Paul Butzi |||

POTA rove lessons learned

Magnetic roof antenna mount

One of the problems I encountered about halfway through the multi-day expedition was an intermittent problem with the coax connection to the three magnet magnetic antenna mount. The feedline is permanently attached to the mount, and the intermittent problem could be fixed/disrupted/fiddled by wiggling the feedline where it enters the mount. Examining the connection when I got home shows that it’s not actually soldered; the center conductor of the feedline is captive under one washer, and the shield is captive under another washer, and one possibility is that one or the other (or both) was/were not making good contact, with the resulting problem.

Another possibility is that the coax itself is failing, perhaps because stress right at the point where it enters the mount. I had previous run the coax in multiple turns around an FT240-31 ferrite as a choke, and the coax failed, presumably because the tight bend caused the center insulation to fail.

So the question is, what do I do about this? Yesterday, I examined the connections and reassembled the mount, and it seems to be working fine. But I am skeptical that the problem has been resolved.

In any case, in the process of doing 11 activations, I’ve concluded that the permanently attached feedline is just not a good idea. Oh, it makes sense if you expect to drive down the road with this mount on top of your vehicle, but I don’t intend to ever do that. What I do is plop the mount on top of the car, feed the feedline into the car (through the sunroof, or a window, or just under the door seal), and the plop the whip on top, and I’m good to go.

Every time you handle the mag mount, either to put it on the car or take it off, or just mess with the feedline, the point where the feedline connects is subject to stress - maybe not major stress, but little pulls and bends and pushes. And all those little stresses erode the integrity of the coax and the connection to the feedpoint of the mag mount.

And the feedline is RG-58u, which I don’t much like, as it’s stiff and obstreperous especially when it’s cold, and it has a PL-259 on the end, which is just not the connector for rapid deployment.

What I want is for there to be a female BNC connector on the mount, so that the feedline can be detached. That way, if I need a feedline of a different length, I just connect a different chunk of feedline. If I want to use RG-316, I just pick that out of the bag, connect it up, and away I go. If I want to use a long length of, say, LMR-400, I connect that, and again I’m good to go, even if the radio is not in the vehicle at all but way over on that picnic table over there.

That arrangement wouldn’t do if you left the mag mount outdoors on a car for a long time. But I have no intention of ever doing that. You don’t drive down the road with a 17’ whip extended, after all.

As far as I’m concerned, the mag mount serves the same purpose as a ground spike, or a tripod - an easy, fast way to support the whip antenna and hold it upright, and an easy, fast way to provide a ground plane. It’s faster to smack the mag mount on the roof of the car than it is to drive a ground spike and spread radials, or put up a tripod and spread radials. As long as I’m operating within, say, 30 feet of the car, using the magmount seems like a great idea. Farther away that that, it probably makes more sense to use the Chelegance MC-750 and ground spike, or the MC-750 and a tripod.

Icom IC-7300

There are definitely things I don’t like about the IC-7300. The touchscreen, for starters, works fine but the UI is annoying to me. I don’t like the filter controls. No matter how much I practice I can never get the hang of adjusting the spectrum display span and sensitivity, at least compared to the equivalent controls on the KX3/PX3 combo.

On top of that, I think the antenna tuner is sort of mediocre. It’ll touch up an antenna that isn’t too far out of whack, but unlike the tuner in the KX3/KXPA100, it won’t tune 30m on my 80-6 Buckmaster OCFD. To be fair, the Elecraft tuner is amazing, I suspect it will tune anything metallic you connect it to.

That said, the IC-7300 compact size and weight and the ability to happily run 100W into a reasonably tuned antenna are pretty convenient, and it does that without the rat’s nest of cables that the KX3/PX3/KXPA100 requires.

Connectors

Part of doing a POTA rove is the radio part - being able to get the 10 contacts (plus at least a few for insurance in case you copied a call sign incorrectly) in a reasonable time.

Another part is the physical challenge - getting from one park to the next, setting up to operate, striking the setup to move on to the next park - which you want to handle with maximum efficiency and minimum time.

It didn’t take me long to realize that each cycle, I needed to deal with antenna connectors many times: connect antenna feedline to RigExpert Stick 500 to check the antenna setup, disconnect from RigExpert, connect to radio. And then when striking, again to disconnect from the radio.

The PL-259/SO-239 connector pair are just not ideal. They’re not ideal in an electrical/RF sense, but they’re also far from ideal in a speed and efficiency sense, as you need to seat the connector fully to engage the anti-rotation teeth, then you need to thread the outer shell home fully, and then to strike the setup you need to unthread the connector.

WD4DAN says he uses clever push on/pull off adaptors and he’s never had a problem.

I’m skeptical. I think the best solution would be one of my favorite connectors - the BNC connector.

Next time, the antenna feedline will be terminated with a male BNC connector, the RigExpert Stick 500 will be fitted with a female BNC to PL-259 adaptor (or the RigExpert fully converted to BNC), and the radio either fitted with an adaptor or converted to BNC.

Band and frequency agility

When I activated Eagle Fish Hatchery I set up planning on, once again, operating on 20m. But when I was set up and started looking for a clear frequency, the entire 20m band had an incredibly high noise floor - s8-s9. I considered just moving to the next park, but thought that first I’d try other bands and see if they were better. The first band I tried was 17m, and it was quiet - maybe s2 noise.

I’m pretty sure the awful noise on 20m was being generated by pumps or other equipment at the hatchery, and there was no room to move away from the buildings with the equipment and still be inside the boundaries of the hatchery.

So that band agility made the difference between a successful activation, and no activation at all.

That has implications for equipment plans that don’t allow for using alternative bands. For example, if your only antenna is a 20m EFHW, you’re occasionally going to find yourself in trouble when 20m is unusable.

Any workable antenna plan needs to include the ability to shift to other bands.

Headphones

I was limited to using either the speaker and hand mike for the IC-7300, or a Heil Pro 7 headset. In every case I opted for the headset. It just makes working a weak signal so much easier. But the Pro 7 headset puts you in a completely isolated bubble, which is sort of uncomfortable from a situational awareness standpoint. It would have been nice to have a headset, like the Heil BM-17.

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