JTDX level and ALC

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Tony EI7BMB
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JTDX level and ALC

Postby Tony EI7BMB » Tue Apr 30, 2019 11:26 am

Hi guys, is anyone here using JTDX 2.0.1.135 ? Perhaps you could check something for me . On the pwr slider on the right hand side in order to get an ALC level of -1.0 in Thetis i have to set the Pwr level slider to -4.2 . Given that I have voicemeeter and TX gain set to zero should the ALC level not closely match the level set on th Pwr slider in JTDX?
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Re: JTDX level and ALC

Postby w9mdb » Tue Apr 30, 2019 1:05 pm

I did some testing and get the same with WSJT-X and have to run the TX Gain on Thetis at -4 in order to stay at -1dB on the ALC meter but that seems unnecessary. If I watch the transmit I see the harmonics at -65dB no matter how high I set the Tx Gain and the ALC never goes above 0dB...then again I'm using an amp and only putting out 6W from the ANAN. And that's with WSJT-X and VoiceMeter at 0dB on transmit.

Are you seeing ALC > 0dB?

de Mike W9MDB
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Re: JTDX level and ALC

Postby Tony EI7BMB » Tue Apr 30, 2019 1:25 pm

Hi Mike, I can adjust to -1 db or less without any problem using the power slider and the display looks clean . Just wonder why there is a discrepancy between JTDX at -4.2 when Thetis is at -1 ALC with TX gain of zero . Unless I'm mistaken the two levels using power sdr and jtdx were pretty much the same
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Re: JTDX level and ALC

Postby w9mdb » Tue Apr 30, 2019 1:40 pm

I just tested with 100W out and WSJT-X and max power and Thetis TX Gain at 0 (I assume that's dB).

Still show -65dB on the harmonics so nothing is being overdriven at all with 0dB on the ALC.

I assume JTDX does what WSJT-X does and only puts on 97% of full power at full scale.

Are you seeing > 0dB on the ALC or harmonic levels increasing?

de Mike W9MDB
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Tony EI7BMB
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Re: JTDX level and ALC

Postby Tony EI7BMB » Tue Apr 30, 2019 1:50 pm

Sorry Mike misread your earlier question . No not seeing anything above 0db even with everything maxed out. Just want to make sure everything is as clean as it can possibly be . Like you I run the Anan at low power, 2W to drive my Acom 600s to around 95w on 6m
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w-u-2-o
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Re: JTDX level and ALC

Postby w-u-2-o » Wed May 01, 2019 3:40 am

Remember that the ALC metering in PowerSDR and Thetis is a bit bizarre. The ALC meter will only show indications up to 0dB. If ALC is being driven above 0dB you can only see that by monitoring the ALC COMP meter.

73,

Scott
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Re: JTDX level and ALC

Postby Tony EI7BMB » Wed May 01, 2019 8:28 am

Thanks Scott, my main curiosity though relates to the output level of JTDX and ALC reading , if its a negative value on JTDX should these two values not be closely matched ?
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Re: JTDX level and ALC

Postby w-u-2-o » Wed May 01, 2019 10:37 am

Tony,

They should, but I don't use JTDX and don't know how that software was written.

One thing that can throw levels off by 3dB is if the the digi app actually puts out a stereo signal and the left and right channels get summed somewhere in the process.

On every other digi mode app that I've tried that offers output level control in dB, the levels match perfectly. In my setup I maintain 0dB TX and RX gain in both Voicemeeter and in PowerSDR and use the control in the digi app to adjust drive levels. Normally I leave the latter at 0dB as well, thereby causing ALC to be 0dB, and ALC COMP to be 0dB. Drive is adjusted with RF drive. Sometimes I reduce RX gain using the channel slider control in Voicemeeter if I think the audio is just a little too hot going into the digi app but I never do this for TX. I don't worry about limiting things to -0.1dB ALC.

73,

Scott
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Re: JTDX level and ALC

Postby Tony EI7BMB » Wed May 01, 2019 1:59 pm

Thanks again Scott, I've just replicated the same behavior using WSJT X FT 8 so it does not seem this is specific to JTDX . I wonder is something different in Thetis compared to Power SDR in the audio chain ?
Anyway I am still able to run a minus ALC value and no ALC comp showing so I guess that's what is important.
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Re: JTDX level and ALC

Postby w-u-2-o » Wed May 01, 2019 6:30 pm

I'm away for a couple of days, but I will take a closer look at this over the weekend.
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Re: JTDX level and ALC

Postby Tony EI7BMB » Wed May 01, 2019 6:32 pm

Thanks Scott, I tried with the default TX profile and got a different level again so perhaps a database re set may be in order .
Edit: I've just noticed the leveller was on in default profile so turning that off gives me exactly the same level on default profile compared to my usual FT8 TX profile.

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