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you think would be optimal? any potential downside? Dave K0XH ----- Original Message ----- From: "Guy Olinger, K2AV" <k2av@contesting.com> To: "Frank C. Travanty" <w9jcc@juno.com>; <force12talk@qth.com> Sent: Friday, September 01, 2000 9:46 PM Subject: Re: [Force 12 Talk] Re: Force12 Braid grounding > > There is a lot more going on in rain/snow static than whether or not an > element is grounded. > > It is NOT particularly clear that grounding yagi elements improves rain > static. Many years of occasional VERY LOUD rain/snow static on W4BVV's > VERY DEFINITELY GROUNDED yagi elements tells me that grounding the > insulated elements on F12 antenna's will NOT be the answer that some > think it will be. > > Think of it this way: The droplet carries a fixed charge. When it comes > in contact with something with an unequal charge it will discharge in a > pulse event quickly reaching a charge equilibrium with the touched > object. IF the second object is NOT CONNECTED to something else it will > retain the charge. > > Assume that this continues, and that the second object (an ungrounded > yagi element, not touching anything else) gets additional touches. At > some point the charge on the yagi element will build up until it is > equal to the charge on the droplets. Then when the droplet hits there > will be no current flow, no pulse event to create the noise. > > That the voltage builds up in this fashion, does in fact happen. If the > droplets are carrying a high enough charge, then the charge on the > element will build up to the point where it will jump across the gap. > F12 owners have reported a "snap, snap, snap" kind of noise where this > discharge is happening periodically. > > What I've not seen reported one way or another, where this charge was > being accumulated from rain or snow, was whether the rain static > gradually diminished leading up the "snap" of the discharge. > > Grounding, of course, will get rid of the "snap, snap, snap" noise. So > will a 10 meg resistor. So will acid rain. So will soot. > > Grounding, though, means that each droplet touch ALWAYS causes the > maximum possible pulse current. The noise you hear is directly related > to the amplitude of the pulse current. If you reduce the pulse current > to 1/10, the noise goes down by 20 dB. Reduce it to 1/100, the noise > goes down 40 dB. > > By having a very high resistance path to ground (NOT an open path), > designed to bleed just barely enough to keep an arcing voltage from > building up, the pulse current is reduced, and I suspect that the > static > will be minimized. And it will probably only be needed for the driven > element. > > The disadvantage of this arrangement is that lightning induction > current > would blow the drain resistor, likely a regular event. > > The point of this exercise? It seems highly UNLIKELY that rain static > is > any kind of a reason to pick or not pick a F12 antenna. Base your > decision on other issues. > > If you've already got one, ANY DC ground path will allow the driven > element to stay at ground DC potential, and guarantee maximum noise > level. > > Has anyone tried spray-painting the driven element to see if it > eliminates the droplet discharge? > > - - . . . . . . - - . . . . - - . . - . . > > 73, Guy > k2av@contesting.com > Apex, NC, USA > > > ----- Original Message ----- > > From: Frank C. Travanty <w9jcc@juno.com> > > To: <Force12Talk@qth.com> > > Sent: Friday, September 01, 2000 9:27 AM > > Subject: Re: [Force 12 Talk] Re: Force12 Braid grounding > > > > > > > I have a C-31XR and have had a ~ 10 over S-9 continuous S-meter > > reading > > > for as long as an hour, when a storm is approacing 50 miles out, as > > well > > > as the typical rain/snow noise. I was considering modifying the > > matching > > > section from a hairpin "coil" to a beta match similar to that used > on > > a > > > TH6DXX, and grounding the neutral point to the boom to DC ground the > > > driven element. Haven't tried it, so can't vouch for its > > effectiveness. I > > > used the TH6DXX for 30 years, and although I did experience > rain/snow > > > noise at times, I don't recal it being as severe as with the current > > > antenna. > > > 73, > > > Frank > > > > > > On Fri, 1 Sep 2000 08:14:11 EDT K7LXC@aol.com writes: > > > > In a message dated 08/31/2000 9:59:39 PM Pacific Daylight Time, > > > > list@qth.com > > > > writes: > > > > > > > > > From: "Barry Kirkwood" <bjk@ihug.co.nz> > > > > > To: <Force12Talk@qth.com> > > > > > Subject: Fw: [Force 12 Talk] Isolated elements > > > > > Date: Fri, 1 Sep 2000 11:11:00 +1200 > > > > > > > > > > Hello Force 12ers, > > > > > Am interested in this. Have had one reply saying that bonding > > > > braid of coax > > > > > to boom upstream from balun works OK. Any other > > > > opinions/experiences? > > > > > > > > I'll always ask "Is it what the manufacturer recommends?". I > > > > don't ever > > > > remember seeing anything about grounding the feedline shield in > any > > > > of the 2 > > > > dozen or so F12 antennas that I've installed. If they don't tell > you > > > > to do it > > > > - DON'T do it. If they tell you to do it - DO it. > > > > > > > > > Would expect this to reduce rain/snow static. > > > > > > > > Snow? New Zealand? > > > > > > > > Cheers, Steve K7LXC > > > > Tower Tech > > > > > > > > > > > > -------------------------------------------- > > > > Force12Talk mailing list provided as a service by Force 12 > Antennas, > > > > Inc. > > > > Force 12 Web site: http://www.qth.com/force12 > > > > > > > > Submissions: send to Force12Talk@qth.com > > > > To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com > > > > Force12Talk Message Archive: > http://www.qth.com/force12/list/force12talk > > > > For problems with the list, contact n4zr@qth.com > > > > > > > > > > > > > > ________________________________________________________________ > > > YOU'RE PAYING TOO MUCH FOR THE INTERNET! > > > Juno now offers FREE Internet Access! > > > Try it today - there's no risk! For your FREE software, visit: > > > http://dl.www.juno.com/get/tagj. > > > > > > > > > -------------------------------------------- > > > Force12Talk mailing list provided as a service by Force 12 Antennas, > > Inc. > > > Force 12 Web site: http://www.qth.com/force12 > > > > > > Submissions: send to Force12Talk@qth.com > > > To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com > > > Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk > > > For problems with the list, contact n4zr@qth.com > > > > > > > > > > > > > > > -------------------------------------------- > Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. > Force 12 Web site: http://www.qth.com/force12 > > Submissions: send to Force12Talk@qth.com > To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com > Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk > For problems with the list, contact n4zr@qth.com > > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact n4zr@qth.com |
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