Observation 3006660: DIWATA-2 (43678) CW transmitter rxed with AM demodulator

Regarding Observation 3006660


I have received Diwata-2 cw transmitter but SatNOGS did use AM demodulation instead of CW
demodulation with a BFO. I checked this observation which is also an AM demodulated CW signal.

73, Norbert

SatNOGS does not (currently) have an AM demodulator. The ‘default’ demodulator if there is nothing else defined is actually FM, but since this observation was for a CW transmitter, then the CW demod would have been used.

Reading up a little bit on Diwata-2 ( https://phl-microsat.upd.edu.ph/diwata2 ), i’m a little but unsure how the CW beacons are sent, and the CW speed (120WPM?) seems a bit odd.

Anyway, from the waterfall and the audio, it sounds like the FM Repeater is being keyed on and off (resulting in rising and lowering noise), insead of the sat actually transmitting CW.

Receiving a CW signal with a FM rx you are not able to decode the morse code. It sounds like inverse CW. Using an AM receiver it’s exactly the way around, like a CW signal bounced back from an aurora borealis, easily to decode for every CW operator. I am sure that the demodulator used during observation 3006660 is not FM. It did not blow away my headphone like FM without squelch at the same volume setting in Audacity.

You can hear and see the AGC slope like it happens in every CW decode like this one https://network.satnogs.org/observations/3012667/ The signal gets louder very slowly during the 1st two minutes.

Oh, what does mode “CW 12” mean? What is the difference between CW mode “CW” in obs 3006660 and “CW 12” in obs 3012667?

I am very interested to read more about the different SatNOGS demodulators, receiver settings…

73, Norbert