Antenna Tuning Precheck

The ol’ 6BTV has been out there for three or four years and has served me well enough. It was about two years ago that I used an MFJ antenna analyzer to see where it’s peaks were after repairing it (from running it down with my truck) and they were all close enough to operating range to leave alone.

However, my interest in more operating means that I’d like to have a better idea where it works best. More than a year ago, I got a Rig Expert AA-170, the HF to 2m range device. Other than firing it up at my desk at work once, I’ve not used it until tonight. Pretty slick box.

10 meters is usable across the band, with a power-peak at the bottom end in the rtty/data sub-band.

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15 and 20 meters are both pretty much smack in the middle of the band.

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30 meters is a pretty narrow band, so it makes sense that it would be pretty flat across the whole thing.

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40 meters is, again, a peak in the lower end of the band. With my interests in JT65 and PSK31, that’s probably as good a place for resonance as any.

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80 meters is where I finally really need to tweak it. The resonance point is a few kHz below the bottom of the band and the antenna bandwidth is fairly narrow, so I need to choose a spot in the band and see how well I can match it.

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If I adjust 10 meters up a little in frequency, the rest of the peaks will move a bit upward as well, as 10 meters is the bottom section of the antenna.

The software that comes with the Rig Expert does a decent job of graphing as well.

This is an SWR scan of 3.0MHz to 30MHz, accounting for 75 feet of RG213 cable. The dips obviously correspond to the tuning of the six bands that the antenna covers, 80, 40, 30, 20, 15 and 10 meters. The software also marks the ham bands in white on the background fill.

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On The Air Again

Well, strictly speaking, I was not really off the air because I was receiving JT65 before I discovered the damage.

We have a friend who visits once a year or sometimes every other year, and while he’s here, it does projects and other work around the house. This time, however, I had inadvertently set a trap.

The coax from my HF vertical antenna comes out of a shallow trench too far away from the workshop. The Husqvarna walk behind line trimmer is a pretty powerful cutter.

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Yesterday, I finally had both time and the materials to repair the damage, protect if from future damage and to add lightning protection along the way.

First, I put a new connector on the coax where it comes out of the dirt and moved my ground rod to the same area. I also added 90 degree elbow of 1-1/2″ PVC conduit to protect the coax at the new spot where it comes out of the ground.

I hit something immovable with about 2 feet of ground rod still sticking out, so I cut it to length.

The ground rod was closer to the radio before, so I had to replace the 10ga solid copper to the inside grounding block. I put a new connector on the coax from the other side of the damage and fed them both through the conduit.

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I put an Alpha Delta stud mount surge protector on the ground rod, using the provided stud to clamp the station ground wire. I sealed the connectors with Temflex tape.

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I dug out enough around the splice enough to put an irrigation valve box around it for maximum protection.

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Finally, I filled and packed the void with soil.

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Although I had a false start assuming the old intermittent transmit problem had returned, the antenna tuned up perfectly on 20m.