Coax vertical dipole and other musings ...

Foundations of Amateur Radio

The other day I celebrated my sixth birthday, no not that one, the one that reminds me when I first became licensed as a Radio Amateur. It caused me to reflect on what I've done with my license and what I've learned and where I'm heading.

A recurring theme in my Amateur life is one of upgrading. Not a month goes by when someone makes a comment about my license status. As you might know, I hold the entry level license in Australia, the Foundation License as it's called. Other countries call theirs different things, but the aim of this license type is to introduce new entrants into the hobby and for me it's done that in spades.

If you've listened to some of my previous mutterings and musings, or if you've listened to all of them, heading for 300 now, you'll have noticed that it's rare that I'm not talking about something I learned, something new, or something that interests me that I've found and I want to share with the community.

This quest for knowledge, learning and curiosity is something that I've always had and I'm sure I'm not alone with those traits. It occurred to me that my newly minted Amateur License achieved exactly what it intended to, Introduce me to Amateur Radio. It did more than that. It set me on a path that I'm travelling down today where I'm learning a new thing most weeks and telling others about it.

I don't yet fully grasp the difference between an NPN and a PNP transistor, nor do I understand the workings of a Valve to the point where I can explain it to you, but the truth of the matter is that I haven't had the need to, or at this stage the curiosity to. That's not to say that a day will come when I do want to know.

So here's the thing.

Would you rather I have the highest level of license, having passed my test, cramming for my exam, guessing answers on a multiple-choice form, or would it be better if I came to know and understand the body of work that makes up the foundations of our hobby? As an aside, I have taken a mock test at some point. If I recall, I managed a score of 75% or so, might have been higher, but it outlined the areas of knowledge that I don't have at this time and that was why I took it in the first place.

There are Amateurs who pass tests and then there are Amateurs who learn.

One final comment about upgrading. When was the last time you upgraded your car license to the next level, say rally driver, or Formula-1 driver? When was the last time you got called out on not having upgraded and admonished for being a lowly car driver?

Onto Amateur stuff.

First of all, the wheel bearing has gone to a better place. It drove away on a big blue truck on Wednesday morning and is no longer. So sad.

In antenna news, you may recall my experiences with the installation and tuning of an antenna for a friend of mine. I made all manner of what some would call outlandish statements, one Amateur all but called me a liar and accused me of making it all up to promote my podcast. All this excitement because I dared query the documentation of an Antenna. I've reached out to the manufacturer, but I've not yet received a response.

I'm told that my hunch that this was a vertical dipole was correct. That in itself is curious since I've been experimenting with a vertical dipole made from coax, not enough to talk about success yet, but enough to be told that it will never work. Gotta love the doubters. As I suspected, the cut-off piece of inner coax, if you recall, the one that was a centimetre or so too long, is half of a capacitor, the other half is in the base of the antenna.

Note that all this is based on what I've been told by a fellow amateur, and I'm looking forward to hearing from the manufacturer what they have to say.

So, my vertical coax antenna idea started off with the idea that I wanted to use a vertical dipole for working portable. I realised that some of the designs I've seen knocking around the 'net are cutting off long chunks of shield, or folding it back, or doing all manner of funky things to a piece of coax. I wondered what would happen if I took a piece of wire, cut it to the length of one half of a dipole, attached a banana-plug to it and stuck it on the end of a piece of coax.

One half of the antenna would be the wire, the other half would be the shield of the coax.

If I could come up with something like a choke that would stop RF travelling all the way back to my radio, I might have myself a vertical dipole with the benefit of not having to cut up coax, no extra connectors and if I made it possible for the choke to slide up and down, my antenna would be simple to transform into something for any band.

As I said, I'm not yet at the success stage. I did some testing with something called an ugly balun, but it's pretty clunky and results are mixed. I tried ferrite-clip-on-beads, but they didn't seem to do the trick - though that could have be the nature of the particular clip-on's that I had at the time.

When I have some more play time free, I'll have another crack at it, since it seems promising and if there are people selling vertical dipoles with curious matching networks at the base, there's hope for me yet.

I'm Onno VK6FLAB