Antenna Maintenance

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.

antenna  yagi  985  w3gms  fm  vhf 

Bug with TYT TH-9800

I can set a repeater offset from Chirp, and that works fine, but it displays incorrectly in the SHIFT setting on the radio. It displays as 7.60MHz for every repeater frequency. Apparently, visiting the setting in the menus gets the really bad value (7.6MHz) applied until you leave the channel and come back.

Reversing the repeater frequencies (assigned to P1 on the microphone) shows the right frequencies. Programming it from Chirp as a split (instead of +/- offset) works, but still doesn’t show correctly in the menus.

The radio also only allows setting by 10kHz manually, so setting my 605kHz shift for W3GMS is impossible to program from the radio.

There’s already a bug filed for Chirp.

tyt  th9800  vhf 

Tape Measure Yagi

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.

Antenna on the Car

I removed the magnet from the inexpensive mag-mount antenna that I had stuck to a baking sheet in the back of the BMW i3 (which is all plastic). The bike rack is always on the car, so I cobbled together some scrap metal parts and clamped the antenna onto the rack. It’s got a screw knob, so I can loosen and reorient it when I flip the bike rack.

It works great now with the antenna outside the car and attached to the metal of the rack.

antenna  vhf  uhf  mobile 

ISS Repeater

The ISS passed at 8:55am EDT at 49 degrees. My vertical 1/4-wave ground plane antenna in the tree picked it up really well. I copied a handful of callsigns pretty easily:

  • KO4PDI - FL
  • KC4Y - AL
  • K4MMD - FL
  • N5ACR - MD
  • KC4YMT - GA
  • KC3MM - SC
  • K3DMM - PA, Harrisburg

I confirmed hearing K3DMM on the Morning Grind round table (K3IR) a few minutes later that morning.

iss  vhf 

VHF Reception

Reception Problems

During 985 net on Monday night, which is VHF on my UV-K5 running egzumer 0.22.0, I’d get periodic static in reception. It got bad enough to completely cut-out. I was using my simple wire dipole hanging in the tree outside.

K3IR had been frustratingly quiet as well, so I checked the antenna with the NanoVNA as it hung outside. There were no fluctuations in SWR, so it’s not connections or proximity.

I tried the Explorer QRZ-1 HT, and it sounded great on the same antenna on the same net. Is my UV-K5 broken?

To test a bit further, I ordered a new UV-K6 to compare. I also downgraded to egzumer 0.21.0 for further testing.

The next day, Tuesday morning, K3IR was sounding better, but I was getting the same periodic noises. The outside antenna doesn’t completely cut out, but shows terrible doubling/overload as if from FM station.

Inside, the magmount antenna on the 3d printer is better. Is the dipole outside too sensitive and bringing in more signal than the frontend of the UV-K5 can handle?