The Doublet Antenna in Practice | Ham Radio
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- Опубликовано: 27 дек 2024
- The Doublet Antenna is one of the most popular HF antennas, and the G5RV is a good example of the antenna. Peter G3uOJV takes a look at the practicalities of installing this antenna in the average domestic garden,
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I love the clear explanation and plain language you use in this video. In so many YT videos I watch, one almost has to be a radio engineer to even understand the subject matter. Thank you
Peter, your timing is perfect. I have wanted to try a doublet for some time. I was worrying about achieving a perfect half wave feeder length at 90 degrees to the antenna, and had assumed that I needed to put the balun at the base of this and run the coax for the full horizontal run back to my shack. Your video shows how simple, easy and cheap this project can be. Thank you, I know where to buy the bits!
Kevin, MW0KXN
I have a 40 metre doublet in my roof space, with only 8 metres out horizontally, I first took the feeder back to the shack then through a commercial 4:1 balun into my atu, I was disappointed with the result, my fan dipole out performed it greatly, I decided to use my own homemade balun instead, also cutting the twin feeder so it only hung vertically, then joining the coax at that point, it made a huge improvement, and I use it for every band 40-10, on 15 metres it is terrific, for an indoor antenna it's quite amazing.
Reminds me of the advice I had when I was first Licensed, nearly 40 years ago. GM3OXX told me to put up the longest wire I could, as high as I could, cut it in the middle and feed it with ladder line. I did, used a balanced ATU / Z-match, and worked loads of stations with QRP. Never had a house since that would allow the same set up. Keep thinking of a remote ATU to do the job. Thanks for sharing Pete.
Hi Steve - that was great advice. Remote ATU gives you all bands or EFHW is cheaper option but less bands.
Thanks peter, really great and clear advice on the subject, especially about off centre feed points...
Just made and installed a doublet, 7'5m each leg, (2:5mm cable) and approximately 6 metre's of 450 line, terminated into a 1:1 current balun, then a short leg of RG8 into a LDG external tuner, Great on 40 , worked A6 on 12 SSB first QSO, and Italy on 20 , doesn't like 15 or 17metres... only 4 metre's above ground, but then I've QSY'd from Dorset to a inner Hebrides island... loving zero QRM again.. cheers Andy MM0###...PS about 20 metres of RG213 into the shack
Thanks for the update Andrew
Great point about being off center to avoid interaction with a metal mast. I pull the window line to a 4m wood post that is near the house, so the ladder line does not drop vertical, but comes off at an angle. Same thing only different.
I must say, so far, of all the wire antennas that I have tried, the doublet is by far and away my favorite antenna.
Another great video with a number of ideas for making the doublet work in many different locations 😃👍!
Thanks 👍
I tried the doublet on a visit back to the old house in Ireland, just used some single house wiring cable and some
Plastic pipe fittings to assemble it. I had spare ladder line.
It’s still laying on the grass across the field but I connected it up and massive signals
appeared. Made a few contacts with FT8 and checked PSK reporter and there were 132 reports. The most distant was PY5EG on 40 Mts.
I did not think it would work laying on the ground. I might try and sling up today. Once I tuned it on 40 the SWR was low
on all the bands going up to 10 Mts without touching the controls on the ATU only 80 showed high SWR without
Changing the settings. Mark EI4JD near Shannon
Thanks for such a thorough video. I already have the requisite materials and was thinking of eventually erecting a doublet, but this gives a few more ideas as to how to fit it within my tight garden and get back on 80m in time for winter.
The days of open line are far from over. My situation: 2 x 59 ft doublet with open line all the way into the symmetrical tuner. Spaced with 4 inch rose clips and fed through the wall at the same spacing. From the end insulator to the tuner is one uninterrupted piece of wire, so no corrosion in the feed point. Worked 1250 miles on topband, 80 and above perform (much) better. Forget coax and the balun.
Great to hear from you.
I have a doublet. Originally it was a 40m long inverted V with 100ft of ladder line hanging from a 25ft flag pole. Oddly, it was difficult to tune on some bands. Based on a web site I visited, I shortened it to 110ft (55 on each side). Now it works better on most bands. It's confusing to me why shortening it would make it better, but I'm just happy it seems to work. The worst part about it is that the two legs are 90 degrees from each other, and one leg bends at the end of the fence and runs a few feet along the fence parallel to the other leg. I call it a "perverted V" antenna. I have a small back yard and a nasty HOA, so it's the best I can do.
Hi Peter a very interesting video and well explained iv been using a doublet antenna for many years it’s so simple and works well I bring the ladder line down to just outside the shack where it’s connected to an sgc 230 auto atu which is flouting above ground as these is only a single wire connector for the antenna the other side of the ladder line goes to the ground of the atu then a short run of coax to the radio it tunes on all band no problem 👌
Great video. I haven't had a doublet in 8-10 years, but I think it is time for another one as they are fun and highly flexible.
My last doublet was a coax fed OCFD dipole that swaped the coax out for 450 Ohm ladder line. I had a blast with it until I got it stuck in a tree on a QRP outting and ended up pulling it apart. I ended up loading the rain gutter on the park pavillion to make contacts on 20m & 40m.
I have picked up a few ideas that I will try on my next doublet. Cutting the antenna a little short to about 3/8 wavelength and feeding with a minimum greater than 1/4 wavelength of ladder line. Sweep the antenna. If one of the higher bands presents a particularly high SWR trim the feedline by 1/8th wavelength of the higher frequency.
The past few years I have mostly used an 80m-10m EFHW for portable operation. It is easy to deploy and allows 80m NVIS which I am fond of for Ecom.
Thanks so much, Peter. These basic instructions are just what I need as a new ham. Bests.
Great video as usual… now I have a friend that runs his feeder line straight up the metal pole to the AntennA and he says it doesn’t make any difference it would be interesting to do an AB comparison between the ladder line being next to the Metal mast and the ladder line away from the metal Mast
I feed mine in the middle but use a fibreglass push up pole. works great
Yes good option although not as strong as a metal mast for greater height
Peter
Thanks for a clear video on doublets. I am 85 years of age, am newly qualified (Intermediate, so only 50w) and am proposing to put up a 40m doublet on the upper storey gable end, with the last few feet of each half wrapped around the soffits front and rear at right angles. I’ll use a 4:1 balance as you suggest. The ladder line drop down will be clear of metal but close to brickwork. What are my chances?
Ladder line near brickwork is no problem. I t all sounds OK. Congrats on the licence.
@@watersstanton Thank you!
I've got a 2x20m doublet with added loading coils at each end and 5 metres wire connected to those to get it to just about match on 160m. Nine metres vertical drop of home-made open wire feeder to a 4:1 balun near ground level, fed to shack with 20 metres of RG213 coax. The matching unit should really be where the balun is, but that just didn't work for some reason and kept getting unpredictable matching...
Best way to feed a Doublet is using a open feeder or ladder line into a true Transmatch followed by a BalUn with a bit of coax going to the transceiver. Only challenge is to manage the Transmatch outside.
Take line through wall into a balanced matching unit and forget the Balun!
@@watersstantonstill need to go from balanced to unbalanced using a 1:1 balun
A very good Friday afternoon to you all from Wellington Somerset
Thank you sir, for Youre lecture in This. I Will create a inverted V with an open feed line 450 ohm And let it run through a FC902 To my FT902.
73” Theo PA3GSR
Interesting. I hadn't thought of a doublet that wasn't center fed before. But if the antenna legs are not equal, does that not mean that the feed line itself will begin to radiate all the way back to the balun since the currents on each side of the ladder line are no longer balanced? Also, doesn't it become more of an end-fed wire antenna when it is off-center fed? That would mean a good ground or radial system might be needed to keep RF out of the shack depending upon the band.
Remember that the balanced line is fed at the TX end with equal but opposite currents. Likewise a balun works fine on an OCF dipole.
John I think you’re right
I would like to put up a vertical doublet. If I attach the ladder line at the center, how far away should it stay from the lower half of the antenna wire? Also, I will be bringing it in a window that already has my ladder line coming in from my 135’ horizontal doublet. Do you think I will be OK if I keep the two ladder lines on opposite sides of the window casing? It would probably be easier to feed the vertical antenna with coax and just call it a dipole. However I would like to avoid the loss of that length of coax. Many thanks. I have learned a good deal from your videos.
I have never used a vertical doublet. I suggest try and run the ladder line at right angles for 1/4 wave at lowest frequency.
Peter, I'm anticipating the arrival of my new Palstar AT2K ATU. I'll be feeding a 160-10m doublet. My dilemma is 450 or 600-ohm balanced line. And, the Palstar doesn't have a built-in balun. It does have a Balanced Line SO-239 input, which requires "either a 1:1 or 4:1 external balun". Can you add your thoughts on the ohmic ladder line and which balun would be best?
73, Ron - K5RPM
Hi Ron. you can use either open line or 450 Ohm ladder with 4:1 Balun. Both work equally well.
I have a 4:1 balun, too. My tuner can handle the balanced lines, and I could use my window-through panel, but I'm afraid my cat would get burned if she touches the connector. So I use the balun outside the window and feed coax through the window to my tuner.
Is that a voltage balun or current balun?
Well done!
i have a antenna tuner an old yaesu fc707 but its unballanced will that work .m7byf
Thank you for the info and sharing. I am preparing to build this doublet & I would like to ask the feed line location and the length of each side from the feed line for doublet. Do the length of each side matters? Even in inverted V?
No the lengths can be different even in inverted V.
@@watersstanton Thank you. I will built this doublet, I do plan for AH-4 tuner between the balance line and short coax to IC-7300. I have checked on the net, that I don’t need to connect the AH-4 to the ground cable when connecting to balance line.
What is your opinion on 300o TV line over 450 ladder.
450 is more rugged.
asked lots of people.....everybody side steps this question.....on my doublet.....how do I know which ladder line to use.....450ohm or 300ohm.
Nick.
It makes no difference. Once 309 Ohm was very popular. 450 Ohm is wider spaced, bit tougher and handles higher power better. I always go fir 450.
Thankyou Peter.
@@watersstanton
How do you connect lightning protection to it, and/or how do you handle lightning protection at your station in general? 73 DE W8LV BILL
Frankly I unplug the antenna! I am not a fan of lightning arresters as they are really static protectors and most rigs can perform the same function internally. A lightning strike will blow the arrester apart! So unplug!
Hi Peter I’m currently studying for the exam I’m thinking of using this as my first antenna would it be ok if half of the antenna was outside sloping down from my roof line to say 6’ and the other half inside my attic as I don’t have a lot of space
Yes that should work.
Thanks for the explanation. Do you need an antenna tuner if you’re only listening?
Yes you do
Thank you for the information. I need to put up another antenna maybe 2. I don't want them crossing near each other because they will be less than 90 degrees from each other. New to HF and the antennas. Everyone is so up tight about how they can be made. Must be center feed and other little things that must be just right. I want to put antenna and run window line to just before it comes into my attic, lot of power wires in the attic. Put a 4:1 just before it comes into the attic, about 3 meters over then about 3 meters down and around to the radio. I was looking at the 'ZS6BKW ' antenna but not sure I have that much space, and the window line will be much longer. I want to do 40 and above. The information you gave will help me. 73. de
well explained, thank you! very much like a ham said to me years ago, throw a line over a tree and get on the air!
How do you use a balanced line on a yagi , does it also become a doublet yagi
A Yagi has a dipole element so it’s your choice what you call that element! Che k out G4ZU Yagi.
Hi Peter great video has ever , would 300 ohm spaced open wire feeder the same has the 450 ohm you use, make any difference, going to feed it into a LDG AUTO ATU with LDG BALUN. Do have 450 ohm but not so good on the old legs today and would find 300 ohm easier to use. Thanks Russell G0OKD.
Hi Russell, good to hear from you. Yes 300 Ohm should work just as well. In fact that was the feeder originally used in the G5RV. So go ahead and give it a go. 73 Peter.
@@watersstanton thanks Peter, remember you well from my rallying days has a DRM for RSGB and Regional Rep for Royal Signals Amateur Radio Society .
Had to give them up following a dicky ticker ho ho keep safe.
@@watersstanton forgot to say wished I had known about yr videos when I was teaching course's at my local club SNADARC, but grateful to know I wasn't waffling phew 😅 cheers.
Thanks for the nice video
Informative video
Thanks
Mine is 57mts long in a Z shape.....short for top band yes.....but it tunes top band great.....gets out great as well.....also tunes on 6m and performs on 6m as well as my dedicated 6m horizontal....
So from 160m to 6m fine for me via my MFJ 941 matcher/ATU.....
Ladder line terminates to a 1-1 balun.....the via an 18inch long length of 50ohm coax to the ATU via my window frame
Why would anybody consider any other antenna?
Mind blowinging
My doublet is 20+ mtrs short for top band..... but works a treat on 160m.
So I can work 160m to 6m....with the help of my MFJ941 matcher or tuner if you like.
The 450ohm feed line terminates at my upstairs window of my shack at a 1-1 balun....18inches of coax though a hole in the window from to the ATU.
Works great...1 to 1 on all of the above bands.
Why would anybody use anything else.
Sounds good. I belive that manual ATUs often have a wider matching range than many Auto models.
Unbalanced antenna into balanced feedline? Interesting ….
Check out End Fed Zepp.
A * doublet * is great if you want , 9 plus 20 of noise. :(
I get a little worried when hams are using MFJ products? Mighty Fine Junk