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ТЕМА: User Manual Addendum

User Manual Addendum 01 Фев 2020 21:35 #61

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A couple of guys are confused regarding the new branch of JTDX. It is built specifically for SDR and, being Russian, had Expert Electronics in mind most of all.

Sample rate and sample size are different things. What is even better for us is you can set 48000 Hz sample rate in ESDR2, then translation is not needed on the way to JTDX.

Sample size: VAC does support 32-bit, you just have to make sure you allowed it in VAC control panel for cables being used by JTDX.

All previous JTDX versions requested 16-bit samples hence dynamic range is limited there to 90dB, new branch requests 32-bit samples where dynamic range is approximately 186dB (assuming the receiver is good enough - EE radios are certainly well in excess of 90dB).

The improvement is really for the crowded band scenario (like 20mtrs), where the audio sampling size is directly proportional to the liklihood of retaining decoding through high band occupancy.

Erik.
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User Manual Addendum 02 Фев 2020 15:11 #62

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Hi Eric. Thank you for your information. I just tried WSJT-X latest version and JTDX_32. I'm at -15dB
RX on the VAC and -4dB TX, put I adjusted the volume option on VAC at the minimum. Undoubtedly the definition is better but the ratioS/B is unchanged and final on the Waaterfall I clearly prefer WSJT-X. By aillers, I didn't feel like there was a gain on decoding. What do you think? 73 Jean-Marie
WSJT-X2020-02-02154830.png


JTDX2020-02-02155109.png
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User Manual Addendum 02 Фев 2020 15:58 #63

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Hello Jean-Marie, I have to say that I prefer JTDX but I have no data of my own in respect of comparisons with WSJTx. The JTDX author and a small team of testers run the tests and publish decoding comparison tables - the number of decodes per period on average. JTDX is a clear winner even at the previous 16bit versions. As for 32bit, so far only theoretical data has been published but it shows a strong liklihood of more completed QSOs when a band is saturated with signals and the radio, like ours, can take advantage of the increased sampling. Therefore the UMA addition giving JTDX 32 bit info is, as always, just to provide as complete a picture of what is available to EE product owners and should not be taken as any endorsement on my part. So to answer your question, if you prefer WSJTx then I think that is fine, stay with it.


Despite clarification, there is still some mis-understandings being aired on Facebook. Igor UA3DJY, the JTDX author has tried to explain further:


Sampling initially came from analog to digital signal conversion. SDR have ADC, sound card have ADC.
Regarding AF frequency good sound card can take samples from analog signal where each sample has 24-bit resolution.

Built in transceiver audio codecs are usually ‘poor man’s’ HW with 16-bit resolution as most transceivers have less than 90dB IMD3 dynamic range and 24-bit resolution can be useless there. In some cases 24-bit resolution can bring advantage if levels being not matched well, in such scenario 16-bit audio stream can get intermodulation products while 24-bit stream will provide greater dynamic range capacity for unmatched levels applied to ADC.

Sampling frequency: as per Nyquist-Shannon theorem en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem it is possible to fully recover signal from samples if sampling frequency is twice greater than signal frequency.

JTDX/WSJT-X operating with 48000 samples per second, so it could be possible to recover 24kHz AF signal from audio stream, at the moment we do not need such bandwidth and perform downsampling in JTDX/WSJT-X to 12000 samples per second. We have been using 0...5000 Hz spectrum out of 6000 Hz available.

This statement is correct concerning rc147_32A: "JTDX is not about sample rate, it' about sample
size»

As WDM KS driver being used in SDR does support 24-bit sample size and JTDX 32A does support 32-bit sample size some software shall convert 24-bit to 32-bit (JTDX RX) and back (JTDX TX). For SDR setup such software is virtual audio cable, for sound card it is operating system responsible for conversion.

From coding point of view 32-bit resolution is easier to implement versus 24-bit, that’s why we have got JTDX 32A.
It is coming of cost of extra CPU cycles, as 3rd party software(or operating system) expanding 24-bit signal to 32-bit resolution (JTDX RX) and back (JTDX TX).

73 Igor

So for our SDRs, which fortunately for us are independent of the OS, provided you set VAC as shown in the UMA you can take full advantage of the new JTDX branch (if you want to of course).

73 de Erik.
Последнее редактирование: 02 Фев 2020 16:08 от g0cgl.
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Addendum manuel d'utilisation 02 Фев 2020 16:13 #64

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Absolutely agree Erik, and we have a choice and there are still others. What just surprised me, and not in overcrowded tape conditions, what is rare in these times, is a much better contrast on the waterfall of the WSJT-X than compared to the 32-bit audio version of the JTDX. 73
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Addendum manuel d'utilisation 02 Фев 2020 16:19 #65

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You can adjust it using the waterfall controls. There is no doubt that to get the same contrast WSJTx<>JTDX, the settings have to be different. Personally, I would not let the waterfall dictate overall preference - well, for me anyway, the bottom line is what is decoded and what is worked. Providing I am maximising the DX going into my log, the waterfall can be pink with blue spots for all I care.

Erik.
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Addendum manuel d'utilisation 07 Фев 2020 07:44 #66

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Hi,
I use VAC 4.62 latest and I am wondering if any additional adjustments are needed?

73,

Gordan
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Addendum manuel d'utilisation 07 Фев 2020 07:58 #67

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Hello Gordan

Additional to what? To its default values? The important parameter in VAC versions later than 4.15, for the purposes of digital mode transmission, is to have MS Int = 3. I will look at 4.62 and check it, as I have not yet done so, but I would run it at the above. Along with Igor (UA3DJY author of JTDX), we had been corresponding with Muzychenko some time ago about the failings in 4.60 so with any luck 4.62 now works well. However, please report here any issues you find.

Erik.
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Addendum manuel d'utilisation 07 Фев 2020 08:47 #68

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My default settings
Вложения:
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Addendum manuel d'utilisation 07 Фев 2020 08:53 #69

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OK FB. Leave it at your settings - should be good. Let us know if not.

Erik.
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Addendum manuel d'utilisation 10 Фев 2020 08:31 #70

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Hi,
Using VAC 4.62 i can see some noise on waterfall so i got back to MME driver. Can anyone else confirm this at 4.62?

73,


Gordan,
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Addendum manuel d'utilisation 10 Фев 2020 08:39 #71

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There is increased latency with MME driver. But I suppose if it works for you then ok. But in my tests, only VAC 4.15 provides the cleanest audio path without latency, of course with WDM-KS driver. I uninstalled 4.62 here, notified Muzychenko accordingly, waiting for any response.

Erik.
Последнее редактирование: 10 Фев 2020 08:41 от g0cgl.
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Addendum manuel d'utilisation 10 Фев 2020 08:46 #72

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Hi Erik,
Is it possible to get an older version 4.15 ? I have paid latest 4.62 ..

73,

Gordan
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Addendum manuel d'utilisation 10 Фев 2020 11:51 #73

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Hi Eric,

I installed VAC 4.15 but for default settings Ms per int was set to 7 . Did I need to change both cables to 3?

73,

Gordan,
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Addendum manuel d'utilisation 10 Фев 2020 11:55 #74

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Yes will will have an email link to the full 4.62 version. In that link, substitute 415 for the 462 and you will get the full 4.15 version.
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Addendum manuel d'utilisation 10 Фев 2020 11:58 #75

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In 4.15 MS per Int at 7 should work fine. If you notice noise, change to 3. There is a small latency trade off using 3 but I do not think it affects anything in practice. Leave at 7 if possible - mine is at 7 and everything is 100% ok.
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