Originally Posted by BOOTY MONSTER
most of us CB
'er only have a vswr meter for checking/tuning antennas . folks have been getting by with just that for decades . using a analyzer could do a better job though . on my mobile my 10k tunes to 1.3 on a mfj259b at the shop , but take it off and put on a 102 whip and it shoots above 2.5 .
resonance smesonance ....... i refuse to try to run a radio into that kind of vswr , so i stuck with the 10k .
BM, do you really think a 102" whip will show a 2.5 SWR if the ground plane part of the installation is suitable? I've heard similar stories for ever, and that is why I decided to do my 1/4 wave work in the summers of 2003/2006... trying to understand what goes on with a 1/4 wave radiator.
IMO, the 10K raised coil antenna is less effected by the physical ground plane presented, or said another way, it just doesn't need as much ground plane to allow it to work effectively...as long as the coil is effective and well in the clear.
Your own experience with your homemade Starduster type ground plane should give you a clue in this regard, because I think you saw a good match. What else besides the ground plane is possible to cause such bad results in your mobile install, assuming it's installed correctly?
A 1/4 wave radiator requires a good ground plane, and what you get or think you get
with a mobile in this regard...is almost always a little less than suitable.
The open coil mobile type antennas are just more forgiving with mobile installs with a poor ground plane.
Compare the match and SWR with these Eznec models below and you'll see what is likely to happen as the ground plane becomes less effective with a 1/4 wave radiator. Your mobile SWR problem probably has little to nothing to do with the radiator itself.
These three models shown are with the same radiator and the radials are:
Slightly slanted like a mobile might present
Slanted less than 50* degrees like your SD'r might have presented. Bm's 102'' radiator idea..pdf