Cobweb Antennas

Since I've done so many posts on the Cobweb antennas I thought it best to separate them on a different page so that potential Cobweb builders can see all the posts together. Hopefully this will make planning and building easier. 

I've tried to give as much information here as I can, but you'll notice I don't go through the actual precise build process, there are plenty of links within these posts or on the right hand side of the webpage that give the detailed measurements etc depending on what type of cobweb you wish to build. 

For starting out from scratch on the G3TPW I would recommend the original Cobweb Revealed Website and the YouTube video by Denmonkey  For the G3TQX version go to Steve Hunt's website 

As I've stated before the Cobweb antenna is fairly easy to build, I'm no great technical genius and yet I have managed to build both the G3TPW and G3TXQ antennas and if I can build this antenna, so can you! 

This is quite easily the best antenna I have used, it's small (8ft circumference) omnidirectional and produces very little TVI. Either type of Cobweb is ideal for small areas or where you are limited in raising an antenna.

If you decide to build a Cobweb do let me know how you get on and good luck!

Servicing the Cobweb G3TPW Antenna

Finally I've got round to begin the service of the home-brew G3TPW Cobweb. Taking it down from the mast wasn’t as bad as I thought, I decided to do it now as the weather forecast is not good with high winds expected over the next few days, so while there was a break in the weather I zipped up the ladder and began the removal process.

Once down the initial inspection was that it didn’t look too bad considering it’s been up on the mast for nearly two years and been subject to some pretty bad weather conditions. A bit of rust here and there on the metal tubes that hold the wooden poles, but perhaps through luck or my building capabilities it has managed to withstand all that has been thrown at it! 

The wooden poles and the box are covered in mildew and slightly bowed, but still sound, the cables are fairly loose which I suspect is the main reason my SWR has been out, especially on 20 meters which at the last reading was 2.5. Interestingly I thought the box would have been pretty rusty inside but surprisingly looks very clean apart from a good ½ “ of water slopping inside, first thought was hmm, I forgot to drill any draining plugs!

The wooden poles are going to be replaced with fibreglass, I managed to find some ex army surplus which should do the job nicely but I will have to wait as I’ve only just ordered them so it will take a few days to arrive. Since the main box is in such good condition I will do little except give the outside a good scrub and more importantly drill a couple of draining holes. 

The silicon grease has done its job and kept the contacts all clean and rust free, I'm amazed there is no rust on the copper wire or the steel screws. Originally I bought a Cobweb (back in the 90s) for the grand sum of £160 and when I sold it I remember inspecting the box and seeing how badly rusted everything was, so I was expecting the home-brew to be the same, just goes to show what a bit of silicone will do to protect.

Over the next few days I will tighten the cables and recheck the SWR and if needs be replace any that are suspect, luckily I have some spare cable that I got last summer from Maplins, (our version of Radio Shack). 

Looking inside the box it is a remarkable simple system that is very easy to build and yet gives great results. This is easily the best antenna I've ever built and quite honestly if I can build one anyone can. If you want further information look at the Cobweb Revealed website or alternatively please ask and I'll be happy to help where I can (but I warn you now I don't understand the theory, hi hi). I will include as many picture as I can during the service process so you can see just how easy it is put together.

Further work on Servicing the Cobweb Antenna

The fibreglass poles have arrived for the Cobweb antenna, these I suspect are fibreglass fishing poles but ideal for what I want and more to the point once I had removed the plastic ends with copious amounts of boiling water fit the metal sleeves perfectly. Their length is 7ft which provides the correct length for arranging the twin speaker cable. One thing to make sure when purchasing poles, you require fibreglass only, no carbon or metal!

I have replaced the 20 meter cable, although I could find no fault. I suspect the SWR was high either because of the element being too short or tapping point misaligned, so I have re-measured and added a few more cm for trimming, twisted and soldered the wire at the correct length for the tapping point. 

I’ve also smothered the internals of the main box with more silicone and added some draining holes to the bottom of the box. then lastly I attached all the poles together and slotted them in to the metal sleeves, ready for re-attaching the elements. 

 With the poles in place I started fitting the elements

Something that I learned whilst originally building the antenna was that the Cobweb plans do not seem to allow for extra lengths when tuning/trimming, so it's worth adding some extra length when measuring up. Also when tuning for a good SWR, if the antenna can be raised to a minimum height of 6ft, tuning may well be easier. Over time building these antennas I've come to learn that although the tuning can be completed at ground level, sometimes raising the antennas will help.The PDF is a very useful guide but there are other very good and possibly simpler instructions besides the G3TPW design. It's worth searching on the web to see what else is about, G3TXQ does a similar antenna but uses a 1:4 balun and single wire which probably makes life a lot easier. 

 Starting to take reading off the MFJ on 28 and 24MHz, wire, bits of string and loops everywhere!

Now comes the usual tricky bit of tuning up the elements for each band, sometimes you get lucky and other times it becomes a real test of patience.

 The ties for holding each element is some simple plastic tie straps with a screw to stop it slipping inwards, Ella one of my labs takes a mild interest!

Generally I start at with 28Mhz and work downwards, (but it doesn't really matter) naturally with new poles and slightly different lengths I knew I was going to have to re-tune. So far I’ve roughly got all 5 bands in to the ball park figure of around 1.8/2.0 SWR but I need to do some final adjustments which consists of individually checking each twin cable with the MFJ and adjusting the loop at each end of the antenna to get a good reading. 

 All elements fitted and just ready for the final trimming.

The only issue I came across was that I had to add some extra twin lead to the 18Mhz band as it was giving me a 1.5 at 18.170, herein lies the mystery because with the wooden poles it was spot on, typical!

For the rest of the weekend I will continue to trim up and hopefully by tomorrow afternoon I should be ready to think about mounting the antenna back up on the mast although there's no real hurry and I may just end up waiting till next weekend.

If It Ain't Broke Don't Fix It!

As the old saying goes "if it ain’t broke don’t fix it", I think I went a bit too far in servicing the G3TPW Cobweb. I tried tweaking the elements to the absolute minimum SWR and got in to a real mess which eventually got me readings of 5 on pretty well all of the bands! 
Just to explain, I'm not an antenna theorist, so I'm not going to go in to the ins and outs of the Cobweb design, my explanations are based on layman's terms, so to all purists out there apologies in advance!
At first I was at a loss as to what I had done and so eventually decided to do a total rebuild and took the main box apart to check that everything was in order and to clean out all the silicone which was causing a mess everywhere. The box was fine, all connections were good and everything was in order.
I removed all the elements and started measuring each one and to my surprise found that some were uneven and out by a few inches, this probably happened from the tuning and trimming when I originally built the Cobweb with the wooden supports, no wonder my SWR was out. It just goes to show if you make alterations such as changing the poles, measurements will go out of the window and you need to recheck them! These things happen and you just have to except your mistakes, learn from them and move on.
So I re-measured all the elements and added wire where necessary, once completed I re-attached them to the box and laid them back on the poles and took some readings, everything looked much better and in some cases the SWR was lower than the original build.
I haven’t done my final tune/trim yet as the weather has turned and there is snow on the ground, the forecast for the week is very cold with more snow predicted. What’s noticeable is how the twin speaker wire which is quite thick (42 strands) gets very hard to manipulate in cold weather so I shall leave things until it gets a bit warmer. These are my SWR readings so far:
28 MHz                   28.782          1:2
24 MHz                   24.248          1.2
21 MHz                   20.633          1:2
18MHz                    17.664          1:2
14 MHz                   14.079          1:1
The only one which is pretty well spot on is the 20 meter band so obviously I now have to adjust the loops on each band element by lengthening or shortening to get the SWR readings to exactly where I want them. 

Bear in mind I use CW most of the time so I want the lowest SWR in those particular segments of each band. I don't find that the gap between each elements makes any real difference, generally its about 6 inches apart and seems to work fine, although theorists may have other ideas.

 Each loop is held by plastic ties so that it can be easily adjusted
For instance on 28MHz I want to lengthen the loop on each end of the element by a small amount to bring the SWR down to around 28.010MHz, whereas on 24 MHz I have to shorten the ends of the element to raise the SWR up to approximately 24.890 MHz. 

 A closer view of one of the loops
When I was working with the SWR readings I did a lot of browsing on the internet to see if I could find any further information. I came across the G3TXQ website which I have seen before but as it was a different design I'd not really had a good read. He uses single wire (as apposed to twin) and a 4:1 balun which by all accounts seems a much simpler and easier design to build. 
So as a further project and from personal interest I have decided as an experiment to have ago at building another Cobweb using G3TXQ design and will compare against the G3TPW original. It will be interesting to see the difference and more importantly how each one compares on the bands. The toroids and other bits are on order so more in later posts!

G3TXQ Cobweb Build

As I said in my previous post I’m going to have a go at building the G3TXQ Cobweb and see just how easy it is to build compared to the G3TPW original. To be honest the only difference will be the terminal box and the single wire elements as opposed to the twin wire elements on the G3TPW design, the frame will be exactly the same, but I suspect with the single wires and smaller terminal box the antenna will be a lot lighter.
Whilst I have the G3TPW Cobweb down from the mast I am going to change the pole support to the proper aluminium set up (before I used an old plastic bread board together with a thin slice of aluminium plate to make it sturdier). The elements have all now been re measured and the antenna is sitting in my shed almost ready to go back on the mast. But I will now wait till I’ve completed the G3TXQ design, compare notes on both and then put up the winner!
So to the G3TXQ build, firstly the terminal box; thankfully as the Cobweb has become more popular there some small companies dedicated to Amateur radio you can find on Ebay that supply bits and pieces ready made for this antenna, one of them being Spratreader which sells the 4:1 Guanella Balun in a kit form which is extremely easy to put together. 

This balun is slightly different to the G3TXQ version, in that it uses the ferrite core, but has 6 winds (as opposed to 8) and uses thick copper wire instead of the RG-58 coax. I have a small enclosure for the terminal box and will use some old copper roof slate tags as conductors for the elements. 

I will be connecting one end of the balun to an SO239 connector (red to center, black to ground) and the other connections to the two copper plates which then connect to each of the 5 element on each side of the enclosure via small bolts. I’ve still got some spare twin 42 stranded wire so I will peel single strips and use these for the elements.

The pictures above show the mock up, I've drilled all ten holes for the element connections and fitted the copper plates I've also fitted the SO239 and its just a matter of trimming the wires from the balun to fit neatly in to place and solder up.

I'm still not sure whether to use the frame I already have or to to purchase some more fibreglass poles and build a separate frame for this version, we'll see. More to follow in later posts.

G3TXQ Cobweb Build Update

The terminal box has now been soldered up and completed and I must admit I’m quite pleased as it is far smaller than the one I had on the original cobweb. 

 All soldered up and ready to go.
I’ve now made up all the single wire elements and soldered connectors on each one so that they can just slip on each of the 10 bolts quickly and easily, I just have to cut the elements to the correct length for each band but that will be done at a later stage. 

Connectors added to each element which then fit neatly on to each bolt.

I decided in the end to go for a completely separate frame and have ordered some more fibreglass poles and will attach these to the aluminium plate that has now arrived, I still have to cut the plate in to two and then drill the holes for the clamps. The 100mm x 150mm plates as suggested by the "cobweb revealed" are quite small so I will increase the size to 150mm square (e.g. just cut it in half) to give me a bit more room to play with. 

 The new aluminium plate is 300 x 150mm
On my first Cobweb the plates were built with a mixture of an old plastic bread board and some thin aluminium sheeting which actually works quite well, but the size is considerably larger than the 100x 150mm, it’s more like 400 x 200mm and therefore a lot heavier. 

 The original frame made out of breadboards and aluminium plating
As the whole idea is to reduce weight on this new antenna I have to come up with better solutions than home brew breadboards etc! The weather here is still miserable, there is snow on the ground and it is very cold, so getting outside to play antennas is a bit of a no no at the moment. Hopefully next week temperatures will pick up and I can get on with building the frame.

Carrying On With the G3TXQ Cobweb

Unfortunately I didn’t get much done this weekend so I’ve only progressed very slowly on the cobweb. But I have managed to measure out the elements and build the plate for holding the fibreglass rods. The aluminium was fairly easy to cut and with some accurate measuring the U bolts holes were drilled and everything fitted smoothly.

I've fitted some more metal tubes (as with the original cobweb build) to hold and strengthen the fibreglass rods when they are fitted. The extra rods I had ordered finally arrived over the weekend so I need to measure them out and mark up where the corners of each element will sit, hopefully that shouldn’t take me too long.

Finally I fitted the plate and the terminal box to the one rod that comes off the inner X, so hopefully the majority of the work is now done and it's a matter of waiting for a reasonable day so that I can fit the four rods and elements and start to begin the tuning process.

However, as the rain continues and I am stuck indoors I had a thought that might prove interesting and that is to try setting up this new antenna in my attic. I had a quick check and it will fit with about a couple of feet to spare on each side. Not sure how it would behave, but the height would be approximately 25ft which should be OK. 

The G3TPW Cobweb website promotes how good the antenna behaves in an enclosed area and does not cause much interference, it maybe worth having a play especially if this horrid weather continues and I'd love to see how much of a difference when compared to my original up on its mast!

Antennas in the Attic

Well I decided to give my “antenna in the attic” plan a try and have installed the new G3TXQ Cobweb up in the roof. I managed to squeeze it in, it was a bit nightmare to get all the elements threaded and in place. Resting on old boxes for support it is approximately around 25 feet above the ground, so it will be interesting to see how well it works.

The trimming proved interesting as surrounded by wood, slate and bricks I knew it might prove difficult, but in the end after much swearing I eventually got the SWR readings pretty reasonable but I am sure I can improve with some further delicate trimming.

14.030 - 1:2
18.070 - 1:2
21.030 - 1:2
24.900 - 1:3
28.030 - 1:1

 On receive it seemed a bit noisy (that could be present conditions) especially when compared to my 30 meter vertical, but a quick QSO on twenty at 5 watts to an SM station proved that I'm getting out and I got 449 but I will give it a proper try tomorrow morning and let you know the results.

Both Cobwebs Now Up and Running

Well after much playing about with tuning and trimming, I finally got the G3TPW Cobweb back up on the mast yesterday evening.
After my initial tuning the other day I had to dismantle the antenna as the weather was proving very bad, so yesterday by the time I had re-assembled and started up the tuning process the morning had passed quickly by. Finally with a bit more trimming completed, I climbed the ladder with antenna in hand and clamped it in to place.
I switched on the MFJ 259 and did some checks, the SWR was all over the place, I had a problem, something was definitely not right and after a quick check of all the coax cables, I had to make the decision to bring the antenna back down, and so I clambered back up the ladder and removed the antenna.
I spent most of the afternoon with the terminal box open trying to figure out what the problem was, I knew it was shorting somewhere but in the end I had to go through each connection to find the short. Eventually I found the problem, it turned out to be one of the 12 meter elements had split at the join to the choc block causing one of the U connections to short and all it needed was re-stripping. Then it was just a case of re waterproofing the box, sealing up and mounting back on the mast.
Dusk was fast approaching when I clambered back up the ladder and attached the Cobweb back on the mast, I quickly said a prayer and then did my checks on the MFJ, thankfully all proved OK. 

Finally back on the mast!

The SWR measurements are now pretty good, they are all set for CW except for 10 meters which I set for 28.500 as I like an occasional rag chew on 10.
14.000 - 1:2
18.070 - 1:0
21.050 - 1:0
24890 - 1:2
28.500 - 1:1
With the G3TXQ Cobweb now set up in the attic I am at last ready to do a bit of testing with both cobwebs. Obviously as this antenna is in an enclosed space there is bound to be a difference. The most noticeable being the background noise but that cannot be helped as the attic naturally has bricks and mortar and electrical wiring.
Here is the final SWR reading for the G3TXQ:
14.075 1:2
18.080 1:2
21.073 1:3
24.890 1:1                        
28.015 1:1    
As suspected there is not a lot of difference, but the SWR is slightly higher on the G3TXQ on a couple of bands (most likely because of the attic positioning). I could trim to match the frequency of the G3TPW, but to be honest I couldn't be bothered to get it exactly the same. 

Physically the G3TXQ is far lighter and easier to handle also the tuning is much quicker because you only have one wire for each element. But that said, I do like my G3TPW, it is heavier and chunkier with my larger home made plates and it definitely feels more solid especially with the windy condition we have round here.

It was very apparent when lifting back on to the mast how much heavier it was compared to the G3TXQ, you feel the lighter cobweb would literally blow away in the wind, although that said it's exactly the same build just lighter materials.
The main difference on receiving is of course the background noise but if the G3TXQ was raised outside on my mast I doubt you would know the difference when listening. On transmit I've now used both Cobwebs on 20 meters and reports from both are good with the G3TPW showing  slightly stronger RSTs, again no doubt due to due location.

So all in all as suspected there is very little difference, for me I'd go for the G3TPW simply because it feels stronger, but that personal choice from QTH circumstances. It's been fun servicing the old cobweb and building a new one and I hope you have enjoyed the entertainment as I've struggled along. I'm not a technical antenna geek so all this is very basic but hopefully gives you a rough guide to both types of the antenna.

Not sure what I'm going to do with the G3TXQ cobweb now, so for the moment it's sitting snugly up in the attic out the way. Currently I'm saving up for either a K2 or a TS590 so I'm tempted to keep the G3TXQ and connect to the new radio, then I'll be spoilt for choice with two cobwebs!

Swapping Over the Cobwebs

Last Friday evening in a bit of madness during a bout of boredom, I decided to dig out the dismantled G3TXQ cobweb from the attic and set it up outside in the garden. I’d wanted to re test it against the present G3TPW cobweb I'm using, just to go over the pros and cons and possibly replace the G3TPW. 

With the G3TXQ quickly set up on a piece of 6ft scaffold pole and after doing an approximate tune I couldn't believe my luck when wondering over the 21Mhz band that I managed to have a qso with a Russian station who gave me a 599 which made me think maybe it was time to swap the cobwebs over. 

Saturday morning I set to work and I did the full tuning with the MFJ 259 which took an age as the G3TXQ definitely has much finer tuning points, it dips very quickly and the freq range is literally a few hundred kilohertz, a noticeable difference to the much wider freq of the G3TPW. 

Because I was tuning/trimming the antenna with the MFJ 259 at only 6ft above the ground I had to take the risk of setting each of the elements to tune a little lower than the freq I wanted to operate on, the theory being that once raised the SWR would rise slightly from the tuning at ground level.

By Saturday evening I had adjusted all the tuning, secured the ties and finally waterproofed the junction box, I hadn't needed to do this before because this antenna had only been set up in my attic, So by Sunday morning the G3TXQ was ready for mounting

I grabbed the ladder, lowered the 40ft mast and removed the old G3TPW cobweb, I’d forgotten just how heavy the antenna is and it took a while to gently bring it down the ladder back to mother earth.

Placing the two antennas side by side it was interesting to see the physical difference. The G3TXQ is so much lighter; certainly the single wire and smaller aluminium central clamps make all the difference. 

The G3TPW has a much heavier clamp and is beginning to look very worn!

The G3TXQ is a much neater and lighter clamp, a definite improvement.

I also needed to do a few adjustments to the mast, add some more kevlar cord guides and do some general maintenance. Once that had been completed I grabbed the G3TXQ and hoisted it up the ladder and clamped it to the top of the mast, I have to admit it was so much easier than with the G3TPW and just looked a lot tidier! 

The final result and there was a definite improvement in performance.

By the afternoon it was all finished and after a quick SWR check I called a CQ and got another Russian Station (Alex R3ZK in Belgorod) who gave me a another 599, I was very pleased with the final results. 

There’s a few little bits I need to do, (like add the top mast clamp cover which I forgot.....doh!) But everything went pretty well according to plan and I shall now dismantled the G3TPW and store it away in the attic until I have another mad moment!

Final SWR results for the G3TXQ:

20 meters   1:2
17 meters   1:1
15 meters   1:1
12 meters   1:1
10 meters   1:1


  1. what type of ferrite core you using? FT140-61?

  2. Hello,
    Fair-rite 2631801202
    Outside diameter 28mm
    Inside diameter 20mm

    73s Richard M0AUW

  3. I just put a cobweb antenna in my attic. My house is a wood frame so the attic is fairly electrically transparent. The height is approx 10-12m above ground.

    My cobweb is of the single-wire type with FT140-61 toroid. Since the attic provides four support points I didn't use any poles; just strung up some Dacron line in an "X" pattern and attached the wires to the line. I machined some plastic thumbscrew adjusters to slide along the line and hold the wires in place. It's very easy to adjust the elements into symmetry this way. Plus, it looks like a real spider web!

    I'm still evaluating the cobweb but am very happy with its performance on 20m compared to my outdoor endfed wire antenna (approx 30m long and 10m high), which has been my main antenna over the past several years. A definite improvement.

    I use the WSPRNet low power beacon system to compare the antennas side by side over the course of several thousand "contacts", both transmitting and receiving. I will do the same for the 10/15m bands for which I have attic dipoles set up. (Also interested to see what, if anything, the cobweb will do on 30m compared to the endfed wire...)

    I have also set up a 40m single band "cobweb" antenna in the attic. Unfortunately, due to the attic dimensions the antenna is more rectangular than square and one end must slope downward a meter or two along the roof line. This antenna performs worse than the endfed wire, but not by so much. An increase in output power of less than 2x should make up the difference according to my WSPRnet data. I have a low power station (10 watts) so will probably get an amplifier to compensate as the endfed wire must be taken down soon.


  4. Hi Drew, Thanks for you note, glad to hear the attic cobweb is a success. I've also been pondering about a 30m cobweb in the attic, but like your 40 it would be more of a rectangle! At the moment I use a 30m vertical which works very well, but I always like to experiment and see if I can improve things. Having now completed the K2 the attic cobweb is permanently connected to that transceiver. It works well especially for European QRP work..... I figured hombrew kit, homebrew antenna!

    73s - Richard M0AUW

  5. Hello Richard,
    this is my CobWebb made from old military phone cable ("PKL"): This is ~G3TPW version + additional 30m element (frame). Next element for 40m will be added soon. Antene works OK, especially with EU stations in contests.
    73, Marek SP2MKT

  6. Hello Marek,
    I like the design, looks very strong. I guess it will be quite big for 40? I just haven't got the room for that size, will be watching with intererest - 73s Richard

  7. This comment has been removed by the author.

  8. Sorry for the double post...

    Anyway, I am in the design phase of building a 40-10m cobweb (G3TXQ syle). I have exchanged a few emails with Steve and he has suggested that I feed the 30/40m elements with a separate feed and balun. His reasoning for this is two-fold. The first is because there would be some 3rd harmonic interaction with the 10 and 15m elements (10 and 15m are 3rd harmonics of 30 and 40m respectively). The other reason is because it would allow the 30 and 40m elements to keep more of a square shape because the balun would be further out from the center.

    I'm still trying to source fiberglass poles/tubing for the spreaders (they will be approx 12 feet long). Once I start building I will take pictures and post them online.

    Geoff, NW7GM

  9. Hello Geoff, My apologies for not getting back sooner sadly sometimes work gets in the way of the hobby !
    This sounds an interesting project, I've thought about building a separate cobweb just for 30 and 40 meters but not all bands combined and I can certainly see the issue with the balun and I guess at some stage I would have worked out the harmonics (but probably not till after build completion!!). With 12' spreaders it will be quite large but even so still reasonably lightweight. I'd be interested to hear how high you intend to mount the antenna, presumably a lot higher than the recommended 30' for a standard cobweb as you are working with lower bands, do you have a tower of some sort?.
    Please do send some photos or a link, I'd love to see how you get on.
    Best luck and many thanks for your comments.
    73s - Richard M0AUW

    1. Hi Richard,

      Sadly, the antenna will only be about 25-28' off the ground - it will be mounted on a mast that is attached to the eaves of my house. Yes, the 12' spreaders will be long. Overall the antenna will be about 17' square but that is still smaller than a lot of 40m beam antennas (which I know this will not be).

      I am getting close, I think I have settled on the MaxGain Hexkit 1 spreaders (they can be used with G3TXQ's broadband hexbeam), but I will have them cut the 1.25" tubing in half instead of at 58".

      I certainly will send a link or some pictures your way once I'm underway and/or finished with the project. Thanks for having a lot of good pictures on this site to reference as well.

      73 - Geoff, NW7GM

  10. Do you think a 6m element could be added with an adjustment to the ferrite in the balun to go to 50 MHz? An Amidon FT-240-K toriod with 8 bifilar windings looks equivalent to the double toroid in your system. It's a 4:1 Guanella too and will go to 50mhz. This would span 6m to 20m then.

    Don - AK4SJ

    1. Hi Don, That looks good to me, I did a quick check on the net and found
      Page 2 section III shows a balun with a freq response of 1 to 50Mhz 98% efficient and a 2kw continuous. You might have to play about a small bit but that should be fine. Let me know how you get on....73s Richard

    2. Forgot to say the balun is using a Amidon FT-240-K toriod!
      - Richard

  11. Hi, really nice post. I was considering the CobWebb (both types) since a few but I am a bit worried about the bandwidth of these antenna. I am mostly a contester and span from CW contests to SSB contests. Is the SWR reliable on both ends of the band?


    1. Hi Stefano
      I would go for the G3TQX it's an easier build and the bandwidth is ok, presumably you have a tuner you may need it for the high end of the bands. Good luck let me know how you get on, love to see some pictures!

  12. I agree with all of the points keep up the good work.Thanks for sharing this.

    3g antenna manufacturer & lte antenna manufacturer

  13. Returning to your web page regularly as I carry out work building my G3TXQ version - great reference particularly as I have not made any antenna for something like 30 years...

  14. hi there ive refurbished a g3tpw twin wired elements cobweb and was wondering instead of using the mis mash of coax inside the box as a balun as it was originaly would I get away with making a 1.1 balun with a t200/2 torroid if so how many windings would I need to do and would it take my ft 2000d 200 watts

  15. Hi,
    There's an excellent article on VK6YSF 's Blog that gives a good explanation about 1:1 baluns using T200-2 toroid's. URL is Looks like 17 turns of 1.25mm of copper wire, the copper wire is 600mm in length, would be OK up to about 400 watts.

    Hope that helps.

  16. I there! I think I've read almost all' about cobwebb (and cobweb) but I still have some doubts.
    1) if I would add a 6th dipole for 50 MHz where I have tapping the twin calle? I can't find that information or the way to calculate measures.
    2) Instead of glass fiber, it would be easier to find PVC tubes for electrical systems. What' the problem about it? Too much fragile? Too much flexible? Are good enough?
    3) instead of coaxial in air (in a box) rf choke I would put a 1:1 current balun to avoid RF come back in the shack. I think that a toroid glued inside the junction box is more clean (I'm afraid that coax choke could damge terminal's interlinked and cause shortcircuit) and maybe more efficient than a (Very) Ugly RF Choke.....don't you?

    Many thanks in advance for your reply and I hope to start cobwebb between next fede days.

    73's Federico, IW0RBS

    1. Hi Federico,
      Sorry,I'm not sure about the tapping points for 50MHz, but the best way I would think is to roughly guess where the tapping point would be and then stick a pin in the twin cables to create a short and read off on your analyser.
      PVC tubes if you can get the right length and size would be fine, but that maybe difficult hence the fibre glass poles.
      A 1:1 balun would be fine, but if built correctly, the coax is good and I have never had a problem.
      It's entirely up to you how you construct, if you feel your design is better, try it and see how it goes, that's half the fun.
      Good luck with your construction, let me know how it goes.
      73s Richard

    2. Thanks Richard for your kind reply.
      At the end I've decided to proceed with the project of G3TXQ, the antenna version with 1:4 balun and single wire. I will use the same kind of fishing rods in your pictures produced in Italy in fiberglass and with a really good price (Lineaeffe Delta 4mt. rods). The balun in a Guanella current balun and is as a 1:4 impedance transformer as an rf choke.
      I will begin collecting the needed stuff in the coming days and keep you informed of the project's developments. Thanks again for your suggestions and best 73's de
      Federico IW0RBS

  17. Richard, I have built the G3TPW version since I live in a noisy urban area, and the doubly folded dipole could help in that respect. Since mine lies on thick fiberglass insulation batting in my attic, I need minimal support structure. To make a long story short (and it has been a LONG story), the antenna is now semi-functional, usable with a tuner on 10 and 12 with SWR <= 3. a) After having horrible SWR problems, a friend suggested I should tie the two conductors at the end of each element. I had not seen this mentioned before and photos do not show it. It seemed to help - maybe coincidentally - on some bands but not others. Do you have any experience with this? b) The gap between element ends seems to have a significant effect. c) Someone earlier asked about determining short points for 6m. In another article I found a formula: Vf x 492 / fMHz. I worked backwards from the values in the table in the Kerry ARG site to determine a Vf value of about 0.28 (although I suspect that the velocity factor is actually double that value). I also experimented with trying to move the short points, using pins - a pain the the ... - but found it wasn't worth the trouble. So, to determine a short point, use 0.28 x 492 / fMHz - in feet. If you want to get really technical, Vf depends on the wire you use, but this seems close enough for ordinary speaker or lamp cord. d) I'm interested in a 30/40m version - in the attic, not outdoors, on a separate coax from the 20-10 antenna to avoid problems with harmonics. Any experience here? Thanks! Bob KE8VU

  18. Hi Bob, Having the Cobweb in the attic does cause some issues as I found out. The SWR with mine was also all over the place (mostly because of all the wires etc running thru my roof)and it was only sorted with a good analyser and plenty of patience! I have not seen the two conductors tied at the end of each element. The gap between elements ends does have a big impact and there are various gap measurements you must follow for each band. Moving the short points via pins is slow but worthwhile (as you have probably found out). Unfortunately I never got round to a 40 or 30m version due to size restrictions at my QTH, instead I went with an inverted dipole for the 40m and a 30m vertical with about 60 ground wires at various lengths laid out, both antennas seem to work well.
    73s Richard

  19. Hi Richard, I am in the middle of building a G3TXQ-style antenna. I'm a new ham, and I am just now setting up my base station, and the CobWebb will be my starter antenna. I see that you wrote: "The gap between elements ends does have a big impact and there are various gap measurements you must follow for each band." Wow. That's the first I've heard of that. Would you mind posting the list of those optimal gaps, or providing a link to that information? I've got the fiberglass spreaders ready to string, so I've tripped across this information just in time, it appears!
    Many thanks!
    David K6DKA

    1. Hi David, yes indeed the gaps will effect the SWR of the antenna, you need to follow the G3TXQ link to make sure you have the elements cut to the correct lengths, then each length gap will need a very slight adjustment by measuring the SWR using something like an MFJ 259 or similar to get the accurate SWR. By doing this in theory you should get 1:1 on each band but inevitably it will range from 1:1 to 1:5 or higher! The build is fairly easy (especially if I can do it!)I have plenty of links on this site for cobweb measurements. I found it more difficult sourcing the poles (which you have) and coming up with a good strong clamp for the centre! Good luck in your build and please let me know how you get on. 73s & Merry Christmas.

  20. Hi Richard,
    Yes, I have an MJF 259 (brand new) (I expect to be making more homebrewed antennae down the road), and was planning to make all the gaps about 4 or 5 inches wide, held by knotted shock cord, and vary the length of the wires themselves from a few inches longer than given on the G3TXQ down to whatever gives the optimal SWR. I've designed and made adjustable gizmos that employ small hose clamps that can be loosened and moved along the length of the spreader. If I could post a photo of one I would, but I don't know if this blog has that capability. Anyway, as I shorten the wires, I intend to take up the slack by moving the gizmos until the shock cord tensions. Does that sound workable to you?
    Merry Christmas and a big 73 to you and yours,
    David K6DKA

    1. Hi David, Yes that sounds about right. Provided you have measured out the element lengths beforehand you should have a small amount of adjustment and with the slip cord you'll be fine. If you intend to build more antennas do have ago at a moxon, dead easy to build and great fun with a good gain. For 10 or 12 meters they are a reasonable size and if you can get them up to about 20 foot high you'll have some fun! 73s & Merry Christmas.

    2. And a Happy New Year!

  21. Thank you for the very useful information and comments. I am just about to complete a G3TXQ and it is nice to be aware of any snags which might occur. I suspect the final tuning might take a while to obtain a good vswr. How much change did you get in the vswr when changing from about 6 feet when setting up on the ground, to 30 feet atop the mast. I plan to use the CW end of the bands.
    Regards, John (G0KFM)

  22. Hi John, thanks for the kind comment, From testing at around 6ft The SWR started at about 1.3/1.4 and once raised dropped to 1.0/1.2. So there is a small difference to see. If you can't get any element lower than approx. 1.3, do raise the whole antenna and see what you get at the working height and you'll be surprised!

    - 73s Richard M0AUW

  23. Thank you for this awesome content! I am in the process of the G3TPW build from scratch. I am trying to determine how much wire to initially fold over for the end loops. I am not sure if I should initially fold at the design specified length point (5310mm, 4400mm, 3440mm, etc) and let in/take out from there, or if that length already took into account the loop.

    Any feedback would be helpful. Thanks!