On Jan 15, 4:13*pm, "François Guillet"
wrote:
a écrit dans le message de news:
...
On Jan 14, 2:08 pm, "Brian Gregory [UK]" wrote:

"François Guillet" wrote in message

...

Here is a much better record:
http://exvacuo.free.fr/div/Radio/Arc...Divers/AM%2030....

Are they definitely double sideband AM and not SSB with a carrier?

--

Brian Gregory. (In the UK)

To email me remove the letter vee.

| * Well, this not pure traditional AM. And *as far as I can discern
| it is not regular SSB either ! * Is this DSB-AM *with reduced or
| suppressed carrierier , or is this SSB plus+ a reduced carrier?
| Signal is not very stable, modulation seems to jump up and down
| constantly. Need to switch to another agc setting,if possible. *This
| last recording is much better than the first and second. May be, if I
| hear a longer transmission they will *accidentally give away *who the
| hell they are. Judging from one party being much, much louder the
| other fellow may be situated very far away. This is not your standard
| literary language,either. *Lots of uncensored expressions. Frequencies
| are really baffling me. Still think it is an intermodulation product.
| What receiver is being used?

The receiver is an old transceiver Icom IC751.
I have added an interface that converts IF signal at 455 Khz down to 12 Khz
then the 12 Khz signal is connected to my PC sound card (band pass is around
15-20 Khz).
I use Dream software for demodulating the signal. Dream was firstly intended
to decode DRM but its last version can also handle AM, SSB, CW and FM.
In Dream one can adjust a filter to match the received signal. I choose the
band pass for the best subjective audio. Dream records the demodulated
signal in .wav files.

After recording the russian stations, I used Adobe Audition for processing
operations of noise reduction, clics removing and MP3 conversion.

It is not DSB AM or SSB+carrier. It is real AM with the two side bands. Some
stations have a frequency shifted by the modulation. It looks like old TX
with VFO pilot (not synthetized). QSB is probably the cause of carrier
fading and modulation distorsion.

Some other samples but not good, band is very noisy, transmissions are
not very long (1mn max), with long pauses so it is difficult to monitor
them:http://exvacuo.free.fr/div/Radio/Arc...Divers/AM%20Ru...

If this was back 20+ years ago, I would say it could be
some sort of high seas radiotelephone transmissions. Only one side of
the conversation is heard in general. But, majority of them,
(practically all) were in USB as a rule. The other party has almost
always used another frequency. None of the offical radiotelephone
transmissions were so brief. None of the official operators spoke with
such a hurry. The s/n ratio is very poor. Power levels seem to be very
low and transmitters don't sound stable enough for reliable
communication . If it is not maritime traffic, it may be something
different. Bootleggers, pirates, or traffickers of some sort
probably. May be we can use D/F them,or establish some pattern .What
time of day or night do they pop- up?