[today’s run: 3.4 miles]
I have not been making much progress on the radio station project in September.
Over the weekend I did start a technical project: build a transmitting antenna.
We want omni-directional, horizontal polarization.
Using information in my ARRL Antenna Book, I built a small transmitting loop out of 1/2 copper water pipe. I used the specifications from a web page tool which will calculate small loop antenna designs. The design has to have a small amount of capacitance to tune it to the right frequency. I used a “trombone” capacitor made from 1/4″ copper pipe inside the 1/2″ copper pipe.
The first thing I noticed from this design is that it needs more physical robustness to avoid moving in such a way as to detune it from the design frequency. That’s not good.
So I have a second idea which I have not yet been able to try: replace the trombone capacitor with a piece of double sided copper circuit board material, about 1 square inch in size and solder to both sides. Then I can use some tin snips and a file to tune it.
I also need to figure out mounting and feeding it.
The thing is a nice little loop about the size of a dinner plate. If I can make it work it will save us a few hundred dollars.