Here's a related note having to do with broadcast car radio. I bought a new car a few years ago and despite my pre-purchase test of the radio, AM reception was almost entirely gone -- none existent after I took delivery. Side note. Before taking delivery of the car, I had the dealer install window tinting. I had a huge battle with the dealer service department, trying to figure out what was wrong with the radio. Through my own research, I discovered that the dealer had subbed out the tint installation and that outfit had installed metalically infused tinting. And since the AM antenna was embedded in the rear window glass, it killed nearly all reception. It took quite a while to get to the bottom of this, but the problem was solved when I insisted on having that metalic tint removed and replaced with something more conventional. JP Pritchard, KG3JPP
_____ From: BVARC [mailto:[email protected]] On Behalf Of Robert Polinski via BVARC Sent: Wednesday, February 22, 2017 5:36 PM To: 'BRAZOS VALLEY AMATEUR RADIO CLUB' Cc: Robert Polinski Subject: Re: [BVARC] Paint and antennas (sometimes an insulator ) Years ago when I was doing Police car installations, I got a service call that 2 Bellaire patrol cars had radio problems. Poor receive and transmit. I open the trunk and put my Bird on the radio (UHF) and got hi swr. Checking the cable all's well, as I lowered the trunk lid I observed someone had painted the antenna to match the car! These were the plastic fin style you see on the trunk lids. Installed new antennas, problem solved. The paint used was the same metallic blue that was on the car. Proof that the metallic paint can affect the antenna. I other cases I have used off the shelf paint like Krylon to paint these same antennas (no metallic colors) with no effect on the antenna. Robert From: BVARC [mailto:[email protected]] On Behalf Of Jon Livingston kb0mnm via BVARC Sent: Wednesday, February 22, 2017 5:08 PM To: BVARC, GMuller885--- <[email protected]> Cc: [email protected]; Robert Polinski <[email protected]> Subject: Re: [BVARC] Paint and antennas (sometimes an insulator ) Guys & Gals: I will first echo what was said about metallic-flake paints, lead-based paints, etc. because increasing the physical diameter of a rod used in an antenna also can increase the bandwidth ( at the expense of gain ). For those portions of an antenna where a good electrical connection is wanted, the above paints are not exactly right either. The problem is that most metal paints actually stick better to slightly corroded surfaces ( as long as they are not deeply perforated ) than to bare metal. Accordingly, some use a slightly corrosive chemical to make the initial bonding better. In order to get a shiny finish, the 'clear' portion usually rises to the top and is non-conductive by comparison. So even metallic paints can insulate to some degree, even though many older ones have real metal flakes included. One solution ( pun not really intended when talking about paints ) would be to prepare all the joints with emery cloth, clean the surfaces of any remaining grit with a neutral solvent ( eg. rubbing alcohol without the soap used in medicinal bottles or lighter fluid ), and apply a conductive 'grease' to those surfaces. What materials would fit the bill for conductive grease? This varies according to what metals are involved. If you are dealing with aluminum, you may wish to use the same grease that electricians use for aluminum to copper wires in building construction- typically clothes dryers. If you are dealing with an all copper ground, you may wish to use a slight amount of "Butter it's Not" (Tm) which is basically ground-fine copper and a 'secret' binder. Where lightning is concerned, some folks would say that no chemicals should be used ( because a thick amount could be propelled by the heat if any water were included ). Others might say that a 'Cold Galvanizing' paint would be more appropriate because the zinc powder inside is combined with an appropriate binder for contact with copper or other metals. Larger two-way radio dealers get that paint from industrial chemical and parts supply houses ( eg. Tessco )- which may require a minimum purchase. Once the intentionally-conductive surfaces ( like the inside and outside mating of telescoping antenna tubes ) are coated, any 'non-conductive' paint could be used. I would recommend using a quick-dry clear polyurethane prior to a color coat, in case the 'camoflage' were to be removed later. Disclaimers: 1. All of the above statements are true to the best of my knowledge, yet I do not sell paint for a living. My brother does, but he has not been consulted on this an lives over 1,000 miles from Houston. For best results, consult an electrician- or- make a sample and test for yourself the conductivity on glass of any paint. 2. Statements made about paints sticking better to corroded surfaces are in my experience true, given to me by a Master Electrician who worked for Ford Motor at both the Assembly plant and Hydroelectric facility in St. Paul, Mn. While I have every reason to believe that this is true, you may wish to again consult a paint specialist. 3. "Gopher Grease" is one name loosely applied to a chemical used for bonding aluminum to copper and other metals. Any electrical supply house and most larger hardware stores should have this 'conductive' grease on hand. It may cost you $15.00 to $65.00 for a small bottle, thus shopping over the Internet may save you money. 4. Do not forget the words of Ralphie's mother in "A Christmas Story(?)", when he asked for a BB gun- "You will put your eye out"- this applies to working with the sharp ends of antenna tubes. Please wear eye protection ( and nose protection ) if you paint with an aerosol can & do so in a well-ventilated area. . Jon L. Livingston, Electronics Technician 17722 Fieldglen Drive ( SE of FM 529 & Barker Cypress Road ) Houston, Texas 77084 <mailto:[email protected]> [email protected] General Radiotelephone license PGGB062294 CET Wireless Communications WCM-R185658 Amateur Radio license KB0MNM -73 www.linkedin.com/in/jon-livingston _____ From: "Robert Polinski via BVARC" <[email protected]> To: "BRAZOS VALLEY AMATEUR RADIO CLUB" <[email protected]> Cc: "Robert Polinski" <[email protected]> Sent: Wednesday, February 22, 2017 3:16:37 PM Subject: Re: [BVARC] Paint and antennas Paint is ok, do not use auto paint or metallic paint, or paint with lead. Child safe paint assures no metals are used. No hi temp paints ether. Another option is to use heat shrink tubing. Robert From: BVARC [mailto:[email protected]] On Behalf Of Tom Watson via BVARC Sent: Wednesday, February 22, 2017 3:05 PM To: 'BRAZOS VALLEY AMATEUR RADIO CLUB' <[email protected]> Cc: Tom Watson <[email protected]> Subject: Re: [BVARC] Paint and antennas Gayle, I've been researching the exact same question, but have not found a definitive answer. Some think it makes no difference; others are skeptical. Below is an exchange I had recently with Al Andzik (WB0TGE) about painting his "Mighty Woof" copper tube 2m/70 cm design ( http://www.hamradioschool.com/wbotges-mighty-woof-2m440-mhz-dual-band-fan-di pole/ ). I am building this antenna and will test it with and without paint by the end of March. I'll post the results. Tom Watson, WZ8Q ---------------------------------------------------------------------------- From: Al Andzik [mailto:[email protected]] Sent: Friday, February 10, 2017 7:39 PM To: Tom Watson Subject: Re: Your "Mighty Woof" 2m/440 MHz fan dipole... Really can't say if paint will affect characteristics. You might try doing some SWR measurements un-painted then paint maybe one element and see if things change. If they do, you can clean it off. Also if a dark color is what you want, perhaps some "cold" gun bluing solution might work instead of paint. You wouldn't have a coating over the metal but it will just change the color. Usually the stuff is for steel, but it might work on copper in some manner too. On Feb 10, 2017, at 4:56 PM, Tom Watson <[email protected]> wrote: Al, Have you heard of anyone painting this antenna? I live in an HOA-controlled area, but members of the architectural committee don't see so well and I believe that if I paint this antenna dark gray, no one will see it. So far, I haven't found any discussions that suggest that an antenna cannot be painted or that doing so will cause a significant decrease in performance. But I want to be sure before proceeding with paint. Also, I plan to run the transmission line inside a 15', 1-3/8" diameter steel tube attached to a wooden fence. Is it possible that the tube will provide enough of a choke effect, or do you think the 4 or 5 turns of coax for that purpose will still be necessary? Thanks again for your help, Tom Watson, WZ8Q From: BVARC [mailto:[email protected]] On Behalf Of Gayle Dotts via BVARC Sent: Wednesday, February 22, 2017 2:31 PM To: BRAZOS VALLEY AMATEUR RADIO CLUB Cc: Gayle Dotts Subject: [BVARC] Paint and antennas Can an tube antenna say a beam or Yagi, be painted for camoflage purposes and not loose any Tx or Rx characteristics by painting it? Gayle KF5LVZ _______________________________________________ BVARC mailing list [email protected] http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org
_______________________________________________ BVARC mailing list [email protected] http://mail.bvarc.org/mailman/listinfo/bvarc_bvarc.org
