SNR in a 3 kHz BW has become a gauging standard. Even when a PSK decoder may see a PSK31 signal some 16 dB better on a 63 Hz bandwidth.
Even when the actual signal is much narrower and the decoder uses a matching bandwidth, which allows a better SNR to the demodulator, it is useful to have a standard to compare, which matches the radios in general use nowadays. Stating different measuring bandwidths for different modes would obscure the results if you want to make such a comparison. A PSK31, detectable at -10 dB on a 3 kHz BW may ideally be a +6dB signal on a 63 Hz BW, assuming equal noise density in the whole 3 kHz passband. Apples remain apples, oranges remain oranges, and you can weigh them with the same scale. 73, Jose, CO2JA --- Tony wrote: > Mark, > >> If the SNR is negative, how is it that you can copy any signal? > > The path simulator adds Gaussian white noise to the input signal to simulate > a signal-to-noise ratio through a 3KHz band pass filter. If the SNR is less > than 0, it's below the noise level. > > The signal is still there, it's just weaker than the noise. > > Tony, K2MO > > ----- Original Message ----- > From: "Mark Miller" <[EMAIL PROTECTED]> > To: <digitalradio@yahoogroups.com>; <digitalradio@yahoogroups.com> > Sent: Thursday, August 21, 2008 5:42 AM > Subject: Re: [digitalradio] Path Simulator Test - PSK FEC31 > > >> If the SNR is negative, how is it that you can copy any signal? >> >> 73, >> Mark N5RFX >> >> At 02:36 AM 8/21/2008, Tony wrote: >>> __________________________________________ >>> >>> Sensitivity Test - Direct Path >>> (no ionospheric disturbance) >>> >>> Minimum SNR for error-free copy >>> >>> Contestia 500/32............-15db >>> DominoEX-4 ..................-15db >>> F > > > ------------------------------------ > > Announce your digital presence via our Interactive Sked Page at > http://www.obriensweb.com/sked > > Check our other Yahoo Groups.... > http://groups.yahoo.com/group/dxlist/ > http://groups.yahoo.com/group/contesting > http://groups.yahoo.com/group/themixwgroup > Yahoo! Groups Links > > > > -- MSc. Ing. Jose Angel Amador Fundora Profesor Auxiliar Departamento de Telecomunicaciones Facultad de Ingenieria Electrica, CUJAE Calle 114 #11901 e/ 119 y 127 Marianao 19390, Ciudad de la Habana, Cuba Tel: (53 7) 266-3445 Email: amador at electrica.cujae.edu.cu
