Wayne wrote:
"JSF" wrote in message
. ..
Anyone used one and if so how did it compare to a 1/4 wave.

I build one for 2 meters some years ago. The element was 1/4 copper tubing
with an air spaced variable at the end, and fed with a modified gamma match.
The antenna was about 3 inches tall, and it fit on top of my van without
hitting the garage on the way in.

That makes sense.

For 80 meters we'd have an antenna 40 times taller and thicker, or a 10
inch diameter copper pipe element 10 feet above a metal plate a
wavelength in radius as a groundplane, and only be about 3dB down from
a 1/4 wl vertical.

I'll run right out and build one. :-)

73 Tom

wrote:
Wayne wrote:
"JSF" wrote in message
. ..
Anyone used one and if so how did it compare to a 1/4 wave.
I build one for 2 meters some years ago. The element was 1/4 copper tubing
with an air spaced variable at the end, and fed with a modified gamma match.
The antenna was about 3 inches tall, and it fit on top of my van without
hitting the garage on the way in.

That makes sense.

For 80 meters we'd have an antenna 40 times taller and thicker, or a 10
inch diameter copper pipe element 10 feet above a metal plate a
wavelength in radius as a groundplane, and only be about 3dB down from
a 1/4 wl vertical.

I'll run right out and build one. :-)

And wait'll you see the bandwidth! You'll be a busy guy running out and
tweaking the capacitor every time you QSY.

Roy Lewallen, W7EL

That's not high enough Q Roy.

C'mon, I can only pass CW and PSK31 signals through mine without
appreciable distortion.

Who needs to use SSB?

....

I did build one for 440MHz once though. Just a gap where the cap goes.
It was one of the 2 ring types; about 1/2 inch spacing. and I could
hit some repeaters with it... I could also hit some repeaters with one
of those mini duckies too... not much to recommend the DDRR.

I think if you're raring to build a vertically polarized, fairly low
profile antenna and you have a big supply of fat copper pipe and a high
voltage, high current, all welded split stator cap, you could build
yourself a fierce magloop.

Still have to retune every time you QSY... and I dunno... for similar
construction quality and materials, how's the efficiency of the DDRR
vs. the magloop? How low is the low radiation resistance of the DDRR?


73,Dan