Let's do some quick math. The change in frequency (delta F in Hz) is equal to (-) (Vs-Vr)/wavelength (a close 1st order approximation when the speed of the wave is much greater than the speed of the observer)
Vs is the velocity of source. For AO-51, that is about 8000m/s Vr is the velocity of the receiver, which would be 0 in this case since I am not taking into account the velocity contributed by Earth's rotation. The wavelength of a 145 MHz signal is 2.05m The wavelength of a 435 MHz signal is 0.69m The delta F for 145 MHz is -3902 Hz The delta F for 435 MHz is -11,594 Hz Pretty close to a 3/1 ratio. -Tim -----Original Message----- From: flexradio-boun...@flex-radio.biz [mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Ray - K9DUR Sent: Wednesday, August 04, 2010 10:09 PM To: 'Brian Lloyd'; 'Ronald G. Parsons' Cc: flexradio@flex-radio.biz Subject: Re: [Flexradio] Another Satellite Question Brian, I believe that you will find that the Doppler shift is a proportional to the frequency. Therefore, the shift at 432MHZ would be approximately 3 times the shift at 144MHz. A simple thought experiment demonstrates this. Assume you have a 144MHz frequency source & it is moving away from the receiver fast enough to cause a 5kHz negative shift. If you decrease the frequency of the source and the shift remains 5kHz, consider what the result would be if you decrease the source frequency all the way down to 5kHz -- the resulting received frequency would be 0Hz. That is obviously not correct. The frequency shift is dependent on BOTH the relative speed and the frequency. 73, Ray, K9DUR http://k9dur.info _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ _______________________________________________ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
