Paul, Using a 5,000 volt power supply sounds like a pretty drastic approach. Does it just boil out the water or blow a hole in the feed line? And if there is no noticeable reaction, the feed line could still be lossy, right?
I'm afraid there is no easy way to evaluate an antenna except from signal reports. Even if you have a field strength meter, which I do not have, the reading would only be relative except on a calibrated test range. Thanks for sharing your experience with me. John -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Finch Sent: Saturday, May 03, 2008 11:31 AM To: [email protected] Subject: RE: [Repeater-Builder] Re: antenna question John, By all means it can, I have seen a good dummy load DB224 antenna several times. It had fairly good reflected reading but like I said, it resembled a dummy load more than an antenna. These problems can be addressed. There can be water in the coax harness or straight out corrosion on the connections. You can check the antenna several ways. I have used a signal generator and a spectrum analyzer and do simple loss test to each dipole with a sniffer antenna. I have a friend that checks his harnesses with the dipoles disconnected with a small 5,000 VDC power supply, any water in the coax shows up really well that way. A really high range VOM and check the resistance will work pretty good also but the 5K VDC seems to ferret out all problems. So far, with the ScotchKote I have not had a problem. I have a DB408 that I am taking to Dayton that I got from my ex-boss when they closed the shop that had one coat of Scotchkote that was looks kind of thin. Before I take it to Dayton I will tighten all connections, check it and slop several coats of Scotchkote on it. I normally slop on at least three coats of the stuff, it's messy but I believe in it. So far I have not found anything better in the Texas sun. Paul _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of John Transue Sent: Saturday, May 03, 2008 8:52 AM To: [email protected] Subject: RE: [Repeater-Builder] Re: antenna question So how do you know your antenna is not performing as it should? When an antenna has a corrosion problem, can it still have good VSWR? I think it can. A resistor can have good VSWR. So what should I do to find out whether I need a new antenna? I'd like to benefit from your experience. Thanks for any advice you can give me. John AF4PD -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of georgiaskywarn Sent: Saturday, May 03, 2008 9:15 AM To: [email protected] Subject: [Repeater-Builder] Re: antenna question Well I thought the same thing. I have a db408 that I have "treated" with plastic dip AND liquid tape. Long story but have several layers (about 3 or 4) of this stuff on there. Each layer I allowed to dry before putting on the next. In the pictures you can see that every joint (metal to metal) is protected by this stuff. I also went up the dipoles far enough for any possible egress of moisture. Might not be pretty, but think it will work. The pics are taken with the antenna temporarily on the side of my tower (not hooked up yet). http://f1.grp. <http://f1.grp.yahoofs.com/v1/0GEcSFgRqZpJVmTlqpB72pv8w7tAZtRcCcnp5vmv6q Vr44p8O-ZFzec_HaY2Ga6TgV2Yj_3lzSUfcMnhJ3JGc57pcJsE-k5gcErJ/pix/IMG_1277. JPG> yahoofs.com/v1/0GEcSFgRqZpJVmTlqpB72pv8w7tAZtRcCcnp5vmv6qVr44p8O-ZFzec_H aY2Ga6TgV2Yj_3lzSUfcMnhJ3JGc57pcJsE-k5gcErJ/pix/IMG_1277.JPG http://f1.grp. <http://f1.grp.yahoofs.com/v1/0GEcSHs2jQFJVmTl6X_XYxKmmCUXuduBzeXqkRzKHC 6GBZz7otBoFOgQDzYeQt3Umjq9dbwHhiGcSIrqsKi9wt2JEamLwVt1E_-7/pix/IMG_1278. JPG> yahoofs.com/v1/0GEcSHs2jQFJVmTl6X_XYxKmmCUXuduBzeXqkRzKHC6GBZz7otBoFOgQD zYeQt3Umjq9dbwHhiGcSIrqsKi9wt2JEamLwVt1E_-7/pix/IMG_1278.JPG (remember, you might have to copy and paste it) This antenna has the bracing that wraps around the pipe, not the hose clamp style dipoles. So I drilled through the metal straps and into the pipe. After that I riveted each strap into the pipe. Waiting for my "contractor" to get the go ahead from the county to replace a Diamond UHF antenna. 73, Robert KD4YDC --- In Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> yahoogroups.com, "Craig" <[EMAIL PROTECTED]> wrote: > > Paul and others: > > Other than using Scotchkote has anyone used DIP-IT which is that > plastic coating sold in cans designed for dipping tools into to build > up a rubber coating on them. Like the scotchkote you would probably > have to put sveral coats on, but since it's a rubber base it may last > longer than the Scotchkote which harderns. > > Craig > > > --- In Repeater-Builder@ <mailto:Repeater-Builder%40yahoogroups.com> yahoogroups.com, "Paul Finch" > <dpaulfinch@> wrote: > > > > Ron, > > > ... > > The second part of making a new DB folded dipole antenna last is > sealing every nook and cranny of the antenna with 3M Scotchkote. I > paint at least two coats on every screwhead, coax end, nut, plastic > molded junction and anything that could be a point of bimetal > corrosion or coax water leak. If I could dip it in Scotchkote I > would. ... > __________ NOD32 2918 (20080303) Information __________ This message was checked by NOD32 antivirus system. http://www.eset. <http://www.eset.com> com No virus found in this incoming message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.8/1412 - Release Date: 5/2/2008 4:34 PM No virus found in this outgoing message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.8/1412 - Release Date: 5/2/2008 4:34 PM __________ NOD32 2918 (20080303) Information __________ This message was checked by NOD32 antivirus system. http://www.eset.com
