Ham Radio - The Doublet. An old but good multi-band single dipole antenna. Part 1

Kevin is right about the benefits of a doublet. I used one from a 2nd story apartment in Seattle for a few years. Doublet was 42' long (including the 'end drops'), bare #14 copper wire and used with 20' of homebrew open wire feedline. This I connected to a homebrew 'Z-Match' tuner on my bench. Coax was maybe 2' long. The doublet ran kitty-corner from living room to bedroom and dropped down vertically maybe 6' on each end. I worked all over the states and the world- from an apartment, using QRP. I could opeerate on 40 no problem, and even on 80 but had to retune the Z match whenever I moved more than a few KHz. lol. Worked all bands from 80 to 10. And not with a shiny new rig.. it was my Heath SB-101. Haha. Nice vid Kevin. Thanks OM & 73

I made a doublet by splitting speaker cord into a doublet and using the non-split speaker line as a balanced feedline. I made it on field day 2019 in about 30 minutes and used it to operate using QRP power. What fun that was. I heartily endorse the doublet!

Great video Kevin - I am a long term fan and user of the simple doublet. It knocks spots off 9:1 random wires in both receive (S/N) and RF radiation. Doublets also work well as long as the length is at least 3/8 wave of the lowest frequency. So 50 ft is ok for 40m and up and 100ft should be fine for 80m and up. The ladderline can also feed into the tuner via a 1:1 current balun if the ATU is not a balanced tuner. The trick here is to keep the coax between balun and ATU as short as possible - less than 10 feet is ideal.

This is the optimal antenna for my 5 watt G1M. I fussed around with EFWH, bought Times Microwave RG8X coax and made an "improved" 49:1 balun. But really, ladder line is the way. I use an Em-Tech ZM2 tuner which is also light weight if a bit bulky. To make mine portable, I built it around a wire wrapper and used really tight fitting banana plugs to make the feed line pack easier. I put it up with a TacMini fiber glass pole (17 feet) and run as inverted Vee. I wish I could have made it a folded dipole but that just wouldn't be compact enough for a back pack already stuffed with other crap for camping. Grateful for this video as it helped me get motivated.

Most modern tuners now have a 1:1 current balun that does not do any impedance transformation. A 4:1 balun like the ones that used to be in turner which was a voltage balun was very inefficient unless it was feeding a 200 ohms load. Since the load impedance varies widely in this application, the manufacturers have finally got smart and started using the more efficient 1:1 current balun that maintains efficiency over a wide impedance range and also converts the unbalanced output of the tuner to that of a balanced condition - a win win situation !

Dude I’m a software engineer and this is so intimidating to me. It’s a pleasure seeing you explain seemingly complex concepts in clear and easy to understand ways.

My 102 feet doublet with 4:1 balun is the best antenna I ever used for sure... Cant believe have many years I messed about with every other antenna going until i tried it out...

Yes I made one of these a few years ago, 110 ft long, and it worked well, out performed a 40-80 trap dipole....from Fred in England.

One of the best antenna we have used, after testing we ended up using this antenna as the ONLY antenna for H.F that is worth our time ( we tested it against other antenna such as multiband verticals and yagi's). Our feed line goes through an open window directly into the antenna tuner ( avoiding using an external balun ). At first we were worried the metal frame of the window will interfere, but found out that the effect was not felt at all ( even when we close the window onto the line ), but then again, this is the only spot were the balanced line could " see" metal. Do try this antenna , it's worth the time. VK4BYE, VK4DJZ , VK4CPR

I use a doublet of ~ 2x12 meters and a tuner, works fine on 160m to 10m. From the tuner i run double coax through the wall and then window line to the antenna. The double coax has center wire as "ladder line", braids connected to each other at ends but not to ground!

Something I’ve seen suggested in bringing window line inside through a wall is to attach each side of the window line to the center conductors of two lengths of coax, then bring the two lengths of coax indoors, leaving the shield unconnected. This will keep the feed balanced yet shielded. Also, IIRC, there used to be a form of ”shielded twinlead” that might also work. 73 de AF6AS

Thanks Kevin, I have been using a doublet about 115 feet long since 2016 and have an outdoor remote tuner (with NO balun) that can tune from 80 through 6 meters even though the tuner is not specified for 6 meters. The wire is just THHN house wire with the insulation on. That does lower the velocity factor a little so that helps with the lower frequencies some. Oh, and I just use some 300 ohm TV twin lead to feed it since I bought out a Radio Shack store when they closed and were selling 100 foot rolls for one dollar. The trick to using a tuner without a balun is to float the tuner at RF so it is NOT grounded at RF (It IS grounded at DC). The tuner I am using is an SGC-239 which is NOT an outdoor tuner, but I added my own waterproof NEMA 4 enclosure. I know the loss from the 300 ohm line is greater than the 400 ohm window line, but it is what I had. I may replace it one day or try some 300 ohm window line which is available. I wanted to thank you for this video since I have found it hard to convince people that an antenna can radiate just fine and NOT be resonant. I have been watching your videos at night on my ROKU box for some time, but there is no way to subscribe or like so I finally decided to get on the computer and do both! Keep it up, this is one of the best things I watch anywhere.

I've been looking forward to this video. I always enjoy these videos and I always learn something and usually quite a bit (mostly limited by my old brain's ability to store new information). I particularly appreciate these technical videos with links to curated articles that keep me from doing the work to search for good articles on my own. That PDF is a keeper. I saved it in my ham info folder. Looking forward to Part 2 for the operation and performance of your doublet antenna and the 700mW CW transceiver.

What I have found in my experience with 450 ohm ladder line is that it's okay to go directly across, for example, a metal window frame for a sliding window, but not okay to run it parallel but very close to, for example, an aluminum gutter on your house. The idea is that any metal near the feedline runs the risk of creating an imbalance in an otherwise balanced feedline. Where your metal object encounters the feedline is where the risk of introducing an imbalance is greatest. But, as long as the effect of the metal object is essentially equal to both sides of the feedline - like when you run it across a window frame at 90 degrees, the effect to the balance of the feedline is minimal. On the other hand, when running alongside and parallel to another conductor, like an aluminum gutter or tower support, where one side of the feedline is closer to the conductor than the other, the imbalance is far more pronounced and problematic. This is why I prefer my fiberglass portable masts when using ladder line and my aluminum portable masts when using coax. Another nice thing about using ladder line is that it is very lightweight and is easily suspended between two supports when feeding a center fed wire antenna, like a doublet. And, I like using a doublet and a tuner because it also makes shortwave listening on non-amateur frequencies more effective. Thanks, for the video! 73 AI4IJ

If there was anything that Leroy B Cebik (SK) didn't know about antennas, it wasn't worth knowing.

20 years ago I bought a antenna called an "All Bander". The reason I didn't build it was because I couldn't buy the material as cheap. It included 100 ft of 450ohm ladder line feed line, even insulators and rope on each end. The cost back then $29.95 and after i realized what a deal this was I ordered a 2nd one. I run this antenna everyday mostly on 75m ssb phone and it is a tiger. I run the 450 line all the way into my basement shack to a Palstar 4kAT tuner. It included a 1-1 balun and has been up 20 years with no trouble. I did make stand offs coming down my Rohn 45g tower about 2ft from the tower spaced every 10 ft and twisted the line several times on the way down the tower to prevent catching the wind and keeping it stiff. BTW the 2nd antenna is still in the package safely stored away.

I have used a doublet fed with ladder line and still do. The advantages I’ve seen are, it’s cheap, it’s easy, and it works very well on every band. The only disadvantage I’ve noticed is it would be impossible to use mobile in motion. Using it from a stationary RV however, would be a different matter entirely. 🙂

Thanks for sharing. Antennas are always so much fun. Never ending story 😉

Good video. I have only 55ft of horizontal run space on my townhouse roof. I set up a doublet 50 ft horizontal run with ends zigzagged to fit for a total of 105ft. It is fed with about 20ft of ladder line to a 4-1 Balun attached to an LDG remote tuner followed by 100ft coax to the rig. It tunes 80 to 6 m. Tom kp2ch

Many, may moons ago, my Elmer talked about the value of Ladder Line and I dismissed its use because it was ugly/messy/sightly and old fashion. I did use it on occasions but was never an enthusiast. Kevin's presentation and his references shows that I should look for ways to utilize Ladder/Open Lines and it should be foundational especially when operating QRP. The difference in line loss between coax and ladder line when an SWR is present is amazing. Another great presentation of practical know-how and experience, with test results, from Kevin. ThankYou Sir....