What I like from Tim's video is the consistent use of metric system. It is weird to watch people measuring wires in feet for amateur bands that measure in meters 😂
Thank you Tim. I am new to the radio hobby. It is very interesting and enjoyable. The simplicity of making these antenna have helped me tremendously and also gave savings in my pocketbook. Commercially purchased items can be very expensive.
They work really well Tim, I was able to do back to back tests with a T2LT that I made, and a shop bought 1/2 wave vertical on 10m, no difference on either TX or RX, I was so impressed I made one for 6m too! 73 M0KED.
Great video Tim. I made the 5 turn coil version a while ago, but for the top portion I used 10 mm aluminium tubing. This way I could mount it on top of my military fiberglass mast instead of hanging it down. Gained extra hight with that.
Rather than stripping the coax, why not just put 2.5 meters of wire on the end. That would save you 2.5 meters of cable. You could leave the PL-259 on the end and solder the radiating wire to an SO-239 and connect it that way. You could also build an antenna from the choke up and put an SO-239 a few inches under the choke and have several antennas made. Thank you for the video. I never really thought of using a coaxial dipole before but I find myself in a flat in Madrid and your idea may be the only option I have for operating.
RG58 isn't pricey, but yes for longer antennas it'd be a waste; I've used a separate piece of wire for this. One suggestion I'd have though - start with a tail of a few cm of the inner part of the coax to take advantage of the insulation, I stripped back to the prescribed length and found it was easy to accidentally short it at the join :(
@@vsmichael1 Hi Mike, I have used it two ways over the years. One is a 10m pole strapped to a fence post, and the other is I have those suction grips (for gripping glass panes), attach one to the side of the car and lash the 10m pole to the side of the car. Both worked extremely well.
Traditionally, the lower element would be formed with another layer of shield, typically sourced from the top section. (Note of course that since the diameter has to be increased, that you'll need significantly more length as it shrinks in length as it is expanded in diameter to fit over the outer jacket.) In other words, the feedline snakes up inside the lower element, which is another layer of shield. The design shown in this video has the lower element effectively formed with the outer surface of the coax's shield, and choked off at the bottom. One concern with this design approach is that the bottom of the lower element is a very Hi-Z point, so there isn't much current to be choked off. It's a high voltage point. So you may see more feedline current (another quarter-wave down the line) than expected, as it escapes past the choke as a voltage (not a significant current). Also worth mentioning, the choke dimensions are not as mm-critical as implied. It's a choke, which is rarely a precision value component in any design. Cheers.
Yes, that is the description of a true, "coaxial antenna." This antenna here I see with a couple of other names. The quarter wave braided shield over the outer insulation used to be thought good for isolating the feed line from the antenna, but the design did suffer from narrow frequency range / narrow SWR range and TVI / television interference, due to feed line radiation. The traditional coaxial halfwave antenna was said to have the lowest angle of radiation or gain. When a choke is added to the antenna, the frequency range / SWR range greatly improves and the TVI is reduced. The choke is to choke current, even if it is an a voltage point on the antenna. Choking voltages does little for antenna performance and causes greater losses. A current choke is still preferred over a voltage choke for function, although a voltage choke may provide a very slight amount of current choking, but a voltage choke causes even greater losses though. I would no refer to the antenna in this video as a coaxial antenna, even if it is made of coax. It doesn't fit the design. Much of the current to choke will be harmonic frequencies, but also to reduce base frequency radiation from the feed line.
The antenna described is electrically similar to the Shakespear Big Stick CB antenna which was very popular back in the 70's. It was a half-wave coaxial sleeve antenna which came in two pieces. The top part was a regular 96-inch fiberglass quarter-wave mobile whip. Most people replaced it with the famous 'three-quarter Francis' whip, thinking the combination got out better. The bottom part consisted of two coaxial fiberglass sections with a braid sandwiched between the two pieces. The bottom section was capped with a metal ferrule the whip screwed into. A piece of RG-58 ran up the center of the bottom section. It terminated under the ferrule with the center lead soldered to the ferrule. The coax shield was connected to the braid. A 5K resistor was placed between the center and shield for 'static bleed' (poor). The bottom fiberglass section had an aluminum sleeve glued to the bottom and a crimped-on SO-239 was crimped into the sleeve. It was mounted to a mast with muffler or hose clamps. It could handle 500 watts and had 2.5 DBD of gain. A simple and very effective design which kept the radiation angle very low and compact making it excellent as a hilltop or field antenna. A military version of this antenna was also made as military radio frequencies surrounded the civilian 11-meter band back then. It was the same design with extra heavy-duty construction. The Big Stick was the best design, better than the famous "Ringo" because the feed point was in the center of the antenna instead of at the bottom. So, the feed point was elevated (antennas radiate most of their energy from the feed point). I always recommend adding a shorted quarter wave stub to the bottom of those antennas. It creates a DC ground for the antenna. The Big Stick had one major failure point: The connector at the bottom. Because of constant flexing in the wind and temperature swings, the RG-58 would eventually pull out of the connector creating an open circuit. I made good money fixing those antennas once I figured this out. I even salvaged 'bad' Big Sticks from people who went on to 'fancier' antennas and resold them after fixing them. Several years ago, I accidentally contacted the creator of the Big Stick suggesting he license the design and let someone make 6 and 10-meter versions of the antenna and sell them. Unfortunately, he would not sell the patent or license the design, therefore no one makes the antenna anymore. Such a shame!
Thanks for showing this, it brought back fond memories. I made one similar to this for 11-meter CB back in 1975 when our ground plane got destroyed in a storm. No balun coil, just took the end of the RG-58 coax, removed a quarter wavelength of the outer jacket and cut it into two equal lengths. I spread the braid where the jacket ended and pulled the center conductor and dielectric out the opening. I then used one jacket piece to tie the center conductor and dielectric to one tree, and the other piece to tie the braided shield to another tree, horizontally polarized. Hooking up the SWR bridge it would barely budge the needle, reading 1:1 across the entire band. Fortunately it was aimed the direction we needed, and I had all kinds of people I spoke with on it saying I couldn't be talking on a piece of coax!
@alvin pope Unfortunately no pictures, I was 17 at the time, going to tech school for electronics. Had started learning it as a hobby, was fixing CB radios and stereos, installing them and other related stuff. Worked part time at a few CB shops. Wish I'd had a camera to take a picture of someone actually mis-wiring RG-58 coax into a PL-259 connector without a UG-175 (176?) adapter, they unbraided the shield and soldered it to the center pin, the center conductor to the shell. If I hadn't seen it I wouldn't believe it, HOW does someone swap polarity on a _coaxial_ connector?!?‽
I just built this antenna after watching your video I had a bunch of surplus rg6 cable tv coax 75 ohm I said what the heck and tried it. It worked great cut it long it was wide banded below 1.4 through the cb band and all the way to the middle of the fm 10 meter band. I finally found a use for all this cable coax. THANKS.
Well i do struggle with an antenna and i do have tones of coax 75 ohm cable. Have to try this definitely. Did you use the one with the pvc pipe or did you made the one with the 110mm pipe??? Very interested
G5TM I made the first one you made today. I ordered 50 feet of RG58 & it came in. I used a gator aid bottle to wrap the coil. This weekend I’ll get the pvc pipe.
Great video Tim. I’ve made and tried both of those versions and both work really well on 10/11m Look forward to working you on your 10m net when it happens.
Thanks Tim! I’ve got one final empty socket on the rig and I fancy a coax 10m vertical dangling from the far tree. Probably something along these lines or the one Mike did 👍🏻
Great video Tim. I wasn't quite right with my earlier guess. Might be fun to try a bit of casual DX'ing with this on either 17m or 15m when the bands pick up in the summer.
Took my T2LT for a test today Tim and the VSWR is 1:2 at 27 MHz and 1:4 at 29 MHz. I am happy with this result. 10 meters was dead this arvo but made a local contact on 28.490 MHz
That's funny it looks just like a sirio gain master antenna lol I just made it and it works well on 10 meters been chatting to my mate's on it and Rx and TX no problems Tim thanks for sharing brilliant
This aerial design was higly used in the past ...the fun part is that peoples pay a fortune for antennas like the "gainmaster".....and this always makes me laugh haha ! Another GREAT video Tim, well done Old Man !
Hello Tim I’ve made the antenna and my swr is high I think it’s because I’ve hooked it up on the ceiling. Because I can’t put an antenna on the house yet,. How do you swr the RG58 dipole in please..
Good job Tim. I have seen one of those commercially made ones that you describe and they are finished off at the top so that the end folds back on itself a little and then held with a little piece of unshrunk heat shrink so that the antenna can be adjusted longer or shorter. I think i will make one this weekend just to see but i will try 6 or 8 ferrite beads slipped over the RG58 at the 2.47m mark and heat shrunk to make the choke that way. Sid.
Pulled up into a tree, perfect, except there are not a lot of trees on top on mountains around here! Factor in a fibreglass pole and price goes up a bit, but of course the pole can be used for other antennas/aerials. Cheers Tim. :-))
Hello Tim, The T2LT is a great antenna. I have redimensioned the T2LT for 2 meters about 47 centimeter per leg (mind the velocity factor) with 8 turns on a 4 centimeter diameter plastic pipe. It is my antenna for my local net. On a 12 meter pole I can get as far as 50 kilometers on 25 watt. I my opinion it can keep up with much more expensive commercial antenna's easily. My greatest distance so for with my 10 meter version is Chilli 12.266 kilometers. (from the Netherlands). Great antennas that keep amazing me.
great job Tim. if the size of coil off a mm or 3 that still fine and works. I used 54 MM with RG-8X . 16 turns. great band width. and their is a 3 Rd way to make it. FT 240-43 Toroid for the coil. great fun in the US as well . 73's
I've heard of these and hear they work well, what I have read is the coax shield should be peeled over the coax itself and pulled down from the radiating portion of the antenna for the counterpoise???, aparently it doesn't matter. Great demonstration, thank you for sharing this with us!!! 🇺🇸
I built and hung one for 11m between 2 trees and at the same tip height as my neighbor's Sirio Vector 4000 and with the same power we hit a guy on a ridge at 110 miles with the same S-6. Now I'm planning to build & hang a home-spun Sirio Gain Master wire and I bet I'll gain 3-5dB.
I've made something similar for 6 Meters, might have ago at making one of these as I've plenty of RG58 to spare! Hope to catch you on 10 meters when we are allowed out again.
Ok, now i have seen the impedance. Tnx. I will try it and probably try to get it a bitt more broad banded (capacitor peace of coax?). They’re great and also great to try out things. 73 HB3XBL 👍🇨🇭
I've been trying to resurrect an old Cushcraft MA5V vertical (20, 18, 15, 12, 10 meters) elevated to about 25 feet on a pole but it lacks effectiveness. However, it is pretty noisy most of the time. I saw another video using this design and it seems pretty quiet noise wise. Will try this design. Thanks for the idea Tim.
Great video. Thanks. Do you have any comments on how high off the ground the bottom end of the antenna (the coil) should be? Can they be mounted close (like less than a meter) to the ground or would a 1/4 height be better?
Yes they can be.. will be increase in ground losses but not so much as you’ll notice. A metre is probably the lowest I’d go before tuning might become problematic with these antennas.
Tim, This video was on the money. Would like to see the shootout you mentioned - to see if there was a discernible difference in performance (maybe use an SDR and SDR Sharp to illustrate the difference?). Since I am still working my way through 100 metres of cheapo 75 ohm coax, I think I may have a go and see how that works for me. Cheers, Pete 2E0WHT
@@timg5tm941 It is on my list. I got a pole and coax out with that intention this morning but being nine days away from the full exam, that takes priority at the moment. Funny how I procrastinate and still make time to watch UA-cam... That said, I am currently using Cornish Radio Amateur Club Training videos to good effect
@Peter Snipe, you could save that 75 ohm Coax for Co-phasing harnesses, should really be using 50 ohm coax for antenna and feed lines. That 75 ohm as far as I know is mostly used for TV Rx or Co-phased harness arrays.
@@stoatrepublic 50 ohm would be easier and more expensive. So far my half wave di-pole is giving very good results with the 75 ohm feeder. Currently throwing together an end fed with same. For me it's about using what is around me and adapting to those materials (like the very early days of amateur radio), rather than out and out performance. 73, Pete M0WHT
For the red part of the antenna on the graphic you just cut the shield there and didn't fold back the shield from the top half? So it's an end fed dipole, not a center fed dipole? Also, what is the black pole, is that carbon fiber or what?
Radio Shack or Tandy Electronics, use to sell an antenna like this made out of fibreglass I think it had a inductor coil in the base so it would fit in the fibreglass tube at the bottom. It's a reasonable antenna, but no where as good as a.. 0.64 wave antenna you can also make with a bit more difficulty. But they do work much better. Tandy etc shut down in Australia it was purchased by Dick Smith Electronics, he eventually sold it to a supermarket chain and they stuffed the retail business up.
Thanks for the video, Tim. 🙂 I am new to ham radio and I would like to built on of these T2LTs as my first HF antenna (for 15 m though). With my humble understanding of antenna technology, I am now asking myself🤔 this as I do not have an idea regarding how sensitive the T2LTs are to - let's say - non-optimal choke dimensions etc.: a.) Is it recommended to actually measure the choke with a NanoVNA or sth like that to make sure the diameter and the number of turns are correct to have the coil have its maximum attenuation at the frequency I would like to trim antenna to? b.) When trimming the antenna, is it required to also shorten the part next to the choke when cutting of a part of the "naked" wire of the top part? (= move the choke up the same amount of centimeters) Maybe you (or someone else who knows the answers) can help a newbie to get started - peferably in easy to understand English, as I am German.
Greetings friends, I need your advice. I have a station Alinco DX-10 and an antenna Santiago 1200, I have it at home, and since I do not have a chance to make a large assembly I bought a small metal stand and a magnetic base, the metal bracket attach it near the window with some Plastic flanges so that it is well suited. My problem is that it is impossible to calibrate the antenna and make it go down Roe .. Just lower the Roe when I hold the magnetic base with your hand. So I think there should be a mass problem, any idea? Thank you and greetings from Andorra (Translated with SR Google)
Great video Tim. Is there a calculator for these T2LT antennas? How did you figure out the lengths of the two sections of the antenna? Then, how did you figure out the length of cable for the choke? Any help would be appreciated. 73's Ernest Bazzinotti, KC1LKB
Hello Tim! Nice little project and neat work. Not a critique but I’ve noticed something wrong on your mfj antenna analyzer. I’ve got the 269 so I should know how it works. The analog needle to right showing impedance seems to be out of calibration. In fact if you check R and X on the display and “add” them up ( with pitagora) they give you the impedence. In the very first example you had R57 and X4 which gives Z 57.14 whereas your needle there shows 90. In the second example R60 X6 which gives Z60.3 but the needle there is reaching 100. Perhaps you might want to run a general check to the mfj. Just wanna let you know. Thank you for all the nice contents you have on your channel. 73s and hope to catch you on the air. Diego
Hi Tony you could either fold the top back to tune it to 29.6 MHz or if you want to try a precise measure try 2.37m for bottom and 2.40m for top half. I’d try the fold back method first. Alternatively make it a few cm shorter both halves and it’ll tune around 28.7 or so and still give you probably less than 2:1 vswr at 29.6 and 28.4 MHz
Thanks Tim, another great video. I have made one of these for 6M and intend to make one for 10M soon. I was very interested how well the second RF trap performed. I have wondered what results would be like with that approach and I think a compromise on bandwidth is worth it for the ease and convenience of option 2.
had some contacts from Israel on 10 meters on FT8 the other week, was very suprised ! be interested to see how the T2LT works out, could be something i put on the 705.
Help! Mounted in the same place and at the same hight, which of these 3 halfwave antennas would work better for DX.... This coax anteena, or a vertical EFHW, or a coil-loaded halfwave like the Antron 99. Or are they all the same? The reason I ask is that it just seems easier to make a 49:1 transformer (and a 1:1 CMC choke if needed), and then cut a halfwave piece of wire for each band. Would that work as well as this coax antenna? Thanks.
Hi Tim, thanks for the video; this deliberate feeder radiation is a trick which is jolly useful but not known by many. Do you know what is the loss of the insulating tape around the wider coil? Also: I guess that the input Z at the feedpoint is 75 Ohm; maybe using a 1/4-wave of ~ 60 Ohm coax (if you can find it these days!) would give an even better match to 50 Ohm? Perhaps therefore also increase the 1.5:1 SWR bandwidth.
Thanks for the video! Would it be worth terminating to an SO239 just below the coil to use your own lower loss feeder? I suppose using 2-3m of RG58 fly lead as the feeder losses would be negligible anyway?
@@timg5tm941 Well, its certainly on my list to build! I started my DX Commander Expedition build today. Your videos also inspired a bit of reading for 6m and 4m versions of the T2LT which are also on the build list!
Hello Tim, I hope you are well I've attempted to make this antenna today but for some reason the swr is high between 2 and 3 any ideas what I can do to adjust this ? I've checked and double checked the measurements and they are all spot on, not sure if it matters or not but I'm on a cobra 148 gtl dx on low mid and high, thanks in advance I really appreciate your time 👍
I’m about to build one of these antennas. Which design is better overall? I like the idea of having more bandwidth, but would it be at the expense of performance? Thanks so much
@@timg5tm941 thanks so much for the response! I’m curious why you recommend the wider one? Just easier to make, or does it perform differently than the thinner, longer one? Thanks
Could you please explain how you came up with 2.47m for the lower shielded length? I have difficulty figuring this out. I assume it has something to do with velocity factor .. but the vf of RG58 is .66 Sorry if this is a dumb question .. I'm new to this.
@@timg5tm941 Thanks for the reply .. but I'm interested to know HOW you arrived at the figure of 2.47 .. and why it is different to the driven element?
This design is based on a half wave vertical dipole / where the top dielectric portion is 1/4 wave and the untouched coax makes up the other half and all works great ! now if a person wanted to make a 5/8 wave length antenna any idea on how the measurement would differ? Would the dielectric portion Be 5/8 long And if so, how long would the untouched coax be before the choke? Supposedly 5/8 Gives a lower takeoff angle and an increase in gain
@@timg5tm941 well I finally got my home brew doublet up about 25’ used 450 ohm LL for all portions I am really happy with it - the legs are 33’ long and also include a center wire weaved between the LL - so triple linear load - could use some help getting 60m tuned in and also 10 meters - do you do do anything differently? The needles will not deflect at all on those bands
I dont strip back the coax i solder a wire to the center dielectric and use the 5 turns choke and i get 1.3x1 from 28.000 to 1.5x1 at 28.700 it works great i dx with it all the time and get great signal reports.
Hi Tim ! I want to adapt this antenna for 2m, and I would like to figure out how to calculate the shoke length / diameter. I haven't found any info online (nothing explained for frequencies above 50 MHz) .Thanks a lot !
RG 58 has a velocity factor of 0.66 and based upon that it appears that the quarter wave sections should be much much shorter This is my calculation do you see anything that I've done incorrectly
how many microhenry's are you trying to chase with these coils. i discovered a website from another video about making ugly balun chokes. if i use the calculator for rg58 with that former of 68mm i played with the formula to get the 16 turns and it appears your about 11.5 microhenry's.
Instead of stripping back a huge length of coax for the upper element, couldn't you solder that same length of solid-core 12-guage wire as the radiating element instead? That would save "wasting" 8-1/2 feet of expensive coax that could better serve as the lead-in. Couldn't the choke be terminated with an SO-259 so that the lead could be detached or even upgraded (say, to RG-8X)? Also, I am curious.. what effect would it have to install the choke so that it encircles the mast? I'm sure that might depend on whether the mast was conductive (metal) or not (PVC).
For this antenna at 60p per metre the expense is £1.50. Given there’ll be no potentially breakable solder join too i think the extra 1.50 is worthwhile. The choke can indeed be terminated at its end to allow lower loss coax as the feed. As long as the pole is non conductive it’s all good.
@@timg5tm941 Maybe it's cheap where you are, but no so much here in the U.S. I'm lucky if I can find plain 12-ga copper wire at $0.60 per foot - more than 3 times your price!
There's something I'm not getting on this one and I don't know if I'm missing understanding it or if it's mislabeled. This is being described as a half wave antenna. Since it's an end fed dipole it's total length maybe a a half wave 5 meters however only 50% of it is the center conductor and the other 50% of it is the ground portion of an end fed dipole. Doesn't that make it an end fed quarter wave dipole not a half wave? A 1/4 dipole has 2.5 meters on one side and 2.5 meters on the ground side. That may make the total length of the antenna 5 meters however because it's half ground and half driven element it's a quarter wave antenna? The choke isolates the ground side from being any longer than 2.5 and the unshielded side is limited by it's own length at 2.5 meters. To me that ads up to a quarter wave antenna. Just food for thought from an old HAM in the U.S. No matter how it works out the SWR speaks for it's self and I look forward to giving it a try.
@@timg5tm941 Whoops, I should know better than to watch these videos at 2 AM. Yes the total length is what determines that it's a half not just the driven element. Thank you for clearing my brain fog LOL. 73 OM
does it have to be 2 meters of the ground, could you put it on the ground to limit height? would it perform well with near a house with chose near the ground? and still near 18 feet from ground to height?
Hi Tim, has anyone on the channel measured the inductance & self resonance of the chokes? From a calculation, the 16 turn is approx. 3x the L, which would certainly explain a different match. I suspect there's very little difference in practical performance. 73 John G0JLF
I surely would try to build one of these antenna. Problem is, we may not have that kind of fibreglass poles from where I'm at. Can I use a bamboo pole instead?
Looks like a fun antenna to build. Without standing on my head to understand the relationship between the number of turns of coax for the choke and the diameter of the form to wind it, I see the general principles. Here in the states, I do not have readily findable PVC pipe of those exact dimensions, although I could come close I suppose. Maybe I am not far away. PVC diameters are measured in inner size, so if find a piece of 4-inch PVC, the outer diameter is closer to the 4.33 inches or 110 mm required. I do not have a caliper to measure the thickness of the wall of the PVC pipe, but perhaps with my antenna analyzer, I can build a prototype to see where the minimum VSWR resides. The plastic pipe I have access to is the white PVC commonly used in home drain plumbing here. I look forward to testing and comparing against my halfwave endfed wire I would typically use in my QRPp activities with my QRPme EFHW tuner (Tuna Tunah). 10M seems to be hot now. Cheers es 72, Davey - KU9L
Nice video Tim. I made one of these for last seasons 10m activity and it worked great. One question though, I couldn't decide if the length of the antenna should be adjusted in length for the velocity factor of the RG58 (.66). Any thoughts on this would be much appreciated.
Great question. I think this design is quite forgiving so I go by the ‘usual’ half wave formula, cut slightly long and trim if needed. I’ve never been far off at all with that approach.
What I like from Tim's video is the consistent use of metric system. It is weird to watch people measuring wires in feet for amateur bands that measure in meters 😂
Thank you Tim.
I am new to the radio hobby. It is very interesting and enjoyable. The simplicity of making these antenna have helped me tremendously and also gave savings in my pocketbook. Commercially purchased items can be very expensive.
Great stuff Bobby and I wholly agree
Excellent portable antenna as we well know & a simple design makes it the go to choice for 10/11m vertical. Great video again Tim. 👍
Thanks mate
They work really well Tim, I was able to do back to back tests with a T2LT that I made, and a shop bought 1/2 wave vertical on 10m, no difference on either TX or RX, I was so impressed I made one for 6m too! 73 M0KED.
Indeed Andy they work very well
Great video Tim. I made the 5 turn coil version a while ago, but for the top portion I used 10 mm aluminium tubing. This way I could mount it on top of my military fiberglass mast instead of hanging it down. Gained extra hight with that.
Sounds a very good build👍
Rather than stripping the coax, why not just put 2.5 meters of wire on the end. That would save you
2.5 meters of cable. You could leave the PL-259 on the end and solder the radiating wire to an SO-239 and connect it that way. You could also build an antenna from the choke up and put an SO-239 a few inches under the choke and have several antennas made. Thank you for the video. I never really thought of using a coaxial dipole before but I find myself in a flat in Madrid and your idea may be the only option I have for operating.
Fair point
RG58 isn't pricey, but yes for longer antennas it'd be a waste; I've used a separate piece of wire for this. One suggestion I'd have though - start with a tail of a few cm of the inner part of the coax to take advantage of the insulation, I stripped back to the prescribed length and found it was easy to accidentally short it at the join :(
Also, I wonder whether normal insulated wire would be a bit less lossy than using the co-ax dielectric?
Back in the day we used 13 amp wire usually off an old appliance found somewhere .
Worked very well
Great video. Love your instruction style, clear and to the point.
Thanks!
Just ordered an Anytone 6666 and this is going to be it's 1st antenna. Outstanding video sir. Thx.
Brilliant!! Enjoy the new radio too. 73
Funnily enough, I made two of them a few weeks ago. One for at home on a 10m pole, and one for out in the car. Fantastic stuff, as always.
Can’t beat them Mike 👍
How did you use it in the car Mike? Stationary or did you mount it on the vehicle some how?
@@vsmichael1 Hi Mike, I have used it two ways over the years. One is a 10m pole strapped to a fence post, and the other is I have those suction grips (for gripping glass panes), attach one to the side of the car and lash the 10m pole to the side of the car. Both worked extremely well.
Traditionally, the lower element would be formed with another layer of shield, typically sourced from the top section. (Note of course that since the diameter has to be increased, that you'll need significantly more length as it shrinks in length as it is expanded in diameter to fit over the outer jacket.) In other words, the feedline snakes up inside the lower element, which is another layer of shield. The design shown in this video has the lower element effectively formed with the outer surface of the coax's shield, and choked off at the bottom.
One concern with this design approach is that the bottom of the lower element is a very Hi-Z point, so there isn't much current to be choked off. It's a high voltage point. So you may see more feedline current (another quarter-wave down the line) than expected, as it escapes past the choke as a voltage (not a significant current).
Also worth mentioning, the choke dimensions are not as mm-critical as implied. It's a choke, which is rarely a precision value component in any design.
Cheers.
Re. your comment: "It's a high voltage point." I guess that it is a high-voltage point only because the choke is there?
Yes, that is the description of a true, "coaxial antenna." This antenna here I see with a couple of other names. The quarter wave braided shield over the outer insulation used to be thought good for isolating the feed line from the antenna, but the design did suffer from narrow frequency range / narrow SWR range and TVI / television interference, due to feed line radiation. The traditional coaxial halfwave antenna was said to have the lowest angle of radiation or gain. When a choke is added to the antenna, the frequency range / SWR range greatly improves and the TVI is reduced. The choke is to choke current, even if it is an a voltage point on the antenna. Choking voltages does little for antenna performance and causes greater losses. A current choke is still preferred over a voltage choke for function, although a voltage choke may provide a very slight amount of current choking, but a voltage choke causes even greater losses though. I would no refer to the antenna in this video as a coaxial antenna, even if it is made of coax. It doesn't fit the design. Much of the current to choke will be harmonic frequencies, but also to reduce base frequency radiation from the feed line.
The antenna described is electrically similar to the Shakespear Big Stick CB antenna which was very popular back in the 70's. It was a half-wave coaxial sleeve antenna which came in two pieces. The top part was a regular 96-inch fiberglass quarter-wave mobile whip. Most people replaced it with the famous 'three-quarter Francis' whip, thinking the combination got out better. The bottom part consisted of two coaxial fiberglass sections with a braid sandwiched between the two pieces. The bottom section was capped with a metal ferrule the whip screwed into. A piece of RG-58 ran up the center of the bottom section. It terminated under the ferrule with the center lead soldered to the ferrule. The coax shield was connected to the braid. A 5K resistor was placed between the center and shield for 'static bleed' (poor). The bottom fiberglass section had an aluminum sleeve glued to the bottom and a crimped-on SO-239 was crimped into the sleeve. It was mounted to a mast with muffler or hose clamps. It could handle 500 watts and had 2.5 DBD of gain. A simple and very effective design which kept the radiation angle very low and compact making it excellent as a hilltop or field antenna. A military version of this antenna was also made as military radio frequencies surrounded the civilian 11-meter band back then. It was the same design with extra heavy-duty construction.
The Big Stick was the best design, better than the famous "Ringo" because the feed point was in the center of the antenna instead of at the bottom. So, the feed point was elevated (antennas radiate most of their energy from the feed point). I always recommend adding a shorted quarter wave stub to the bottom of those antennas. It creates a DC ground for the antenna.
The Big Stick had one major failure point: The connector at the bottom. Because of constant flexing in the wind and temperature swings, the RG-58 would eventually pull out of the connector creating an open circuit. I made good money fixing those antennas once I figured this out. I even salvaged 'bad' Big Sticks from people who went on to 'fancier' antennas and resold them after fixing them.
Several years ago, I accidentally contacted the creator of the Big Stick suggesting he license the design and let someone make 6 and 10-meter versions of the antenna and sell them. Unfortunately, he would not sell the patent or license the design, therefore no one makes the antenna anymore. Such a shame!
Thanks for showing this, it brought back fond memories. I made one similar to this for 11-meter CB back in 1975 when our ground plane got destroyed in a storm. No balun coil, just took the end of the RG-58 coax, removed a quarter wavelength of the outer jacket and cut it into two equal lengths. I spread the braid where the jacket ended and pulled the center conductor and dielectric out the opening. I then used one jacket piece to tie the center conductor and dielectric to one tree, and the other piece to tie the braided shield to another tree, horizontally polarized. Hooking up the SWR bridge it would barely budge the needle, reading 1:1 across the entire band. Fortunately it was aimed the direction we needed, and I had all kinds of people I spoke with on it saying I couldn't be talking on a piece of coax!
Brilliant example Bob
@@timg5tm941 Thanks! I always look back at it fondly as a good example of putting theory into practice.
Do you have any pictures of the antenna 73s from 416 Trinidad.
Love to see a diagram of this
@alvin pope Unfortunately no pictures, I was 17 at the time, going to tech school for electronics. Had started learning it as a hobby, was fixing CB radios and stereos, installing them and other related stuff. Worked part time at a few CB shops. Wish I'd had a camera to take a picture of someone actually mis-wiring RG-58 coax into a PL-259 connector without a UG-175 (176?) adapter, they unbraided the shield and soldered it to the center pin, the center conductor to the shell. If I hadn't seen it I wouldn't believe it, HOW does someone swap polarity on a _coaxial_ connector?!?‽
Nice work Tim, very informative will be giving that a go.
Have fun!
Look forward to the shoot out Tim when we’re back out n about.
Great video 👍👏👏
I just built this antenna after watching your video I had a bunch of surplus rg6 cable tv coax 75 ohm I said what the heck and tried it. It worked great cut it long it was wide banded below 1.4 through the cb band and all the way to the middle of the fm 10 meter band. I finally found a use for all this cable coax. THANKS.
Great!!
Well i do struggle with an antenna and i do have tones of coax 75 ohm cable. Have to try this definitely. Did you use the one with the pvc pipe or did you made the one with the 110mm pipe??? Very interested
I used pvc pipe
@@hendrikvandermerwe3970
G5TM I made the first one you made today. I ordered 50 feet of RG58 & it came in. I used a gator aid bottle to wrap the coil. This weekend I’ll get the pvc pipe.
I wish you well Mike, hopefully you’ll have a great time using it 73
Top vid, i use a hawkins ssd 1/2 wave for mobile static dx 20 quid! Great bit of kit. Its a great starter antenna to practice building 👍👍👍
thanks for the clear instructions and as 10m is opening more now I will be trying this out.
Brilliant Chris I can’t wait for 10 to wake up
@@timg5tm941 yes 10m opened for a little while a few days ago and my inverted V seems to work quite well in skip conditions to europe.
Great video Tim.
I’ve made and tried both of those versions and both work really well on 10/11m
Look forward to working you on your 10m net when it happens.
Thanks Stu 👍
Thanks Tim! I’ve got one final empty socket on the rig and I fancy a coax 10m vertical dangling from the far tree. Probably something along these lines or the one Mike did 👍🏻
Give it a go for sure Ian
Great video Tim. I wasn't quite right with my earlier guess. Might be fun to try a bit of casual DX'ing with this on either 17m or 15m when the bands pick up in the summer.
Indeed James I can’t wait for the higher bands to wake up
Thank you Tim, I will have a go at your antenna, good luck.
Have fun Brian - 73
Great video Tim, this just got suggested to me - I think I might build one for 10 metres. All builds I've done so far have been on 6 metres.
Worth a go Hayden!
Ignore my last comment on the last video I commented on, this answers the questions I had haha.
Thanks for this!!
Glad it helped!
Just saw the video on 20 meters. Okay, you now have me hooked. I have to try this. I will of course make another comment on its results. Tom, KB0QIP
Great stuff Tom let me know how you get on with it
Great antenna so simple will make one for the 11 meter band thanks.
Have fun
Took my T2LT for a test today Tim and the VSWR is 1:2 at 27 MHz and 1:4 at 29 MHz. I am happy with this result. 10 meters was dead this arvo but made a local contact on 28.490 MHz
Brilliant!
I use this antenna at home & /P and is the only antenna I have had contacts to Qz & New Caledonia on 11m. I'm going to make the 20m one this week.
They work great I hope the 20 version works well
great video tim 👍👍👍 i recommend the sdr receiver and an antenna switch for the shoot out, you get a great visual analysis for qrm/n and gain
Very good idea!
That's funny it looks just like a sirio gain master antenna lol I just made it and it works well on 10 meters been chatting to my mate's on it and Rx and TX no problems Tim thanks for sharing brilliant
Thanks Jon 👍
This aerial design was higly used in the past ...the fun part is that peoples pay a fortune for antennas like the "gainmaster".....and this always makes me laugh haha ! Another GREAT video Tim, well done Old Man !
Thanks Adriano! I agree.. cheaper the better
Or people pay for " fabricated long lasting quality "
@@DynoDieselWagon also as well as long lasting quality, if you are disabled as I am you cannot build it yourself! 👍
Hello Tim I’ve made the antenna and my swr is high I think it’s because I’ve hooked it up on the ceiling. Because I can’t put an antenna on the house yet,. How do you swr the RG58 dipole in please..
Thanks for the video ❤ very clearly presented and good content ☺️
My pleasure thank you!
Good job Tim. I have seen one of those commercially made ones that you describe and they are finished off at the top so that the end folds back on itself a little and then held with a little piece of unshrunk heat shrink so that the antenna can be adjusted longer or shorter. I think i will make one this weekend just to see but i will try 6 or 8 ferrite beads slipped over the RG58 at the 2.47m mark and heat shrunk to make the choke that way. Sid.
Sounds interesting Sid let me know if the choke works ok
Pulled up into a tree, perfect, except there are not a lot of trees on top on mountains around here! Factor in a fibreglass pole and price goes up a bit, but of course the pole can be used for other antennas/aerials. Cheers Tim. :-))
Exactly Bob
Thanks for the reply Tim. Jujst have to put a PL-259 plug on and check the VSWR.
Brilliant !! Totally new thing for me, worth a try !!!
Great stuff give it a go
Hello Tim, The T2LT is a great antenna. I have redimensioned the T2LT for 2 meters about 47 centimeter per leg (mind the velocity factor) with 8 turns on a 4 centimeter diameter plastic pipe. It is my antenna for my local net. On a 12 meter pole I can get as far as 50 kilometers on 25 watt. I my opinion it can keep up with much more expensive commercial antenna's easily. My greatest distance so for with my 10 meter version is Chilli 12.266 kilometers. (from the Netherlands). Great antennas that keep amazing me.
Fabulous! I use a 2m version too.
great job Tim. if the size of coil off a mm or 3 that still fine and works. I used 54 MM with RG-8X . 16 turns. great band width. and their is a 3 Rd way to make it. FT 240-43 Toroid for the coil. great fun in the US as well . 73's
Brilliant stuff
Hi made the antenna, but used RG213 , and 11cm plastic tube with 8 turns. very low swr, and great band width
Fabulous!
I've heard of these and hear they work well, what I have read is the coax shield should be peeled over the coax itself and pulled down from the radiating portion of the antenna for the counterpoise???, aparently it doesn't matter.
Great demonstration, thank you for sharing this with us!!! 🇺🇸
Thanks Eric. Yes that is an alternative way to do it but this way seems a bit simpler. 73
@@timg5tm941 Your welcome Tim, and thank you!
Mr Tim - u r great!!!
Good one, Tim. Thinking about something like this for portable work. Will be interested in a 15m version too.
Yes I’m looking forward to trying out the version for 15 Andrew
Brilliant idea I’m doing this with ham sticks. Using braid as the othe half of antenna.
Nice!
just what I needed! TA!
I built and hung one for 11m between 2 trees and at the same tip height as my neighbor's Sirio Vector 4000 and with the same power we hit a guy on a ridge at 110 miles with the same S-6. Now I'm planning to build & hang a home-spun Sirio Gain Master wire and I bet I'll gain 3-5dB.
I've made something similar for 6 Meters, might have ago at making one of these as I've plenty of RG58 to spare! Hope to catch you on 10 meters when we are allowed out again.
Nice one! Yes fingers crossed on 10
Ok, now i have seen the impedance.
Tnx. I will try it and probably try to get it a bitt more broad banded (capacitor peace of coax?).
They’re great and also great to try out things.
73 HB3XBL 👍🇨🇭
I've been trying to resurrect an old Cushcraft MA5V vertical (20, 18, 15, 12, 10 meters) elevated to about 25 feet on a pole but it lacks effectiveness. However, it is pretty noisy most of the time. I saw another video using this design and it seems pretty quiet noise wise. Will try this design. Thanks for the idea Tim.
Nice one matey back to,basics ;)
Thanks Dave 👍
Great vid, will give it a go 👍
Thank you and good luck
Great stuff, really helpful,🙂👍
Thanks!
Tim, you can build it very easy when you take a chocke after w1jr. That is running very well. 73 de Jürgen.
Great video. Thanks. Do you have any comments on how high off the ground the bottom end of the antenna (the coil) should be? Can they be mounted close (like less than a meter) to the ground or would a 1/4 height be better?
Yes they can be.. will be increase in ground losses but not so much as you’ll notice. A metre is probably the lowest I’d go before tuning might become problematic with these antennas.
Nice one Tim.
Thanks Colin
I noticed the impedance is a lot better on the second one with it being nearly resonant on all the frequencies being closer to 50ohm. 73's
Indeed .. my thinking is the second design is nearer the money
Tim, This video was on the money. Would like to see the shootout you mentioned - to see if there was a discernible difference in performance (maybe use an SDR and SDR Sharp to illustrate the difference?). Since I am still working my way through 100 metres of cheapo 75 ohm coax, I think I may have a go and see how that works for me. Cheers, Pete 2E0WHT
Brilliant Peter give it a try and thank you for the sdr suggestion
@@timg5tm941 It is on my list. I got a pole and coax out with that intention this morning but being nine days away from the full exam, that takes priority at the moment. Funny how I procrastinate and still make time to watch UA-cam... That said, I am currently using Cornish Radio Amateur Club Training videos to good effect
@Peter Snipe, you could save that 75 ohm Coax for Co-phasing harnesses, should really be using 50 ohm coax for antenna and feed lines. That 75 ohm as far as I know is mostly used for TV Rx or Co-phased harness arrays.
@@stoatrepublic 50 ohm would be easier and more expensive. So far my half wave di-pole is giving very good results with the 75 ohm feeder. Currently throwing together an end fed with same. For me it's about using what is around me and adapting to those materials (like the very early days of amateur radio), rather than out and out performance. 73, Pete M0WHT
What about changing the radiating part for 10mm2 copper flexible cable?
I did that, and my antenna is performing much better.
Yep, an option 👍
I imagine that choke V2.0 would have lower insertion loss? The lower bandwidth might be due to higher Q factor of this coil??
For the red part of the antenna on the graphic you just cut the shield there and didn't fold back the shield from the top half? So it's an end fed dipole, not a center fed dipole? Also, what is the black pole, is that carbon fiber or what?
Your answers: 1. Correct; 2. End fed physically ; 3. It is fibre glass
Radio Shack or Tandy Electronics, use to sell an antenna like this made out of fibreglass I think it had a inductor coil in the base so it would fit in the fibreglass tube at the bottom. It's a reasonable antenna, but no where as good as a.. 0.64 wave antenna you can also make with a bit more difficulty. But they do work much better. Tandy etc shut down in Australia it was purchased by Dick Smith Electronics, he eventually sold it to a supermarket chain and they stuffed the retail business up.
Interesting info thanks!
Thanks for the video, Tim. 🙂
I am new to ham radio and I would like to built on of these T2LTs as my first HF antenna (for 15 m though). With my humble understanding of antenna technology, I am now asking myself🤔 this as I do not have an idea regarding how sensitive the T2LTs are to - let's say - non-optimal choke dimensions etc.:
a.) Is it recommended to actually measure the choke with a NanoVNA or sth like that to make sure the diameter and the number of turns are correct to have the coil have its maximum attenuation at the frequency I would like to trim antenna to?
b.) When trimming the antenna, is it required to also shorten the part next to the choke when cutting of a part of the "naked" wire of the top part? (= move the choke up the same amount of centimeters)
Maybe you (or someone else who knows the answers) can help a newbie to get started -
peferably in easy to understand English, as I am German.
For the choke, can you wind the coax about 3 times around a ferrite toroid?
You can use a ferrite toroid - google G3TXQ choke chart for the toroid needed and number of turns.
Greetings friends, I need your advice.
I have a station Alinco DX-10 and an antenna Santiago 1200, I have it at home, and since I do not have a chance to make a large assembly I bought a small metal stand and a magnetic base, the metal bracket attach it near the window with some Plastic flanges so that it is well suited.
My problem is that it is impossible to calibrate the antenna and make it go down Roe .. Just lower the Roe when I hold the magnetic base with your hand. So I think there should be a mass problem, any idea?
Thank you and greetings from Andorra
(Translated with SR Google)
Great video Tim. Is there a calculator for these T2LT antennas? How did you figure out the lengths of the two sections of the antenna? Then, how did you figure out the length of cable for the choke? Any help would be appreciated. 73's Ernest Bazzinotti, KC1LKB
Hey there. You can use the usual 468/f for the two lengths. Choke wise, if you search for G3TXQ choke chart and that will help for different bands
Hello Tim!
Nice little project and neat work. Not a critique but I’ve noticed something wrong on your mfj antenna analyzer.
I’ve got the 269 so I should know how it works. The analog needle to right showing impedance seems to be out of calibration.
In fact if you check R and X on the display and “add” them up ( with pitagora) they give you the impedence.
In the very first example you had R57 and X4 which gives Z 57.14 whereas your needle there shows 90.
In the second example R60 X6 which gives Z60.3 but the needle there is reaching 100.
Perhaps you might want to run a general check to the mfj.
Just wanna let you know.
Thank you for all the nice contents you have on your channel.
73s and hope to catch you on the air.
Diego
Thanks I will check that out.
Thank you for the video. What lengths would you recommend for 10FM 29.600mcs ? De G0PZX
Hi Tony you could either fold the top back to tune it to 29.6 MHz or if you want to try a precise measure try 2.37m for bottom and 2.40m for top half. I’d try the fold back method first. Alternatively make it a few cm shorter both halves and it’ll tune around 28.7 or so and still give you probably less than 2:1 vswr at 29.6 and 28.4 MHz
Thanks Tim, another great video. I have made one of these for 6M and intend to make one for 10M soon. I was very interested how well the second RF trap performed. I have wondered what results would be like with that approach and I think a compromise on bandwidth is worth it for the ease and convenience of option 2.
Good point. Hope you enjoy both of those antennas.
Is this otherwise known as a flowerpot antenna? I think I built one a long time ago for 2m and it was great. Might have to try this for 20m!
Same design just a difference to the choke. I’ll be trying out versions for 15 17 20 soon 👍👍
had some contacts from Israel on 10 meters on FT8 the other week, was very suprised ! be interested to see how the T2LT works out, could be something i put on the 705.
Worth a try!
Help! Mounted in the same place and at the same hight, which of these 3 halfwave antennas would work better for DX....
This coax anteena, or a vertical EFHW, or a coil-loaded halfwave like the Antron 99. Or are they all the same?
The reason I ask is that it just seems easier to make a 49:1 transformer (and a 1:1 CMC choke if needed), and then cut a halfwave piece of wire for each band. Would that work as well as this coax antenna? Thanks.
49:1 are convenient but some designs can be lossy. In reality there isn’t much between them except of course the 49:1 is a multi-band option.
Hello, Excellent Video. Question .... Could you use RG8X coax with similar results?
Yes but with a slightly less degree of flexibility to make the choke
Hi Tim, thanks for the video; this deliberate feeder radiation is a trick which is jolly useful but not known by many. Do you know what is the loss of the insulating tape around the wider coil?
Also: I guess that the input Z at the feedpoint is 75 Ohm; maybe using a 1/4-wave of ~ 60 Ohm coax (if you can find it these days!) would give an even better match to 50 Ohm? Perhaps therefore also increase the 1.5:1 SWR bandwidth.
Interesting observations 👍
Thanks for the video! Would it be worth terminating to an SO239 just below the coil to use your own lower loss feeder? I suppose using 2-3m of RG58 fly lead as the feeder losses would be negligible anyway?
Yes for long runs of coax you make a good point. For 10m or less then rg58 on 14 MHz won’t make hardly any difference
@@timg5tm941 Well, its certainly on my list to build! I started my DX Commander Expedition build today. Your videos also inspired a bit of reading for 6m and 4m versions of the T2LT which are also on the build list!
@@motodevcam that’s great to hear. I wish you well with the build
@@timg5tm941 Thank you! Hope to work you on 40m at some point. I know you've given up with 80m!
@@motodevcam fingers crossed!
VERY NICE
Thanks!
Can you use ferrite beads for the the choke? Thanks for the idea.
Yes I would say so but how many? I’m not sure
Hello Tim, I hope you are well I've attempted to make this antenna today but for some reason the swr is high between 2 and 3 any ideas what I can do to adjust this ? I've checked and double checked the measurements and they are all spot on, not sure if it matters or not but I'm on a cobra 148 gtl dx on low mid and high, thanks in advance I really appreciate your time 👍
Ok now what were the measurements you used? I’m thinking of you might’ve made a 10m version for CB maybe?
@@timg5tm941 hi Tim, 2.50 meters top section and 2.47 meters bottom section and 16 turns for choke, thanks for getting back to me👍
I’m about to build one of these antennas. Which design is better overall? I like the idea of having more bandwidth, but would it be at the expense of performance? Thanks so much
I’d go with the wider coil
@@timg5tm941 thanks so much for the response! I’m curious why you recommend the wider one? Just easier to make, or does it perform differently than the thinner, longer one?
Thanks
I wonder if I've been trying to keep too close to 50-52 ohms with my antennas, which can be a headache.
Don't get too hung up about the perfect match.
Could you please explain how you came up with 2.47m for the lower shielded length?
I have difficulty figuring this out. I assume it has something to do with velocity factor .. but the vf of RG58 is .66
Sorry if this is a dumb question .. I'm new to this.
VF plays far less of a role here. So 2.47 is about right
@@timg5tm941 Thanks for the reply .. but I'm interested to know HOW you arrived at the figure of 2.47 .. and why it is different to the driven element?
This design is based on a half wave vertical dipole / where the top dielectric portion is 1/4 wave and the untouched coax makes up the other half and all works great ! now if a person wanted to make a 5/8 wave length antenna any idea on how the measurement would differ? Would the dielectric portion Be 5/8 long And if so, how long would the untouched coax be before the choke? Supposedly 5/8 Gives a lower takeoff angle and an increase in gain
Check out M0MSN’s channel .. he’s made the 5/8 version (Gainmaster copy) using coax.
@@timg5tm941 awesome - will do - Thanks for the recommendation
@@timg5tm941 well I finally got my home brew doublet up about 25’ used 450 ohm LL for all portions I am really happy with it - the legs are 33’ long and also include a center wire weaved between the LL - so triple linear load - could use some help getting 60m tuned in and also 10 meters - do you do do anything differently? The needles will not deflect at all on those bands
I dont strip back the coax i solder a wire to the center dielectric and use the 5 turns choke and i get 1.3x1 from 28.000 to 1.5x1 at 28.700 it works great i dx with it all the time and get great signal reports.
Sounds great! They do work well don’t they
@@timg5tm941 yes they do im making a 10 meter POTA one now then a 20 meter Pota one. My elmer has a 40 meter one
Merci ! The best video to understand. Sorry for my english, i'm french :) I have a a RG 214 U since 25 years. it will work ? Thank yo :)
Which could I use on 11 meters the one with five turns or the one with the sixteen turns greetings from 416 Trinidad 73s
5 is fine for 10 and 11.
Is there a good simple technique to strip back the outer plastic jacket?.
Yes .. maybe I’ll show a quick video on that 👍
Hi Tim ! I want to adapt this antenna for 2m, and I would like to figure out how to calculate the shoke length / diameter. I haven't found any info online (nothing explained for frequencies above 50 MHz) .Thanks a lot !
Try this from my video archive: ua-cam.com/video/CgLW0Vz11zM/v-deo.html
@@timg5tm941 Thanks a lot !
I was wondering do you factor in the velocity factor we doing your measurements and cutting the coax?
Yes… 👍👍
The question about velocity factor has come up again.
RG 58 has a velocity factor of 0.66 and based upon that it appears that the quarter wave sections should be much much shorter This is my calculation do you see anything that I've done incorrectly
Using the measurements that you gave, how close to 28.444 is the VSWR? To fine tune do I trim the top section? thks
You should be under 1.5:1 depending on your environment. You can either trim or fold back the top part.
how many microhenry's are you trying to chase with these coils. i discovered a website from another video about making ugly balun chokes. if i use the calculator for rg58 with that former of 68mm i played with the formula to get the 16 turns and it appears your about 11.5 microhenry's.
The choking impedance is the key aspect here. These air chokes are pretty much band specific. In this case it should offer around 2k ohm plus.
Instead of stripping back a huge length of coax for the upper element, couldn't you solder that same length of solid-core 12-guage wire as the radiating element instead? That would save "wasting" 8-1/2 feet of expensive coax that could better serve as the lead-in.
Couldn't the choke be terminated with an SO-259 so that the lead could be detached or even upgraded (say, to RG-8X)?
Also, I am curious.. what effect would it have to install the choke so that it encircles the mast? I'm sure that might depend on whether the mast was conductive (metal) or not (PVC).
For this antenna at 60p per metre the expense is £1.50. Given there’ll be no potentially breakable solder join too i think the extra 1.50 is worthwhile. The choke can indeed be terminated at its end to allow lower loss coax as the feed. As long as the pole is non conductive it’s all good.
@@timg5tm941 Maybe it's cheap where you are, but no so much here in the U.S.
I'm lucky if I can find plain 12-ga copper wire at $0.60 per foot - more than 3 times your price!
How critical is diameter of the choke are there alternates as for diameter/turns?
Pretty critical. The other alternative I know of for 10/11m is 16 turns around a 68mm diameter. Otherwise it’s trial and error.
There's something I'm not getting on this one and I don't know if I'm missing understanding it or if it's mislabeled. This is being described as a half wave antenna. Since it's an end fed dipole it's total length maybe a a half wave 5 meters however only 50% of it is the center conductor and the other 50% of it is the ground portion of an end fed dipole. Doesn't that make it an end fed quarter wave dipole not a half wave? A 1/4 dipole has 2.5 meters on one side and 2.5 meters on the ground side. That may make the total length of the antenna 5 meters however because it's half ground and half driven element it's a quarter wave antenna? The choke isolates the ground side from being any longer than 2.5 and the unshielded side is limited by it's own length at 2.5 meters. To me that ads up to a quarter wave antenna. Just food for thought from an old HAM in the U.S. No matter how it works out the SWR speaks for it's self and I look forward to giving it a try.
Hi nope it’s a half wave. Full 5m on 10m band. Hope you give it a try it’s a v good antenna 73
@@timg5tm941 Whoops, I should know better than to watch these videos at 2 AM. Yes the total length is what determines that it's a half not just the driven element. Thank you for clearing my brain fog LOL. 73 OM
No problem! I get brain fog 24/7. Have a good day on the bands 73
does it have to be 2 meters of the ground, could you put it on the ground to limit height? would it perform well with near a house with chose near the ground? and still near 18 feet from ground to height?
Best to be at least 50 cm above ground. Any antenna is much better away from a building 73
Hi Tim, has anyone on the channel measured the inductance & self resonance of the chokes? From a calculation, the 16 turn is approx. 3x the L, which would certainly explain a different match. I suspect there's very little difference in practical performance. 73 John G0JLF
I suspect you are correct John.
I wonder if I could change the air-cored coil with 2x FT240-52 with 11 turns RG58?
Yes it can!
I surely would try to build one of these antenna. Problem is, we may not have that kind of fibreglass poles from where I'm at. Can I use a bamboo pole instead?
Anything non conductive is ok
@@timg5tm941 Thank you so much sir and all the best to you and your family. 73....
Looks like a fun antenna to build. Without standing on my head to understand the relationship between the number of turns of coax for the choke and the diameter of the form to wind it, I see the general principles. Here in the states, I do not have readily findable PVC pipe of those exact dimensions, although I could come close I suppose. Maybe I am not far away. PVC diameters are measured in inner size, so if find a piece of 4-inch PVC, the outer diameter is closer to the 4.33 inches or 110 mm required. I do not have a caliper to measure the thickness of the wall of the PVC pipe, but perhaps with my antenna analyzer, I can build a prototype to see where the minimum VSWR resides. The plastic pipe I have access to is the white PVC commonly used in home drain plumbing here. I look forward to testing and comparing against my halfwave endfed wire I would typically use in my QRPp activities with my QRPme EFHW tuner (Tuna Tunah). 10M seems to be hot now. Cheers es 72, Davey - KU9L
4 inch diameter and 5 turns should still be ok
What adjustments would be needed to use Mini 8 ?
Very good question John .. I’m unsure myself
Tim I don't have any RG58, could I use ultraflex 7 instead? I have loads of that knocking around.
Would be a lot harder to make the choke
@timg5tm941 yeah I didn't think about that, thanks
Great design, thank you for sharing it. I will try to build one. Question how much power can this antenna handle ?
Cheers 73 de Juan TG9AJR
I know someone who has comfortably used 400w SSB with this antenna
@@timg5tm941 OK great Tim looks like a great antenna design. 73 and cheers from Guatemala
@@TG9AJR thank you Juan! 73
Nice video Tim. I made one of these for last seasons 10m activity and it worked great. One question though, I couldn't decide if the length of the antenna should be
adjusted in length for the velocity factor of the RG58 (.66). Any thoughts on this would be much appreciated.
Great question. I think this design is quite forgiving so I go by the ‘usual’ half wave formula, cut slightly long and trim if needed. I’ve never been far off at all with that approach.
@@timg5tm941 Good to know because a 66% velocity factor would really shorten the antenna