Recently I went to Boston to visit my parents for 10 days. I like to get on the air from different locations, especially the east coast of the US because I can hear Europe much better there. On one previous trip I brought almost my entire home station with me – it was pretty ridiculous. Other times I have borrowed a friend’s Norcal 40A CW transceiver, but my CW skill was much too weak to make much use of it. But a few months ago I finished building a KD1JV ATS-4a transceiver, and I started using it at lunch time on work days, trying to practice CW regularly. I’ve gotten good enough, and come up with a portable station compact enough, that I was looking forward to getting on the air on this trip.
My portable station now consists of the ATS-4a, a no-name 3Ah LiPo battery, 10 feet of RG-316 coax, a simple plastic dipole interface thingy, and an American Morse Equipment Porta-Paddle. With a properly tuned dipole this setup works really nicely and is very light. I also had been thinking about buying an antenna analyzer, so before this trip I finally pulled the trigger and bought a YouKits FG-01A.
Last time I visited my parents I brought some wire and cut a 40 meter dipole, and since I had some left over I went ahead and made up 20m and 15m ones as well, and left them tucked away for a future trip. So this time I thought I would try an antenna design I’ve always been interested in, the fan dipole.
My parents have a 3 story house with a small porch facing the back yard on the middle floor. They have a large yard, with a tall tree on one side and a garage on the other. I thought I would try to hang the dipole using the tree and garage as supports, with the feedpoint near the porch, so I could sit there or in the living room to operate. After measuring things out and rummaging in the garage for useful items, my dad and I took a trip to Lowes and bought 100′ of clothesline rope, a ball of twine, a package of small zip ties, some heavy steel washers, and some $5 wire strippers.
My dad helped me rig everything up, which was cool. I explained antenna resonance and why the lengths of the wires mattered. One problem we had was that there is a smaller tree in between the porch and the garage, which was going to make lowering and raising the antenna repeatedly infeasible. This also led me to give up on the 15m wire because there wasn’t enough vertical space for it. Jason, NT7S, pointed out that the 40m wire should also work on 15m because 15m is a harmonic of 40.
In the end I took all the rope up to the garage roof, heaved it over the small tree, and dad pulled it up to the porch. He attached one leg of the 40m wire to the rope with zip ties, then tied the end of one leg of the 20m wire to the rope with 12″ of twine, using washers to weight it down. Then I pulled all that back across to the garage. Then we attached the other wire legs to the remaining rope, I climbed the pine tree, dragging the rope up behind me, and tied it off. My dad lashed a pole to the porch to hold the antenna up a few feet above the railing, I hooked up the coax, and turned on the new antenna analyzer.
The analyzer showed pronounced dips in SWR at about 6.400 MHz and 13.500 MHz. Not bad, just a little too long! I climbed back up on the garage roof and up the pine tree and cut off 6″ from each end of the 40m wire. Checked it again and it was better, but still too long. 7″ more removed, and the dip was right at 7.000! Shortening the 20m wire was easier because it was only attached to the rope at the end. I just cut 12″ off at the feedpoint and it matched up nicely. The antenna did look OK on 15m too, though the SWR was a bit higher, in the 2.5:1 range instead of below 2.
Performance on the air proved that the antenna was working nicely. Over the next few days I made contacts with WA4HHC (FL), WE4G (KY), VE2ZA (Montreal), LZ2RS (Bulgaria), 9A2AJ (Croatia), SM7ZDI (Sweden), HA8WZ (Hungary), RA6AN (Russia), K1USN (Braintree, MA, the next town over!), and K3RNC (MD). Most of these were on 20m, a couple on 40m. I heard many other stations but couldn’t work them, sometimes because they couldn’t hear me, other times they were just going too fast and working a pileup. I made good use of the Reverse Beacon Network, though sometimes I think I spent too much time staring at that and jumping to a spot frequency hoping to hear someone, instead of just calling CQ or tuning listening for callers. Also I had much better luck at night than during the day for some reason, even on the weekends.
It was good to get some more CW practice, and I was really pleased with how well the antenna worked. I would definitely try that design again in the future. It was also cool to see the antenna analyzer in action. Of course there are always things you would try or do differently next time. Because of the layout of things in the yard, the legs of the dipole were not perfectly straight. I ended up with a horizontal V shape, with maybe a 120 deg. opening instead of 180 deg. If I’d had a longer feedline I could probably have made it straight, and I wonder how much difference that would have made.
Also, my parents’ house is built into the side of a small slope. The antenna was probably about 20′ off the ground directly below it, but just on the other side of the house it would only have been maybe 6′ off the ground. I don’t see many options for getting it up higher, although it did occur to me that I could try to hang it up in their attic. That would probably get it more than 30′ off the ground. Could be interesting to try.
Here are some pictures of the setup. First, the SWR plots before adjustment. The frequency shown is where the SWR is lowest.
Then, the plots after adjustment. Center frequency is set to my desired target, I was still a little long but close enough.
Finally, some pictures of the antenna itself. It’s always hard to photograph wire in the air, though. Note what looks like (and is) an old car rearview mirror on top of the center support pole. My parents are avid bird watchers, and use this contraption to look into bird nests to see if there are any eggs!