[aprssig] Re: Ants for Bikes WAS: Broken digis (Ohio to Oklahoma and everywhere inbetween
wa7ixk at earthlink.net
Wed Aug 1 18:49:57 CDT 2007
Stephen H. Smith wrote:
> A much smaller alternative, currently available that works very well, is
> the Diamond NR-770 which is a no-ground-plane 2M/70cm dual-bander with
> an open (corkscrew) coil at it's center-point. This antenna is about
> 38-40 inches tall (i.e. 2M half-wave). Available in both NMO and UHF
> base versions in either chrome or matte black, it's perfect for screwing
> into a UHF bulkhead ("barrel") connector mounted through an L-bracket on
> no-ground-plane vehicles. It's also ideal with all-in-one ammo-box
> trackers. Just place a barrel plug through a 5/8th-inch hole in the
> top of the case and screw it in. It works VASTLY better than simple
> 1/4-wave whips when the box is too small to be an effective ground
> plane, with vastly less RFI into the GPS or Tinytrack. [ You need a
> surface of at least 19" radius to be an effective ground plane on 2M.
> Further, even when properly ground-planed, a quarter-wave will NEVER
> have as low an angle of radiation as a half-wave. ]
> I have used a 770 taped to a fiberglass pushup mast as a temporary
> base-station antenna. Just splice the male UHF connector in it's base
> to a run of coax with a barrel plug and hoist it up. No radials or
> ground plane needed. Or pull it up into a tree by tying a piece of
> nylon string or 20-lb-test mono-filament fish line to it's tip.
I use the 770 nmo on all my vehicles.
When used on my motorcycles I do not have to worry about a ground plane.
One has a good ground plane, the other does not.
On my truck I replace the 770 with a shorter 1/4 wave for around town so
I can get into the parking garages.
The 770 will lay down tho.
It is a ideal mobile antenna.
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