dipole – 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…

2m dipole performance

The 2m dipole attachment I made for my monopod seems to be working well. It’s a definite improvement over the Diamond SRH77CA and SRH999 antennas (which already work fairly well) when it comes to receive. I can receive a pretty clear signal from the repeaters from inside the house, whereas with the Diamond antennas, the repeater signal was on the scratchy and noisy side. When I’m outside, all of the antennas perform pretty well.

The two repeaters closest to the house that I can reach (and use) are about 7-8 miles away, so they’re a bit of a reach to hit standing on the ground with a 5W HT. The repeater beeps at me after I transmit, so I think I’m hitting the repeater with the dipole attachment, although I’m not sure how well I’m getting in. The repeater has a voice playback function, but I still need to learn how to use it.

In any case, the dipole attachment seems to be a success, and I can at least monitor some of the repeater activity more easily.

Time to start planning for a dual band VHF/UHF radio for the house.

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.

6m dipole testing

Tested out the 6m dipole with a nice QSO with W4QYV (who happened to be pretty close by) up at 52.525 MHz (FM) and it worked out pretty well except for towards the end when I mysteriously stopped receiving/transmitting anything. The noise was still there, but apparently W4QYV wasn’t hearing me. Very weird.

I was also checking out the JT-65 activity at 50.276 and noticed that the signals there look a lot stronger with the ZS6BKW antenna than they do with the 6m dipole. The ZS6BKW is a good deal higher though and doesn’t have a bunch of houses in the way.

At any rate, I know that it can reach out at least a mile from the house. I was getting a bit concerned after tuning around the band and hearing nothing but noise. Now to decide if I want to leave it up at the house permanently or keep it handy to go portable with. Then again, I have enough wire around, so I could always make another one.

A 6m dipole

Built myself a 6m dipole using a dipole center and some of the hamfest wire I picked up back in February. As it’s also Towel Day, I had mine handy just in case.

I wanted my antenna to be resonant at 51 MHz. Using l = 149.35/f ¹ gave me a length of 2.96m, so I cut a 3m length of wire and then cut that in half. I soldered some stranded wire to one end of each wire to connect to the dipole center and attached a couple of ceramic insulators to the end. One end got tied off against the house and the other end to my PVC mast propped up against a ladder.

The first look with my antenna analyzer showed the antenna resonating around 49.3 MHz with an SWR of 1.0 (wires a bit on the long side). A bit of math (49.3MHz/51MHz = 0.97) told me the antenna needed to be 2.9m long (3.0 * 0.97) so I trimmed 5 cm off each end and got 1.0 SWR right at 51 MHz.

With the dipole connected to the radio, the receive is definitely louder than the ZS6BKW on 6m. I wasn’t able to pick up any other stations, but there was a lot of electronic noise. In the fldigi waterfall, there were lots of periodically spaced vertical lines all across the band. I’ll have to give a listen later when it cools down a bit and people turn off their AC units. Maybe it’ll get better then.

At 2.9m long, it’s small enough to be very easily portable. I’ll need to get a much shorter length of coax to use with it to minimize losses (it’s connected to the radio using about 23m of coax) and something to hold it up in the air. Could be neat to carry this around and break it out when a 6m opening pops up.

1. Take l = 490/f, which gives you the length in feet when f is in MHz, and multiply by 0.3048 to convert to meters. Metric is how I roll.