Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

afilip
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Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby afilip » Mon Mar 27, 2023 2:31 pm

I got back to SSB listening during last WPX Contest. It turned out that filters 2.1kHz and wider are ringing very strong making SSB signals impossible to copy. Only 1.8kHz filter is free of artifacts however it's too narrow making signal copying difficult.
It doesn't matter I use TAPR Hermes or 14-bit Hermes, the same problem persists.
I adjusted DSP filter size, buffer size and filter type but this did not help.

I tried PowerSDR mRX PS v.3.4.9 with both Hermes's and while NR2 was on, SSB signals sounded great.

I would like to continue using Thetis due to its few features which are not available in Power SDR.
Any help would be appreciated.

Adam AC8CE
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w-u-2-o
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby w-u-2-o » Mon Mar 27, 2023 3:12 pm

You may be one of the people that are very sensitive to the transient response of the low latency filter, and/or the very steep skirts used in even the least sharp filter.

Buffer size does not matter, but if you are worried about it simply set it to maximum (you will get more latency, of course).

Go to Setup > DSP > Options and select Linear Phase, size 1024, BH-4 window type. That will give you the least steep skirts and linear phase filtering.

Assuming your are not running some horribly old version of PowerSDR, the filtering and the DSP code for both PowerSDR and Thetis are identical. If the same filtering setup in both programs sounds different to you then you have some other problem going on.

Are you by chance using VAC for audio?
afilip
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby afilip » Mon Mar 27, 2023 5:21 pm

Scott,
I'm not using VAC for audio.
My headphones are plugged in directly to Hermes headphone connector.
Is it possible that Thetis filters ringing problem is caused by PowerSDR still installed on my PC?
By the way I've been using PowerSDR mRX PS v.3.4.9.

Adam AC8CE
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w-u-2-o
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby w-u-2-o » Mon Mar 27, 2023 6:50 pm

No, the two installations will happily coexist, just don't try to run them at the same time.
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kc2rgw
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby kc2rgw » Tue Mar 28, 2023 12:14 pm

The ringing the buffer types changes sounds like someone jangling change in a pouch as people are talking. However it in no way is loud enough to make copy nearly impossible as the OP stated. It's an irritating but very minor jangling on the peaks of words but the speech is entirely copyable.

If the copy is unintelligible, it's likely something else wrong.
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w-u-2-o
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby w-u-2-o » Tue Mar 28, 2023 1:04 pm

I have never heard these sounds you are all posting about. I would love to hear a recording of them, since I can't reproduce them here.
K4IBC
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby K4IBC » Tue Mar 28, 2023 7:43 pm

Curious if too high of AGC or rf gain could cause ringing or would it be more like AGC pumping.
afilip
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby afilip » Wed Mar 29, 2023 2:56 pm

I've installed Thetis v2.9.0.6 on my laptop. That was fresh install, FFT bins had to be created.
Started listening SSB on 40m and... no SSB filters ringing.
This test proved that my PC somehow influence Thetis.
I re-installed Thetis few times on my PC but it did not help.
To do fresh install I will have remove FFT bins but I can't find them.
Can anyone tell me how to delete existing FFT bins?

Adam AC8CE
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w-u-2-o
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby w-u-2-o » Wed Mar 29, 2023 3:03 pm

Go to C:\Users\yourwindowsusernamegoeshere\AppData\Roaming\OpenHPSDR\Thetis-x64 and delete the wdspWisdom00 file.

This is a hidden directory. You can navigate there easily by typing %appdata% (including the percent signs) into the Windows File Explorer address bar.
afilip
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby afilip » Fri Jul 07, 2023 1:24 am

I deleted the wdspWisdom00 file and re-installed Thetis. It did not help. SSB filters were still ringing.
So the last resort was clean Windows 10 install, however all important data, passwords etc. had to be saved.
After clean Windows installation I've installed Thetis and tried it with Hermes. This time no problems with SSB filters.
I enjoy listening very nice sounding SSB audio across all bands.

Scott, thanks for your help.
Best 73
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NJ2US
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby NJ2US » Fri Jul 07, 2023 12:40 pm

I'm not an expert on filters however, my experience is if the DSP->Options->Filter Size->(RX and TX) SSB/AM is set any higher than 2048, the ringing gets increasingly annoying, Im using Low Latency/BH-7, but Filter Type and Window doesnt seem to have much influence on the ringing. In fact, when I listen to other Thetis stations, the transmit ringing artifact is plainly audible to me, and I usually guess that the transmitting station has their Filter Size (TX) set to 8192 or higher, and Im usually right. So, for what its worth, and Your mileage will probably Vary, this is what I use for virtually no detectible ringing.

Apache 7000DLE Thetis v2.10.0 x64 Windows 11, i9, Nvidia RTX2060

Jeff NJ2US

dsp_setup_filters.png
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dynamicfusion
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Re: Thetis v2.9.0.6 SSB Filters 2.1kHz and wider are ringing

Postby dynamicfusion » Thu Jul 13, 2023 6:15 pm

Flip your low-latency toggle to phase-linear and all your ringing will disappear. :D

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