[Antennas] QRP/P Direct Feed of 1/4 and 3/4 Wires?

Sat Nov 6 05:36:10 EST 2004

Jay,
I am using a 41' wire with a single 8' counterpoise. I can throw one end 
over a tree, or out a window. The theory is that the single counterpoise 
acts with a similar length of wire on the antenna as a open wire feed line, 
for an end fed antenna. That's the way a W3EDP antenna works, but a W3EDP 
antenna is 85' long with a 17' single counterpoise, and it is too long for 
portable work. This one is about 1/2 a W3EDP antenna. On 40 it is a 1/4 
wave wire antenna, end fed with a single counterpoise, on 20 a 1/2 wave 
wire antenna end fed, and so on. The position of the counterpoise can be 
any direction: alongside or opposite,the antenna or laying on the 
ground. I am using it with a K2 or a KX1 which have build-in antenna 
tuners which make short work of tuning, but there's no reason you can't use 
a manual tuner. The normal way the antenna is connected is using a UHF or 
BNC connector with alligator clips with the antenna connected to the center 
and the counterpoise to the ground. I also made up an extension using about 
a 8' length of RG58 with a bead balun on the antenna end to get the antenna 
out a window when I am using it inside.
73, Chas
At 07:30 PM 11/5/2004, J. Coote wrote:
>I'm considering using 1/4 or 3/4 wavelength (end-fed) wire antennas and
>radials, connected
>directly to the antenna port of monoband QRP portable transceivers. The
>operative word
>is portable, so I want to eliminate coax, tuners, SWR meters and so forth.
>>I'd like to hear from antennists who have actually strung up a 1/4 or 3/4
>wavelength wire
>(maybe a 1/4 wave radial ot two) and operated with the wire connected
>directly
>to the antenna port. Was the match good enough for your QRP transmitter?
>Did your antenna
>always work in different or unusual locations? Did your QRP monobander have
>a
>fit over a 2:1 or 3:1 SWR the way some civilian radios do?
>>It's my understanding that a 1/4 wave radiator and radials (a groundplane if
>you will)
>may have a 30-40 ohm feed impedance, and that a 3/4 wave wire and radials
>will have
>a slightly higher one of possibly 60-90 ohms.
>>If you've tried this, I'd like to hear from you.
>>Thanks,
>Jay
>AAR9QM/W6CJ
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