Yagi

I’ve been thinking of ways to get more power to W3GMS, and coax might be the weakest link. I have about 75ft of RG-58 outside and maybe 8 ft of RG-174 inside. I took down the flag pole Yagi to replace the coax.

I learned how to measure loss with a “through measurement” on the nanoVNA watching Youtube:

• The old coax run measured at least -6.5dB loss total
  • -4.5dB for the RG-58 by itself
  • -2.0dB for the RG-174 by itself
• The new coax, 100ft of KMR-400, by itself measured -1.5dB, and -3.3dB with the patch of RG-174
• SWR sweep of antenna on old coax showed lots of wiggles and hung generally low, because of all the loss.
• SWR sweep of the antenna with the new coax runs much higher on the 100MHz side, and takes a nice dip at the resonant frequency.
• Incoming signals look good and strong by the S-meter on the TYT-9800

I took down the YAGI flag pole during a tornado warning. While I had it down, I attached the paracord that turns it with zip ties to make positioning reliable and less slippery. I shifted the paracord that secures it to avoid wear, and I straightened some elements.

The 1/4-wave ground plane antenna in the tree dropped its feedline, so I brought it down to reattach it and resolder the radials.

I also walked down the yagi on the pole to straighten some elements, since it was a nice day. The yagi was spinning around in the wind, so I also changed the way it’s mounted to clamp it more securely.

I also added some reigns to the mast, so I can (try to) spin it from inside the window. It works well some times but not others. The pole can freeze to the ground.

My Week in Radio

Contesting

I finished the FT Challenge. There was no special exchange this year. We could use other defined subbands in addition to the regular frequencies to alleviate crowding. We could work anyone, even if they’re not participating explicitly.

I operated QRP, so it was nice to find the quieter subbands and more FT4 activity. You earned multipliers for each 3000km, so I don’t really know on my score yet.

I found wsjtx-improved on the Debian Linux repository, so used that. I saw the color improvements, the better location labels with states, and it had filters.

AllStar

I learning some obvious things about AllStar: it can’t hear my DTMF if it’s currently transmitting, since it’s simplex, so it’s hard to control on a busy net.

Yagi in the Wind

Finally, I watched my home-built yagi flapping around on that windy day. I guess I can stop worrying about it, since it held up fine.

The Yagi spun around like a wind vane at times atop its flagpole, but it held up just fine. The aluminum pole swayed quite a bit as well. I’ve wrapped a loop of cord around the pole to use as reigns. so I can spin it straight again without really going outside.

The home-brew yagi blows around in the wind a bit, so I brought it down this morning as it started to snow, so I could straighten and tighten the elements. I realigned it for the 985 repeater, and checked it to be giving -96dBm.

I also resoldered some radials on the 1/4-wave ground plane antenna that go knocked loose in the tree.

I added some sections to the flag pole to reach 37 feet, and I increased elements on the home-made yagi from 2 elements to 4 elements. Upon adding elements, I needed to stretch the driven element a couple millimeters longer to tune it. In testing, I’m seeing about -100 RSSI listening to W3GMS on a Quansheng. It was about -105 RSSI when mounted lower and only 2 elements.

Tilt-up Flag Pole

I figured out to do a tilt-up flag pole against the house reaching 25 feet into the air. It sits on a stake in the garden, and is secured to the house with paracord in an eyelet and hook screwed into the side of the roof.

2-Element Yagi

I built a new 2-element yagi using an online calculator It tuned OK with the banana-clip adapter directly connected to the driven element. I first tuned the dipole, and then added the reflector element. As predicted, it shifted the tuning slightly, so I trimmed the driven element to retune. The nice thing is that the spacings and sizes of the original elements don’t change as you add more director elements, so I calculated it with 2 or 3 directors, but put none in for the first iteration. I can add more elements later.

I gave it a try to reach 985 with the TYT TH-9800 running 50W. It was scratchy, but copy-able. I have more flag pole sections ordered to make it a little higher.

There are easy instructions to build your own yagi on Instructables. I had just picked up some hose clamps and had the other necessary pieces: a broken tape measure and some 3/4-inch schedule 40 PVC and connectors; so I was ready to build.

The wiring on mine is held in place by the clamps and banana clip adapter. I always like those for prototyping. As directed, I tuned the antenna by moving radiators in and out and measuring with the NanoVNA.

The antenna is noticeably directional, so I can use it to find directions of signals. The S-meter and dB signal strength numbers on AUBS firmware make it easy to evaluate strength and direction.

I transmitted with it to the K3IR repeater as a test during a net.