Upgrading Modified Inverted V to 40/20 m Dual Bander Antenna

I had homebrewed a Modified Inverted V 40 m Antenna to fit in the limited space in my compound. Yesterday I could hear a VU station from the North at nearly 2000 km from here, loud and clear, on 20 m. But the built-in antenna tuner in my radio would not tune for 20 m, as expected, being second harmonic of 40 m, and not an odd number harmonic like 15 m. So I thought of adding a 20 m dipole as a fan dipole antenna on the same feedline. I could bring down the 40 m antenna quickly as I had put a pulley like mechanism using nylon threads into a hole near the top of the 6 m GI pipe used as the mast. Instead of de-soldering the SO 239 joint, I thought of adding 5 m of insulated 2.5 sq. mm copper wire on either side of the feedpoint after removing the insulation of the existing antenna a few centimeters from the feedpoint.

That lazy method was chosen to avoid re-soldering the  SO 239 joint which sometimes result in dry solder even with my 65 W soldering iron. But things did not turn out to be so easy for me. Murphy’s law came into play soon. By the time I had fixed the two limbs of the 20 m antenna to the existing 40 m antenna, the soldered joint on SO 239 gave way! I had to resolder it. Then I tried to pull the new fan dipole antenna up, the nylon thread used to make a pulley mechanism gave way! So I had to untie the 5 ties on the GI pipe and bring it down to recreate a pulley mechanism.

As the pre-drilled hole was about 1 foot below the top, I used an insulated aluminium wire to make the pulley system and have it at the very top using another round of winding at the top. Though I should have anticipated it, after fixing the GI pipe with thicker nylon rope and raising it up, the moment I started raising the antenna, the ring of insulated aluminium wire at the top gave way and slipped down! Not only that, the nylon rope, this time a thicker one, used to pull the fan dipole antenna up, got stuck within the turns of the insulated aluminium wire. Instead of raising the antenna 1 foot above the previous position, I ended up having the antenna over 1 m lower than the previous position. So that is Murphy’s law: “Anything that can go wrong will go wrong” or better put as: “Anything that can go wrong will go wrong, and at the worst possible time.”

I didn’t want to test Murphy’s law further and stopped work for the day, and tested the fan dipole antenna. 40 m component has an SWR of 1.1:1 at the lower end of the band and 1.9:1 at the upper end of the band. On 15 m, the values are 1.6:1 and 1.8:1. The ratios were the other way round on 20 m, with 3:1 at lower end of the band and 2:1 at the upper end of the band. I could hear some stations on 20 m after the antenna experiment. But I was not able to work any stations on 20 m, though the built-in antenna tuner in my radio is able to tune it well. On 40 m I am continuing to work stations, and today’s distance record was 1000 km, almost twice that of previous personal record, probably because of better band condition, as the antenna was lower. I am yet to work any station on 15 m either.