RE: [Repeater-Builder] Anetenna Help

[Jeff DePolo]

Somebody, maybe Larsen or Antenna Specialists, used to make a "stiffener" for use with NMO mounts.  It was basically an oversized brass fender washer with a 3/4" hole in the center.  It was thick enough that it stiffened the body near the mount, but flexible enough that it would take the shape of the concave contour of the roof when you tightened down the NMO.  I haven't seen them advertised in a while, not sure if they're still made.   I had a Diamond dual-bander act as a can-opener to the roof of one of my previous trucks (Chevy Tahoe).  It got snagged on a low-hanging ice-laden branch on the way up to a tower site.  The roof gave up before the antenna did.  I guess that says something about Diamond mobile antennas...?                                   --- Jeff     From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, April 20, 2006 3:46 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Anetenna Help Just about any 5/8 wave antenna mounted on top of a Ford pickup truck. The roof metal is so thin that frequent flexing from antenna sway, wind resistance, low tree branch contact can cause metal fatigue on the cab roof.  The antenna NMO mount was installed directly above the cab interior light. Nice install but the metal finally cracked about 1/2 inch circumference further out from the outer edge of the NMO mount. The singing problem was resolved by wrapping thin fishing line around the full antenna length at about 1 turn per 1 1/2 inches for its full length. The thinner the whip antenna the higher the audio frequency. Observe automobile antennas and you will see many factory manufactured AM/FM antennas wrapped as mentioned above. Go out and wiggle your mobile antenna. Look at the automobile metal near the base. Watch it flex. The longer the antenna the more flexing. I solved the problem by relocating the antenna using a homemade bracket mounted between the front fender and hood near corner of windshield.   Gary  K2UQ   YAHOO! GROUPS LINKS  Visit your group "Repeater-Builder" on the web.    To unsubscribe from this group, send an email to:  [EMAIL PROTECTED]    Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.