I just looked at the TX/RX catalog - looks like you're referring to their CC Series antennas; the description indicate that the "lightning spike" (their term) is connected to a solid brass support pipe. They're not made for 900 MHz though, only UHF/700/800. Looks like the price for the 6dB gain version is around $2K.
Their collinear description does not mention anything about a lightning spike, just "internal DC grounding for lightning protection and reduction of precipitation noise." It also occurs to me that the lightning spikes I've seen on 900 MHz DB Products antennas are not in the center of the cap, but offset to one side. They appear to be molded into the cap, not just part of the antenna passing thru it. Well I guess worst case, the Maxrad 900 antennas can be had fairly cheaply on eBay. I picked up 3 of the 6dB models for around $80 shipped. Much cheaper to replace than the Comet GP-15's! (Plus I've got a three year supply at my current lightning strike rate.) Doug K4AC From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Monday, November 02, 2009 7:05 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Lightning Rod (Bolt)? I haven't seen any for that band either, but don't know what they utilize for the various panel antennas that are covered with a radome. TX/RX makes a vertical that has integral folded dipoles and an aluminum extrusion goes all the way to the tip of the antenna for lightning. I suspect it might survive a direct hit. To look at it, you'd think is was just one more fiberglass collinear. I'm pretty sure it's available in both 800 and 900, but it won't be cheap. Chuck WB2EDV ----- Original Message ----- From: Doug Rehman <mailto:d...@k4ac.com> To: Repeater-Builder@yahoogroups.com Sent: Monday, November 02, 2009 6:59 PM Subject: RE: [Repeater-Builder] Lightning Rod (Bolt)? I was told by someone that took an antenna out of the radome that there did not appear to be any connection to the conductor on the cap. The antenna slid right out of the bottom of the radome. I agree about the survivability of folded dipole arrays, but they don't seem to be an option at 900 MHz- at least I don't see them in commercial catalogs and have never encountered an 800 or 900 MHz. Doug K4AC From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Monday, November 02, 2009 6:43 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Lightning Rod (Bolt)? Although I've never had one apart, I believe the cap is attached to the radiating element. Also, I have never seen any fiberglass collinear antenna survive a direct hit. I have, however, seen folded dipole arrays survive a lightning strike. Chuck WB2EDV ----- Original Message ----- From: "Doug Rehman" <d...@k4ac.com <mailto:doug%40k4ac.com> > To: <Repeater-Builder@yahoogroups.com <mailto:Repeater-Builder%40yahoogroups.com> > Sent: Monday, November 02, 2009 5:45 PM Subject: [Repeater-Builder] Lightning Rod (Bolt)? > Looking at some DB Products fiberglass radome antennas, they all have a > metal protrusion on the top cap; it looks like bronze perhaps. I presume > that it is some form of lightning mitigation device. Is this just a piece > of > metal in the cap, unattached to the internal antenna element? > > I'm curious as I need to mount a Maxrad 900 MHz antenna on top of a long > mast on the top of a tower. The tower takes a lightning hit about once a > year. The Maxrad is in PVC tubing and it'd probably be simple to add a > stainless bolt to the top of the antenna if it would do any good. > > The previous 3 antennas on top were Comet GP-15's. They have a thin metal > cap on the top of the radome. The first one took a pretty significant hit, > melting part of the cap and making a mess out of the antenna. The second > one > took a lesser hit, heating the element enough that it burned thru the > radome. The third strike was even less, just discoloring the fiberglass on > the top 8" of the radome. > > I know that I'd be better off with a DB Products antenna, but their weight > likely well exceeds the mast capability for a top antenna (where it needs > to > be). > > Thoughts??? > > Thanks, > DOUG > K4AC > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > >
