it to "see" 50 ohms to the loop so you only have to tune for resonance.
All my Magloops tune to 1.1 SWR still after so many built from small 6M Magloops up to my current 2 element in series.
Gastite Pexal tube from Bunnings - magic in 16mm and 20mm.
Capacitors are RG-213 inner slid into one end.
s12.postimg.org/jj6ocra99/TWO_TURN_PEXAL_MAGLOOP.jpg
Have fun Peter.
Myles VK6ZRY
+Myles Nicholas Aperture makes for a much bigger signal but I love the idea of using self capacitance.
hello vk3ye excellent project for apartment is possible for CB 27mhz I have very limited space and would put it on the porch and by my accounts is 2.63 meters copper tube and 52.6 the smallest circonferencia and I will leave a length of coaxial cable RG213 about 1.85 meters ok do not know if that's my doubts is like tuning the stationary excuse my English is poor ok ..73
+MultiJorgecardoso cardoso El largo total del tubo, tiene que ser un poco menos que 1/4 de onda. En tu caso andaría bien un caño de 2,5 metros, formando un círculo de algo más de 80 cm. Para sintonizarlo en 11 metros, vas a necesitar muy poca capacidad. Creo que con 30 cm de coaxial, ya tienes suficiente. Muchos le sacan la vainja de PVC y suben y bajan la malla hasta encontrar la sintonía. En esa freciencia, el ancho de bnd va a ser de unos 300 Kc, de modo que tampoco necesitarás un ajuste dentro de la banda.
El aro interior, tiene que ser de unos 20 cm de diámetro y hay que retorcerlo hasta bajar la ROE.
Que tengas éxito en tu proyecto. Un abrazo desde Argentina. LU1AR.
+Edgardo Maffía Buenas tardes Edgardo, veo que tienes buenos conocimientos del tema, me podrías indicar cual sería la longitud del aro para una antena que funciones en 7 MHz y si es posible usar esa misma antena para los 14 MHZ? Cuanto coaxial necesitaría para formar el capacitor? tengo necesidad de construir una antena loop para poder ubicarla en mi unidad residencial ya que no dispongo de mucho espacio para instalarla. 73 Cordiales HK6PAN hk6pan@gmail.com.
La banda de 14 Mhz te limita el perímetro del aro a 4,5 metros es decir 1,5 metros de diámetro.
El aro puede ser un cable coaxil viejo, ya que solo se aprovecha la malla debajo del PVC que equivale a un caño de 10mm.
En este artículo hay una antena para 7 Mhz que te va a interesar:
www.carc.org.uk/downloads/A%20Coaxial%20Magnetic%20Loop%20%20for%207MHz.pdf
Y esta nota es lo mejor que vi, en español:
lu6etj.host-argentina.com.ar/lu6etj/tecnicos/loop/antena_de_cuadro.htm
Saludos. LU1AR
Peter I love your videos but this one in particular worries me a little bit...
Encouraging people to touch a "high power loop" without specifying (in capital letters) that doing so during TX might result in injuries or even death is a bit dangerous, don't you think?
Moreover, the design of your variable capacitor is a clear invitation to touch the plates during tuning. I think its dangerous...
We are talking about 4KV in this case. You should specify that the loop might spark fires at the coax capacitor (happened to me) and WILL KILL if you are not careful enough.
Putting aside the other safety considerations about magnetic loops, I would say:
NEVER EVER TOUCH MAGNETIC LOOPS - ESPECIALLY IF YOU ARE NOT QRP.
73's
Alain
he explicitly says to not touch the antenna while transmitting, at 5:38
Magloop calculator is here, www.66pacific.com/calculators/small_tx_loop_calc.aspx
I wish I still had access to tubular copper bus for substations. I worked at a small foundry that used tubular bus. They stuff could easily do 1000 watts. Bending it would take a hydraulic bender and special shoes, & follow bars. I like the 40 meter band. (7MHz). I want to make some loops for listening, and probably just use dipoles, bazookas (single double) or verticals for transmitting, and have TX RX relays. My high power amp is 1500 watts and I just made one that will even do 1500 watts AM. It was a headache, as I went with valves, and used SIX 4-125A tubes. With 80 watts drive, it will do about 2000 watts out FM, and less than that on 2 meters, but I am still at about 1 KW. I have become totally disgusted with the quality of the products MFJ makes. If not for fixing brand new MFJ, Ameritron, Cushman, and other junk made under the MFJ company names, I'd have probably never renewed my license. Most of their stuff is cheaply made, but serviceable, but the poor quality of assembly makes these products prone to catastrophic failures. I just bought one of the best antenna tuners Heathkit ever sold. I went though it, cleaned all the silver, wrapped all the straps in high voltage silicone, & rubber slicing tape, carefully measured and bent all the blades on the variable caps to center, adjusted the counter, reflowed the solder, cleaned polished & lightly greased the contacts on the coil, hi potted it at 3000 volt AC, and buttoned it back up. Running the Heathkit 2060A feels like driving a Cadillac, whereas the MFJ 3K legal limit tuner feels like driving a worn out Yugo. You can go in and tighten things up, clean this and that up, replace the cheap connectors, and it feels like driving a well cared for Yugo. It's still cheap feeling, but not quite as bad. 73s KI7AQJ
Bello ma non consiglio di usarlo in un appartamento con potenze dell'ordine dei 100 watt, personalmente non andrei oltre i 10 watt per non rischiare, potrebbe creare danni alla salute dato l'elevato campo magnetico e le tensioni particolarmente elevate che vengono generate dal loop magnetico.
Good presentation bro..
Warm regard.
YG5WDC
Thanks for all your work! interesting and informative! Howard M0AYO
Super simple solution. I like it. I also use a capacitor made from a piece of coaxial cable with my 11m CB MagLoop. However, this can be adjusted wirelessly via 433 MHz to the exact CB channel required, see the text below my video: ua-cam.com/video/eKzy6q4C9Zg/v-deo.html
The variable capacitor is a bad idea. It will not stand bad weather!
Most of your signal is warming the Earth. It's up side down matey. No, its not an antipodean joke ;)
Current should be at the top or facing your fave direction.
the problem is the inconvenience of keeping the feeder away from the high voltage part of the main loop.
Great work. I am interested in the length of these antennas versus transmitting effectiveness at different frequency bands. I've been experimenting with a much longer 40 meter loop using multiple windings as shown here:
ua-cam.com/video/07yP5ToA-ao/v-deo.html
73s. K7NXT
I've watched 2 of your videos now and you seem to miss the point and challenge of QRP. My antenna will be indoors as will my 500 mW to 1W radio. And that is the point. What can I accomplish with those limitations. If I wanted a heavy antenna and 100W I'd simply go commercial and not home brew.
Why? Ham radio is all about experimenting. Most of Peter's videos are of him using 5W or less and often with home brew equipment. He's allowed by the class of his license to use 100w if he chooses so doing experiments with that from time to time is no sin. Go and watch some more of his videos then comment again
+Dazzwidd Dazzwidd you are spot on. People forget about experimenting which is a shame. Ham radio or even CB 27MHz is really like fishing in my way of thinking. How much fun would fishing be if you used an explosive or a huge net and just went there for 5 minutes got a huge load of fish and went home. The fun is using less easier way of getting the fish. Its more fun using home brew antennas and smaller wattage's to see what you can drag in. But if a person wants hi power and huge antennas to guarantee range then why not just use the internet or a phone? Peter brings back to life the old way of radio to me.
He should consult with you in the future to ensure his projects align with your interests. Spot on.
it's so funny to tell the QRP god that he's missing the point of QRP :D
looks like you missed the point THE POINT IS A HOMEBREW ANTENNA THAT CAN DO 100 WATTS FOR SOMEONE WHO HAS LIMITATIONS ON THE SIZE OF ANTENNA OR PLANNING RESTRICTIONS
он че не мигает ваще? ))
You don't need the BBC-voiceover style, it's odd to listen to. Relax and be yourself.. Do you need a few beers first?
I think it sounds ok. He is giving technical details and wants to be precise.
I thought he had a few beers and that was why he sounded like he did
Rust... I think it's odd that you have no sense of humor...
I think he has done enough videos not to be nervous about it, and I like his style. No silly background music and just the technical details. Many of his viewers won’t speak English as a first language.
I like this