The CB-whip 2/440 HAM "J" Antenna
by N6JSX June, 2012
Here is my very successful 2m/440 dual-band single-feed "J" mobile antenna made with a 102" CB whip.
I've been using this J for more than 25yrs on my mobiles. Over the years through trial-n-error I've modified my basic design making the J more effective and very durable.
In general a VHF/UHF "J" :
• has a low, almost flat angle of radiation, for maximum distance,
no ground-plane or radials
The "J" is the BEST antenna for flat-lander's giving them the longest transmitted signal distance possible. This is due to the exceptional low main lobe, nearly flat, angle of radiation of about 1-3 degrees.
The more common antennas have much higher radiation angles that may be good for mountain top repeaters but will significantly shorten flat-land distances. The 5/8 wave has ~3-6 degree radiation angle with the highest angle of ~4-9 degrees is from a ¼ wave. These ¼ wave & 5/8 wave antennas require a good counterpoise for optimal omini-directional performance.
The "J" has approximately 3dB of gain over a 1/4 wave ground plane. Technically, the "J" antenna is an end-fed 1/2 wave antenna using a 1/4 wave matching stub. In years past it was referred to as an "end-fed Zepp". The matching section acts as a matching transformer, the 1/2 wave radiator sees the 1/4 wave matching section as an image of a false ground. In best terms, the "J" is a balanced 1/4 wave matching stub feeding an unbalanced 1/2 wave load. The long element is 3/4 wave with a 1/4 wave matching element creating a tuned 1/2 wave active radiator that needs no counterpoise (ground plane/radials).
save the entire construction details here to see how I built
If you had rather buy than build, see the Arrow 2/440 J Pole here!