[time-nuts] "Better" gps antennas than a Symmetricom 58532A

Jim Lux jimlux at earthlink.net
Wed Jan 23 23:59:09 EST 2013


On 1/23/13 8:50 PM, Jim Lux wrote:
> On 1/23/13 7:26 AM, lists at lazygranch.com wrote:
>> For a single frequency use like GPS, the impedance should be close to
>> the target. It is true for scanners and such, 50 ohms is quite
>> nominal. (This notion of DC to daylight and maintaining 50 ohms is
>> fantasy. ) But for a GPS, you know exactly the application.
>>
>
> You assume that the antenna designer actually tried to hit a particular
> Z.  They may have been going for "about 60 ohms" which would be about
> 1.2:1 for both 50 and 75 ohms.  Or, they were more worried about
> optimizing the pattern or axial ratio, and the Z could be "good enough".
>
> I've got a SWR plot from a passive L1/L2 antenna here (specified as
> better than 1.5:1) and it varies somewhat randomly with no apparent
> pattern between 1.5:1 and 1.1:1, and is about 1.3:1 at L1.  Another
> antenna (same mfr, same model, slightly different installation and
> cable) ripples between 1.45:1 and 1.05:1, mostly oscillating around
> 1.2:1. At L1 it's about 1.1:1
>
forgot.. 1-1.8 GHz measurement span



> It meets the spec everywhere.
>


More information about the time-nuts mailing list