🚀 go-pugleaf

>I am setting up a CB in my house, and I am having problems with a ground 
>plane.  The equipment works fine in my car, so I know its not broken or 
>anything.  I want to put the antenna on my roof, but I am having trouble 
>finding a good ground plane.  The manager at Radio Shack suggest getting a 
>peice of sheetmetal for a ground plane.  How big should I make the sheet 
>metal? 

At a minimum, 1/4 wavelength radius, centered on the antenna.  (At CB 
frequencies, that's about 109", or a bit over nine feet.)  But you don't
need a solid sheet; several "radials", or grounded wires of about this
length stretched radially from the grounded mount at the base of the antenna,
will work just as well and be a whole lot simpler.  You've probably seen the
CB "ground plane" antennas, with a 1/4 wavelength vertical whip surrounded
by 3 or 4 drooping horizontal elements of about the same length - those
sorta-horizontal elements are the ground radials.

For a home installation, you'd be much better off making a full-length
1/4-wave whip than using a loaded mobile antenna (the kind with a coil in the
middle or at the base), and at least 3 or 4 ground radials (the more the
merrier; keep 'em symmetrically spaced about the vertical element, i.e., if
you have four, they should be 90 degrees apart.   "Drooping" the radials
slightly - as you see on the commercially-made base antennas - raises the
feedpoint impedance slightly for a better match to 50-ohm line (a vertical
whip with a "perfect, flat" ground plane has a feedpoint impedance of about
37 ohms).

Another option would be a half-wave dipole (about eighteen feet overall at
the CB frequencies) mounted vertically; this'll only work, though, if you
can keep the bottom end as well as the top well off the ground and away from
any conductive structures such as towers.

(Obligatory plug for ham radio - have you heard about the new no-code
Technician license?  Now may be a good time to consider "stepping up" from
CB!)

Bob Myers  KC0EW   HP Graphics Tech. Div.|  Opinions expressed here are not
                   Ft. Collins, Colorado |  those of my employer or any other
myers@fc.hp.com                          |  sentient life-form on this planet.