SDS100: Horrible digital sound on PRI channel

Status
Not open for further replies.

dazza0768

Member
Joined
Feb 18, 2019
Messages
197
Location
Timaru, New Zealand
I have an SDS100 and I have a mix of analogue and digital systems programmed.

When I scan digital I like to have some analogue channels set as priority and the PRI setting to DND.

Whenever an analogue channel comes alive for about half a second I hear the DMR digital buzz as it comes from a digital DMR site and the analogue priority channel takes over.

Is this a known issue, is there any point to this as its bloody annoying having a loud DMR motor type sound for half a second before I can hear what the analogue pri channel has to say.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
6,931
Location
Stockholm, Sweden
The DSP that handles the audio have a long delay in the audio process. It's a very obvious echo if you have another scanner tuned to the same frequency.

The squelch and other signals are taken from the reciever chip and are an instant signal that says "I am now receiving an analog carrier so unmute the audio. But the audio are still processed in the DSP processor and are some 200mS delayed. So when the scanner unmutes the DSP is sending out the audio from a previous transmission.

If you only scan analog channels you will hear that each transmission starts with a noise burst that comes from the previous scanned channel or before the carrier where started from the transmitter. Also the audio mute when the SQ sense that there's no more carrier works immediatly and the delayed audio from the DSP gets cut of prematurely.

I have a system that clears down its conversation by a 5 tone sequential signal with 100mS for each tone. The last tone are never heard as the SQ mutes before the full audio have been monitored.

If it's any consolation the Whistler TRX has the exact same problem but the mute and unmute are so sluggish that it masks the problem, but are heard in its audio recording files.

One positive thing are that squelch tails are totally eliminated.

It could be easily fixed in software to delay the unmute 200mS and the mute could be delayed 100mS. That would make the DSP delay work to our advantage. The SDS firmware are far from a finished product and still needs lot's of bug fixes.

/Ubbe
 

dazza0768

Member
Joined
Feb 18, 2019
Messages
197
Location
Timaru, New Zealand
Beauty thanks for a good explanation on this.
It gives me a good fright on a monday night when I'm watching tv and the scanner is quiet for 2 hours then...BAM....loud sound of a DMR control channel followed by voices.

It sure can wake a guy right up!
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
6,931
Location
Stockholm, Sweden
You can probably fix it if you set your analog conventional channel to do both analog+digital and then in the systems option you set a 200mS Digital Waiting Time. You might need to adjust that time and I don't know if it works if you set the channel to analog only, if you need to set a CTCSS or similar to the channel.

/Ubbe
 

dazza0768

Member
Joined
Feb 18, 2019
Messages
197
Location
Timaru, New Zealand
You can probably fix it if you set your analog conventional channel to do both analog+digital and then in the systems option you set a 200mS Digital Waiting Time. You might need to adjust that time and I don't know if it works if you set the channel to analog only, if you need to set a CTCSS or similar to the channel.

/Ubbe
I have them set to ctcss search if they're not set and digital off. The slower scan speed and slight delay at the start of analogue transmissions drove me crazy.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
6,931
Location
Stockholm, Sweden
The only delay should be that the audio doesn't open up until after that digitial wait time. It should not affect scanning rate.

I tested and that timer only works in the All setting with analog+digital but it searches CTCSS tones there as well.
It was only with carriers below -100dBm that I get the delayed audio phenomen and only when using the All setting for the mode, it doesn't happen in analog only mode with my scanner and I didn't manage to get it to happen in any of the prio modes.

So it should be ok for you to change the mode to All and set the Digital Waiting time to a value high enough to get rid of the audio bursts. For me it was enough with the 100mS setting.

What you shouldn't do are to set the filters to any of the auto modes, that will slow down scanning.

/Ubbe
 

dazza0768

Member
Joined
Feb 18, 2019
Messages
197
Location
Timaru, New Zealand
Filters are custom set, none to auto.
Yeah it slows my scanning down setting to all as the scanner slows to work out if its digital or analogue.
Albeit, I'll just leave it and cope with the noise.
Thanks for the great understanding of it though.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
6,931
Location
Stockholm, Sweden
Yeah it slows my scanning down setting to all as the scanner slows to work out if its digital or analogue.
It shouldn't do that. It only stops if it is a carrier on the frequency and only then it starts to use the Digital delay time and at the same time evaluates the signal if its analog or digital.

Only if it's a carrier on the frequency needs it to stop and check if you have set CTCSS or whatever to that channel that needs to be taken into consideration. If it's no carrier on the frequency then it doesn't need to do anything, it just scans past it at a 50-100ch/s rate. There's nothing with the All-Analog-Digital settings that can slow down scaning. If you set a 100-200mS digitial delay it will only take that time until the audio are unmuted with an analog signal, if there's a carrier on the frequency.

/Ubbe
 
Status
Not open for further replies.
Top