Post by Admin1 on Dec 25th, 2020 at 4:58pm
C/N means Carrier to Noise ratio.
To measure Carrier power and Noise power requires some skill, since you normally have a mixture of the carrier and noise power.
If you have a spectrum analyser then this page is intended to help you: https://www.satsig.net/lnb/ebno-calculator.htm
In this figure the (C+N) is 9 dB higher than (N).
Hopefully the noise floor is flat across under the carrier and there are no hidden interference spikes.
Some spectrum analysers have a Noise power per Hz marker display. MARKER NOISE ON. This gives a readout that allows for the noise bandwidth of resolution bandwidth analyser filter and also the way the power measurement circuits deals with the peak to mean of random noise inputs such as digitally modulated carriers. Use the normal level display for CW carriers and the analyser assumes sine wave RMS power.
Eb/No means Energy per bit to noise power spectral density ratio.
As above, you can use the MARKER NOISE ON to get a good idea of the carrier energy plus noise level and noise level. It is important to note what type of bit rate is being referred to, as it is rarely specified. It is supposed to be "information rate" before FEC is applied. It is definitely not the transmission rate. Information rate might well be the customer information rate as well, but beware systems with added data framing / packet structures and encryption. If in doubt ask the modem manufacturer what their specified Eb/No figures refer to.
If you are a theory type person the Eb/No might appeal to you. If you are an engineer actually trying to make a system work properly then C/N will be more useful.
See Wikipedia: https://en.wikipedia.org/wiki/Eb/N0
To measure Carrier power and Noise power requires some skill, since you normally have a mixture of the carrier and noise power.
If you have a spectrum analyser then this page is intended to help you: https://www.satsig.net/lnb/ebno-calculator.htm
In this figure the (C+N) is 9 dB higher than (N).
Hopefully the noise floor is flat across under the carrier and there are no hidden interference spikes.
Some spectrum analysers have a Noise power per Hz marker display. MARKER NOISE ON. This gives a readout that allows for the noise bandwidth of resolution bandwidth analyser filter and also the way the power measurement circuits deals with the peak to mean of random noise inputs such as digitally modulated carriers. Use the normal level display for CW carriers and the analyser assumes sine wave RMS power.
Eb/No means Energy per bit to noise power spectral density ratio.
As above, you can use the MARKER NOISE ON to get a good idea of the carrier energy plus noise level and noise level. It is important to note what type of bit rate is being referred to, as it is rarely specified. It is supposed to be "information rate" before FEC is applied. It is definitely not the transmission rate. Information rate might well be the customer information rate as well, but beware systems with added data framing / packet structures and encryption. If in doubt ask the modem manufacturer what their specified Eb/No figures refer to.
If you are a theory type person the Eb/No might appeal to you. If you are an engineer actually trying to make a system work properly then C/N will be more useful.
See Wikipedia: https://en.wikipedia.org/wiki/Eb/N0