Waterfall displays - IF long-term? Not AF short-term?

Discussion in 'Working Different Modes' started by KC8QVO, Nov 16, 2019.

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  1. KC8QVO

    KC8QVO Ham Member QRZ Page

    I am working FT8 and I got to thinking about this after stretching out the waterfall display as far as it would go (and blowing it up on a 49" screen)... I ran 160m last night and let the software run while I was off doing other things (just monitoring the band, not transmitting). I saw people working DX but I wasn't hearing DX. I was curious what band conditions would show over time. I let things run for probably 15 minutes then came back to it and scrolled through the decoded message list - just hearing NA (Canada and US). In any event, it got me thinking about what I was doing...

    I don't have any SDR radios (like a Flex), the closest I have is an Elecraft KX3 (my understanding is that it is an SDR - just with a box, display, buttons, and knobs). I also have a Yaesu FT-991A that has a spectrum and waterfall display - but it is very limited (there is 1 IF in that radio that splits out to the receiver/AF and the spectrum = the VFO governs both, you can't sweep the spectrum around the band while leaving the VFO in place live - you can do it paused, where the IF is feeding the AF at the VFO frequency while the band image on the display stays but you can't sweep the two independently live).

    While I was playing with the waterfall on FT8 I scrolled over to some SSB stations. The bandwidth on SSB is too wide to resolve in the AF spectrum - and the waterfall in WSJT is solely the AF through the soundcard.

    What I'd be curious about is if there are ways to create a long-term waterfall that can watch over a much wider frequency range at the IF level. Maybe this is a dumb question to those that have been running SDR radios for years and years - but is there software that you are aware of that will do this already? Are there as user-friendly ways of averaging noise and smoothing spectrum graph response rates?

    What I would like to do is record entire bands to see propagation and activity as an image. For example - on the low bands when the sun starts coming up the band noise increases, and the opposite - as the sun goes down the band noise decreases. Is there a type of waterfall display that will record this - say, over the course of 8-10 hours and not several minutes? As far as bandwidth goes - maybe up to 5-10MHz?

    I have a service monitor with a spectrum analyzer in it. I used to use it at one point for watching over a commercial band to find activity while I was surveying coordinated channel options. The spectrum analyzer will hold activity until you clear it. By using that function over a wide enough frequency range to get the list of channels in there and watching over a period of time it was possible to see where activity was, but only seeing the spectrum in one plane (an accumulation of data, not a time-base spread/distribution as a waterfall does) was very limited. For example - birdies, spurs, and other environmental artifacts would show up on the spectrum analyzer hold screen skewing the results. If those artifacts could be shown on a waterfall instead they would be very easily identified and skipped over.

    One antenna I use is a Tarheel model 400 screwdriver mobile antenna. It will load up 160m. I first noticed this on 160 but the spectrum and waterfall displays actually show the resonance of the antenna also. The bandwidth of the antenna is very narrow thus the sensitivity of the antenna on further frequencies adjacent to the resonant frequency fades off. You can visibly see that - best on 160 but 75/80 show it as well to some extent.

    So anyway - just thinking of waterfall displays here and what is possible to do. It's neat stuff!
     
  2. KC8QVO

    KC8QVO Ham Member QRZ Page

    I have been spinning some ideas in my head and did a bit of research on the subject of long-term waterfalls. I came across the website in the following link. They provide 24 hour waterfall recordings of the entire HF spectrum - 0-29MHz. I am impressed!

    http://websdr.ewi.utwente.nl:8901/fullday/

    So the idea I am after with being able to record is possible. More over, the waterfall in the above link has time and frequency displayed as a function of the mouse cursor over that huge waterfall. Then if you click around on the traces, or the noise, you get a signal strength in dB also. However, I found my screen stuck on 20.1dB so that signal strength isn't apparently working (at least not for me at the time I tried it), but the idea of being able to do that is awesome - above and beyond the awesome span (time and frequency) of the waterfall display to begin with.

    There have been a few threads, blog posts, and websites I've read related to long-term waterfall recordings and from the sounds of it the ability to get that data is not "common". However, the articles I have read have also been a few years old also. That isn't to say there has been software developed in the time since that makes the flexibility in tuning/smoothing/averaging possible that I am after - I just haven't come across it yet.
     
  3. W1VT

    W1VT Ham Member QRZ Page

    KC8QVO and N0TZU like this.
  4. KC8QVO

    KC8QVO Ham Member QRZ Page

    Thanks for the link. I read both articles in their entirety.

    That is along the same lines of what I am after with the ability to display long-term waterfalls. However, the RFI hunting aspect of it didn't really occur to me. So that is above and beyond. Good stuff!

    The RF I hunting aspect does go to show, also, how much utility there is in the recorded data, though.

    Something else I thought about that would be neat to see is a VHF-UHF+ waterfall from a good antenna and good location of a major metropolitan area - like NYC or Chicago. Building rooftops and commercial towers are extremely challenging RF environments as there is so "much" there. It would be interesting to create an image that would be able to visually describe the intensity of it.

    Lots of ideas and lots of possibilities.
     

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