At last, tunable SWR on 80m band!
I have been trying to come up on 80m band with various types of antennas for the past several weeks, with no success at all. All installations ended up with ‘HI SWR’ on 80m band. In the bargain I could get pickups on Reverse Beacon Network on the WARC bands 30m, 17m and 12m. Finally I removed all the loading coils and linear loading type of installations and decided to go for conventional half wave dipole antenna. Main motivation was the Sacrifice Rock DXpedition coming up in my region. They have announce their frequency plan and has 3520 kHz on CW and 3690 kHz on SSB. I want to work them on these frequencies on 80m band. Being just about 40 km from here, I hope to get them on 80m. DXpedition starts on 7th February and I have just 3 days to get my 80m setup ready.
I started the renewed effort to come on 80m band today morning. I had 4m of wire on either side already installed for the recent 17m antenna. Took all the wire available from the dismantled linear loaded dipole antenna for 80m. There were multiple wire joints, but I did not want to buy more wire. Measured 16m wire for two sides of the antenna and folded back the remaining part. Marked each 4m on the wire with insulation tape as well.
Installing new support
I was planning to use a one and quarter inch PVC pipe as support on Northern side. The PVC pipe was 3m long. I used this galvanized iron pipe as a support for the PVC pipe.
Used a hammer to drive down the GI pipe into the soil for about a meter. As this pipe is of 3/4th inch diameter, I can easily slide the PVC pipe over it. Kept it near my Moringa plant so that it can act as additional support.
Now I have finished installing the GI pipe support for the PVC pipe mast.
Slided the 3m long PVC pipe over the GI pipe. PVC pipe has a hole at the top in which a twisted wire acts as a pulley! Nylon rope has been placed through it to pull the antenna wire up and down when needed.
Constructing the zig-zag half-wave dipole antenna for 80m band
Added 16m wire to either side of the previous 17m antenna. Brought down the feed point to suit the mounting pattern. Used several supports for the wire on either side due to limited space. Used 15m long RG213 cable to connect to my FT-710 radio. Kept surplus cable as a coil to act as a common mode choke. 19m of wire had North – South orientation. Then there was an angulation towards feed point. The wire rises up from the feed point to a maximum height of 7m. That is on to a fiberglass mast on the terrace. After that it descends to the West in a zig-zag fashion. Lowermost supports on garden fence are 2m high.
In spite of this compromised mounting, I was happy to get SWR 2.6 on 3510 kHz and 2.5 3600 kHz. Both were tunable with the auto-tuner in FT-710 radio. Interesting pattern seen in the radio seems to be radio frequency interference. I will have to check at night to see if it goes away. If so, it can be presumed to be from solar panels in the vicinity. I did try calling CQ in CW and could not get picked up on reverse beacon network at 11.30 am. QRZ.COM tells me that propagation on 80m is poor during day time. I will have to check at night if I can get picked up on RBN and hear stations as well. Next step is to tune the antenna for better SWR. I am planning to do that in the coming few days. Stay tuned to this channel for further updates.