Good afternoon everyone,
Although this wasn’t a SOTA-specific project, it should come in handy for those doing VHF activations:
I’ve wanted a way to compare handheld antennas, but the problem is always getting an analyzer hooked up. Also, handheld antennas depend on the radio itself underneath the antenna to provide part of the total “antenna system”.
While I was researching handheld antennas I came across an article by Richard Kiefer, K0DK, called “High-Efficiency Antennas for Hand-Held Radios.” In the article he talked about half-wave end fed antennas (good info), but what really grabbed my attention was the testing rig he used. It is basically an Ht imitator with a cable coming out the bottom to hook up to an analyzer. I took the idea and expanded on it a bit, making a radio imitator with both BNC and SMA connectors. Here is a close-up of the tester:
Another view of the fixture. It is just block of 3x1 aluminum stock with the middle cut out. I then mounted connectors into a piece of flat bar on the top, and made the top removable so that it is easy to work on.
Below are the handheld antennas I have which I tested.
Everything set up and ready for testing. Technically I should probably keep everything further away from the antennas so that I can get a “truer” reading. However, since these antennas are always used in a messy near-field environment I figured that this was good enough.
2-Meter band test results shown below. I put everything into an Excel workbook and added a graph to make it easier to visualize the results. Based on the dummy load testing it looks like the fixture is adding 0.7 to the SWR, so these numbers are all probably a bit high. I’ll be doing further testing to confirm.
SWR by itself isn’t everything, but it’s nice to be able to quantify what I can expect from different antennas. One of the ones that I’ve been using a lot lately actually turned out to have the 3rd worst SWR curve out of the bunch! Not going to use that one on 2 M any more.
I think that by substituting a radio for the analyzer I could also measure relative gain - at least in terms of comparative S-units on the same receiver. That’s a project for another day though.