what data mode did I hear on 2m SSB?

[Jim_Shaffer]

I'm a monitoring enthusiast with an SDR. I've successfully decoded APRS and a packet BBS on 2m FM, but a few nights ago I saw some signals I didn't recognize appearing higher than those frequencies but below most of the repeaters around here. The signals appeared to be very narrow in bandwidth and didn't produce any audio when I tried to decode them as FM, so I switched to USB and they sounded like PSK31. But trying to decode them as PSK31 produced garbage in both FLDIGI and MultiPSK. Is there some secret to tuning that I'm missing, or is there some other mode that sounds almost exactly like PSK31? It sounded like a single tone with a slight warble. I tuned about 1kHz below it. I think these were real signals and not interference because they weren't continuous and there was no pattern to them.

 

[popnokick]

Most likely FT8 or FT4 based on your written description (and no audio sample).

 

[wowologist]

Could be anything, but try here:
( Signal Identification Wiki )

May actually be DMR or variant or a hotspot your picking up. I'd also add a decoder like DSD+ to your toolbox in case it actually is digital audio or a hotspot you've come across.

 

[Jim_Shaffer]

Most likely FT8 or FT4 based on your written description (and no audio sample).

I doubt it, as they weren't fixed-length transmissions. And it didn't sound like the FT/JT modes, I've heard them on HF.

May actually be DMR or variant or a hotspot your picking up. I'd also add a decoder like DSD+ to your toolbox in case it actually is digital audio or a hotspot you've come across.

Much too narrowband to be anything like that. PSK31 really is the best match to the sound from what I've heard so far, but I'm wondering whether there's some variable I'm missing.

If I come across it again, I suppose I'll have to record it so I can keep trying different modes til I find what works.

If I had my license, I'd post on the local repeater club's facebook page (it was simplex, but it was loud enough it has to be nearby), but I figured it'd sound weird trying to eavesdrop on a QSO. I don't really care what they're saying, I'd just like to know what modes are on the air.

 

[K5MPH]

Maybe slow scan Tv slow scan is about 2.5 khz wide.....

 

[edweirdFL]

Possibly MSK if it sounded like this.

 

[wowologist]

Possibly MSK if it sounded like this.

Ya that's kewl, but without knowing what the other station is driving, distance is eh. I mean you get a great a signal on the scope and it reads out a loc and call - but without the my station info; like 1.5kw into a beam @ 175' meh mars heard you too. But a rec'd signal from a 500mw station into a coat hanger yagi @ 35' that's 800 miles from you ....now that's golden.

 

[jwt873]

What frequency?

Pretty well all the non-FM stuff on 2 meters takes place at the low end of the band. The meteor scatter calling frequency is 144.140 Mhz USB

MSK144 mode is used for scatter. Stations transmit a steady stream of data for 15 seconds then listen for 15 seconds. If you're near someone, you'll hear the whole 15 second transmission. If not, then all you'll hear is occasional little buzz sound (like in the movie above) as the signals bounce off meteor trails. To hear the echos, you need a directional antenna with some gain that you can rotate.

Things were really hopping back on December 14th-16th during the Geminid meteor shower. I've been doing scatter on six meters for about a year now.. I'm just in the process of getting set up on 2 meters. Just need the feedline to come and I'll be in business.

 

[krokus]

Are you sure it is an actual intended transmission, and not noise from a switch-mode power supply?

 

[ka3jjz]

It would be very helpful to know the frequency and where you are (county/state is fine)....Mike

 

[Jim_Shaffer]

Are you sure it is an actual intended transmission, and not noise from a switch-mode power supply?

Pretty sure, because it wasn't constant. It came and went with different lengths like two people having a QSO.

It would be very helpful to know the frequency and where you are (county/state is fine)....Mike

I think it was under 145 MHz. Pennsylvania, Lycoming/Northumberland County area.

 

[ka3jjz]

<sigh> If you get this signal again, please get the exact frequency. See the ARRL website below Tying down the frequency as used in a particular area might help identify the mode; you might just have found someone experimenting in the local area. It's not unheard of.

Band Plan

The American Radio Relay League (ARRL) is the national association for amateur radio, connecting hams around the U.S. with news, information and resources.

www.arrl.org

Mike.