[amsat-bb] Re: Good mobile antennas to use
aa5jg at fidmail.com
Thu Sep 15 10:34:35 PDT 2011
Thanks for the plots Bob. The 2m havewave appears to do well on 70cm above
30 degrees, and fairly poor below that elevation. The 70cm 1/4 wave appears
to suffer from no real nulls except at the very high elevations. It is
about 5 DB down from the 2m 1/4 wave, but is also much more usable on the
below 30 degree passes.
So, would a dualband that is 1/4 wave on each band cover things pretty
well? It appears like it would.
73s John AA5JG
On Thu, Sep 15, 2011 at 12:07 PM, Bob Bruninga <bruninga at usna.edu> wrote:
> I donno. The only 1/4 19.5" antenna I ever used I just drilled into the
> roof above the dome light and installed an NMO mount and simple whip. For
> conversion of an existing mount, if it is a 5/8's wave vertical (most
> mobiles are) then there is a matching network in the base.
> The little tiny micro whips are ideal, but most of them now are being made
> as "dual band" which then destroys their 7 dBi gain above the horizon.
> No easy answers here.
> -----Original Message-----
> From: Ng, Peter [mailto:Peter.Ng at bccdc.ca]
> Sent: Thursday, September 15, 2011 12:47 PM
> To: 'Bob Bruninga '; AMSAT-BB
> Subject: RE: [amsat-bb] Re: Good mobile antennas to use
> But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does
> not have gain on the horizon (so it is rarely used for terrestrial mobile)
> but its pattern is ideal for satellite work on high passes. It does NOT
> then have a null in its pattern that causes the "crappy" contacts, and it
> does have plenty of gain above about 25 degrees.... and it is a smooth
> pattern.... not like the multi lobes of a standard mobile gain antenna.
> Hi Bob,
> This is off topic and didn't want to start something on the list... :), but
> can I convert my current magmount gain antenna simply by replacing the whip
> or is the "gain" stuff in the magmount itself? If so, would any thin steel
> rod do? I'd really like to give this a try!
> 73's Peter VE7NGP
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