Saturday, December 3, 2016

Simple Ham Radio Antennas--Ultra-compact Multi-band Wire Antenna. Post #971.

Ultra-compact Multi-band Wire Antenna
(http://www.nc4b.org/wordpress.org/ultra-compact-multi-band-wire-antenna).
Author:  NC4B.
Accessed on 03 December 2016, 17:30 hrs, UTC.
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Comment:

Here's a fascinating multi-band HF antenna for those radio amateurs facing severe space restrictions or who live in HOA/CC&R-controlled housing.

According to NC4B, as long as you have at least 12 feet/3.65 meters of free horizontal or vertical space, you can build an antenna that will get you on the air at minimal expense and exposure.  The design is based on an antenna originally built by WB2JNA and can be found in various Amateur Radio publications.

The antenna is simple and can be made from locally available PVC pipe, #14-#16 AWG wire, various screws, and alligator clips.  NC4B says an automatic antenna "tuner" will help tame SWR, although adjusting the coil tap and the length of the "counterpoise" wire will prove satisfactory.

NC4B supplies a complete list of materials, SWR graphs, and performance records of the bands covered by this antenna (40 meters through 6 meters).

Basically, the antenna is a 12 foot/3.65 meter piece of wire connected to a wire coil wrapped around a 2 inch/5.08 cm diameter schedule 40 PVC pipe.  The center wire of a 50 ohm coaxial feed line is connected to the coil with a clip, with the shield of the coax connected to either a 16 foot/4.87 meters or a 32 foot/9.75 meters "counterpoise" wire, depending on the band you choose.  Two 16 foot/4.87 meters of wire can be clipped together or separated to get the desired SWR for the antenna.

I've built several of these antennas for portable use, and they work fairly well in a low noise environment.
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