Must say that I second this, as the "sampleing" in MANY swr meters not
only DON'T read accurately, at VHF, but actually induce a "Impedence
Mis-Match" (and gives you a FALSE reading , at VHF) ! In fact, have
seen "Flat antennas, show some hideous SWR's " ! And, tho length is
of the antenna element is
the determining factor, you need a good meter if you want to minimize
the swr. As to insulating the J-Pole, BELOW the 2 vertical elements,
this shouldn't be necessary- and - keep in mind that this antenna wants
a Balanced feedline-, so, that your coax WON'T radiate! BUT- as you
probably will use (unbalanced) coax (No BALUN) that your coax becomes
PART of the antenna system ! But this should not present itself
as much of a problem, unless it lets RF into the RIG/Power Supply in
a quantity to cause problems in those devices! As to coax, use the
lowest loss you can afford, tho, again, in this instance, will mean
LITTLE! At 20 foot length, RG 58 should work fine! Just build it, get a
fairly good match to keep the rig happy, and enjoy! Jim NN7K


Alan WA4SCA wrote:
Tom,

Most of those CB SWR meters are good for HF and probably 6 meters or
so. My experience is that they are highly inaccurate at best, and
often completely unusable on 2 meters. I lend my Bird wattmeter out
frequently for people doing installations because of this.

Of course, there are so many units out there it is impossible to say
with certainty that they won't work, but that's what to expect. You
don't what an additional unknown in building up a new antenna.


--
Alan
WA4SCA