Antenna Testing Day ...

Foundations of Amateur Radio

Last week I went outside. I know, it was a shock to me too. The purpose of this adventure was to test an antenna that has been sitting in my garage for nearly a year. Together with a friend we researched our options and at the end of the process the Hustler 6BTV was the answer to our question. Before the commercial interest police come out of the woodwork, I'll point out that I'm not providing a review, good or bad, of this antenna, it was the antenna I purchased and went to test.

Between the two of us we have three of these antennas. I have the idea to use one as a portable station antenna and another as my base station antenna. Glynn VK6PAW intends to use his as a base station antenna.

To set the scene. The antennas came in quite large boxes, just over six bananas long, or more than 180 cm. When they arrived I opened my boxes and checked their content, then sealed it all up and put the boxes on a shelf. Last week Glynn proposed that we set one up and see what we could learn from the experience.

You know that I love a good spreadsheet, so planning went into overdrive, well, I put together a list of the things we'd need, starting with the antenna and ending with sunscreen to protect my pasty skin from the fusion experiment in the sky. In between were things like an antenna analyser, spare batteries, tools, imperial, since apparently there are still parts of the world that haven't gone beyond barley measurements. I jest, they authorised the use of the metric system in 1866. My list also included a magnetic bowl to capture loose nuts and washers, you get the idea, anything you might need to test an antenna in the field.

Our setup was on a rural property where we had lovely shady trees and oodles of space to extend out a 25m radial mat. We tested many different set-ups. I won't go through them all, but to give you an idea of scale, in the time we were there, we recorded forty different antenna frequency scans. The 6BTV antenna is suitable for 80m, 40m, 30m, 20m, 15m and 10m. We tested with and without radials, raised and on the ground and several other installations.

We learnt several useful things. For starters, sitting on the ground with radials the antenna measurements line up pretty well with the specifications and with a suitable base mount to protect the plastic base the portable station antenna is usable out of the box.

Any variation on this will result in change, sometimes subtle, sometimes less so. For example, we came up with one installation where the SWR never dropped below 3:1. That's with the antenna on the ground without any radials in case you're wondering.

Other things we learnt were that manually scanning each band is painful. When we do this again we'll have to come up with a better way of measuring. The aim for my base antenna is to install it on my roof, bolted to a clamp on the side of my metal pergola. This means that we're going to have to do some serious tuning to make this work for us. It might turn out that we'll start with installing the antenna at Glynn's QTH first, but we haven't yet made that decision.

Other things I learnt are that I had actually put together the base clamp when I checked the boxes a year ago, so that was a bonus. The magnetic bowl saved our hides once when a spring washer fell into the lawn. The hose-clamps that come with the antenna require a spanner, but there are thumb screw variations of those that I'll likely use for my portable setup.

Other things we need to do is learn exactly how the traps work and how adjusting them affects things. In case you're unfamiliar with the concept of a trap, think of it as a radio signal switch that lets signals below a certain resonant frequency pass and blocks signals above that frequency. In other words, a 10m trap resonates just below 28 MHz. It lets frequencies below 28 MHz pass, but blocks those above it, essentially reducing the length of the antenna to the point where the trap is installed.

One test we did was to only use the base and the 10m trap. We discovered that this doesn't really work and that the metal above the trap, as-in the rest of the antenna, isn't just for show, even though it's on the blocked side of the 10m trap.

Given that I intend to use my base antenna as my main WSPR transmission point, I need to adjust things so the antenna works best on WSPR frequencies. I intend to use a tuner for when I want to work outside those frequencies.

One unexpected lesson was that the awning that Glynn attached to his vehicle was an absolutely essential item. I don't think I'll ever go portable again without one. Life changing would be an understatement. I'm investigating if I can fit one to my vehicle.

Having had some health issues over the past months I was anxious about going outside and being somewhat active. I paced myself, protected my back, took regular breaks, sat down a lot, drank litres of water and slept like a baby that night. No ill effects, very happy.

As a bonus, I even transferred our measuring data to a spreadsheet.

I can't wait to see the results of our next adventure.

Oh, we did connect a radio. Heard a beacon in Israel, heard a QSO in Italy, listened to WWV on 10 MHz and almost missed the bliss of not having to tune or switch when moving from band to band.

What have you been up to in the great outdoors?

I'm Onno VK6FLAB