[time-nuts] GPS from a window seat

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Oct 2 02:39:11 UTC 2009


Magnus Danielson wrote:
> jmfranke wrote:
>> I used a bias tee with a capacitor block.  I varied the resistor
>> until I could see signals coming from the external antenna, the built
>> in patch was shielded with aluminum foil and the receiver verified
>> that no signals were coming from the internal antenna.  Some
>> receivers needed only a 10K resistor, some models needed 220 Ohms.
>
> In my case I still want it to pass 5 VDC, but let the receiver see
> some additional current, so I put a coil in series with the resistor,
> to not load the RF too much.
>
> Cheers,
> Magnus
You need to ensure that the coil/inductor doesn't have its first
resonance below 1575.42MHz for an L1 receiver, otherwise it isn't very
effective.
There are some wideband chokes with first resonances well above 10GHz
when mounted correctly.

Bruce





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