One of the things I notice about the differences in the two is not only the different "culture" of them, but a vast difference in the technical approach to the radios themselves. Without getting into a vast discussion on one of these subjects, I
do notice the constant attention of CB ops to so-called
coax length and an obsession with what they call
SWR's (ssssssssssss) whose plural pronunciation (more often than not) indicates a lack of basic understanding of what SWR (SINGULAR!) is!
On the CB boards that I casually read, there is almost an
OBSESSION with this "coax length" issue whereby the operators seem to be "tuning" their antennas by trimming their coax to a
certain length while completely IGNORING the REAL way to set an antenna so it will resonate on a particular band or frequency! Many of these "experts" proudly launch into a vast discourse on
velocity factor (VF) and complex formulas that seem more intent on impressing the reader than actually achieving
RESONANCE.
So what IS this velocity factor thing? Simply put, it is the speed at which an RF signal travels thru a medium. It can be AIR, WATER, WIRE, or a CABLE (same thing as wire, really). But that is ALL it is. PERIOD!!!!
IT HAS LITTLE TO DO WITH 'TUNING' OR RESONATING AN ANTENNA! Worrying about it and including it in a bunch of formulas is utter horses---!!!!!
I see this formula that goes something like 492+ or - VF/frequency in mhz-yada yada yada= so 'n so coax length! HA! It, for the most part, and for a CB or any OTHER antenna, IS-UTTER-HOOEY-AND HORSE-DUNG!
The question is: can you "tune", or SHOULD you "tune" your CB antenna by trimming your coax to a
certain length? NO! So what SHOULD you do?
For a normal installation that has adequate metal, enough to serve as the other half of your antenna (remember that that whip sticking up on your car IS only HALF of your antenna system) you should first assure that the whip is in the clear of obstructions (let it "see" over the car). Then you should loosen the set screw for the whip (for coil type antennas) and slide it UP or DOWN in the collet while observing the
SWR (NOT SWR'sssssssssss). Another hint is to straighten out a hanger and use it as a substitute for the whip if the stainless whip doesn't let the antenna "tune". This way, you don't ruin a good whip by accidentally cutting too much off! :headbang Run whatever length of coax you need to the radio and fergeddaboudit! Can you tune antennas cutting coax? Yes and no. What you are doing is fooling your SWR bridge into reading a 50 ohm match and a "good" swr. BUT! The antenna
IS STILL MISMATCHED BECAUSE IT HAS NOT BEEN SET TO A "TRUE" AND ACCURATE RESONANCE!!!! What you have is an
inefficient antenna. Remember those little 5 watt "dummy load" things that ALWAYS show a "good SWR no matter what? That's because they are nothing more than a RESISTOR with an 50 ohm impedance!!!! In effect, your antenna, because it is being "tricked" by the coax (which IS 50 ohms, BTW) becomes, more or less, a sort of
resistor that exhibits varying kinds of radiation because it has not been "set" to a "true" SWR.
If the coax at a
certain length was so good at radiating a signal, then WHY would we even NEED the antenna?
Finally, the only time that coax should be a "certain" length is in certain "phased" setups or when the ground (or counterpoise) is not sufficient. (Remember the above comments about the vehicle being the OTHER half of the antenna system?)
One of the glaring differences in amateur operations and CB is the LACK of the obsession with coax length with respect to CB. Look at the amateur discussion boards where you find very little discussion of "coax length" or the same preoccupation with it vs CB boards. While there ARE
some situations where coax may be required to be certain lengths (some special folded dipoles, verticals, etc), it is generally very unusual.
Here's ONE amateur who has NEVER resorted to "cutting" coax to a
certain length in order to resonate an antenna system unless it was an integral part of the mfr's design! (ME!)
73
CWM
