Observation 249962: ORSTED (25635) - Voice on top?!


#1

Regarding Observation 249962

This is a recording of the first Danish satellite, Ørsted. A clear signal can be seen on the waterfall, but if you listen to the audio, a clear voice can be heard on top of the tone. It sounds like an AM broadcast station being demodulated with an SSB receiver, so you can’t make out what they say, and one minute before the end of the recording, you can hear music.

How is this possible on 2296 MHz? Also, the strength of the voice follows the strength of the signal.

The reason I started looking for this satellite is that there is talk in Denmark now about start listening to it again.

Best regards,
Steen


#2

Also part of the reason the voice is not received well in audio is its almost outside the bandwidth of the demodulater.


#3

Also it found be the upper side band of the AM signal being demodulated by the lower side band part of the demodulator which causes a lot of distortion.


#4

If @cshields provides some info about his RF and SDR setup, we might be able to conclude that it is just some mix product of an AM radio station.


#5

this would have been on my 2.4ghz parabolic grid, fed in to a ursp b200 mini.

That’s weird, and seems to be mixed in for all of my observations, and not impacted by doppler correction.

I looked at this frequency on my desktop and didn’t see anything local, but I do have a broadcast FM station next door which is likely where the signal is getting mixed in from. (the LNA has an FM notch filter in it)


#6

But if it’s local, how can it not be influenced by the frequency correction for Doppler shift?


#7

If its intermodulation interference it could be “tuned in” to the resulting signal… That said, 2296Mhz is not mathematically an intermod product of the FM station next to me (100.7Mhz). The other stations on that same tower are around 851Mhz and would not be broadcasting continuously like the signal we hear.

this is where I brain-dump without a clear answer so I (or someone else) can dive in further later. :slight_smile:


#8

Fair enough! Thanks for the explanation - it sounds reasonable :slight_smile: