Ft8 Continuous Dips in Transmitted Signal
Hi
This question keeps coming up every now and then. FDM-DUO is the first rig I've had that doesn't have any kind of transmit ALC meter. I and many others with me I believe, would appreciate if an ALC meter was implemented in the stand-alone DUO.
Maybe that will happen since the support ELAD provides is fantastic.
73 and a Happy New Year
Kjell-Goran SM4GRP
Andy puts it much more succinctly than I did!
If you need any more help, please just ask, there are loads of really helpful souls on here.
Neil
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On 24/12/2018 21:22, Andy TALBOT wrote:
No sound card is necessarily the same as any other sound card.
But at least in the Duo, you know you won't be overdriving the Tx. 100% is full power. And turn ALC off, it's not doing anything when the drive is correct
On Rx, set the playback level to give the recommended setting for WSJT-X, which is something like 30% on the level meter on pure background noise.
But its's not that important
On Mon, 24 Dec 2018 at 21:12, Michael Gottlieb via Groups.Io <michaelgottlieb=yahoo.com@groups.io> wrote:
Just started with FT8 on my FDM-DUO.I have set my playback fdm-duo line setting at 60 so I am not triggering alc and causing splatter.
Is it safe to assume that sound cards are consistent and my 60 level setting is the same as others set at 60?
For receiving, I have my recording tab line fdm-duo level at 5 because that gets me a 60-70db level on my wsjt-x meter. (in the green).
My next question is if that is correct because this doc from Elad shows that the level should be at 100:
http://sdr.eladit.com/APPLICATION%20NOTES/ELAD%20AN_003%20-%20(EN)%20Using%20FDM-DUO%20with%20WSJT-X%20-%20rev%201.1.pdf
But at 100, my meter on wsjt-x is pinned at 80 in the red and never goes down on receive.Finally, when I am transmitting ft8, I don't hear anything from the pc speakers, I assume that is correct as well.
KB6D
The record level needs to be set to give you around 30dB on the WSJT-X meter. Reason for that is that iit gets you the maximum possible dynamic range. I almost always run with AGC off in digimodes, and set the gain to give me about 30dB at half volume (I use the AUX output via VAC, but the same applies however you do it).
FT8 is a single-tone constant-carrier mode, so you cannot cause "splatter" other than at tone transitions and at the start and end of the transmissions. The level of overdrive you would need to cause any detectable problems above those inherent in the sharp zero-point transitions is pretty extreme.
Assuming you are not overdriving an amplifier and causing ALC pumping, it is not really possible to overdrive the DUO via USB in FT8 mode. Even if you are pushing an amplifier well into ALC, you would only cause clicks at the start and end of the transmission, and as FT8 does not have soft-start, those happen anyway.
Assuming you are going directly from WSJT-X to the DUO sound device, and not through any soret of intermediate audio or digital process, I would not worry.
Make sure you are using Fake-It CAT split so you don't get any in-band harmonics (although they are minimal with a DUO anyway). That keeps the TX tones into the DUO between 1500 and 2000 Hz even if you are transmitting on what WSJT-X says is 300Hz (it would send 1800Hz but drop the TX freequency by 1500Hz to compensate).
Neil G4DBN
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On 24/12/2018 21:12, Michael Gottlieb via Groups.Io wrote:
Just started with FT8 on my FDM-DUO.I have set my playback fdm-duo line setting at 60 so I am not triggering alc and causing splatter.
Is it safe to assume that sound cards are consistent and my 60 level setting is the same as others set at 60?
For receiving, I have my recording tab line fdm-duo level at 5 because that gets me a 60-70db level on my wsjt-x meter. (in the green).
My next question is if that is correct because this doc from Elad shows that the level should be at 100:
http://sdr.eladit.com/APPLICATION%20NOTES/ELAD%20AN_003%20-%20(EN)%20Using%20FDM-DUO%20with%20WSJT-X%20-%20rev%201.1.pdf
But at 100, my meter on wsjt-x is pinned at 80 in the red and never goes down on receive.Finally, when I am transmitting ft8, I don't hear anything from the pc speakers, I assume that is correct as well.
KB6D
Andy G4JNT
No sound card is necessarily the same as any other sound card.
But at least in the Duo, you know you won't be overdriving the Tx. 100% is full power. And turn ALC off, it's not doing anything when the drive is correct
On Rx, set the playback level to give the recommended setting for WSJT-X, which is something like 30% on the level meter on pure background noise.
But its's not that important
On Mon, 24 Dec 2018 at 21:12, Michael Gottlieb via Groups.Io <michaelgottlieb=yahoo.com@groups.io> wrote:
Just started with FT8 on my FDM-DUO.I have set my playback fdm-duo line setting at 60 so I am not triggering alc and causing splatter.
Is it safe to assume that sound cards are consistent and my 60 level setting is the same as others set at 60?
For receiving, I have my recording tab line fdm-duo level at 5 because that gets me a 60-70db level on my wsjt-x meter. (in the green).
My next question is if that is correct because this doc from Elad shows that the level should be at 100:
http://sdr.eladit.com/APPLICATION%20NOTES/ELAD%20AN_003%20-%20(EN)%20Using%20FDM-DUO%20with%20WSJT-X%20-%20rev%201.1.pdf
But at 100, my meter on wsjt-x is pinned at 80 in the red and never goes down on receive.Finally, when I am transmitting ft8, I don't hear anything from the pc speakers, I assume that is correct as well.
KB6D
Just started with FT8 on my FDM-DUO.
I have set my playback fdm-duo line setting at 60 so I am not triggering alc and causing splatter.
Is it safe to assume that sound cards are consistent and my 60 level setting is the same as others set at 60?
For receiving, I have my recording tab line fdm-duo level at 5 because that gets me a 60-70db level on my wsjt-x meter. (in the green).
My next question is if that is correct because this doc from Elad shows that the level should be at 100:
http://sdr.eladit.com/APPLICATION%20NOTES/ELAD%20AN_003%20-%20(EN)%20Using%20FDM-DUO%20with%20WSJT-X%20-%20rev%201.1.pdf
But at 100, my meter on wsjt-x is pinned at 80 in the red and never goes down on receive.
Finally, when I am transmitting ft8, I don't hear anything from the pc speakers, I assume that is correct as well.
KB6D
Many thanks for the effort and your interesting findings, Neil.
Well, I think these are really good results overall & that ALC
overshot, guess it is something we've to live with.
As for the possible problems with lower tones and also for
possible harmonics when using an additional amplifier:
One may enter a lower frequency in wsjt-x. Where it
reads 20m e.g. enter 14073 or even 14072 then everything
moves up to the range above 1500Hz.
73, Andy, DF4WC
--
Diese Nachricht wurde von meinem Android Mobiltelefon mit GMX Mail gesendet.
Am 21.02.2018, 14:33, Neil Smith <neil@...> schrieb:
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Hi Charlie, setting the DUO to 5W out on 28MHz, when the Line Properties level slider is set to 62 or more, the output is full power with FT8. At slider level 32, the output drops to 500mW, so on mine it is definitely controlling the output level correctly.
Starting from the generated audio, I set WSJT-X FT8 to use a VAC as output, and used Spectrum Lab to view that, with no connection to the DUO and with SW2 not running. Here is that is looks like with with FT8 TX set to 890Hz:
That is what you'd expect from 6.25Hz spaced tones at 6.25 symbols per second. The spikes and pattern of dips are the result of all those Bessel functions. Some of the tone shifts are 6.25Hz, some 12.5, and so on, up to 8 x 6.25Hz. At about 60dB down relative to the peak, the bandwidth is about 450Hz. Starting from this as the ideal, let's see what the DUO does to the signal.
Looking at the output spectrum, with the level set to 100 on the slider, the 0dBm output looks like this:
That looks pretty much similar to the raw audio from WSJT-X, again about 400Hz wide (two divisions) at about -60dB relative to the peak tone levels. Thsi was using much wider FFT bins on the 4406 than on the SpecLab. The blip as the left is carrier feedthough, and the cutoff from about 300Hz above that is the audio tailoring in the DUO. So it looks like, even at 100% on the slider, the 0dBm output is pretty much a perfect copy of the input, with no additional spreading.
The main output looks like this at the same power level:
Now there are some new artefacts in there, one is a bit of 100Hz hum on the carrier at -80dB relative to the tones, and that is mixed with the main tones. Same with the carrier feedthrough at -70dB, it has a bit of the signal at -80dB on the LF side. Very low-level, all of those. At the -60dB level, the width is still about 400Hz. Remember this is at full blast (100%) on the slider. I'd say that was remarkably clean.
A closer-in view of the 5W output looks like this:
That is in 2Hz bins, and shows the same 400Hz width at -60dB as in the original WSJT-X audio source.
A 20kHz wide view is like this (note that the larger FFT bins mean the noise floor is raised by 17dB relative to the plot at 2kHz wide)
Pretty damn good, I'd say.
HOWEVER.....
With the slider set to 100, when the transmission starts, there is sometimes a wideband splat as the radio starts to transmit. Averaging over 10 minutes, the transmission looks like this. Pretty ugly:
Blue trace is the peak over the integration period, yellow is the current level.
I tried again with the slider set to 60, so the power was reduced to about 90% of normal, and over a ten minute integration of FT8 transmissions at 4.8W, there were
no wideband splats!
I think that indicates that there is the ultimate evil involved, ALC! It takes a few milliseconds to go active, and as the envelope is reduced, the resulting amplitude modulation causes a brief splat.
But... This image shows another issue. The spectrum on the LF side is quite truncated, so it might be wise to set your DUO to use tones around 1500Hz for FT8 where possible (AFC Fake-it), or to extend the transmit bandwidth to something much wider than the 300-2700 to which mine is currently set. It will start to be important when the main tones go below 600Hz. As your tones approach the skirts of the TX filter, it will cause distortion of the FSK and you might find it harder to get decodes.
If you have tweaked the level on digimodes to give just under full power (as Charlie rightly mentioned in a previous post) and someone is complaining of splatter, they may need to look at their receiver performance. Assuming they have some proper outboard attenuators, you could get them to try with 10dB and 20dB attenuation and make sure any "splatter" reduces by 10dB or 20dB and not more. If it drops faster than the main signal, the problem is in their radios. The splatter with the level on the FDM-DUO Windows device set too high will sound like a short click, akin to CW key clicks on nearby frequencies. No sign of any splatter *during* an FT8 transmission, it is only right at the start where this happens.
Very interesting. I've set the TX level on my Windows settings to 56 now, as a clean signal is a matter of professional (or should I say Amateur?) pride.
Neil G4DBN
On 21/02/2018 00:17, Charles Ristorcelli wrote:
Hi Neil.Yes, I've tried adjusting drive levels of the sound card drivers. I've worked with the Windows sound management system for som many times, that I now consider myself a certified Windows sound manager technician... :=))
I've dropped the drive down to 10% with no appreciable change in the modulation seen on the waterfall.
The popular digital modes, RTTY, psk-31, psjk-63, contestia, FT-8, etc. are all SSB transmitted. So I am unaware of any way other than sound drive/ALC as a means to control the modulation level.
Attached is the desktop image of an FT-8 signal showing the fairly pronounced side tones in the spectrum as well as the waterfall. Those were sourced with the drive level set 1t 30%.
_
I wrote up my findings about levels and filtering when using FT8 with the DUO in a blogpost in case anyone might find it useful.
http://www.g4dbn.uk/?p=783
Neil
Thank you Neil.
Well, that certainly answers my question.
Sure is nice to have access to what must be an amazing array of test equipment!
This reflector group is very fortunate to have access to somone as dedicated as you.
You answered my question, and I am a happy camper.
73
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From: EladSDR@groups.io [mailto:EladSDR@groups.io] On Behalf Of Neil Smith
Sent: Wednesday, February 21, 2018 5:34 AM
To: EladSDR@groups.io
Subject: Re: [EladSDR] FDM DUO Drive Level
Hi Charlie, setting the DUO to 5W out on 28MHz, when the Line Properties level slider is set to 62 or more, the output is full power with FT8. At slider level 32, the output drops to 500mW, so on mine it is definitely controlling the output level correctly.
Starting from the generated audio, I set WSJT-X FT8 to use a VAC as output, and used Spectrum Lab to view that, with no connection to the DUO and with SW2 not running. Here is that is looks like with with FT8 TX set to 890Hz:
That is what you'd expect from 6.25Hz spaced tones at 6.25 symbols per second. The spikes and pattern of dips are the result of all those Bessel functions. Some of the tone shifts are 6.25Hz, some 12.5, and so on, up to 8 x 6.25Hz. At about 60dB down relative to the peak, the bandwidth is about 450Hz. Starting from this as the ideal, let's see what the DUO does to the signal.
Looking at the output spectrum, with the level set to 100 on the slider, the 0dBm output looks like this:
That looks pretty much similar to the raw audio from WSJT-X, again about 400Hz wide (two divisions) at about -60dB relative to the peak tone levels. Thsi was using much wider FFT bins on the 4406 than on the SpecLab. The blip as the left is carrier feedthough, and the cutoff from about 300Hz above that is the audio tailoring in the DUO. So it looks like, even at 100% on the slider, the 0dBm output is pretty much a perfect copy of the input, with no additional spreading.
The main output looks like this at the same power level:
Now there are some new artefacts in there, one is a bit of 100Hz hum on the carrier at -80dB relative to the tones, and that is mixed with the main tones. Same with the carrier feedthrough at -70dB, it has a bit of the signal at -80dB on the LF side. Very low-level, all of those. At the -60dB level, the width is still about 400Hz. Remember this is at full blast (100%) on the slider. I'd say that was remarkably clean.
A closer-in view of the 5W output looks like this:
That is in 2Hz bins, and shows the same 400Hz width at -60dB as in the original WSJT-X audio source.
A 20kHz wide view is like this (note that the larger FFT bins mean the noise floor is raised by 17dB relative to the plot at 2kHz wide)
Pretty damn good, I'd say.
HOWEVER.....
With the slider set to 100, when the transmission starts, there is sometimes a wideband splat as the radio starts to transmit. Averaging over 10 minutes, the transmission looks like this. Pretty ugly:
Blue trace is the peak over the integration period, yellow is the current level.
I tried again with the slider set to 60, so the power was reduced to about 90% of normal, and over a ten minute integration of FT8 transmissions at 4.8W, there were no wideband splats!
I think that indicates that there is the ultimate evil involved, ALC! It takes a few milliseconds to go active, and as the envelope is reduced, the resulting amplitude modulation causes a brief splat.
But... This image shows another issue. The spectrum on the LF side is quite truncated, so it might be wise to set your DUO to use tones around 1500Hz for FT8 where possible (AFC Fake-it), or to extend the transmit bandwidth to something much wider than the 300-2700 to which mine is currently set. It will start to be important when the main tones go below 600Hz. As your tones approach the skirts of the TX filter, it will cause distortion of the FSK and you might find it harder to get decodes.
If you have tweaked the level on digimodes to give just under full power (as Charlie rightly mentioned in a previous post) and someone is complaining of splatter, they may need to look at their receiver performance. Assuming they have some proper outboard attenuators, you could get them to try with 10dB and 20dB attenuation and make sure any "splatter" reduces by 10dB or 20dB and not more. If it drops faster than the main signal, the problem is in their radios. The splatter with the level on the FDM-DUO Windows device set too high will sound like a short click, akin to CW key clicks on nearby frequencies. No sign of any splatter *during* an FT8 transmission, it is only right at the start where this happens.
Very interesting. I've set the TX level on my Windows settings to 56 now, as a clean signal is a matter of professional (or should I say Amateur?) pride.
Neil G4DBN
On 21/02/2018 00:17, Charles Ristorcelli wrote:
Hi Neil.
Yes, I've tried adjusting drive levels of the sound card drivers. I've worked with the Windows sound management system for som many times, that I now consider myself a certified Windows sound manager technician... :=))
I've dropped the drive down to 10% with no appreciable change in the modulation seen on the waterfall.
The popular digital modes, RTTY, psk-31, psjk-63, contestia, FT-8, etc. are all SSB transmitted. So I am unaware of any way other than sound drive/ALC as a means to control the modulation level.
Attached is the desktop image of an FT-8 signal showing the fairly pronounced side tones in the spectrum as well as the waterfall. Those were sourced with the drive level set 1t 30%.
_
For clarity, this is the setting I am talking about in Windows sound settings to control the output level from WSJT into the DUO playback device ( the USB audio input on the DUO):
Neil G4DBN
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On 21/02/2018 13:33, Neil Smith wrote:
Hi Charlie, setting the DUO to 5W out on 28MHz, when the Line Properties level slider is set to 62 or more, the output is full power with FT8. At slider level 32, the output drops to 500mW, so on mine it is definitely controlling the output level correctly.
Hi Charlie, setting the DUO to 5W out on 28MHz, when the Line Properties level slider is set to 62 or more, the output is full power with FT8. At slider level 32, the output drops to 500mW, so on mine it is definitely controlling the output level correctly.
Starting from the generated audio, I set WSJT-X FT8 to use a VAC as output, and used Spectrum Lab to view that, with no connection to the DUO and with SW2 not running. Here is that is looks like with with FT8 TX set to 890Hz:
That is what you'd expect from 6.25Hz spaced tones at 6.25 symbols per second. The spikes and pattern of dips are the result of all those Bessel functions. Some of the tone shifts are 6.25Hz, some 12.5, and so on, up to 8 x 6.25Hz. At about 60dB down relative to the peak, the bandwidth is about 450Hz. Starting from this as the ideal, let's see what the DUO does to the signal.
Looking at the output spectrum, with the level set to 100 on the slider, the 0dBm output looks like this:
That looks pretty much similar to the raw audio from WSJT-X, again about 400Hz wide (two divisions) at about -60dB relative to the peak tone levels. Thsi was using much wider FFT bins on the 4406 than on the SpecLab. The blip as the left is carrier feedthough, and the cutoff from about 300Hz above that is the audio tailoring in the DUO. So it looks like, even at 100% on the slider, the 0dBm output is pretty much a perfect copy of the input, with no additional spreading.
The main output looks like this at the same power level:
Now there are some new artefacts in there, one is a bit of 100Hz hum on the carrier at -80dB relative to the tones, and that is mixed with the main tones. Same with the carrier feedthrough at -70dB, it has a bit of the signal at -80dB on the LF side. Very low-level, all of those. At the -60dB level, the width is still about 400Hz. Remember this is at full blast (100%) on the slider. I'd say that was remarkably clean.
A closer-in view of the 5W output looks like this:
That is in 2Hz bins, and shows the same 400Hz width at -60dB as in the original WSJT-X audio source.
A 20kHz wide view is like this (note that the larger FFT bins mean the noise floor is raised by 17dB relative to the plot at 2kHz wide)
Pretty damn good, I'd say.
HOWEVER.....
With the slider set to 100, when the transmission starts, there is sometimes a wideband splat as the radio starts to transmit. Averaging over 10 minutes, the transmission looks like this. Pretty ugly:
Blue trace is the peak over the integration period, yellow is the current level.
I tried again with the slider set to 60, so the power was reduced to about 90% of normal, and over a ten minute integration of FT8 transmissions at 4.8W, there were
no wideband splats!
I think that indicates that there is the ultimate evil involved, ALC! It takes a few milliseconds to go active, and as the envelope is reduced, the resulting amplitude modulation causes a brief splat.
But... This image shows another issue. The spectrum on the LF side is quite truncated, so it might be wise to set your DUO to use tones around 1500Hz for FT8 where possible (AFC Fake-it), or to extend the transmit bandwidth to something much wider than the 300-2700 to which mine is currently set. It will start to be important when the main tones go below 600Hz. As your tones approach the skirts of the TX filter, it will cause distortion of the FSK and you might find it harder to get decodes.
If you have tweaked the level on digimodes to give just under full power (as Charlie rightly mentioned in a previous post) and someone is complaining of splatter, they may need to look at their receiver performance. Assuming they have some proper outboard attenuators, you could get them to try with 10dB and 20dB attenuation and make sure any "splatter" reduces by 10dB or 20dB and not more. If it drops faster than the main signal, the problem is in their radios. The splatter with the level on the FDM-DUO Windows device set too high will sound like a short click, akin to CW key clicks on nearby frequencies. No sign of any splatter *during* an FT8 transmission, it is only right at the start where this happens.
Very interesting. I've set the TX level on my Windows settings to 56 now, as a clean signal is a matter of professional (or should I say Amateur?) pride.
Neil G4DBN
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On 21/02/2018 00:17, Charles Ristorcelli wrote:
Hi Neil.Yes, I've tried adjusting drive levels of the sound card drivers. I've worked with the Windows sound management system for som many times, that I now consider myself a certified Windows sound manager technician... :=))
I've dropped the drive down to 10% with no appreciable change in the modulation seen on the waterfall.
The popular digital modes, RTTY, psk-31, psjk-63, contestia, FT-8, etc. are all SSB transmitted. So I am unaware of any way other than sound drive/ALC as a means to control the modulation level.
Attached is the desktop image of an FT-8 signal showing the fairly pronounced side tones in the spectrum as well as the waterfall. Those were sourced with the drive level set 1t 30%.
_
Interesting. The drive level from my 0dBm output was definitely fully controllable using the level of the FDM-DUO device, right down to zero output. I don't know how accurate a picture of the actual signal is given by the transmit waterfall, I think I need to do a comparison using the waterfall and a the E4406A set to sub-1Hz bins to see what the actual spectrum looks like. With 6.25 symbols per second at 6.25Hz spacing on 8 tones, and only a single tone at any time, there cannot be any normal intermodulation distortion, but there is a set of products caused by the phase and frequency modulation out to several times the basic 50Hz bandwidth. Those modulation products will certainly cause spreading, and putting them through a non-linear amplifier will case additional widening
I'll test with FT8 from my 0dBm output, then I'll try the same with the main output and see what the difference is at various power levels.
The 4406 won't go down to baseband, so it isn't easy to check the spectrum of the raw signal, but I can certainly do that using a separate laptop running Spectrum Lab or something.
Neil G4DBN
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On 21 Feb 2018, at 00:17, Charles Ristorcelli <nn3v@...> wrote:
Hi Neil.
Yes, I've tried adjusting drive levels of the sound card drivers. I've worked with the Windows sound management system for som many times, that I now consider myself a certified Windows sound manager technician... :=))
I've dropped the drive down to 10% with no appreciable change in the modulation seen on the waterfall.
The popular digital modes, RTTY, psk-31, psjk-63, contestia, FT-8, etc. are all SSB transmitted. So I am unaware of any way other than sound drive/ALC as a means to control the modulation level.
Attached is the desktop image of an FT-8 signal showing the fairly pronounced side tones in the spectrum as well as the waterfall. Those were sourced with the drive level set 1t 30%. <FT_8 SSB.png>
Charles Ristorcelli <nn3v@...>
Hi Neil.
Yes, I've tried adjusting drive levels of the sound card drivers. I've worked with the Windows sound management system for som many times, that I now consider myself a certified Windows sound manager technician... :=))
I've dropped the drive down to 10% with no appreciable change in the modulation seen on the waterfall.
The popular digital modes, RTTY, psk-31, psjk-63, contestia, FT-8, etc. are all SSB transmitted. So I am unaware of any way other than sound drive/ALC as a means to control the modulation level.
Attached is the desktop image of an FT-8 signal showing the fairly pronounced side tones in the spectrum as well as the waterfall. Those were sourced with the drive level set 1t 30%.
Hi Charlie,
Have tried changing the level on the Windows FDM-DUO playback device?
Mine is usually set to 100, but I can reduce the output of the radio by turning down the level on that device (see screenshot below). Perhaps see if that changes the output and the spectrum if you drop the level until the output power starts to drop back a bit?
If that doesn't work, which digimodes does this happen in? Most of those I use are constant-carrier single tone, so there is no concept of overdrive, unlike in SSB or AM. What will happen though is you will see modulation sidebands even in constant carrier modes, as FSK or MSK/PSK are modulations and as a result, they produce sidebands with a characteristic pattern. The maths of it is complex, Bessel functions and so on, but you will tend to see peaks at multiples of the modulation rate, but they will be broad and will depend on which tone is being sent.
Although they are full-carrier modes, there is an issue when driving an amplifier, as the modulation sidebands should really be send through unchanged. Can you do a screenshot of the waterfall and spectrum that you see, and which modes it happens in. I can try my DUO into my Agilent E4406A and HP spectrum analyser to see what the output really looks like in the modes you are using, and see if the monitored spectrum matches what you are getting, and if that actually reflects what is being transmitted. Some digimodes need full linearity, but all of the WSJT-X/WSPRX modes don't.
If possible, can you get a screen shot of the spectrum and waterfall when you are transmitting SSB as well? Be interesting to compare with mine. Have you tried changing the MIC GAIN on menu 36 to see if setting it negative makes any difference on voice? I have to run mine at +12dB as I'm using a Heil HC-5 insert instead of a proper Icom-style electret.
Neil G4DBN
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On 19/02/2018 16:36, Charles Ristorcelli wrote:
This is a question about modulation drive level. I will be detailed in my expression so anyone interested can consider my experience.I
This is a question about modulation drive level. I will be detailed in my expression so anyone interested can consider my experience.
I perceive what might be characterized as "overdriving" the modulation the ELAD-DUO when transmitting digital mode signals using FDM-SW2.
Specifically, when transmitting a digital mode signal, the PANSCOPE displays the transmitted signal in the electronic envelope spectrum of the PANSCOPE, and above it a display on the waterfall that represents the outwardly sent waveform.
There is definite evidence of overdriving the modulation, as the waterfall shows what appears as "splatter" in the transmission.
Reports from nearby hams who have helped monitor my transmission also allude to overdriven receive signal,s event though they are sufficiently removed from my location so received signal level should not be the cause of too high a level on input to their receiver.
My experience is that this condition usually is related to the audio drive level into the soundcard that is generating the digital modulation. That is what I experience with all with my other transceivers if the audio drive level is not properly adjusted.
In all other transceivers, this can be observed by carefully examining the ALC LEVEL, and rigs usually have a control (usually as potentiometer knob) that can be turned so that the ALC is lowered, and if one is experienced, one lowers the ALC to the point that the output power level just starts dropping.
The most diligent fix for this is to adjust the audio levels of the soundcard drive, and in Windows that is accomplished by using the Windows sound management settings when opening the audio d rive settings using the speaker icon in the lower right hand corner of the desktop. Most times, the audio drive level should be set at 50%.
HOW IS THE FMD-DUO DRIVE LEVEL CONTROLLED?
I've asked this question before, but not received any answers. Is it uncontrollable? What ekse besides drive level might cause this problem?
I've dropped the soundcard drive level to nearly 0% with no improvement.
Some alluded to using the ADV TX setting to do this. HOW? I see little information of the effect of ADV TX function on the transmitted signal.
Source: https://groups.io/g/EladSDR/topic/12125969?p=Created,,,20,2,0,0
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