I guess this won’t be read by anyone but I have to make these notes on an experimental antenna I have made.
If I don’t all the paperwork will be lost and this idea may be lost forever.
It may have been made before information may be on the Internet about it but I have not found it yet.
After building an Extended Double Zepp for 15m of good quality wire and the feeder continuous from the top elements, it worked even better on 40m so that’s the band I am now using it for.
I am not an expert on antenna theory or Smith Charts ext., but I thought there must be something that makes it better than dipole cut for 40m.
It’s obvious that 7 MHz is x 3 for 21 MHz so that’s where I started, I wanted an antenna for 80.
I wanted a frequency of 3.740 so I times that by 3 and came up with 11.220 then I divided that into 598.5 and came up with 53.44 feet per element.
I built the antenna and put it up but when I checked the resonant frequency of that with an analyser on the open feeder it was 4.256 MHz.
With the feeder at 3.66m I increased that to 4.66m but only brought down the resonant frequency down to 4.100 mhz.
I looked at the frequency I wanted which was 3.740 and the difference to 4.100 or so, I decided to take the difference from 3.740 which was 516 kHz.
Unfortunately I made a mistake doing this subtraction and ended up with 1 kHz less, my frequency calculation ended up with 3.124 mhz.
So with this mistake I carried on and x that by 3 and the magic number of 9.368, divided that into 598.5 (EDZ formula for top elements), so the final top element came up with 63.88 feet per element.
So with that in mind and nearly forgetting where and how I got there with all the scraps of paper, my final top elements are…
19.44m per top elements feeder 4.66m into 1 to 1 coax coiled balun into 50 ohms.
Reports so far have been outstanding at my qth never before in 15 years have I ever got out so well on 80.
This antenna will require an atu and is 80m only.
