Adding an ‘Ugly’ Balun to My End Fed Antenna!

Performance of the End Fed Half Wave antenna (EFHW) which I bought recently has not been good on 40 m, due to compromised mounting as a result of space constraints at home. My friends advised me to try adding a 1:1 balun in addition to the regular 49:1 balun at the feedpoint, to avoid the unbalanced current on the outer surface of the coaxial cable shield, also known as common mode current. As I did not have a regular 1:1 current balun at hand, I thought of adding an air core balun made out of surplus part of the feedline itself. Looked around for a three inch PVC pipe and found none in the store. It was then that the nice PET bottle in the kitchen table attracted my attention. It was exactly three inch in diameter.

Started working on it after documenting the initial VSWR on 40, 20, 15 and 10 m amateur radio bands. It was 1.9 at the lower end of 40 m band and 1.1 at upper end of the band. On 20 m it was 1.7 at lower end 1.0 at upper end. On 15 m it was 1.08 through out the band, while on 10 m, it ranged from 2.5 at lower end to 2.2 at the upper end.

Surplus HLF 200 cable in the shack was just enough to add 4 turns on the PET bottle with 3 inch diameter. Total length of HLF cable from radio to 49:1 balun was only 10 m, with precrimped PL 259 connectors at both ends.

Though there was no significant change in the VSWR on 40 and 20 m, there was a sharp rise in VSWR on 15 m band to 2.5 at lower end of band and 2.2 at upper end of the band. There was a minor drop in VSWR at the upper end of 10 m band to 2:1.

So I thought of adding one meter patch cable with precrimped PL 259 connectors at both ends, which I had as surplus, using an SO 239 barrel connector. Rechecked VSWR once again, keeping the patch cable in almost a U shape.

There were only minimal changes in VSWR across all four bands, as expected, by adding one meter length of patch cable.

As the final step, I coiled the patch cable on to the PET bottle so that almost three turns were added to my ‘ugly’ balun, with an SO 239 barrel connector in between.

There was no significant change in VSWR on 40 m. VSWR on 20 m improved a lot with range being 1.1 to 1.0 across the whole band. Change on 15 m was minimal. Improvement was noted on 10 m with 2.0 at lower end and 1.1 at upper end. All these values across the four bands were tunable using the automatic antenna tuner of the radio. Testing on 40 m was done after that and a couple of friends noted significant improvement in my signals while another could not find any change. Anyway I am quite happy with the audio recording sent by one of them.