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About 40 signals around 430Mhz in France (audio sample)

Posted: Wed Aug 19, 2020 4:02 pm
by JayMore
Hello All.

Help me to identify this signals. I receive them all the day, from 430,600Mhz to 431,300Mhz. I'm located close to Paris, France, Europe.
Nothing is clearly audible, when I go to USB/LSB or DSB I hear like someone is playing an old video game (sound like a jumping Mario on a Nintendo).

It seems there is several "channels", all separated by 12,5Khz

Audio signal : ... sp=sharing

What kind of signal cloud it be ? Which decoder ?

Re: About 40 signals around 430Mhz in France (audio sample)

Posted: Tue Sep 29, 2020 9:25 am
by Username
1) its some Weird Amateur Radio stuff
2) its "just" noise

If you have a Laptop take them and drive in a different district and see if its there to.

Re: About 40 signals around 430Mhz in France (audio sample)

Posted: Sun Oct 04, 2020 9:30 am
by snn47
1) its some Weird Amateur Radio stuff
2) its "just" noise
To 2) Noise would not have distinctive frequencies, be not repetivie and would be diffuicult to generate with the strength you see here.

To 1) Why is it weird just because it is in the 70 cm Ham-band? The 70 cm is in part shared worldwide e.g. industrial devices centered on 432 MHz.
Some modulations like OFDM utelize a large number of subcarrier to transmitt data. The width, modulation employed on a subcarrier and number of carrier transmitted at a time will vary. Not all defined sub-carrier will be transmitted at a time to reduce the required spectrum and limit the Peak to Average Power variation. The strength of the PAPR varyation can exceed +10 dB while the occurance is specified by the a CCDF curve for this OFDM modulation. Since the spectrum of the subcarrier overlapp to a bell form and we see seperate frequencies and because we have gaps where I would expect supcarrier to be used, I think it is not a OFDM signal.
A lot of strange interference can originate also from pwoer-supplies eg. those for LED devices.

Do you have a directive antenna, e.g. HB9CV, to limit the direction of the signal source?

Is it originating from one direction, in case the signal is reflected somewhere this can produce additional, but nearly always weaker signals. Unless the direct pass to the source is obstructed providing a hgh attenuation, or the reflecter has a high gain. Unless you are in a urban area reflections can make it very hard to locate the direction of a signal source. Colleagues told me, that they once had reflections at a parabolic dish, which increased the reflected power significantly above normal refelctrions on a flat metallic surface

In addition to transmissions from an antenna it may be also
- cable leackage (e.g. CATV doy you have CATV service in your area?),
- distribution of signals on a power wire like PLC (I have not followed if PLC is already defined/produced >100 MHz in Europe so I don't know)
- spurious emissions of an electronic device radiating
- cabinet leakage or from cables attached to an electronic.

Two other options are intermodulation in a transmitter which you receive
or Intermodulation of your receiver due to other strong signals, which you can tests by adding a 20 dB attenuation. If the signal are also attenuated by 20 dB then the signal is real, if the signal is attenuated by more than 20 dB or totally gone it it is receiver intermodulation.

I hope my limited information helps you to identify the type and source.

Re: About 40 signals around 430Mhz in France (audio sample)

Posted: Fri Oct 16, 2020 2:11 pm
by fe8769a
hello from France

these are mobitex signals from taxis in Paris . Transmitters are on the "Tour Montparnasse " . It can be decoded easyly with PDW (pocsag decoder) and sdrsharp .

They are from 428 MHz to 430 MHz but huge signals

Most messages are encrypted

Fe8769 (TSF70 forum)