On 8/14/2011 10:33 AM, K8RI on TT wrote:
> Jim, you've given me some positive thoughts and ideas on using that
> LMR-600UF, particularly on six and 2 meters.
OK, BUT: because the effectiveness of stubs is directly related to R
(at the freq of interest), foam coax is not the best choice for stubs
unless the conductors are also larger, because Vf requires that they be
longer to achieve resonance. This is not a slam dunk though -- with
foam, center conductor must be larger to hit the Zo goal if shield
diameter remains constant.
Another note -- W2VJN noted that some stubs he built from LMR400 and
stashed in his garage for 5 years didn't measure as well as they did
when he built them.
Here's some data to chew on http://audiosystemsgroup.com/StubData.pdf
The old coax was rescued from the shack of N6RZ (SK) when I helped his
XYL get rid of his considerable stash of gear, junk box, and antennas.
Some of it looked pretty bad, but was fine electrically. 3227 and 2427K
are Commscope, new foam, #10 solid copper center, copper braid plus foil
shield, measures like LMR400, except that 3227/2427K is slightly better
on 160M. 2427K is the plenum version.
73, JimK9YC
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