SDS100/SDS200: sds200 P25 distorted audio

[n1moy]

Perplexed by the flawed reception of a conventional P25 public service repeater. SDS200 receiving over a ~6.8 mile route with no sizable obstacles. [low-lying hills] No scan priority, weather alert, attenuation or filters employed.

Firmware:
Main Version 1.23.03
Sub Version 1.03.02

In my judgment the choppy garbled voice is unacceptable. NAC detection to open the schelch is also affected. This problem is unshared with any other channel. The attached WAV.ZIP file is illustrative of the matter.

Reception of the signal with the same antenna and a RTL-SDR.com V3 dongle using DSDPlus is excellent.

Seeking an assessment, diagnostic comments and/or recommendations.
[recording attached]

Thanks in advance,

 

[RandyKuff]

The current version is 1.23.05 Main/1.03.05 Sub...

 

[nessnet]

Customize your display to show D-error and RSSI.
Then, what are they?
Garbled digital audio is indicitive of packet errors - usually caused by signal <-110, or simulcast / RFI.

Have you enabled the waterfall?
Any real close signals?
Or, look at the DSD+ waterfall display.
It'll also show you if something is TX'ing close.
That would certainly do this, considering how 'wide' the rec'v chip on there things are....
(That is what the filters/IFX is for...)

Also, check to make sure you are actually scanning the nearest site.
Maybe use site hold to make sure.

 

[n1moy]

Unaware of d-error display, can you provide a link ?

Waterfall is not enabled, nothing strong nearby. Will work on gqrx.

This is a conventional repeater. [single machine, tower]

 

[nessnet]

Unaware of d-error display, can you provide a link ?

Waterfall is not enabled, nothing strong nearby. Will work on gqrx.

This is a conventional repeater. [single machine, tower]

Yea... you said "conventional' in your OP.
My bad.

Out of curiosity - how do you know something isn't TX'ing close to the target freq?
I'd still take a look at that DSD+ waterfall - RFI certainly would explain this.

Easier to Read SDS100/200 Digital Scanner Manual

 

[n1moy]

Upgraded the firmware and added d-error to the display. Collecting data ...

Have looked at this frequency/problem in the past with SDR# and did not see any suspect signals, will look again.

 

[buddrousa]

Did you set the IPX on the offending Frequency?

 

[n1moy]

IPX on the offending frequency ... Could you explain ?

 

[KC1UA]

Have you tried a different filter setting?

 

[buddrousa]

Google, Look up in the Manual, Youtube video it is explained how and when it is used.

 

[wtp]

IFX was meant,
FTM: Press Func then 7(IFX) to toggle Intermediate Frequency Exchange for a channel/frequency in Hold Modes.
and that is from the "easy to read manual,

Easier to Read SDS100/200 Digital Scanner Manual

and then the hard to read one i guess

https://www.uniden.info/download/ompdf/SDS200om.pdf

 

[ka3jjz]

Google, Look up in the Manual, Youtube video it is explained how and when it is used.

Or you can look it up in our FAQ which has, among the other linked threads on the filters, a PDF on the subject

SDS100 and SDS200 FAQ Page - The RadioReference Wiki

wiki.radioreference.com

Mike

 

[n1moy]

Experimenting with IFX - Intermediate Frequency Exchange

Channel/Frequency in Hold mode, press Func then 7(IFX) to toggle.

"Changes the IF used for a selected frequency to help avoid image and other mixer-product interference on a frequency."

 

[hazrat8990]

I was having issues with my SDS200 where 50% of the time, the audio sounded just like the clip you provided. I messed around with filters a bunch, but it was still giving me issues. I ended up going to the 'miscellaneous' tab in Sentinel, and adding all of the frequencies from the two sites I can receive to IFX, and now it decodes everything perfectly!

 

[n1moy]

Using SDR# scrutinized the waterfall neighboring the target frequency. Nothing atypical or noteworthy discovered.

 

[n1moy]

Firmware upgraded:
Main Version 1.23.05
Sub Version 1.03.05

After enabling IFX the garbled P25 audio remains.
[sample WAV.ZIP file attached]

Thinking filter settings are next. Is the Inverted High Pass Filter the recommended default ?

Do users typically enable this filter globally ?

 

[R0am3r]

There is no right or wrong answer for the filters. You apply a filter that works best for your environment. With that said, I set my Global Filter to Wide Invert and make exceptions for each system I monitor. It also helps to live in a rural area.

Just wondering - did you ever add the D-Error to the display? And what is the RSSI value of the system you are monitoring?

 

[nessnet]

Do users typically enable this filter globally ?

I wouldn't - each freq you monitor may have - or not have RFI and each should be addressed individually.

Remember, any filter does attenuate somewhat.
So, if you do have a weak RSSI, a filter will make it even weaker...

My suggestion (for global) is off or normal.

 

[n1moy]

Decode Error 0 – 100 [Filters have different ranges]

Receive Signal Strength Indicator -100 dBm

Continuing to experiment with filters. Does D-ERROR have units ?

 

[jtwalker]

So an RSSI value of -100 is on the bottom edge of a signal that can be reliably decoded.

Errors should be lower than 80, ideally 15 or 20 as a max for a good signal.