17m dipole antenna for the WARC band
17m band is one of the WARC bands, which I listen to often. 17m amateur radio band extends from 18.068–18.168 MHz. I searched Reverse Beacon Network for a period of previous 3 years. It showed that VU2GSM had been active on the band for the past few days. 4m of wire will be needed on each side for a 17m dipole antenna. Fixed 4m of wire to either side, in an inverted V fashion, with apex height of 7m. Mounting at 7m is above the quarter wavelength mark of 4m and below the half wavelength mark of 8m. Connected the wires directly to a 15m long RG213 feedline.
I made a coil with surplus length of RG213 cable to function as a common mode choke. A common mode choke can prevent the unbalanced current on the outer surface of the coaxial shield. Coaxial cable has three currents flowing through it. One current flows through the inner conductor and another one along the inner surface of the shield. A third current flows along the outer surface of the coaxial shield. The last one is called common mode current. We use the common mode choke to prevent the flow of common mode current on the outer aspect of the coaxial shield.
I had a little more than 4m of insulated copper wire in my previous loaded coil dipole for 20/80m antenna. Folded back that wire on either side and twisted back on itself to produce a span of 4m wire on either side. Mounted the wire tips on supports on the garden fence. One side was about 3m high. Support on the other side was 2m high. I used nylon ropes to secure the 17m dipole antenna ends to the supports.
Came back and checked the standing wave ratio (SWR) in my FT-710 radio using low power. I got an SWR of 1.6 at the lower end of 17m band. At upper end of the band it was 1.8. Both values were perfectly tunable with the built-in antenna tuner of FT-710. I am not tuning the 17m dipole antenna further for the time being. That is because I am expecting to get a NanoVNA antenna analyzer soon. NanoVNA will give exact point of resonance and guide me in tuning the antenna well.
As you have seen, my 17m dipole antenna is functioning fairly well regarding SWR. Now I wanted to know my prospects of working stations on 17m band. I checked Reverse Beacon Network for a recent period of 1 month. There were plenty of stations being picked up from South America, Africa, Europe and Asia. The stations were working between 18072 kHz and 18111 kHz. Signal to noise ratio ranged from 2dB to 18dB, mostly on the lower side. CW speeds ranged from 16 wpm to 37 wpm. Stations were picked up at various times of day and night as well. Majority of the SNR were below 10 and many below 5.
Next I checked https://www.dxwatch.com/ with filter set for 17m and Asia. The maximum number 50 contacts were over in two days, yesterday and today. I could see contacts from Asia to Europe, North America and South America. I could see reports of CW, SSB, FT8 and FT4 contacts. You may remember that last year I posted picking up special event callsign HS72KING on 18.139 MHz. That station was quite strong, but none of my antennas would tune to 17m band then. Hence I have been waiting for an antenna which will work on 17m since then.
Finally, I checked propagation from my 17m dipole antenna by calling CQ in CW mode, on 18075 kHz at around 9 am local time. I am quite happy to see my signals being picked up by RBN skimmer at VR2FUN-77. That was at a distance of 4133 km! Very good performance for an inverted V antenna at just 7m height and SWR 1.6. I will be tuning this antenna further as soon as I get my NanoVNA antenna analyzer. Now I will be on the lookout for stations on 17m at various times of the day and night. Stay tuned for further updates on this channel.