On 7/5/12 10:45 PM, Robert Atkinson wrote:
Hi Ed, It's not just just "cheap and nasy" regens that cause this problem. Some aircraft navigation and communication receivers where found to have enough local oscillator harmonic leakage at 1575 MHz through the antenna port to jam GPS then tuned to specific frequences. The cure was a tuned stub filter on the Nav or Comm. see http://www.aircraftspruce.com/catalog/avpages/tednotch.php for an example.
or choosing the UHF link frequency for Mars Reconnaissance Orbiter at 400 MHz, nicely the third harmonic of the 133 MHz flight computer clocks (or 6th harmonic of 66, etc.)
Unlike GPS, though, the desired signal is narrowband (though the receiver isn't) so a DSP software fix in the FPGA could implement a new filter (and shift the desired signal to the other end of the IF passband.
EMI/EMC problems, your name is legion. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
