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It would definitely have to stand up to ultraviolet. There could probably be a good discussion on what paint to use. HOWEVER.... The real problem here is setting up a CONTROLLED EXPERIMENT. Otherwise, at the end of the day, there would be just one more anecdote that might or might not sway someone else to do it. NO SCIENCE. A carefully crafted controlled experiment is necessary. Given the feed configuration of a C3, it may not be possible. Let me explain by telling you what I would do with a C31XR. 1) Set up the C31XR with separate feedlines. This uses the fairly separate secondary mounting for the 15 meter DE. Put it up UNpainted to start. 2) Wait for some number of snow/rain static events. In each event, go back and forth quickly on the three bands and record the peak noise levels. I would expect this to reveal a gradually diminishing noise level as the frequency goes up, for two reasons: a) the discharge pulse has fewer components as the frequency goes up b) the element is smaller for the higher frequency and so has less surface area to intersect the falling droplets. 3) After establishing reference ratios between the bands, THEN and only then paint the 15 meter element ONLY. It might take a year of observations to accumulate enough observations to set the ratios, and might involve rather technical discussions on the data accumulated. 4) Repeat the same period of observations. If a killer difference is noted that zonks the noise on 15 meters, then the experimenter is a hero. If a small diff is noted, then maybe paint the 15 meter reflector and the first 15 meter director and see what happens (repeat the observation process). Using a C3, I'm not sure the functional separation exists to insure that the 15 meter element was getting mainly noise from droplets hitting it, and that the noise on the 15 m DE was the main source going into the feedline. The close coupling between the three DE's could cause noise a different DE to couple into the 15 DE and be received, even though it was painted. Actually, I think I can model that by placing sources on the three DE's and watching the currents in a load at the end of a feedline. There may be an alternate strategy for the experiment, but one does not occur to me at the moment. Later... - - . . . . . . - - . . . . - - . . - . . 73, Guy k2av@contesting.com Apex, NC, USA ----- Original Message ----- From: David LaBat <dlabat@earthlink.net> To: Guy Olinger, K2AV <k2av@contesting.com>; <force12talk@qth.com> Sent: Saturday, September 02, 2000 10:14 AM Subject: Re: [Force 12 Talk] Re: Force12 Braid grounding > I am willing to experiment with a brand new C3E, what type of paint would > 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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