@Oct/06 2015
In Oct , i have a long festival, building a 40 Meter DC receiver, and this is first DC receiver i ever build. and also, my first antenna need to be setup for 40M reception. the only antenna i can setup for laboratory use is the Long Wire Antenna. it's obviously easy to setup. i do some google, of course.
here is what i got:
at least 10 M, suggested, i use 12 Meter long wire(also a suggest length), diameter 1 mm copper wire.
http://vk6ysf.com/longwire_antenna.htm
don't use any band's half wave length and it's multiplier.
if you can not have a perfect ground, use another 1/4 wave-length wire as another counter pole.
what i built is not a true long wire antenna, more precisely, it's random end-feed wire antenna (true long wire at least one wave length, also, refer:http://vk6ysf.com/longwire_antenna.htm)
ARRL's suggestion is everywhere on WWW:
actually my antenna hook up a tree which is below my apartment. and i can not have a ground, so ARRL suggestion is, use another 1/4 wave length as counter-poise, like this:(from W8JI: http://www.w8ji.com/long_wire_antenna.htm )
W8JI's site suggest the counterpoise should above the ground, and, ARRL mentioned the counterpoise could be 1/4 wave length, and can be folded. let me jump the theory and experiment that later after i have a transmitter ready. one thing worthy to mention: the antenna-tuner should near the feed point, then the RF energy go out off your lab.
ok, let's build it, here is the insulator, cheap and easy construction:
Effect? there is audio sample from the DC receiver use this antenna, for now i use it as receive antenna only, so no tuner, no counterpoise:
more? waiting for a transmitter...