I implemented a short/long adjustment mechanism at the feedpoint side of the antenna. That basically adjusts the antenna length about 29 inches (0.73m). I did that to be able to cover the entire 20 and 40m bands with a VSWR under 2:1. The beauty of it is that I can easily adjust it without collapsing the pole. Of course, I only needed to adjust it if/when I wanted to work SSB. What I also discovered is that the short adjustment (antenna 29 inches shorter) lowered the VSWR on 17m to an acceptable level. Perhaps you can call this adjustment mechanism a “link” ;-). Go to my QRZ page and scroll down until you see the diagram and associated VSWR plots.
Yes, links seem to make sense if you want 15m. It is interesting that I got 17m by just shortening the endpoint 0.73m. I wasn’t intentionally trying to tune it for 17m – it just worked out. These trapped EFHW antennas are certainly interesting the way everything interacts! And then you have antenna height and ground conditions that will have an effect on things. I’ve noticed that my VSWR will change when the wind bends my pole closer to the ground depending on activating in the treeline or on a rocky summit. I’m glad a now have a KX2 with internal tuner so I don’t have to worry so much about antenna resonance and such!
My traps reduced the length of the wire required (which is nice) but also reduced the 2:1 bandwidth. Not a big deal if you have a tuner or only work either CW or SSB. Or, just live with reduced power ;-).
attached, please find a sketch of how the antenna looks like in an inverted-L deployment as inspired by Brad’s description on his QRZ page, WA6MM - Callsign Lookup by QRZ Ham Radio, this time with the links shown. I drew this while Heinz was drafting his reply, so likely, his values for the position of the links are closer to the truth. But you have to tune the antenna anyway. My initial lengths for the 3-band version are for SOTAbeams antenna wire and an inverted-V configuration at a 6m mast.
PS: I would expect that in particular on the short bands, the too narrow angle at the top would cancel out part of the RF energy. But I agree that an inverted-L is much handier in terms of deployment.
The next Funktelegramm, April 2018, features a 6 page article about my new EGA30 antenna. An end-fed antenna for 30/17/12m (WARC) with an overal length of 6,6m.
Main focus is the background of end-fed antenna design: how to calculate and solve the math for a cascaded end-fed antenna.
The article is for DIY hobbyists and there are also specific build instructions (value of the coils, length of all antenna segments, etcetera …) to build your own version:
• V.S.W.R: 30m: between 1:1,1 and 1:1,3
• V.S.W.R: 17m: between 1:1,2 and 1:1,7
• V.S.W.R: 12m: ≤1:1,1
But you can also tackle the math and calculate your own version with other bands …
73 de Joerg DJ4WD
PS: If someone is all thumbs, this antenna is also available in my shop www.dj4wd.de …
hopefully necroposting is accepted here. I did not want to start a new thread for asking how to build one of the antennas mentioned here. My interest is a portable 40/30/20 antenna, which works without a tuner and on a 6m carbonfiber mast (Decathlon offers theses currently for the cheap).
I read through the great document linked by @DK3IT and also visited the QRZ.com profile of WA6MM.
I wondered about the materials required. SOTAbeams sells these microtrap kits, but they weren’t referenced here. I can get my hands, in Germany, on T44-6 and T44-2 toroids no problem, but it’s harder to find the mica capacitors. Would others work? Could I instead use SMD capacitor of comparable capacity? I am bit lost at that point
For the antenna wire, I mostly going to go for DX-Wire UL, since sotabeams is out of stock and I can’t find POLYS #26 in Germany.
A source for mica capacitors with a nominal voltage of 500 V could be
An alternative to Polys #26 could be the new micro wire sold by DX-WIRE (I have not yet held this wire in my hands).
73 gl, Heinz
thanks for your reply and the hint to the box73 store. I will check it out and order some from them
The rest of the material I can source from reichelt.
Thanks for your detailed descriptions, also for the coupler.
EDIT: Found a source for my needs on ebay-kleinanzeigen
Please note the information provided by the manufacturer
“We do not recommend this wire for portable operation, DX-WIRE UL or FL is more suitable for this.”