SDS100/SDS200: SDS200 low audio in AM waterfall while sweeping

[dcommins]

I haven't seen anything about this but when using the waterfall display on my SDS200 in the air band (AM) and have a span set to less than 5.76MHz, the audio is really low. I have it set it to more than 15 to hear anything. If I turn off Sweep, the volume seem to go back to the normal range. I have to remember to turn it down before hitting Hold.

I'm running F/W Main: 1.23.05 and Sub: 1.03.05

Is this a known issue?

 

[gary123]

Almost sounds like a internal FW setting where the audio band width is too wide. can you check and see how far from the center freq you can hear signals?

 

[Ubbe]

SDS (Non-US) new firmware with waterfall

Latest firmware now available on Uniden Australia Main: USDS100_V1_23_03 Sub: USDS100-SUB_V1_03_05

forums.radioreference.com

/Ubbe

 

[m25man]

I haven't seen anything about this but when using the waterfall display on my SDS200 in the air band (AM) and have a span set to less than 5.76MHz, the audio is really low. I have it set it to more than 15 to hear anything. If I turn off Sweep, the volume seem to go back to the normal range. I have to remember to turn it down before hitting Hold.

I'm running F/W Main: 1.23.05 and Sub: 1.03.05

Is this a known issue?

Certainly is over this side of the pond.. 50% of our users have actually rolled back to V1.22 as a result, overall the verdict is "disappointing".

 

[dcommins]

Almost sounds like a internal FW setting where the audio band width is too wide. can you check and see how far from the center freq you can hear signals?

Sorry to reply late, I was out of town...

I'm listening to one of the active frequencies from the Atlanta airport on 128.000MHz. I can hear signals about 75kHz out from the center so between 127.9925 and 128.075. The volume doesn't change so it's still low but the clarity of the signals degrades.

I've sent a note to Uniden support about it so maybe if they get enough reports on this, they'll do something about it.

 

[gary123]

Sorry to reply late, I was out of town...

I'm listening to one of the active frequencies from the Atlanta airport on 128.000MHz. I can hear signals about 75kHz out from the center so between 127.9925 and 128.075. The volume doesn't change so it's still low but the clarity of the signals degrades.

I've sent a note to Uniden support about it so maybe if they get enough reports on this, they'll do something about it.

This seems to verify that the default bandwidth in AM mode is too wide. It should default to 5Khz. Ill try and conncet my 200 to a sweep generator and see what I get.

As far as I have determined the NA and EMEA waterfall code is the same so fixing one should fix both.

 

[dcommins]

I got a response from Uniden support on this.

They suggest I return the unit for repair. Really???

I think given that others are experiencing this, it's not a broken unit but a broken development/QA team.

 

[werinshades]

I've sent a note to Uniden support about it so maybe if they get enough reports on this, they'll do something about it.

I got a response from Uniden support on this.

They suggest I return the unit for repair.

I guess you received your wanted response.

 

[gary123]

if you can accept the loss of the unit for the turnaround time, and they are doing it under warranty. I would say send it out and see if it is a component issue. I doubt that it is. I tested my 200 on the bench. With a aircraft freq of 123.450 AM programmed and injecting a 1K tone at 60% modulation when I swept off freq more than 8k the signal became super weak and the squelch had no trouble muting the off freq signal. At 10k off freq the generated signal was not heard. I then selected the waterfall centered on 123.45 hit the hold to unmute audio and could hear the test signal 20Khz + from the center freq. Again the further away the weaker the rx audio of the signal got. I did notice too that the over all volume on 123.45 directly programmed was about twice the volume vs what was heard in waterfall mode.

This seems to indicate that the units are in a wide bandwidth RX mode vs a narrow band mode. BUT there could be some hardware issue causing it as well such as a set of audio filters enables in direct freq mode that are not selected in waterfall mode.

 

[dcommins]

I did notice too that the over all volume on 123.45 directly programmed was about twice the volume vs what was heard in waterfall mode.

Sounds like you're seeing the same thing with generated signals that I'm seeing with live ones.

They didn't acknowledge there was a known issue but suggested I send it in for "repairs". If it's a hardware problem and they're fixing it under warranty, they should say so. I've had the radio for several years so it's well out of warranty.

I told them I'd seen others report the same problem and I didn't think it was hardware-related. They're escalating it to management so I'll add their response here when I get one.

 

[JoeBearcat]

The support will improve in the coming weeks.

In the mean time I will see if the issue can be duplicated.

To clarify, while using the waterfall the audio is low but when you hold on a frequency the level increases?

 

[JoeBearcat]

Unfortunately I found that is a side effect of the waterfall balance between display and audio. If the gain were raised to increase the audio the floor of the display would rise too. The engineers said use HOLD to hear audio for AM.

 

[dcommins]

The support will improve in the coming weeks.

In the mean time I will see if the issue can be duplicated.

To clarify, while using the waterfall the audio is low but when you hold on a frequency the level increases?

Correct.

For reference, my SDS200 is at Main F/W version 1.23.07, and Sub version 1.03.05

I have the DMR, NXDN, and Waterfall keys installed, if that matters.

I select the Air Band under Start Preset Waterfall and manually tune to an active frequency for a nearby airport (126.975). Squelch is at 0. Gain is Auto. Mode is AM since this is the air band.

I set the Span such that I can hear audio while it is sweeping (less than 5.76MHz). I need to turn the volume up to 17+ to even hear anything when a transmission comes in. If I tune to another frequency while Sweep is active, the volume stays low.

If I change the Gain to manual and increase it to the max of 15, the volume increases a little but not as much as when I hit Hold.

If I hit the Hold button, the volume jumps up to the level it would be during a normal scan.

The volume problem only seems to be for AM modulation. If I edit the waterfall to have NFM, the volume does not decrease but stays at the expected higher level.

Is this normal behavior?

I've also observed that if I increase the span to 5.76MHz or greater and keep Sweep active, I hear no audio when a transmission comes in, regardless of the volume level or squelch setting.

I'm not sure why the span matters during a waterfall display. Sweep should be allowed and signals should be heard if they come in on the frequency being displayed regardless of the span value.

 

[Ubbe]

Is this normal behavior?

Yes. Am are level sensitive as it is an amplitud modulated signal. FM are a frequency modulated signal that are immune to any level changes and it is the amount of frequency variation that produce the audio.

I've also observed that if I increase the span to 5.76MHz or greater and keep Sweep active, I hear no audio when a transmission comes in, regardless of the volume level or squelch setting.

I believe that 5.76MHz are what the SDR receiver can output as max bandwidth to the DSP that then produce the waterfall. If it goes any higher in bandwidth for the waterfall the SDR receiver needs to instead start searching the frequency range and can then not pick out one single frequency to demodulate to get audio.

/Ubbe