Seeing spectrum of UHF (HDTV) Broadcast Band

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Bill787
Posts: 2
Joined: Sat Sep 09, 2017 8:31 pm

Seeing spectrum of UHF (HDTV) Broadcast Band

Postby Bill787 » Sat Sep 09, 2017 8:41 pm

Hi everyone. My first post.
If I were to use SDRplay to view the U.S. HDTV broadcast band (470-806 MHz), could I see spectra of all the HDTV channels coming down from my rooftop antenna? Could I see the entire spectrum at once? Maybe not, as I see the SDRplay description says "Up to 10 MHz visible bandwidth.".

Thanks in advance for any clarification . . . SDR seems like an amazing new world to me :)
Last edited by Bill787 on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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g1hbe
Posts: 228
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: Seeing spectrum of UHF (HDTV) Broadcast Band

Postby g1hbe » Sun Sep 10, 2017 8:48 am

As you suspect, you could see only 10 MHz at a time. There's not a lot to see with digital TV, just 'blocks' of what looks like noise. Looking at analogue TV signals used to be quite interesting as you could pick out the main video signal, the chroma subcarrier and the sound channel.

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Andy

Bill787
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Joined: Sat Sep 09, 2017 8:31 pm

Re: Seeing spectrum of UHF (HDTV) Broadcast Band

Postby Bill787 » Sun Sep 10, 2017 3:31 pm

Hi, Andy. Thanks for the confirmation of the 10MHz viewable spectrum limitation on SDRplay. Not a problem of course, as I can still explore the entire band as I rotate a rooftop antenna. I live close to St. Louis in America, and can remember those very rare occasions when analog UHF signals came skipping in from hundreds of miles away. Not like the chaos that would happen to the VHF band when the skip was up, but here in the U.S. at the time of digital transition the vast majority of TV stations were moved up to UHF from our previous VHF television band of 54-216 MHz. Our analog TV was turned off in October 2012.

I miss the wonderful quirky days of Analog. Except of course every time I turn on the TV and see the glorious quality of broadcasting in our Digital age :D

P.S. - For those on this side of the pond, there is a great web site about U.S.TV allocations:
http://www.fcc.gov/media/television/tv-query
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dlritter
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Joined: Fri Dec 04, 2015 7:12 pm

Re: Seeing spectrum of UHF (HDTV) Broadcast Band

Postby dlritter » Mon Sep 11, 2017 2:33 am

I don't believe anyone has created a Spectrum Analysis app for the Mirics chip set..
I use Spektrum and touchstone with the RTL dongle and Spectrum Spy with the Airspy...
the actual bandwidth of the device is of no concern if it can be stepped/scanned fast enough..

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F1BJB
Posts: 108
Joined: Wed Jul 15, 2015 4:24 pm
Location: Beauvais France

Re: Seeing spectrum of UHF (HDTV) Broadcast Band

Postby F1BJB » Mon Sep 11, 2017 7:00 pm

g1hbe wrote: There's not a lot to see with digital TV, just 'blocks' of what looks like noise.

That is not true :)
If the top of the noise is not flat it indicates either a badly oriented aerial with echoes or SFN or MFN interference.
mystere.JPG
mystere.JPG (198.99 KiB) Viewed 799 times

Here you see the difference between channel 22 correctly received and the 23 where two SFN TX are interfering
There was a sudden frequency drift between the 2 transmitters as can be seen in the waterfall.
You can also see the +166KHz offset of french TV transmitters.
The snake like display in the waterfall is typical of interference from 2 TX .
For echoes the lines are straight.

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ab1jx
Posts: 2
Joined: Thu Sep 28, 2017 3:23 am

Re: Seeing spectrum of UHF (HDTV) Broadcast Band

Postby ab1jx » Thu Sep 28, 2017 4:39 am

rtl_power doesn't have a limitation like 10 MHz, but it doesn't exactly do it in real time either, it retunes.
Image
This is output from Heatmap, a little Python script that plots from the csv output. There are also several forks of it but it's part of the rtl-sdr suite.

If you have any serious funding, take a look at what Pentek offers, but as somebody put it you could buy a whole ham shack for what one of their boards costs. They apparently sell to industry, military, NASA. Take a look at http://www.pentek.com/selectguide/IO_SelectGuide.cfm But doing the number crunching with FPGAs or ASICs makes sense, it just isn't cheap. A/D sample freqs in the GHZ? Jeez. They don't list any prices, you contact them for a quote.
Last edited by ab1jx on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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