5/8 20m antenna

For this year IARU Contest I decided to add to my antennas farm an omnidirectional antenna for 20m band. 20m still seems to be the most important band despite the generally bad propagation on higher frequencies. This band is considered as "best DX band" so many stations have good antenna systems here. The analysis of the last years contest show that most of QSO is done just here.

The choice is the 5/8 vertical antenna - has the lowest angle of radiation from all verticals and I already have 12m masts necessary for 20m antenna.

I found interesting website related to this kind of antenna: 5/8 Wave vertical antennas for HF

First I have destroyed some old power cable to get wires for the radials. Got 12 x 6m radials and equipped them with 3mm connectors. Recommended is more radials (at least 16) so maybe will find some new "old" power cable and make some additional ones.

Next I cut 12.5 meters of the wire for the main element. It was expected that will be too long (calculated value was 12,14m but finally was just perfect).

The 5/8 requires additional coil in the bottom. I used the variable coil from some old russian military radio.

Today early morning I visited my "antenna field". After erecting the mast I connected the VNA and measured the resonance frequency. According to description the resonance freq should be x/2.5 of the freq where the antenna is supposed to work. My resonance was at 5.7 MHz what gives 14.25 MHz final freq. Ok for contest, for CW operations will have to make it little bit longer.

Finally connected the coil and using variable slider fine tuned the desired 14,25. Connected to radio antenna works with SWR 1.3 in whole 14MHz band.

I listened for a while - probably my "DXes" were still sleeping because I could hear only the local stations (Germany, Italy, Malta, Poland).

Screen from RBN:

Not bad...