Since my first Sota activation in 2013, I have only used a 20m long efhw. I almost throw the wire into a tree using a 20m long plastic cord. In the meantime I was able to improve my throwing technique.
The inv vee with a height of 12m and an acute angle creates a very flat beam angle at 30m and 20m . The gain is mostly near 0dbi in all directions. On 60 und 40m of course the wanted steep radiation.
73 Chris
Setting
I do not understand arithmetics.
c^2=a^2+b^2
12 m height, 10m and 2,5m sides???
1:49 transformer is high in the air and not on the ground?
N
Yes, the transformer and the ends of wire are 2.5m over the ground. On both ends are cords and hold the wire.
73 Chris
Hi Chris,
So this is a 40m band EFHW that also works on 20 & 30m? Interesting radiation patterns on 20 & 30m - as you say, a low take-off angle, for DX contacts.
As well as the 49:1 UNUN do you also use an ATU?
(I’d be interested to see how this works on 17,15,12 & 10m - I suspect those two WARC bands might not work too well as they are not related to the other bands).
73 Ed.
Hi Ed!
Yes, for the bands 60m, 30m, 17m and 12m I use the ATU from the KX2. But imho without noticeable disadvantages compared to real half-wave antennas.
Apart from the radiation pattern from 17m and higher. That’s why I’m planning to use a second vertical EFHW with a length of 7.5m, which will then cover the upper bands.
73 Chris
Hi Chris,
Interesting patterns.
I was under impression that apex angle should be larger than 90deg, could this be explanation why antenna gain dBi values are relatively low?
73 Marek
For the last two activations, I set up two EFHW and switched them over using a antenna switch.
The vertical for 17, 15, 12 and 10m was better by 1 to 2 S steps on this bands.
73 Chris
For WARC bands you can cut the wire at the half wave points, 7.85m for 18.080 and 14m for 10.120, for example.
I made it for two times, one with cocodriles and another with fastons, here is the pic, same for 30m. Then you got in the same antena: 10, 15, 17, 20, 30 and 40, for example.
If one is going to the trouble of multiple links, you might as well make a linked dipole. For me the benefit of an EFHW is its simplicity of use and I accept its performance is not quite as a good as a [linked] dipole. I have both and choose which one based on summit and/or events.
My LNR Precision EFHW has a removable SMA plug link to shorten the length for 30m or lengthen it [to 19.8m] for 40m and 20m. Fortunately, the excellent internal ATU in my KX2 makes the EFHW usable on 17m - 10m.
I feel the same way. To change the bands in a matter of seconds is a big advantage with my hobby horse, the S2S contacts.
I couldn’t tell a noticeable difference in performance between a traped and a tuned EFHW.
73 Chris
An EFHW is still much more convenient. There are half as many links to change and for some bands you don’t need to change a link at all. For example the 40m wire also works on 20m.
