RaDAR – Deploying the 160m end fed half wave antenna

You need good height and preferably vertical polarization if you wish to work DX on the top band. Well that is quite possibly true but what we did here, with a relatively ineffective antenna, didn’t make the fun any less. It worked! Don’t be deterred by the “impossibilities” we sometimes encounter in our ham lives …..

From a previous post on modifying the MFJ945e ATU to that of an end fed tuner, after many strange results I stripped the wafer switch from the equation and also found one of the capacitor plates shorting during rotation. It was evident while looking at the signal on an oscilloscope and finding the signal dissapear while tuning! The ATU was second hand with an unknown usage history so difficult to say whether damage occurred some time during it’s life.

The 32 uH inductor wound on a T157-2 toroid wired directly without any switching (Besides the ATU bypass switch)

The variable capacitors wired in parallel to give a maximum of 200 + 200 = 400 pF

I bought a roll of a 100 meters of 1.5 mm pvc covered copper wire usually used for house wiring of lighting circuits. The idea was to unroll the wire without kinks and tangles in the veld! Young Eduan, my grandson, and I took on the challenge in my “RaDAR playground”. It eventually became fun for him and he wanted to take part in all the deployment activities including the roll of RaDAR photographer!

We used the trees and bushes as supports for the wire, using a rock and throwing the wire over them as we progressed towards our home around two hundred meters away.

Some trees or bushes were bigger than others and not necessarily in line with one another but we zig zagged between them, the sole purpose of getting the wire off the ground through it’s entire length. Darkness was setting in, we had to move fast!

We eventually got home but there was no time to go back and I had to be happy with the hope that most of the wire was hanging between the trees!

The calculated length of the 160m half wave end fed was 79.5 meters so I measured 20 meters of wire while reeling it in and cut it off hoping that the total wire length was actually close to 100 meters long as advertised on the label! I connected up the FT-897 and modified ATU and the best I could get was around 2:1 SWR with a slight dip when tuning the capacitors but the capacity was not much and should have been around 200 or so picofarads ….

I called on 160m, Johann ZS4DZ heard me but could not hear what I was saying but through many retries we completed the QSO. Lukas ZS6LH just made out what I was saying, my audio was so distorted. I thought RF was possibly the culprit and then I did something which I don’t normally do running end feds on 40m and higher. I used the 20 meter piece of wire which I cut off as a counterpoise off the GND terminal of the ATU and just laid it on the ground, walking around the building. I could then get around 1.1:1 SWR on the ATU’s meter and that of the rig and then I was getting clear reports of 59+20 and the evening was still young as far as NVIS propagation was concerned!

I came back a little later and there was Ed ZS6UT, he was pushing my S Meter further to the right than I had ever seen …. is that 59 + 60dB ??? There’s around 300 km between us.

I wasn’t really part of the top band contest as such but I could give a contact to four participants before packing up. Unfortunately no CW yet there were CW capable operators on the band.

I went back yesterday (Sunday) afternoon to tie down the end point for use on another weekend. I found it lying on the ground and one or two places where the wire was sagging between the trees which probably accounted for the low capacity settings on the ATU!

The wire is tied down nicely now and nicely tensioned too. Possibly the 160m end fed wire could be used for the higher bands. It’s pointing NNW so it could be a good “end fire” system for DX on 40m or 20m !!! The next test phase …..

As always, it was fun. And I learnt that a counterpoise IS required, however small but it IS REQUIRED if only a SINGLE wire lying on the ground!

73 de Eddie ZS6BNE



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