[time-nuts] Homemade GPS Receiver

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Fri Sep 26 05:07:56 EDT 2014

On 17 Sep 2014 23:38, "Peter Putnam" <ni6e at sbcglobal.net> wrote:
> Greetings,
> The link below describes a homemade GPS receiver.
> It is presented in a detailed and elegant manner that is certain to
appeal to this reflector's subscribers.
> Peter
> http://www.aholme.co.uk/GPS/Main.htm

I don't understand the units of signal strength

"The L1 carrier is spread over a 2 MHz bandwidth and its strength at the
Earth's surface is -130 dBm. Thermal noise power in the same bandwidth is
-111 dBm"

Then goes on to talk about the signal being 20 dB below the noise.

Unless the -130 dBm is over the whole surface area of the earth,  which I
doubt, the units make no sense to me. The units of signal strength should
be V/m, A/m or W/square metre.

The noise power should be in Watts or dBm. So taking the difference (19 dB,
which is approximately 20 dB) between these figures seems odd to me.


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