Antenna – AB4UG Radioblog

6m/10m attic dipole

Joining the 2m ground plane antenna in the attic now is a 6m/10m fan dipole.

There are too many rafters and roof supports above the ceiling to easily get a longer antenna into the attic, but a 10m dipole is short enough to get up there with some reasonable effort. I decided might as well make it a fan and add 6m to it as well.

Getting the antenna installed in the attic and connected up turned out to be a process that spanned a few weeks, but yesterday I finally got it connected up to the antenna analyzer (RigExpert Stick 230) and got everything trimmed up to about as good as it was going to get.

SWR screen grab from the RigExpert 230 for the 6m band

6m/10m fan dipole SWR across the 6m band — SWR screen grab from the RigExpert 230 for the 6m band

The SWR is under 3 for most of the 6m band dipping down to just above 2 around 51 MHz. For the 10m band, the SWR is under 2.6 across the band and dipping down to just above 2.2 at about 28.8 MHz.

The radio’s internal antenna tuner seems to handle the antenna pretty well. Now to see if I can make any contacts with it…

Antenna and filter books

Two new additions to the library arrived in the mail this week thanks to the 2018 ARRL auction.

In this year’s auction, I managed to score a copy of Antenna Theory: Analysis and Design 2nd ed by Constantine Balanis, and Rapid Practical Designs of Active Filters by DE Johnson and JL Hilburn.

Both books are in pretty good condition, especially the Filter book considering that it was published in 1975. The Antenna Theory textbook still has the 3.5″ disk in the back unopened.

I was hoping to get at least one of the Vibroplex bugs that were also in the auction, but a flurry of last minute bidding drove the price higher than I wanted to pay for them. Oh well.

Happy with the books I managed to get though. They’ll be good additions to the library.

2m antenna monopod attachment

A while back, I made a monopod to use with my camera. Handy thing to use when I don’t feel like lugging around a tripod. Also serves as a nice walking stick.

On one of my last visits to Radio Shack, I picked up two telescoping antennas thinking that I could use them as dipole elements.

Add one section of aluminum angle stock, a bulkhead BNC jack, a couple 1/2″ 4-40 screws and nuts and now I’ve got a telescoping 2m dipole antenna attachment for the monopod.

It took me a while to figure out how I was going to insulate one of the telescoping elements from the angle stock. While I was studying the problem, a solution struck me: plastic wall anchor. Worked perfectly.

Tuning the antenna was a simple matter of adjusting the length of each telescoping antenna to get close to 1:1 across the 2m band.

Looks pretty good. I’ll check it again outside over the weekend and try it out with the HT.

If I hold it up in the air by the base of the pole, I can get the antenna about 2.5 m up in the air. I’m hoping I’ll be able to reach the two repeaters that are about 8 miles away a little better than I can with the HT antennas I already have.

Up over the roof

Extending the mast all the way gave me enough height to swing one wire of the dipole over the roof.

The more open arrangement along with both wires of the dipole being more exposed seemed to make the antenna work better. The radio’s internal tuner will match on 40 m now (below that is still a no go), so it’s nice to be able to get that band back.

Noise floor on 40 m is still pretty high (around S7) so I probably won’t be able to hear much except for stronger signals.

First contact with the antenna and new mast was with W9ISF, Indiana State Fair special event station, on 20 m. Got a nice 57 signal report from him and he got a 55 from me.

Raising and lowering the mast isn’t too difficult, and hooking the antenna to the top of the mast makes it easy to attach and remove. Gravity helps with lowering the mast, and I think most of the work will be spent coiling the antenna back up for storage.

Now to acquire another 20 or 25 m of coax that I can use as additional feed line for experimenting with other antennas.

Antenna works!

The antenna works. There wasn’t a whole lot to hear on the bands, so I’m not sure if the antenna’s performance is crap in its current configuration, or if it’s just the bands are crap today. I’ll spend some more time on the antenna and playing on the radio tomorrow.

The radio’s internal tuner will match the antenna from 20 m up to 6 m, but not on any of the bands below that. Better than I expected, although not having 40 m is a bit of a downer. The noise level on all the bands below 20 m was pretty high too (S7-9).

Now the dilemma is what to do with the antenna when the radio isn’t being used. The antenna and mast are pretty conspicuous when deployed, and we would no doubt get some naughtygrams from the HOA police.

With the mast down, there’s not much to see from the road or even the side of the house.

The antenna becomes pretty messy though and obviously makes mowing more difficult if I just leave it lying on the ground. The antenna would also exposed to full sun, which would probably shorten its life.

I think what will most likely end up happening is that the antenna will come off the mast and get coiled back up when it’s not being used. I can use an S hook to attach the antenna center to the top of the mast which will make for one less rope to deal with.

That means playing radio will end up being a little bit more work and a more planned activity. Won’t have to worry about the inevitability of the antenna or coax getting chewed up by the lawn mower though.