Eagerly consuming your old videos, Dave. Your communication in these lessons never gets stale and the info you share is as fresh today as it was when you first released them. Thanks for your diligence and hard work within RUclips's amateur radio community.
Dave. I have the 1786 and am VERY happy with it. It is quiet and I've made over a 1,000 QSO"s with it in the past two years. Thought I'd mention, when vertically mounted, there is a null along the axis on either side of the loop. Makes a difference on A/B antenna comparisons where the other guy is located. Many thanks for your vids. Great stuff. Need more on propagation now that the sunspot cycle is waning.
I've been running one of the these for about 3 weeks now with an IComm 7300. It's mounted horizontally about 25 feet up on a pole attached to the side peak of my roof. The manual is quite clear about putting up at least 20 ft. if you plan to run it horizontally. That eliminates the directional null but you will lose NVIS as your null will be a 15 degree circle pointing straight up. I can't talk to anyone closer than about 600 miles on 20m and I've managed one contact at 330 miles on 40m. No one from anywhere closer comes in even when they're in my home town. Additionally, I've found that mounting it at the very top of pole is important if you're using a metal pole. So, don't leave metal sticking through the "donut" so to speak. So far I'm quite happy with it. I'm in Oregon and my longest contacts have been Hawaii and New Hampshire both 2500 miles away on 20m. I've also heard Belize, Australia, Japan, Mexico, Brazil and New Zealand, but I don't think I've got the power (100w) to talk back to them except under ideal conditions (I've tried.) I don't expect that will be possible until solar cycle comes around. I've had contacts at 1200, 600 and 330 miles on 40m. As far as Dave saying that it doesn't cover all of 40m meters, mine does and did out of the box. As Dave finds out later in his videos apparently some of the antennas don't have properly calibrated switches and/or shafts on the capacitors and can't tune down low enough, but it is an easily repairable problem. One problem I have had is that the tuner will sometimes freeze in place if the weather is really cold (in the low 20's.) When it warms up the problem goes away. I'm not sure what you'd do about this. My brother suggested some kind of low voltage heater in the antenna's tuning box. That would would require a power cable to be installed, but might be worth it if you live in a really cold part of the country.
My 1788 is installed on a rotator in the attic of a town house in a HOA. I used PVC piping for all mounts and found the 1788 works BEST on 40M. SWRs vary with position as does the signal strength. Length of coax is important to keep it down to less than 25ft. Of all my options dipoles, capacitive hat horizontal multi-band dipoles etc - the 1788 was the best de AC4PS.
I am testing a friend's AlexLoop. I am really enjoying it. I also concur that 40m suffers, but higher bands work quite well! If you are in a noisy city area, and want to work DX, these Small Transmitting Loops are a heap of fun on everything above 40m. Amazing how clear the signals are. I am going to run this as a receive antenna, and transmit with a vertical dipole, flipping the switch, next.
Thanks for posting this, David. I was eagerly awaiting what you thought of the antenna because, despite it's price, I was considering looking into buying the 1788 for 40M use in my HOA. It is too bad the results weren't better. Let us know in the future if you get better performance out of it either in a different configuration of after tweaking it. I'd be very interested to know. Anyways, thanks again. Love those mountain ranges by the way.
Hi Dave. I truly appreciate your work here. Great work. I believe you’ve actually opened Pandora’s box to something really important and big for the Ham Radio community. A new way of working the bands.
Which of the MFJ Mag loops, the 1780, the 1786, or the 1788 would you recommend now that you had a chance to see how the 1788 works on 40 meters? I'm torn between going with the 10 to 30 meter versus 15 to 40 meter. 40 meters is very popular but very finicky at 40, as I understand it. On the other hand, the 10 to 15 meter bands are coming alive again soon.
Mine work super on 40m ! Hope you found your problem. (Horizontal polarisation in ...the loft !) No poles, suspended by strings to the eves of the roof.
Great video Dave. Mine (1786) stopped tuning as the motor broke. Replaced with a new motor as close as I could find. It tunes great on 20m but 10 15 etc are over 2:1. I assume the motor is slightly faster so I need to slow it. I see the adjusters inside but I can’t find any instructions in my manual on how to adjust and what they all do. Anyone have any info?
Alas....the long awaited review!! Not too surprised with the results..... Not hating on MFJ, as it seems to be mostly functional but not very well refined, especially for the asking price. Like many other items in their product line, it seems kinda bulky, poorly laid out and awkward to use. In my opinion, MFJ is kinda the ham radio equivalent of Harbor Freight.....lotta stuff, mostly cheap....some works....some don't and some don't work very long. Thanks for the great review Dave, look forward to seeing if you can make it play on 40 meters.
I have lots of MFJ equipment (and they once published a book of mine) and overall think highly of the company. I have to admit I was disappointed by the antenna's 40m performance. I hope a solution will be found. I have a couple ideas....
Hi Dave. Can you tell us if the MFJ loop is actually 3 feet in diameter? This would make the circumference more than 1/4 wavelength on 10M. All the "experts say a loop must be less than 1/4 wavelength. I am confused.
Just a thought...adding the steel mounting pipe may cause some problems. The mounts are connected to the antenna so any metal attached to the loop will add to the system. I use a fiberglass mast on mine
Dave, any issue with constantly keying up the transceiver to tune the antenna. As I understand it, transmitting when a transceiver is attached to an antenna with a high SWR can damage the output circuits.
Hi Dave I have a 1788 and it tunes well on 40. It has a pvc section between the rotor and antenna and aluminum pipe under rotor. Byron K1cme. Have a photo of it on qrz.
Dave, thanks for the video. I am not surprised that the loop does not do well on 40 meters. I build my own loops and make them as large as possible to get the most efficiency out of them. So for instance my 20 meter loop is 15 feet in length or about 4.5 feet in diameter. Whereas the MFJ loop is a smaller diameter antenna and therefore not as efficient. Most loop are great on one band, good on another, ok on another band and bad on the rest of the bands. I am willing to bet your loop is great on 20 meters. Again, thanks for the video. 73 from N2LRB
good review but a little pricey I think . I just upgraded from being a Tech after 20 years to General last Sunday and to start I will be running a end Fed wire. Also thank you for the I instructional videos I found them vary helpful in getting my licence. Look out Extra will be doing that in August :) .
Thanks for another great review! I have watched several review videos of the MFJ-1786 and 1788 and it seems one person is thrilled and the next is sorely disappointed with the antenna's performance. First off, the price is ridiculously high! $199 would be more than enough and I am sure more people would be willing to try it at that price. This would be the ideal antenna for me in my HOA antenna restricted community. It would install easily and fit in my garage attic. If only there were consistent reports. I am confused..... do I try one or not? $500 is a lot of money for an aluminum Hula-Hoop!
Yes, that makes since. I may try one if my 37' OCF 6-40m Dipole I plan to configure in my garage attic some way doesn't work out very well. Might be able to get away with mounting the MFJ Loop outside the house as long as it is not up more than 10 feet or so. It is small, looks high tech and would not be an eyesore, especially if mounted horizontal. I can claim it is an HDTV antenna...lol! Thank for your reply.
Hi David couple of questions, if the loop was bigger could it be made to work on 40 and 80 meters?, also nobody ever seemed to use one horizontally will they work horizontal and prob be omni directional......from Fred g4vvq in England.
The manual says to use steel or thick-walled aluminum. I might be able to mount it directly to the 2x4--I'll add that to the list of things to try. 73, Dave
Hi Dave, thanks for all you do! Dumb question coming.....I just bought the MFJ-1786, and the manual specifically states NOT to seal the holes, except the areas on the coax connectors.So that's what I'll do. However, although it might look odd, but could you put a covering over the antenna to protect it a bit from the elements without affecting the performance? 73!
Hello Dave I got a Mfj1786 and mounted it horizontal It worked well. But when I mounted it vertical with a 3 metres long steel mast stand in a steel tripod. I can't tune it low swr. Is it wrong mounting mfj1786 with mental mast? It seems to make a wood mast better. TNX & 73 bh4eag from China
You have to avoid metal going too far into the antenna when using it vertical. I think there is something in the instructions about that. Personally, I'd just use a non-metal pole if I were you. It does needs to be a few above ground in the vertical mode, like 3 ft or so.
Hi Dave, another great review! I'm sure you will get it going on 40m. I've been thinking about purchasing this unit for use on 20m and 40m. It might be more fun to build my own. Is it generally true that a larger loop will have more radiation efficiency and greater bandwidth (lower Q)? Thinking about approx. 6 ft diameter using two 10' sections of 1" diameter copper pipe and a HV adjustable cap. 73 KE8EUI
I think the loop is correctly sized for 20 m. For 40 or less you'd want a larger loop under ideal conditions. That would cost you on 20m and up though. Loops are very finicky about frequency.
Hi Dave! First, thanks for the videos. Very helpful. Now tell me please, could you imagine or suppose that this MFJ-1788 would provide any success indoors, I mean, inside an apartment or in a balcony of a flat at the third floor? Would it performe well? Thank you.
MY MFJ LOOP COVERED ALL OF 40 METERS AND I ALWAYS HAD A FLAT SWR. ALSO IT WAS MOUNTED INDOORS ON THE 4TH FLOOR AND I HAD STEEL ABOVE ME BELOW ME AND EVEN THE MFJ MANUAL SAID IT WOULD NOT WORK. I SENT THEM AA COPY OF 44 DX CONTACTS I MADE IN 1 NIGHT RUNNING 15 WATTS BOB AF2DX SORRY FOR CAPS HAD EYE SURGERY
My comment : In 12 months you'll have dust all over this equipment. It's great to learn and experiment but it's hardly a good system. I won't be trying one. My next antenna will be an Omni-directional curtain nest array built on 3 acres of land for the 20m band and low angle dx. See you in 5 years Dave, cheers :-) Wish me luck.....
We'll soon be full-time RV'ing (my wife's idea) so small portable hf antennas are of great interest to some of us hams. Right now I'm planning on using an end-fed antenna where I can (may RV parks frown on stringing wire around the camping spot) or my Buddipole vertical...........both of which are compromised antennas. Gud luk DX'ing k6sdw
Check out the work here on You Tube by VK3YE. He is the loop expert in Australia. He has much success. Good luck and safe travels. cheers, from vk4soe / la8pv
I've heard from hams who use them in attics with success. Need to have a wood roof. If it's covered with aluminum or copper foil, that will keep the antenna from working.
Yes, they're DC shorts, but at RF work as a tuned circuit with inductance (single turn) and capacitance. They're inefficient radiators, so they have to be made of stout materials to reduce losses.
Eagerly consuming your old videos, Dave. Your communication in these lessons never gets stale and the info you share is as fresh today as it was when you first released them. Thanks for your diligence and hard work within RUclips's amateur radio community.
Dave. I have the 1786 and am VERY happy with it. It is quiet and I've made over a 1,000 QSO"s with it in the past two years. Thought I'd mention, when vertically mounted, there is a null along the axis on either side of the loop. Makes a difference on A/B antenna comparisons where the other guy is located. Many thanks for your vids. Great stuff. Need more on propagation now that the sunspot cycle is waning.
I am using a Magnetic Loop antenna that I built. Cost was less than $30.00. Mine will do 15 to 40 meters. I learned how on RUclips.
I've been running one of the these for about 3 weeks now with an IComm 7300. It's mounted horizontally about 25 feet up on a pole attached to the side peak of my roof. The manual is quite clear about putting up at least 20 ft. if you plan to run it horizontally. That eliminates the directional null but you will lose NVIS as your null will be a 15 degree circle pointing straight up. I can't talk to anyone closer than about 600 miles on 20m and I've managed one contact at 330 miles on 40m. No one from anywhere closer comes in even when they're in my home town. Additionally, I've found that mounting it at the very top of pole is important if you're using a metal pole. So, don't leave metal sticking through the "donut" so to speak. So far I'm quite happy with it. I'm in Oregon and my longest contacts have been Hawaii and New Hampshire both 2500 miles away on 20m. I've also heard Belize, Australia, Japan, Mexico, Brazil and New Zealand, but I don't think I've got the power (100w) to talk back to them except under ideal conditions (I've tried.) I don't expect that will be possible until solar cycle comes around. I've had contacts at 1200, 600 and 330 miles on 40m.
As far as Dave saying that it doesn't cover all of 40m meters, mine does and did out of the box. As Dave finds out later in his videos apparently some of the antennas don't have properly calibrated switches and/or shafts on the capacitors and can't tune down low enough, but it is an easily repairable problem. One problem I have had is that the tuner will sometimes freeze in place if the weather is really cold (in the low 20's.) When it warms up the problem goes away. I'm not sure what you'd do about this. My brother suggested some kind of low voltage heater in the antenna's tuning box. That would would require a power cable to be installed, but might be worth it if you live in a really cold part of the country.
Thanks for the info. I plan to mount mine horizontally soon.
Cannot get mine to match at all in Horizontal mode - seriously regretting the expense
My 1788 is installed on a rotator in the attic of a town house in a HOA. I used PVC piping for all mounts and found the 1788 works BEST on 40M. SWRs vary with position as does the signal strength. Length of coax is important to keep it down to less than 25ft. Of all my options dipoles, capacitive hat horizontal multi-band dipoles etc - the 1788 was the best de AC4PS.
Wow! Do you have any pics of your installation?
Yes, I do have some...
Please go to www.dcasler.com/ask-dave and send me your email address. I'll answer and then you can send me the pics.
I want to like these, as they suit my needs well. In practice, they have driven me half mad with problems.
I understand. I finally got mine working well.
I am testing a friend's AlexLoop. I am really enjoying it. I also concur that 40m suffers, but higher bands work quite well! If you are in a noisy city area, and want to work DX, these Small Transmitting Loops are a heap of fun on everything above 40m. Amazing how clear the signals are. I am going to run this as a receive antenna, and transmit with a vertical dipole, flipping the switch, next.
Thanks for posting this, David. I was eagerly awaiting what you thought of the antenna because, despite it's price, I was considering looking into buying the 1788 for 40M use in my HOA. It is too bad the results weren't better. Let us know in the future if you get better performance out of it either in a different configuration of after tweaking it. I'd be very interested to know. Anyways, thanks again. Love those mountain ranges by the way.
Thank you for biting the bullet for me Dave! Great reporting as usual.
73
Hi Dave. I truly appreciate your work here. Great work. I believe you’ve actually opened Pandora’s box to something really important and big for the Ham Radio community. A new way of working the bands.
Which of the MFJ Mag loops, the 1780, the 1786, or the 1788 would you recommend now that you had a chance to see how the 1788 works on 40 meters? I'm torn between going with the 10 to 30 meter versus 15 to 40 meter. 40 meters is very popular but very finicky at 40, as I understand it. On the other hand, the 10 to 15 meter bands are coming alive again soon.
Mine work super on 40m ! Hope you found your problem.
(Horizontal polarisation in ...the loft !)
No poles, suspended by strings to the eves of the roof.
I've set mine up for horizontal polarization, and will mount it either atop the roof or atop a 20 foot pole. I hope to do that soon.
Always good. Always appreciated Dave.
nice review for the expensive antenna. Mr. Casler, you really bring Amateur radio to the masses. Thank you for that.
Great video Dave. Mine (1786) stopped tuning as the motor broke. Replaced with a new motor as close as I could find. It tunes great on 20m but 10 15 etc are over 2:1. I assume the motor is slightly faster so I need to slow it. I see the adjusters inside but I can’t find any instructions in my manual on how to adjust and what they all do. Anyone have any info?
Alas....the long awaited review!!
Not too surprised with the results..... Not hating on MFJ, as it seems to be mostly functional but not very well refined, especially for the asking price. Like many other items in their product line, it seems kinda bulky, poorly laid out and awkward to use.
In my opinion, MFJ is kinda the ham radio equivalent of Harbor Freight.....lotta stuff, mostly cheap....some works....some don't and some don't work very long.
Thanks for the great review Dave, look forward to seeing if you can make it play on 40 meters.
I have lots of MFJ equipment (and they once published a book of mine) and overall think highly of the company. I have to admit I was disappointed by the antenna's 40m performance. I hope a solution will be found. I have a couple ideas....
Hi Dave. Can you tell us if the MFJ loop is actually 3 feet in diameter? This would make the circumference more than 1/4 wavelength on 10M. All the "experts say a loop must be less than 1/4 wavelength. I am confused.
Just a thought...adding the steel mounting pipe may cause some problems. The mounts are connected to the antenna so any metal attached to the loop will add to the system. I use a fiberglass mast on mine
I tried mounting it without the steel pipe today with a direct attachment to a wood mast. No luck so far.
Dave, any issue with constantly keying up the transceiver to tune the antenna. As I understand it, transmitting when a transceiver is attached to an antenna with a high SWR can damage the output circuits.
Thank you Dave regards from the UK>
Hi Dave I have a 1788 and it tunes well on 40. It has a pvc section between the rotor and antenna and aluminum pipe under rotor. Byron K1cme. Have a photo of it on qrz.
Very good pic. I'm looking for any and all ideas about getting it to work on 40.
mine works great on all bands. get rid of the metal pole and put the antenna up higher or lower. mine works best at about 3 feet high or 20 feet high
Thanks for the tip. I'll give it a try.
Dave, thanks for the video. I am not surprised that the loop does not do well on 40 meters. I build my own loops and make them as large as possible to get the most efficiency out of them. So for instance my 20 meter loop is 15 feet in length or about 4.5 feet in diameter. Whereas the MFJ loop is a smaller diameter antenna and therefore not as efficient. Most loop are great on one band, good on another, ok on another band and bad on the rest of the bands. I am willing to bet your loop is great on 20 meters. Again, thanks for the video. 73 from N2LRB
Its confuse Dave you are reviewung the 1788 its supose to be only 40/80 mts the 1776 is 10/30 mts maybe this was the problem. thanks for the video
Thanks Dave for the «heads up». Will avoid this antenna for sure!
good review but a little pricey I think . I just upgraded from being a Tech after 20 years to General last Sunday and to start I will be running a end Fed wire. Also thank you for the I instructional videos I found them vary helpful in getting my licence. Look out Extra will be doing that in August :) .
Thanks for another great review! I have watched several review videos of the MFJ-1786 and 1788 and it seems one person is thrilled and the next is sorely disappointed with the antenna's performance. First off, the price is ridiculously high! $199 would be more than enough and I am sure more people would be willing to try it at that price. This would be the ideal antenna for me in my HOA antenna restricted community. It would install easily and fit in my garage attic. If only there were consistent reports. I am confused..... do I try one or not? $500 is a lot of money for an aluminum Hula-Hoop!
The expensive part to construct is the air-variable butterfly capacitor. It's huge and has to be heliarced. I think that's why it's so expensive.
Yes, that makes since. I may try one if my 37' OCF 6-40m Dipole I plan to configure in my garage attic some way doesn't work out very well. Might be able to get away with mounting the MFJ Loop outside the house as long as it is not up more than 10 feet or so. It is small, looks high tech and would not be an eyesore, especially if mounted horizontal. I can claim it is an HDTV antenna...lol! Thank for your reply.
Hi Dave....I want to know how many pf variable capasitor use mfj( min and max) do you know ? 73 de TA1DR
"Use both feet when walking"... hmmm... that may well be the answer that I was looking for :) 73 NE5U
I have mine up about 25 feet and horizontal. Works good but not on 40. Waiting to see what you do to fix that.
Dave, did you ever make the follow-up video to this? If so, can you share the link, please?
73, kc8kbk
How works this antenna on fm 11 meter cb band ??
Dave, sorry if I missed something but a loop might be best if rotated for best signal.
Yes, true if mounted vertically. If mounted horizontally, the "deaf spot" is straight up and down.
Interesting. I have seen (and have) much better results in a $50 homebuilt magnetic loop.
Hi Ethan! Could you please post a video about it? Thanks in advance.
Is it less noisy (QRM) than your vertical?
Yes, it does appear so on 20 meters, where it works well. I don't really know on 40 meters until I get it to work right.
Hi David couple of questions, if the loop was bigger could it be made to work on 40 and 80 meters?, also nobody ever seemed to use one horizontally will they work horizontal and prob be omni directional......from Fred g4vvq in England.
Yes on both counts.
I really appreciate your expertise and honesty!! What's the other loop you are evaluating? 73
Chameleon P-Loop
Congrats on being a NaNoWriMo winner! I've been participating in NaNoWriMo for several years as a winner most years.- K5RHA
Congratulations! Writing is fun, but lots more people watch my videos than read my books!
WOW!
You just won a subscriber :)
Welcome aboard!
Hi Dave are they any better on receive then a G5RV half wave which I'm currently using.
By the way mines in a loft if this helps?
Dave,
Nice review. Ideally, you should not have any ferrous material near the loop. Aluminum would be better, and PVC the best. 73 WB3BJU
The manual says to use steel or thick-walled aluminum. I might be able to mount it directly to the 2x4--I'll add that to the list of things to try. 73, Dave
Hi Dave, thanks for all you do! Dumb question coming.....I just bought the MFJ-1786, and the manual specifically states NOT to seal the holes, except the areas on the coax connectors.So that's what I'll do. However, although it might look odd, but could you put a covering over the antenna to protect it a bit from the elements without affecting the performance? 73!
The reason is to let condensation out of the box. I think the instructions state that you can put it in a box, but you will lose some performance.
Dave, look at my set-up on QRZ
(de G1HYD)
Nice QRZ page!
Hello Dave
I got a Mfj1786 and mounted it horizontal It worked well.
But when I mounted it vertical with a 3 metres long steel mast stand in a steel tripod.
I can't tune it low swr.
Is it wrong mounting mfj1786 with mental mast? It seems to make a wood mast better.
TNX & 73
bh4eag from China
You have to avoid metal going too far into the antenna when using it vertical. I think there is something in the instructions about that. Personally, I'd just use a non-metal pole if I were you. It does needs to be a few above ground in the vertical mode, like 3 ft or so.
Hi Dave, another great review! I'm sure you will get it going on 40m.
I've been thinking about purchasing this unit for use on 20m and 40m. It might be more fun to build my own. Is it generally true that a larger loop will have more radiation efficiency and greater bandwidth (lower Q)?
Thinking about approx. 6 ft diameter using two 10' sections of 1" diameter copper pipe and a HV adjustable cap.
73 KE8EUI
I'm no expert on loops, but the larger loops do better on lower frequencies.
I think the loop is correctly sized for 20 m. For 40 or less you'd want a larger loop under ideal conditions. That would cost you on 20m and up though. Loops are very finicky about frequency.
Hi Dave! First, thanks for the videos. Very helpful. Now tell me please, could you imagine or suppose that this MFJ-1788 would provide any success indoors, I mean, inside an apartment or in a balcony of a flat at the third floor? Would it performe well? Thank you.
It could. If you have a balcony, put it out on that. Try it both vertically and horizontally. Keep in mind that at full power you're pretty close.
It is pricey enough that if it dose not work as intended is definitely a no go as I have to spend my money wisely.
MY MFJ LOOP COVERED ALL OF 40 METERS AND I ALWAYS HAD A FLAT SWR.
ALSO IT WAS MOUNTED INDOORS ON THE 4TH FLOOR AND I HAD STEEL ABOVE ME BELOW ME AND EVEN THE MFJ MANUAL SAID IT WOULD NOT WORK.
I SENT THEM AA COPY OF 44 DX CONTACTS I MADE IN 1 NIGHT RUNNING 15 WATTS BOB AF2DX SORRY FOR CAPS HAD EYE SURGERY
My comment :
In 12 months you'll have dust all over this equipment.
It's great to learn and experiment but it's hardly a good system. I won't be trying one.
My next antenna will be an Omni-directional curtain nest array built on 3 acres of land for the 20m band and low angle dx.
See you in 5 years Dave, cheers :-) Wish me luck.....
We'll soon be full-time RV'ing (my wife's idea) so small portable hf antennas are of great interest to some of us hams. Right now I'm planning on using an end-fed antenna where I can (may RV parks frown on stringing wire around the camping spot) or my Buddipole vertical...........both of which are compromised antennas.
Gud luk DX'ing k6sdw
Check out the work here on You Tube by VK3YE.
He is the loop expert in Australia. He has much success.
Good luck and safe travels.
cheers, from vk4soe / la8pv
Much appreciated 73
Does the MFJ=1788 fit into a standard sized garbage pail?
It would have to be one that could contain a loop 3 feet in diameter
73 👍😉
Hi DAVE - Thanks for your reviews. Have you reviewed (or planning to review) the Alexloop loop antenna? Ralph WA2QYA
Hi Ralph, unless one shows up on my doorstep, I won't. Too expensive to buy them all. The MFJ-1788 was a big hit on my wallet.
How would this work in an attic? Anyone try that yet?
I've heard from hams who use them in attics with success. Need to have a wood roof. If it's covered with aluminum or copper foil, that will keep the antenna from working.
2x4 now as expensive as antenna
I've never understood how these magnetic loops work at all, much less efficiently. They look like dead shorts.
Yes, they're DC shorts, but at RF work as a tuned circuit with inductance (single turn) and capacitance. They're inefficient radiators, so they have to be made of stout materials to reduce losses.
$500........... I really thought Hams were more sensible......