[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: 10 dB signal improvement on ao-40 - free



Mal et al,

As Wayne points out, there are two principal reasons why CW has a 
significant advantage over SSB in S/N ratio:

1.  Whenever a CW transmitter is keyed, it is putting out full, i.e. peak, 
power.  The average power output of an SSB transmitter will depend upon 
speech processing and voice characteristics, but is always less than 100% 
of peak power.

2.  The ear must copy an SSB signal in a noise bandwidth of, typically, 2.1 
kHz.  In contrast, research cited by W1JR, the late W2IMU and others shows 
that the human ear copies a CW signal in an effective noise bandwidth on 
the order of 50-100 Hz (depending upon pitch, fading, speed, etc.), 
regardless of the IF filter setting.  Depending upon the CW and SSB 
operators' abilities, that can add up to 13 dB, or more, to the S/N ratio 
difference.

While attending the AMSAT-UK Colloquium last year, I and others present 
noted solid copy of many CW signals though AO-40 using only a G3RUH/ON6UG 
patch antenna, with no dish.

73,

Ray, W2RS    

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home