Compression taking place

JJ4SDR
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Compression taking place

Postby JJ4SDR » Thu Mar 09, 2023 3:39 am

I have been enjoying use of PS for some time now and get unsolicited reports on how clean my signal looks like from people who have stations that truly "see" my signal. I always have DUP turned on when I am on the air. However, on just one band, it appears that my signal isn't as clean as I would like it to be. Of course, I also recall having read Scott mention that anything below - 70 is not to be worried about as that can't be seen by other stations. Now, are any of the things that I mention below some ways of perhaps improving the situation? What is written at "1." is helping, but I think I am missing something here.

Below, see screen capture of the Linearity form as it stands right now.

Pure Signal Form.jpg
Pure Signal Form.jpg (77.14 KiB) Viewed 3219 times


1. On 20 meters (antenna is a mono-band inverted V), the "Amp view" shows that I am running my SS amp into compression (observing the top right-hand corner of the plot in Amp view). The amp can easily deliver full-legal limit (NOT that I would do that though) so I am not sure why I am seeing this compression. On all the other bands that I operate on (40, 17, 15 and 10), the plot in Amp view looks pretty nice and "regular." Only on 20 do I observe a plot that clearly indicates compression. When I dial the exciting RF input to the amp back some, the Amp view changes to a more "normal" plot, very similar to those on other bands.

2. While re-reading some many threads on PS, I came across mention of the "TINT" parameter that I can see on the Linearity form. I don't think that I have ever changed that, but it reads 1.1. In one thread I got the idea that having 0.5 in the TINT box may work better, but again, I have no idea what TINT actually does so why 0.5 would work better or not isn't very clear to me.

3. Another thing that was mentioned in another thread was "Single Cal" that I may want to experiment with although I thought that this is a sort of "one-off" feature after which NO continuous auto-calibrating takes place until I hit "Single Cal" again", I am not sure if I got this right :roll: . In fact, I have NEVER used it. For PS, I use the 2 TON button to "auto-calibrate" for each band (I do that again when I bounce from one amp to another and/or if I build another antenna for a band) and not mess with PS after that.

4. I also read that one may want to play with the Max Gain of the Leveler (mine is set at 5dB) as increasing that number may help the CFC when using PS. I have also heard that increasing the Max Gain of the Leveler beyond 5dB wasn't a good idea (that discussion had nothing to do with PS if my memory serves). However, I have some compression applied even before the audio from the MIC even sees the ANAN so I am not sure if increasing the Leveler Max Gain would help. Or, perhaps, I reduce any pre-ANAN compression (I usually don't run a lot of compression) and make up for the reduced compression by increasing the Leveler Max Gain dB figure.....

5. ALC Comp is hitting 3dB (even 5dB) at times when I transmit. Would I do better to switch the meter to ALC Group and hit 3dB at times?

Any suggestions from more experienced users of PS would be welcome :) .

Juha
NI2M
Thetis v2.9.0.6 x64 Protocol 2 v2.1.18

P.S. I use a VST Host (a "stripped down" version of a full-blown DAW) for some of the audio processing, prior to feeding result into ANAN.
PC: 8 Core i7-10700 CPU @ 2.90GHz, NVMe SK Hynix 512 GB SSD, 32GB RAM
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w-u-2-o
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Re: Compression taking place

Postby w-u-2-o » Thu Mar 09, 2023 1:19 pm

Juha--you are the KING of asking a large number of totally disconnected questions in a single post!

To address the title of this post, "Compression taking place", and, I'm assuming, your primary, core question:

PureSignal has NOTHING to do with the compression you see with your amplifier.
Audio processing has NOTHING to do with the compression you are seeing with your amplifier.

But it is great that we have AmpView to help us recognize it is happening.

What IS happening is that, for whatever reason, the design of the amplifier has more gain on 20M than it does on other bands. Therefore you must lower your drive level to keep it out of compression. It's that simple. And it has nothing to do with anything other than drive level. Of course PureSignal will help this by effectively reducing the drive for you, but you will get better performance by making a gross reduction in drive so PureSignal doesn't have to work so hard.

As for your other questions:

2. While re-reading some many threads on PS, I came across mention of the "TINT" parameter that I can see on the Linearity form. I don't think that I have ever changed that, but it reads 1.1. In one thread I got the idea that having 0.5 in the TINT box may work better, but again, I have no idea what TINT actually does so why 0.5 would work better or not isn't very clear to me.

Yes, you want TINT to be set to 0.5dB. It will work better.

You can actually blame that all on me. I asked Warren to expose this adjustment with the idea that it might be helpful in certain situations. AFAIK it never has been. You can read more about it at the main, tacked, PureSignal post which I'm sure you are familiar with: viewtopic.php?f=20&t=3166

I strongly recommend you change this back to the 0.5dB default.

3. Another thing that was mentioned in another thread was "Single Cal" that I may want to experiment with although I thought that this is a sort of "one-off" feature after which NO continuous auto-calibrating takes place until I hit "Single Cal" again", I am not sure if I got this right :roll: . In fact, I have NEVER used it. For PS, I use the 2 TON button to "auto-calibrate" for each band (I do that again when I bounce from one amp to another and/or if I build another antenna for a band) and not mess with PS after that.

Unlike TINT, Single Cal is often quite useful. If you want PureSignal to make a single measurement and correct based on that measurement this is the way to do that.

It is more often used with two-tone. Assert a two-tone test signal, normally done at your full drive level, and then hit the single cal button as many times as you like until you see a correction you like. Then don't mess with it. You'll notice the PS-A (automatic) button turns off. That just means PureSignal is no longer in automatic mode, not that PureSignal is deactivated. You also don't see a correcting indicator, which is probably a bug, and a bit disconcerting. But you can see that transmitted IMD is low, so obviously PureSignal is still running.

So why might this be useful? I find it most useful during digi mode operations where I don't want PureSignal to be making any corrections or changes during, for example, a long FT8 transmission. So after tuning to the dial frequency I want, I make a transmission, fire off a single cal, then operate digital with low IMD. Another example might be if you are seeing occasional "blow outs" for some reason you can just hit single cal and then PureSignal won't have any opportunities to "make a mistake".

4. I also read that one may want to play with the Max Gain of the Leveler (mine is set at 5dB) as increasing that number may help the CFC when using PS. I have also heard that increasing the Max Gain of the Leveler beyond 5dB wasn't a good idea (that discussion had nothing to do with PS if my memory serves). However, I have some compression applied even before the audio from the MIC even sees the ANAN so I am not sure if increasing the Leveler Max Gain would help. Or, perhaps, I reduce any pre-ANAN compression (I usually don't run a lot of compression) and make up for the reduced compression by increasing the Leveler Max Gain dB figure.....

This question has nothing to do with PureSignal. Increasing leveler max. gain will not help, or hurt, CFC, assuming you do your part and ensure internal levels remain below 0dB. The leveler is merely another type of compression stage, just like you apparently have some compression going in your DAW prior to the leveler.

How much compression you use, what kind of compression it is, and where you use it is a very personal decision and depends very much on the characteristics of your voice, how you use your microphone, and other intangibles.

IMHO the three stages and types of compression available in Thetis, the leveler, CFC, and ALC, are more than enough by themselves and no external compression is required. (I don't count COMP or CESSB because they are, IMHO, obsoleted by these other compression stages.)

As a rule of thumb, most people do quite well with 5dB of leveler gain. To use myself as a corner case, my leveler is set to 15dB and 100ms decay, which is quite aggressive. But while I get great signal reports like this when others have tried it the results were not desirable.

So you will have to experiment, there is no single answer.

5. ALC Comp is hitting 3dB (even 5dB) at times when I transmit. Would I do better to switch the meter to ALC Group and hit 3dB at times?

Again, this question has nothing to do with PureSignal. And it has nothing to do with the extra gain your amp has on 20M.

ALC Comp and ALC Group meter modes read exactly the same when ALC is in the positive numbers. ALC Group meter mode is merely a composite of the ALC meter (which only reads to 0dB) and the ALC Comp meter (which only reads above 0dB), i.e. it's a convenient way of looking at all ALC data on a single meter. You can safely, and conveniently, use ALC Group in place of the other two meter modes.
K9RX
Posts: 414
Joined: Fri Apr 14, 2017 3:47 pm

Re: Compression taking place

Postby K9RX » Thu Mar 09, 2023 1:27 pm

Juha,

It sounds to me like the amp just has more of an issue on that one band!

If I recall TINT is best left at the default (along w/ all of its other parameters). I mentioned its use (in other threads) only to (try to) get PS to start working again as it will occasionally lock up and not work after having used SPLIT. That issue has been replicated and confirmed by Richie. Hopefully, it is in the mix to be looked at.

I don't think any of the internal audio settings impact what you are talking about. The amp compression status is more a factor of the amp itself (assuming you are not hitting it too hard)... I know that my KPA1500 'likes' bands differently at least as seen in the efficiency of the amp varying from 57% to 75% at full legal power and depending on the band. [yeah - I know - 75% is not cool re Class AB or even B... but Elecraft doesn't seem to what to address it... ]

I will say that I use COMP (contrary to some belief that it sounds bad - it works for DXing with little audio sound impact)... and the downside of this is that it smacks PS at the start and PS will jump around because of it. As a result of this finding I will hit "SINGLE CAL" on a clear spot in a band and I will get decent correction w/o the jumping around. I mention this to see if using it solves the amp COMP issue.

Gary
K9RX
JJ4SDR
Posts: 436
Joined: Fri Jul 30, 2021 10:09 pm
Location: TEXAS, USA

Re: Compression taking place

Postby JJ4SDR » Fri Mar 10, 2023 12:14 am

Scott,

Thank you for bestowing the title KING on me :lol: .

Your comments may keep my heirs apparent from making themselves too - well -apparent - here :P .

Seriously, your comments are much appreciated.

Juha
NI2M
PC: 8 Core i7-10700 CPU @ 2.90GHz, NVMe SK Hynix 512 GB SSD, 32GB RAM
Windows 10 Home, Version 22H2
Thetis v2.10.4.3 x64
Protocol 2 v2.1.18
JJ4SDR
Posts: 436
Joined: Fri Jul 30, 2021 10:09 pm
Location: TEXAS, USA

Re: Compression taking place

Postby JJ4SDR » Fri Mar 10, 2023 12:14 am

Thanks Gary,

Nice call-sign, by the way!

Juha
PC: 8 Core i7-10700 CPU @ 2.90GHz, NVMe SK Hynix 512 GB SSD, 32GB RAM
Windows 10 Home, Version 22H2
Thetis v2.10.4.3 x64
Protocol 2 v2.1.18
JJ4SDR
Posts: 436
Joined: Fri Jul 30, 2021 10:09 pm
Location: TEXAS, USA

Re: Compression taking place

Postby JJ4SDR » Fri Mar 24, 2023 1:20 am

The Dual Male SMA connector (sits between the RF coupler and a variable one) came apart when I was disconnecting everything so I bet that played into the funky plots I saw in Ampview.

Juha
PC: 8 Core i7-10700 CPU @ 2.90GHz, NVMe SK Hynix 512 GB SSD, 32GB RAM
Windows 10 Home, Version 22H2
Thetis v2.10.4.3 x64
Protocol 2 v2.1.18

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