Cheap and simple T2LT/Coax Dipole antenna for CB Radio PART ONE (remake from earlier video)
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- Опубліковано 21 бер 2015
- Cheap and simple D.I.Y T2LT/Coax Dipole antenna for CB Radio PART ONE (remake from earlier video)
A more in-depth and hopefully a bit less shaky video than the previous T2LT construction video. Rather a long video, but wanted to catch all aspects of the antenna construction plus some background info too.
Part two has the deployment, tuning and on-air testing of the actual antenna constructed in this video • (PART TWO) Cheap/easy ...
Link to my 2021 2-piece 'Alternative Build' version here: • T2LT/Coax Dipole CB/11... - Навчання та стиль
If you're not interested in the history/theory, the construction phase starts at 8:28
Brilliant video. I think you hit the perfect balance, very easy to follow and answered all my questions about the t2lt without a load of waffle. Will be giving if a go very soon.
Glad you liked the video Bob and good luck with the build - a 'built not bought' antenna makes the contacts that much sweeter. Cheers.
This is great as I am really interested in this subject. Thanks for taking the time.
Thank you for sharing this guide with us and giving all the lil hints in planning and building. Due to the radio connects at the end its so much easier to erect this antenna (vertical) and have a stable (V)SWR than a center fed dipole. Your video made it look so easy and that encouraged me to try my luck in building my own and guess what, it turned out great and I love it! 73`s from 13NH211
Glad you found the video of use and good to hear the build worked out Ok. That's it in a nutshell with this antenna, electrically it's a centre-fed dipole, but physically an end-fed, which is ideal for a vertical installation.
I join end of coax with normal cable and save aprox 275 cm of coax, SWR is great: ch1=1,0 ch40=1,1.. thanks a lot for instructional video... I show this t2lt to my friends in Slovakia and they like it a lot, it is very easy to carry so very useful for portables, expecially in our mountinuous part of state... nice job, keep doing the videos...73
Followed your instructions and worked for me a treat on a 7m telescopic pole. SWR 1:1 mid and 1:1.3 UK ch40. 26CT1071 Keith
***** Also worked well when tuned to 10m ham band
MNI TKS for this video! I'm going to build a 6m / 50 MHz T2LT for this sporadic season.
Good luck with the build - I see the G3TXQ chart only covers to 30Mhz, so you will have to experiment with the choke size or find alternative info as one size does not fit all applications karinya.net/g3txq/chokes/
made mine from some leftover RG6 (i know i know, i get it dirt cheap) with 8 or so coils wound on a 4" pvc former.. swr'd in nice, 1.1:1 - 1.6:1 across the us 40ch CB band.. works a treat :)
I just posted about that since I have a 1,000' roll. Glad it works well! *_How did you come up with the 8T x 4'' choke vs a 5T x 4.25'' choke?_*
Hello. Activation in Montejunto Mountain, a lovely place near Lisbon, with T2LT, with very good results, from North to South of Portugal, with clear audio and strong Signals. With 12 watts output. Tks again 7351 all the best.
Excellent - may hear you on the Sporadic E this summer!
I hope so, 7351.
Hi Gary
Made mine from RG-8 as for the coil turns its just the same and cut all to the same dimensions good band with of 1.5MHz to but only thing I used a antenna analyser and got the most out of tuning it up and my feeder length is built in so no probs there with loads of connections I'm going to build 1 for 40m ham band sometime il let you know how that works !
I'll have to add, I built one of these using the five turn on a 4.25 inch former and it was a piece of excrement or what my friend called an "Abortion".
I then took the idea of the Sirio Gain Master 16 turn choke, calculated a half wavelength of coax multiplied by its Velocity Factor, and came out with a 2.4 inch former by 16 turns - and that worked perfectly.
With the five turn by 4.25 inch choke I had massive RFI in the shack and an SWR that wandered all over the place and made no sense until I added the 16 turn choke, and now it works as it's supposed to - and quite well I might add.
Thanks for the video!
I built one out of 75 ohm coax and it works great horizontal or vertical, SWR 2.0 across the 11 meter band
Good job - nice to hear from someone who has used 75 Ohm with success.
Tuned very well 1:1 1:5 26925 to 27895. TKS for the very nice video. 7351.
Excellent - glad the video was of help!
without any doubt tks a lot 7351
well just built one my coax ant as good but hopefully it will do hunted round the house for sevral hours for somthing 4 1/4 insh round only to look at the desk and see an ashtry so hopefully i can test tomorrow with the am hand held and hopefully get some contacts
well, thankyou sir, what a fabulas, informative ,and well presented instructual to anyone that has an innkling to experement with radio, i applaud ypu.
Thanks Mike - most appreciated 👍
Excellent, it is all you need to get on the air and 100 times better than a DV27 on a biscuit tin. You do need a pole or a handy tree.
Hi I can make this antenna with coaxial cable rg59 for tv? Thanks
Very nice project. I have been one tonight, I have a little problem, when I connect the pl to the radio I have a lot of stationaires, but if I plug only with the center of pl, I have a very nice value 1,5 1,3 and in 27890 1,5. I don't know what is happening. TKS for Charing 7351.
Well, this was ex-damn-actly what I was looking for! Thank you for the imperial units, I won't bow down to Napoleon!
Good stuff - hope the build goes well. I think this metric thing is some modern idea - I doubt it'll take off though!
Great instruction but you sure can ramble on ;-]
Thanks! Gonna give it a try.
HEY! I built your F'n Antenna....
It worked GREAT!! ;-]
Thanks Brother!
Ken
@@greybeard804 Durham .. thats where the Pink Panther is from...
Durham, Durham, Durham Durham Durham, Durham Durhaaaaaam..Durham..Di-didilyham..
I have this antenna for about four months. 9 plus all over my town.
Excellent - it will work well for you on the Sporadic E skip too!
@@ukcbtv Yup. Yesterday was the day. Inner country connections: 600 km. That was great fun. I like this antenna.
Its not about failure, crimp one fittings allow high levels of ingress and egress. Basically it leaks signal. That's why cable and telco moved to compression fittings. They couldn't get reliable enough signal through crimp-ons for digital and HD transmissions as well as data even on analog. So basically their noisy and useless. You may not here the ingress where your radio is tuned but you will be suffering signal loss and irregular signal strength fluctuations.
Great videos 104!
I was amazed that you were making contact 60-70 miles away with this set up. Pretty amazing really. A couple questions if I may:
- Someone said in the comments they used RG-6, which is 75 Ohms (as opposed to RG-58 which is 50 Ohms) to make this antenna. Have you heard of someone doing that and having good SWR readings?
- Can this antenna be used up the center of a tree connected to a branch at the top of the tree as opposed to using some kind of telescopic mast?
I'm still trying to figure out how this is working without some kind of ground plane, unless that is what the 4.25" choke with five wraps is being used as.
I just received my Bearcat 980SSB radio yesterday in the mail and need to get a base station antenna up and you have convinced me to build this.
Thanks for your time. 73's from across the pond.
Hi James - the antenna uses a thing called "skin effect" to work. In a nutshell, the RF rides on the inner and outer surfaces of the braid, so the braid actually works like two conductors (all the choke does is to stop that happening on the outer surface after a 1/4 wave down the braid, thus defining the lower half of the antenna (this antenna is electrically just a centre-fed dipole with a more convenient physical feed point)). Being a centre-fed dipole the feedpoint impedance is around 70ohms, so a 75ohm coax cable is actually a closer match than a 50ohm and could be used for this antenna - problem is, a clever guy called Steve G3TXQ tested and listed ideal choke configurations and this is where I got the data for the 4.25" choke, however Steve's chart only covers RG58 and RG213, so whilst possible to use other cables and choke dimensions, it's beyond my knowledge to test properly. To make matter worse, Steve has sadly passed away, so it would be a matter of someone else picking up where he left off. The chart is here though with a few more chole/cable options (green is good and red is bad) www.karinya.net/g3txq/chokes/
To answer another of your questions, indeed it does work fine just hanging from a tree branch and many constructors put some sort of loop at the top for that very purpose. I have noticed some impairment in performance when in the middle of a tree which is understandable, but sometimes needs must.
Hope this helps and good luck with the build!
I just got off the phone with an older ham friend of mine who's been hamming since he was a teenager in the late 1950s, and he said that he thinks there was a misunderstanding somewhere along the way because he said that he built a TTLT antenna when he was still a teenager to take camping for 20m use
and he thinks that someone misheard someone else say TTLT and thought the second T was a 2
because it doesn't make sense that there would be a 2 in the acronym to represent the word, "transmission".
I think the T2LT name came from the original German patent back in the 1930s. The antenna is known under a few other names too. Cheers.
Is there a maximum distance from the choke to the pl259 connection? I'm interested in building this antenna for my base station, but would like to go directly to it.
I have a large roll of webro wf100, will this do the job?
Hi Gary - no maximum distance as such as far as the operation of the antenna is concerned, but max length would be dictated by coax losses which would apply to any antenna. Work on a rough guide of no more than 10 metres for a high quality RG58, 15m for RG8 mini and high quality stuff like RG213 for lengths longer than that. Most make the antenna out of RG58 with a join just after the choke - then they have the option of using what ever feeder cable they like. Cheers.
hi man, nice guide. can i know why this time you removed completely the braid??? it doesnt help, does it? if i use RG8, i still need the balun?thanks cheers
Hi - this antenna does not need the braid due to a thing called "RF skin effect' - it does need the choke to work no matter what coax is used though. Cheers
hey bro, i made this antenna andits amazing!!! but i didnt install the small ferriteon it....where can i finf it?? i used rg8 cable. thanks alot
Hi Bairam - if you have no RF feedback from the antenna, there is no need for the ferrite. If you decide to add one, look on eBay for a ferrite size that will fit over the RG58. Cheers.
So you've got a current choke at the voltage node???
I believe that's why Sirio have so many turns (16T) at the voltage node at the base of the Gain Master.
+Aerial Heights Hi - I must admit I'm not too up on the technicalities as I just wanted to create a simple easy to make and deploy antenna for emergency and portable ops - however my understanding is that this is electrically the same as a centre-fed dipole which uses conductor skin effect to allow it to work (basically turning the coax into three conductors) with the outer skin of the braid is acting like the lower leg of the dipole, so it's choked at 8ft 6ins down from the point where the dielectric is exposed as per the standard centre-fed dipole calculation (for a centre frequency of 27.5Mhz). Some more info here dl7ahw.bplaced.net/Superantenne00E.htm (it is an old German design, but I have also seen it referred to as coax dipole). Not having owned or researched one, I don't know much about the Gain Master - I do know that a few guys have recreated them in wire and coax for portable use though. Cheers.
Tuned Transmission Line Trap antenna
Hi There, in total how much coax cable is used ?
Did you buy a pipe and cut it down ?
What size ?
Thanks.
Hi Ben - approx 7.5 metres of coax needed for the antenna (excluding the run needed from the antenna to the radio). Former is cut from 110mm soil pipe - you can use anything that's 110mm in circumference though and you don't have to leave it in place afterwards - I keep it in there so the coil doesn't get squashed out of shape when I put it in the kit bad for portable work. Cheers.
Is there a way to do this if u don’t have a soldering iorn or a pl connecter
You could get Knights or Thunderpole to supply a length of cable with a plug already fitted, but if you don't have the kit, a guy is selling the whole antenna for £19.99 on eBay which might be the way to go. www.ebay.co.uk/itm/DRX111-T2LT-1-2-Wave-CB-11m-Portable-Antenna-System/293347571837
ever thought of an inverted full wave delta, easier to build, and transport, perhaps better, ?? I am going to give a delta a try as well as one of these.
think a v shape , 2 fish poles, 36.5 feet of single wire, up the poles and across the top, they are said to be great for dx at low heights, so 2-- 12 foot poles would do the trick .
Not really - this one has fitted my needs well for the applications I use it for. Good luck with your ongoing antenna builds though. Cheers.
Hello and thanks for the video. I was planning to try this as a camp antenna, does it work good for 26.9650 to 27.450mhz ? Again thank you.
Yes, mine covers 26.965Mhz to 27.99125Mhz with good SWR 👍
@@ukcbtv Thank for fast answer, going to transfer it to Metric unit, hope it works well, because not sure if you miss some that the swr will go up. Greetings from the Southwest coast of Norway.
@@nortonis3565 Maybe see my later "Alternative Build" video - I have included some metric units in that one. Also if you only want to cover 26.965 to 27.405, you could optimise centre frequency for 27.205 👍
@@ukcbtv Thanks my good man, i will look into that. I dont have FB or i would contacted you there and asked you, im new into this so it will be all experimenting for me.
I am looking at that choke - if my calculations are correct, a 110mm diameter, that means the circumference is 345.5mm. So at 5 turns it makes the choke roughly 1.73m. Should the choke not also be a 1/4 wave or 2.7m? Or am I missing something?
Hi Will - I just went with the choke chart G3TXQ did and went with that (unfortunately the guy is now R.I.P but did some great work). Worked great, so didn't delve any further karinya.net/g3txq/chokes/
@@ukcbtv OK, so I built it exactly as per your dimensions and it has a very good SWR across the CB frequencies, much better than I actually thought it would. Only issue is I dont have a nice long non conductive type sturdy pole to mount in on top of my steel mast. I tried 2" PVC conduit but its a bit wobbly and bends a bit too much. Still looking for a nice telescopic fiberglass pole but not easily sourced in my country.
So simple and easy, its almost funny. Gonna replace my old aluminium dipole with with one of these asap. Will it be affected if I put it inside a 50mm PVC conduit?
I've heard of others putting it in a PVC tube - might need some tweaking with the tuning perhaps. Cheers.
@@ukcbtv would it only be the top end that needs tweaking? in other words can a laymen adjust like a standard lenght adustable or would it need a whole re working of the of all lenghts including choke. I wish to weather proof mine
@@mikeriverajr4447 - indeed, if the rest of the antenna is made to spec, the top is all that will need to be adjusted (if at all). Only 'specialist' test kit needed is a basic SWR meter.
@@ukcbtv thank you, i have a follow up question if you dont mind, i learned that a inverted v dipole works well in a attic, my question is could use a t2lt and invert v it in an attic?? would prefer it in the attic then a 18 foot wire out the house, the goal is a permanent care free install , hence the question about the pipe to make it last, many thanks!!!!!!!!!!!!!!! for your help!!!!!!!!!!1
@@mikeriverajr4447 - I've not tried it in an attic or in a V configuration but it should work although it will probably need some playing about with (Inverted V antennas are generally around 2% to 5% shorter depending upon the angle of the V. In addition, proximity to objects in the attic may well have an effect too. Anything like foil on the underside of the roof or roof tiles with a carbon content will deteriorate performance and make the natenna difficult to tune. Worth a try though - some attic antennas can work well. Cheers.
I see again the video. The problem is the coil, in wrong way. TKS 7351
Is a DIY antenna legal in the UK?
The only issue I can think of is if a D.I.Y antenna posed a risk if constructed or installed in a manner that could cause injury to the public should it fall down or have sharp edges etc.
By your own admission you said that RG58 coax as a velocity factor of 66% Why did you not account for that velocity factor when you were cutting your stinger length and the regular coax for the quarter wave portions of the dipole. Instead you treated it as though it has a 100% velocity factor because you did not reduce the cable length according to the requirement. 😊 It should be much shorter than you actually cut it
Once the coax is split apart, VF is largely irrelevant, so don't over-think it, just make it and experiment as you so wish.
Is this antenna good for dxing ?
I've always had good results from it - best contact UK to Canada on 3.5W FM.
Question is which works best in your opinion ,,,this or Bazooka. .? Thanks Shane ct1017
They're both the pretty much the same (electrically a centre-fed dipole) but, so I've been told, the Bazooka is an older design which was designed before RF skin effect was understood. So, due to it being easier to make, the T2LT edges it - but, and it's a big but, the choke has to be right or it'll all go out of kilter big time! Cheers.
Can you make a double bazooka for 11mtr?
Not made one myself, but others have for 11m and apparently it's worked well. Worth a go. Cheers.
You also obtained 106 inches of desoldering braid.
And... That's about my average per project need for desoldering braid 🥺
Hi bud where can i buy the ferretts things from plz thanks
Hi Martin - from eBay, just search for 'TDK Clip-on ferrite'. Optional for this antenna though and most people don't bother fitting one. Cheers
Ok thanks bud thought id fit one as i was told i had a bit of noise so thought it might help what u reckon
@@martinbradley3686 - sometimes helps. If you've some noise on your transmitted audio, one on the mic lead may help too. Cheers
Ok thank you for your help i will order 1 and see how that goes thanks again bud.take care stay safe 👍
end fed surely ?
Physically end fed but electrically it's centre fed - works via RF skin effect on the braid. Cheers.
When you look at G3TXQ's chart you see 5T RG58 on 4.25" is perfect from 26-28MHZ but a larger diameter will pull this down into the area we want. Soil pipe is slightly larger than 4.25" at 110mm. What I am thinking about is 125mm pipe like this www.irrigationonline.co.uk/20mm-125mm-pvc-pipe/ which has an internal diameter of 117.6mm. RG58 is about 5mm so winding 5T inside would be far closer to 4.25" (107.95mm) or a slither under. An inaccuracy in that direction won't have any detriment unless working down close to 26MHZ. Not sure what real world effect this would have as I'm just starting out my radio hobby. 73s 26CT1757
Why dont you use metric units ?
Hi - the use of the imperial system is still in widespread use in the UK (especially by older folk like me!). There are online conversion sites online to convert the measurements to metric should anyone wish to do so. Regards.
How wide is the former?
4.25 inches
I meant width, not diameter. I'm assuming it's about an inch wide? I'm sorry for the misunderstanding.
...Yeah, well, er uhm,
for decades I've been making Choked Vertical Coaxial Dipoles for me Radio Bruvs to shoot up a line over a tall tree and pull up for excellent local vertical comms.
I never knew it was named a "T2LT".
Just so I'm certain;
- I make a:
¼ λ of exposed unshielded center conductor and ¼ λ down from the point of separation, or about 17.7'.
- So is this what is referred to as a *T2LT?*
And here for all this time I've been calling it a *CVCD* for Choked Vertical Coaxial Dipole.
Hi there - pretty much the same thing and the names are interchangeable (seen them called both, although for the purist, the German designed 1930's T2LT choke has a capacitor across it for fine tuning). This one has a 5-turn choke with a 4.25inch inner diameter and, after tuning for a centre freq of around 27.5Mhz, usually ends up 102ins top section and 102ins bottom - total length from tip to the start of the choke is 204ins (17ft).
Seen a few similar designs and no doubt they all work well - totally agree, super-easy antennas to build and deploy! A.t.b.
Use any single conductor wire for the top 106",don't waste 106" of coax!
I mention that method of construction at 15:40 into the video, but I prefer to 'waste' £1 of coax in order to have no joint in the middle of the antenna. Cheers.
@@ukcbtv Yes, I understand, you said you don't like splicing.
cheap shite RG58 who cares ?
I find it a bit easier to cut a piece of 4.25'' PVC choke former about an inch longer than needed for the coil only, then I drill a hole next to each edge and push the coax up from the inside and out through the lower hole, wrap the 5T, then back down into the 2nd hole on the other edge and on out the inside toward the top. This seems to help to hold the coil shape intact.
Another thing I've done is cut the top at 3/4 wavelength ( 318'' ) instead of only 1/4λ, then using a 2nd support line and folding 90° at the 102'' point up from the split, I pull up the T2LT with the primary parachute cord wrapped and taped or zip tied to the antenna and tied to the choke to prevent stretching, then pull out to the side the 90° 216'' 1/2 wave, *_broadside toward the DX direction I want to TX._*
- It seems to provide a rather circular polarization covering the many diagonal angles of polarization as well as both vertical and horizontal polarizations.
Sounds a neat way of dealing with the choke - perhaps try winding the coax on the inside of the former with the coax exiting to the outside via the holes? Maybe a little more neat and affording the coax some mechanical protection.
The DX config of yours looks interesting - was the SWR OK with the 3/4 top section?
Great to see folks experimenting with the basic design 👍
The 5/8 version would add about 1.5 s units of gain. Compare the A99 to the M2000 in performance or follow the Gainmaster 5/8 ua-cam.com/video/5VxHNTttpEc/v-deo.html build using the tuning stub. Glad to see a comment about using 75-ohm coax, being I have some hardline cable company coax so I may use some of it. I have watched several of your videos, well done, of course for us Yanks in the USA talking a little slower might get through to us better?
Hi there - Sirio claim around 3dBd for their 5/8 wave Gainmaster which would be about half an S-Point up on this 0dBd antenna - doesn't sound a lot, but could make the difference between getting the contact or not and the equivalent of doubling the TX power - perhaps to the detriment of high angle Sporadic E skip-shooting though. The input impedance of dipole antennas such as the centre-fed and this T2LT will vary with height above ground etc. but is typically around 70ohms, so 75ohm coax feeder is actually a better match. I've got a West-Country rhotic accent which is fairly unusual here in the UK, but should be fairly understandable for most of the USA. Cheers.
@@ukcbtv Had not thought of making the entire run into the house, shack using 75 9hm but you could, and adding a 1/4 wave of 52 ohms on the end would match the 75 to 50 ohms at the radio being this is a mono-band antenna.
Why waste so much coax!!!! Either just trim the end of the coax and solder a cheap wire for the top section or build a J pole which will eliminate the need for a coax choke.
Both will not waste so much lovely coax :)
I do cover the alternative method of adding wire instead of stripping back the coax in the video. Cheers.
lol its just cheap RG58 !
I think iam going to build this with RG'400 double braded teflon dialectric silver plated conductor.
RG-58 wont last with 380w rolling through it.
Too technical
I think it's important to have an understanding on how this antenna works, hence the explanation, but just skip to the construction bit if it's too heavy. Cheers.
@@ukcbtv it IS a good video but for thos who are not very technical..really.. you should have drawn out a very simple plan so people can see the lengths they need.. ie, how much coax after the choke ? it was never mentioned.. I know its not relevant but others might not..its very hard to find any coherent simple plans online for this antenna... ideally you could start by stating how much cox ( in all ) you need. and take it from there. also an S0239 socket would be better than a PL259 plug, eliminating the need for a barrel connector ... not having a go.. just saying. cheers rob