Do you have some old speaker wire laying around? Don't have an antenna for your QRP or full-power rig? Is the RTTY contest just 2 hours or less away and you're panicking because your antenna broke or is out of commission???
Well, don't worry, because today, we're going to be building the Zip Wire antenna! This antenna has been around for a while and was popularized by KG6HQD (SK). I went back on YouTube and found the video where Jerry builds his antenna and demonstrates it. If you have some speaker wire, one of those balun adapters (like a BNC to screw terminal type), and some extra time, you can get on the air in no time!
Antenna Theory and Math
The first question you might be asking is, "why does this antenna not have any coax?" Well, it's actually quite simple. This antenna is configured in two pieces - the elements and the feedline. The feed line is built into the antenna elements, which acts as a balanced feeder.
For the first equation, we will focus on the elements, which follow the conventional 1/4-wave equation:
234/f
Where f is the frequency in MHz. This will give a final result in feet. For me, my frequency is 14.060, which results in just under 17ft. For now, I'll cut to the nearest foot and trim later.
Now, we'll focus on the feedline. The equation will look like this:
492/f * (vF)
Where f is the frequency in MHz and vF is the velocity factor. A velocity factor is a comparison ratio between a medium and the speed of light. For speaker wire, 0.7 (70%) will work for vF. My equation results in 24.5 feet. In total, I will need 41.5ft of speaker wire.
When you're done, tie a knot at the point where you measured your antenna elements. Start splitting the wire down the center up to the knot. When you've completed this DON'T SPLIT ANY FURTHER! Tie an electrician's knot, as displayed here:
Pull your ends tight, add some insulators to the end, cut your antenna to resonance, and you're done! Just add a screw terminal BNC connector and you're done!
The complete Instructable for this can be found here: https://www.instructables.com/No-Solder-Easy-Speaker-Wire-Dipole/.
I'll post photos later, I've gotten busy again and need to attend to school for a bit now. Until next time, 73s!
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