"Frank Gilliland" wrote in message
...
On Thu, 4 Nov 2004 20:07:21 -0500, "M-Tech"
wrote in :

snip
Please explain how a poor "RF ground" can be corrected by increasing coax
length??


A given length of coax runs from the radio to the antenna mount. If
the shield is not adequately grounded (RF ground) then RF will crawl
onto the outside of the shield. When that happens your coax behaves
like an antenna, having resonant and non-resonant lengths. When that
happens, different lengths of the coax will put the antenna mount at
different phase angles, therefore changing the load impedance and SWR.
There are only two solutions: Provide a good RF ground to the antenna
mount (preferred), or change the length of the coax to 'tune' the
input impedance of the antenna.

That's all assuming your radio is fixed to a good RF ground.

Yeah, check-check. I'm with ya. I was just trying to ask(albeit,
sarcastically) who the hell would loop coax through their vehicle instead of
looking for a ground problem!!! I'm also assuming that if the above case
was true, you'd NEVER get enough of a ground to get a decent(say 2:1)swr
unless you have a few hundred feet in the trunk!!

I just always was told that if you have a swr problem, it won't be fixed by
changing coax lengths.

Also, why do people have negative comments about mag mounts? Mine works
fantastic. Maybe the paint on my Passat is thin:-)

Don
313

On Fri, 5 Nov 2004 19:27:06 -0500, "M-Tech"
wrote in :

snip
Yeah, check-check. I'm with ya. I was just trying to ask(albeit,
sarcastically) who the hell would loop coax through their vehicle instead of
looking for a ground problem!!! I'm also assuming that if the above case
was true, you'd NEVER get enough of a ground to get a decent(say 2:1)swr
unless you have a few hundred feet in the trunk!!


More than you might think: http://tinyurl.com/5z49m


I just always was told that if you have a swr problem, it won't be fixed by
changing coax lengths.

Also, why do people have negative comments about mag mounts? Mine works
fantastic. Maybe the paint on my Passat is thin:-)


I don't know if you have ever run anything else, but I have and the
difference is significant.






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