Discussion in 'Amateur Radio News' started by KB7TBT, Aug 28, 2019.
Ham Radio - An end fed half wave antenna with built in counterpoise. (Experimental)
Are you sure that the coax shield is not the counterpoise?
The coax WILL radiate. But---if choked properly the counterpoise does a phase cancellation on that electrical length, kinda like a J pole.
Basically this is a method to end-feed the antenna, normally not easy because the voltage max lies at the ends, and matching it is lossy and not easy. Here the 'end' is really an OCD point electrically. The antenna is designed as a convenience to stop the drooping coax such as you see on a dipole.
These designs have been around for a while. Nice to see it discussed here.
how do you get a 49:1 match?? how much po
How do you get a 49:1 match to take much power, will how much power will it take? I'm inpresed it will take 40 watts
I run QRO
Version of that in an RSGB antenna book 50' long with 25' counterpoise made with speaker wire and a toroid wrapped at the end, the speakerwire goes straight into a tuner, covers 40-10, a half size covers 20-6. They show it as a vertical and it has pretty low radiation angle, they also show a dual phased array, quick and dirty, a roll of speaker wire 2 toroids and a balun.
Match with an LC resonant tank circuit between antenna and counterpoise. Couple the coax feed with a one or two turn link to L.
Just Hit that 49:1 setup made of small speaker wire and a small toroid with 1.5 kilowatts and see what happens !!!!
Better be a big donut and very thick wire, hi!
Design attributed to K9ESE, phased version to M3KXZ. The book is RSGB Successful Wire Antennas.
For QRO, I've put 1.5 KW into the matching network I described above. No problem. Use air wound coil and capacitor with sufficient spacing.
You can make the one or two turn link with a variable capacitor in series so you don't have to vary the spacing of the link coil.
1 to 1 swr.
The counterpoise doesn't have to be fancy twin lead... just hang or lay out a few feet of wire... 3 or 4 ft.