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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 |
#2
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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 |
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