[time-nuts] Re: Testing a GPS mag mount antenna

[Azelio Boriani]

I used to test cheap GPS antennas with the network analyzer, using a
bias-tee to feed 5V power to the antenna and to avoid damaging the VNA
RF input (even if the RF input is 50V tolerant).

On Sat, Aug 21, 2021 at 6:14 PM Dana Whitlow <k8yumdoober at gmail.com> wrote:
>
> I love Dan's idea, with one caveat.  The transmission through a
> powered-down LNA
> is an unknown, probably even to the manufacturer.  Thus comparing output
> signal
> levels with power on or off is pretty meaningless.
>
> But his test with power on should be a great way to get some clue that the
> antenna
> is working, and is clearly simpler to perform than what I was suggesting
> yesterday.
>
> Dana
>
> On Sat, Aug 21, 2021 at 9:49 AM Daniel Schultz <n8fgv at usa.net> wrote:
>
> > > Should I be able to "see something" on or around the GPS frequency other
> > > than what I suspect will be something visual looking like a noise/pulse
> > > source/signal?
> >
> > You could try sweeping a harmonic from a signal generator across the
> > antenna
> > passband, this would be visible on the spectrum analyzer and might give
> > you an
> > idea if the preamp is amplifying or attenuating the signal. Try it with the
> > preamp power on and off. If your signal generator does not generate
> > sufficient
> > harmonics at L band you can feed the signal into an overdriven MMIC
> > amplifier.
> >
> > Dan Schultz N8FGV
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