What is the Waterfall for?

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BillRoss
Posts: 4
Joined: Thu Sep 06, 2018 7:50 pm

What is the Waterfall for?

Postby BillRoss » Thu Sep 06, 2018 8:11 pm

Brand new user of the RSP1A. I"m a SWL listerner, mostly am broadcast but do listen to some amateur stuff on sideband. I've never had a receiver that went above 30 mhz so I'm sure I will eventually play with VHF stuff.
Loving the spec analyzer but I'm curious as to the benefit of the waterfall. I think I understand what it is showing me but not sure what I can glean from that info. Can anyone enlighten me?
Thanks for your considewration.
Last edited by BillRoss on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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AussieSusan
Posts: 23
Joined: Wed Aug 16, 2017 6:50 am

Re: What is the Waterfall for?

Postby AussieSusan » Fri Sep 07, 2018 2:51 am

If you look at the frequency/spectrum plot, it is showing the strength of a signal at a frequency at that point in time. If a signal starts, the plot at the frequency will rise higher. When the signal stops, the the line at that point will drop back down to the background noise level.
This is showing the signals in the part of the band you are monitoring but at the current instant in time.
The waterfall plot shows the same information but OVER time. It also shows the strength of the signal as a colour (or brightness) rather than how high the plot line is.
At any instant in time, the waterfall shows the same information as the spectrum plot. However, because it also shows the 'history' you can use it to see the characteristics of a signal over time.
A trivial example is an FM signal that is broadcasting (say) a rising single tone. When the tone is not there, the spectrum plot will show the carrier frequency and as the tone rises, you will see the peak shift upwards in frequency. However all you will see is the frequency at that time. If you ha d the (proverbial) 'memory of a goldfish' then you would not know if the tone is rising or falling, or how fast it is changing etc.
On the waterfall plot, you would see the initial carrier as a line of colour at the frequency but as the tone rises, you would see the plot shifting to the right. You would also see the rate of change and other things from the slope of the line.
I find it very useful on the amateur bands when I'm looking for a contact. Because there is the 'history' aspect to the plop, I can see when someone has transmitted but just stopped. I can also see if others are using the same frequency (perhaps a conversation is going on) as there will be a 'dashed' line going up the waterfall as stations come and go.
I can the use the cursor to set the receiver to the carrier frequency, even if no one is actual transmitting at that time (the spectrum plot would be showing nothing at that that) and start listening fr the next transmission.
Of course there is a lot more information that can be gleaned from the waterfall but that I hope that explains the basics.
Susan

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BillRoss
Posts: 4
Joined: Thu Sep 06, 2018 7:50 pm

Re: What is the Waterfall for?

Postby BillRoss » Fri Sep 07, 2018 10:15 am

Thanks much Susan. The usage you explained for the amateur radio make a lot of sense. I'll have to try that. I appreciate your response!
Last edited by BillRoss on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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