I love end-fed antennas. My first one was a PAR 40/20/10, and is has become my permanent antenna at home. I have reached 5200 miles on 1.3W and 830 miles with 100mW with it! And numerous other such contacts. I also have a tunable 6-40m I built, and am getting a 15-40m end-fed tuner kit in the mail this week. Why end-feds? Because they work, really well. They are easy to deploy in the field and weigh very little. LNR Precision (bought PAR) has a new trail model by the way: http://www.lnrprecision.com. But this is about building your own 80m version. I wanted something rugged and simple. An end-fed is simple by design, though the theory isn't so simple. It is an impedance transformer. Here is the schematic I found online (http://www.spirat.com.au/vk5zvs/pic54.htm):
Not much to it really... Let's see with all the components in the box:
The box is a Hammond cast aluminum. The capacitor is a 100pF 3500V doorknob type. I could have used a cheaper ceramic disk type, but you know me by now.. The resistor you see there (black) goes to an isolated ground plug for use with a weather balloon or kite (1.5M 3W). When connected to the earth, it bleeds static electricity to the ground to avoid frying the radio (thousands of volts).
And the finished product:
I though about connecting grounds together via wires, but the box does that well.. The optional counterpoise (we'll see about "optional" later.. (0.05 WL, about 13ft)) binding post (black) is electrically connected to the box, while the antenna wire post (red) of course is isolated. The magnet wire is 18ga. Opinions?
After testing I will pot it with liquid rubber... I did some preliminary testing with a 135ft wire strung around the house and got a 3:1 SWR; just enough to send my call sign and "testing" in CW of course. I very rarely use a microphone.. Higher up the band the SWR goes up, so the antenna is a bit too long. Having many turns at weird angles and a house with all it's wiring around it of course doesn't help. Once stretched outside I expect it to work great. I will post an update.
Now I'll be able to check in CW nets on 80m!
Gil.
« Last Edit: April 03, 2013, 02:48:19 PM by gil »
