CB Antenna help
 

RF grounds and DC grounds are not necessarily the same. You can feed a
grounded vertical part way up with good results. One could have an RF
choke in a circuit which is essentially a short circuit to DC, but is an
open circuit for RF.

Interesting point: if you take a 1/4 wave section of coax (taking into
account velocity factor) and solder the inner conductor to the braid, you
will measure zero ohms at the far end on an ohm meter. If you try and feed
rf into it, it will appear as very close to an open circuit! Should you cut
that short off the end, leaving it open, it will test open with a meter, but
will be a short circuit to the rf.

Things ain't always what they appear to be :)


73 from Rochester, NY
Jim



"SNA" wrote in message
et...
I have a question which I need to ask. This may sound stupid but I just
don't understand. I have a cb base antenna that is a "DC Grounded "
antenna.
When I hook up a ohm meter to it at the coax end ...it shows a direct
short.
The swr on the antenna is excellent.....so how can this be?
Any help will be appreciated




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A short at DC isn't necessarily a short at AC.. charging a capacitor
or energizing an inductor causes an impedance at AC. When the fields
are being built up and collapsing (electrostatic in the case of
capacitors and electromagnetic in the case of inductors) an impedance
is created. Impedance is to AC as resistance is to DC.

-SSB

SNA wrote:

I have a question which I need to ask. This may sound stupid but I just
don't understand. I have a cb base antenna that is a "DC Grounded " antenna.
When I hook up a ohm meter to it at the coax end ...it shows a direct short.
The swr on the antenna is excellent.....so how can this be?
Any help will be appreciated