Quotes

Never let your sense of morals prevent you from doing what's right.
-Isaac Asimov (1920-1992)

plumber’s 10-meter ham radio antenna


One avenue for local two-way radio communication is through the use of the 10-meter frequencies. I have not had a decent antenna for joining the conversation that is exercised most Wednesday evenings at 1915 hours on 28.350 MHz.

For visualization purposes, CB radios are just slightly longer, around 11 meters – that is, very similar in antenna requirements – a fairly tall antenna like the spring-mounted whips you sometimes see on pickup trucks.

I have had an antenna that transmits and receives ten meter okay, but it is in my little canyon (problem one) and is a horizontal while the rest of the local operators are using verticals (problem two).

So I launched a project to design, build and install a vertical 10-meter above the crest of the hill next to my house that has my signal trapped in my canyon. A pro scaled a pine tree uphill from me and put a rope and pulley 135 feet up into the tree. It took me several tries and a lot of extra hands to finally get it in the air above the hill-crest, but it is finally there.

The design is very unique. While most antennas have a particular frequency sweet spot where their transmissions are strong, I wanted a broader response range covering the ham 10-meter spectrum, but also in case of emergency, I wanted it to be capable of working the 11-meter CB range. This inspired me to use 3/4″ copper pipe for the elements rather than small gauge wire as the fatter the element the broader the range.

With some plumbing experience in my past life and a bunch of shade-tree engineering, I got this contraption designed, fabricated and suspended well above my radio shack. One of my helpers nicknamed it “Sputnik”.

Radio guys might want to know that the copper pipe elements are all 2.7 meters (8.8 feet) long. Old-school plumbers will recognize application of 3/4″ copper female adapters, PVC male adapters and a special-ordered side outlet cross as the required plumbing parts. I am not going into all the little details in assembling this contraption and connecting the coax cable to it. It would take me a chapter to describe.

My intent was to have it installed so I could easily raise and lower by myself. That has not happened. I’m feeling lucky that it is up at all. Forget easy for a while, though I do have a plan. Along with easy up and down, I designed it a bit long so I could bring it down a few times to trim little bits each time until it resonates in the center of my desired frequency ranges. I am pleased with how well that part came out. It is just a scosh long and has excellent capability there.

I put my antenna analyzer onto it today and found an absolutely wonderful SWR in the 12-meter band that was straight-line flat just a hair over 1.0 across the whole 24.890-24.990 range. In the target ranges of 27.405 +/- 440KHz and 28.750 +/- 850KHz it returned SWRs between 1.7 and 2.6, which is pretty good for covering a relatively wide range.

While I have an outstanding 12-meter antenna and tolerable 10/11-meter, sometime before winter I will make it easier to service and trim the length a bit so that 12-meter sweet spot moves into the range where I want it.

By the way, at almost 9 feet across the bottom and over 13 feet tall, Sputnik is awkward to handle, to say the least.