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Spectrum Scans in FM 88-108

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Nathan McBee:
I, as I'm sure many, have been doing scans and analyzing the FM band.
I have a few questions regarding the following attachment from a recent scan I did here in LA.

What are the sidebands I'm seeing on either side of TX 89.3 (KPCC)? There are no registered stations there.
I am aware that the broadcast station could own more than one FM channel. Is this then the case and if so, are these separate transmissions?

Cheers

Jason Glass:

--- Quote from: Nathan McBee on June 12, 2020, 06:46:17 pm ---I, as I'm sure many, have been doing scans and analyzing the FM band.
I have a few questions regarding the following attachment from a recent scan I did here in LA.

What are the sidebands I'm seeing on either side of TX 89.3 (KPCC)? There are no registered stations there.
I am aware that the broadcast station could own more than one FM channel. Is this then the case and if so, are these separate transmissions?

Cheers

--- End quote ---

Those aren't sidebands.  They're broadcast stations on 89.1 and and 89.5 MHz.  Otherwise known as FM channels 206 and 208.

https://radio-locator.com/

When you measure signals that your search doesn't reveal, expand the search radius to identify them.  There are lots of legit stations on those freqs, within range of central LA.  https://radio-locator.com/cgi-bin/locate?select=city&city=90003&state=CA&band=Both&is_lic=Y&is_cp=Y&is_unl=Y&is_fl=Y&is_fx=Y&is_fb=Y&format=&dx=3&radius=100&freq=&sort=freq

Henry Cohen:

--- Quote from: Nathan McBee on June 12, 2020, 06:46:17 pm ---I, as I'm sure many, have been doing scans and analyzing the FM band.
I have a few questions regarding the following attachment from a recent scan I did here in LA.

What are the sidebands I'm seeing on either side of TX 89.3 (KPCC)? There are no registered stations there.
I am aware that the broadcast station could own more than one FM channel. Is this then the case and if so, are these separate transmissions?
--- End quote ---

Without knowing the RBW, VBW, antenna type and if there are any preamp stages, it's not really possible to determine what the plot is showing. Though Jason is likely correct.

If you want to know all the FM stations in a specific market as point radius, these database will provide that:
https://fjallfoss.fcc.gov/General_Menu_Reports/engineering_search.cfm?accessible=NO
https://www.fcc.gov/media/radio/fm-query
http://fmfool.com/index.php?option=com_wrapper&Itemid=29

Nathan McBee:

--- Quote from: Jason Glass on June 12, 2020, 09:27:08 pm ---Those aren't sidebands.  They're broadcast stations on 89.1 and and 89.5 MHz.  Otherwise known as FM channels 206 and 208.

https://radio-locator.com/

When you measure signals that your search doesn't reveal, expand the search radius to identify them.  There are lots of legit stations on those freqs, within range of central LA.  https://radio-locator.com/cgi-bin/locate?select=city&city=90003&state=CA&band=Both&is_lic=Y&is_cp=Y&is_unl=Y&is_fl=Y&is_fx=Y&is_fb=Y&format=&dx=3&radius=100&freq=&sort=freq

--- End quote ---




They totally were. I mapped all 100 FM channels and found the same.
Thank you though for the help!

Jason Glass:

--- Quote from: Nathan McBee on June 13, 2020, 07:54:38 pm ---They totally were. I mapped all 100 FM channels and found the same.
Thank you though for the help!

--- End quote ---

Noice!

I wish the RF Explorer crew would develop an audio demodulation utility for their platform, but I understand that they're already delivering huge bang for the buck.  Enormous, actually.

I only mention this because listening to demodulated FM signals often very quickly helps us identify or at least characterize them.  Public Radio broadcast is almost instantly identifiable within a very short time, just by its sound and content.  And if $20 USB SDR dongles can deliver the necessary data to do it, the more sophisticated RFE certainly can.  You might consider expanding your toolbox in the SDR direction if you'd like to go further down the RF rabbit hole.

Anyway, one of the reasons that I so heavily favor Signal Hound devices is analog RF demod & listen processing.  From day 1, they've included them in their platform.  Of course it's around $700 more cost than RFE for their entry level tier, but for serious RF work anything under $5K is a bargain.

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