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Spyserver on Pi 3 - Screeching on Digital? #sdrsharp #spyserver #raspberrypi

Mike Krueger
 

I just got the latest version of spyserver running on a fresh Raspian install. All devices are in my LAN. 

It seems that analog voice works OK, but my primary interest is decoding digital V/UHF traffic with DSD+. I'm decoding with the latest SDR# release and DSD+FL. 

In SDR#, the expected "motorboating' sound of P25 and DMR is replaced with an awful screeching that sounds nothing like what it should. Obviously, DSD and other decoding tools can make no sense of it. Happens with both an Airspy R2 and a mini. 

What might I want to check? Thanks! 

prog
 

On Mon, Mar 19, 2018 at 10:01 pm, Mike Krueger wrote:
the expected "motorboating' sound of P25 and DMR is replaced with an awful screeching

If you can describe the problem in a more technical way, maybe someone will understand what's going on and probably provide some help.

EB4APL
 

You are probably too young, but "motorboating" is a classic term in electronic engineering. It refers to a sound that reminds a small boat with a one cylinder engine. Usually it was used to describe low frequency oscillations in audio amplifiers and also some AGC malfunctions.

In this case it refers to the aural characteristic of a digital transmission; if you are used to listen to those signals, you can usually identify the kind of mode just by ear, like CW Morse, RTTY, Fax, FT8, Stanag 4285 and a lot more, so you can use the right decoder. It would be more "technical" to have a recording but this is a first notice.

Regards,

Ignacio, EB4APL



El 20/03/2018 a las 11:24, prog escribió:
On Mon, Mar 19, 2018 at 10:01 pm, Mike Krueger wrote:
the expected "motorboating' sound of P25 and DMR is replaced with an awful screeching

If you can describe the problem in a more technical way, maybe someone will understand what's going on and probably provide some help.
_._,_._,_

prog
 

On Tue, Mar 20, 2018 at 08:19 am, EB4APL wrote:

You are probably too young, but "motorboating" is a classic term in electronic engineering. It refers to a sound that reminds a small boat with a one cylinder engine. Usually it was used to describe low frequency oscillations in audio amplifiers and also some AGC malfunctions.

In this case it refers to the aural characteristic of a digital transmission; if you are used to listen to those signals, you can usually identify the kind of mode just by ear, like CW Morse, RTTY, Fax, FT8, Stanag 4285 and a lot more, so you can use the right decoder. It would be more "technical" to have a recording but this is a first notice.

Regards,

Ignacio, EB4APL

This still doesn't look like an engineer's description of the problem. Or maybe I'm expecting too much.

Mike Krueger
 

I'm no engineer - but perhaps a more clear description is that the audio received in SDR# from the spyserver is heavily distorted, with what sounded like a constant-pitch tone mixed in.

I tweaked a few values in the config and it's been working fine for several hours. I'm guessing one of the default settings there wasn't playing nice with the hardware I have.

FWIW I'm running the spyserver  locally on my LAN because SDR# would peg the CPU in my Win10 VM. Now, SDR# stays around 30% CPU... which is great.

Cheers,
Mike




On Tue, Mar 20, 2018 at 8:26 AM, prog <info@...> wrote:
On Tue, Mar 20, 2018 at 08:19 am, EB4APL wrote:

You are probably too young, but "motorboating" is a classic term in electronic engineering. It refers to a sound that reminds a small boat with a one cylinder engine. Usually it was used to describe low frequency oscillations in audio amplifiers and also some AGC malfunctions.

In this case it refers to the aural characteristic of a digital transmission; if you are used to listen to those signals, you can usually identify the kind of mode just by ear, like CW Morse, RTTY, Fax, FT8, Stanag 4285 and a lot more, so you can use the right decoder. It would be more "technical" to have a recording but this is a first notice.

Regards,

Ignacio, EB4APL

This still doesn't look like an engineer's description of the problem. Or maybe I'm expecting too much.