RadioBanter - View Single Post

Michael Coslo · February 13th 09, 01:36 PM posted to rec.radio.amateur.antenna

wrote:
Trying to design a 13' vertical with a loading coil at 3'. It will be
mounted on an aluminum tool box on a pickup. I modeled this on EZNEC
and came up with loads to resonate on 14.2 and 7.2 mhz. Wind the
coils with calculated inductance and it is way lower in frequency than
predicted.

Tapped up the coils and eventially got matches, but was wondering why
the design and real world are so far apart?

The real world and modeling are a lot different with vehicles than they
are with land mounted antennas. Your ground on your truck is very complex.

side question: Did you bond the bejabbers out of the truck? You
really should have hood, doors, tailgate, exhaust system in several
places, frame in several places, radiator, engine block, and any other
place of interest you can think of.

Rule of thumb is that you need at least one more bond than the maximum
amount you'd dare to place on the vehicle.

The vehicle bonding and grounding is more important than the aerial part
IMO.

- 73 de Mike N3LI -