June 2022 - A new inverted V doublet

Six months on from moving our home to Gloucestershire and I had still not managed to do anything about an antenna.

My good friend Ian G3ROO decided there needed to be an intervention. So before his visit I sank an 8 foot by 4 inch fence post into the ground with enough concrete to keep it there long after I am gone.

The post would support an 11 metre tall Spiderbeam pole but with the top two sections removed. This pole was transplanted from my much smaller Dartford location and has proven to be up to all the weather can throw at it. These are not the same as cheaper telescopic fishing rods and they are well worth the extra cost.

Ian was keen to replicate the versatile wire antenna at his Dover location and which was the subject of an article in September 2002 Radcom. [The G3ROO multiband Multimode Antenna]

Using the same dimensions as a G5RV, the top length of 102 feet my antenna slopes at each end to a height of around 10 feet. That saves me the bother of erecting poles at each end to support a flat top.

The resulting aerial appears in the photo below.


The spiderbeam pole is guyed half way up and that I think is necessary.

The photo below shows me fitting those guys. It was perfectly safe because Ian G3ROO was footing the ladder to stop it slipping. - Except when he strolled off to take the photo!

adding guy ropes

The ATU was sited remotely at the base of the Spiderbeam pole with RG213 coax running to the shack. Also run was a Cat 5 cable to provide 12v DC to power the ATU using one pair. Later another pair would be used to operate remote relays to switch the aerial into Marconi "T" mode. But more of that in a later article.

A simple 1:1 balun was constructed to convert the unbalanced ATU output to the 300 ohm balanced feeder that was passed up the inside of the Spiderbeam pole - making a neat installation.

The results from the doublet far exceeded my expectations. Certainly my new location provides a far less noisy environment than my old home but the height of the new aerial must help enormously. I had a doublet before but it was lower and much shorter. Surprisingly, the ATU did manage to get a match on Top Band but Ian thought it could be improved if we could arrange to remotely strap the legs of the feeder together and load it against ground. This is the Marconi "T" configuration and I resolved to build this unit at a later date.