Re: [Flexradio] TX in Digital Mode
Tim and Brian, Thank you both for this interesting operating tip and the clear explanation of it. I usually check my psk signal with KF6VSG's pskmeter that says my signal is ok with SDR-1000 and Delta44 soundcard. Drive set at 30 Watts and TX Audio Gain at 0. Now I have checked with your procedure and found Mic level to be little over 0dB. So, that is at, or just over the very limit for clipping. New settings are now Drive 100 Watts and TX Audio Gain at -5dB for 30 Watts output. Mic level is now -5dB. So, no risk at all for clipping. The PSK31 IMD measured on a second receiver is -29 to -30dB. Again, thanks a lot and 73. Eddy ON5UQ. - Original Message - From: Brian Lloyd [EMAIL PROTECTED] To: Eddy Van de Velde [EMAIL PROTECTED] Cc: flexradio@flex-radio.biz; Tim Ellison [EMAIL PROTECTED] Sent: Thursday, October 30, 2008 11:29 PM Subject: Re: [Flexradio] TX in Digital Mode On Oct 30, 2008, at 8:18 PM, Eddy Van de Velde wrote: Tim, Can you give some information why it is preffered to leave the Drive at 100 Watts and turn the RF output down with the TX Audio Gain ? I use to set the Drive to 30 Watts in PSK on my SDR-1000 and leave the TX Audio Gain unchanged. I understand this is not the best way, is it ? What Tim told you is correct but I haven't seen anyone tell you why so I thought I would chime in. In the olden days, the mic gain was how you controlled power output from your radio so to those of us who grew up with older radios, this approach seems natural. You would just advance the mic gain until just below the level where you actuated the ALC (onset of clipping) and you were all done. If you wanted less power you just turned down the mic gain. Now most radios have a separate output level control so newer hams are used to using this control to set power output. What typically happens is that people set the mic gain control a bit too high and then compensate by turning down the drive level. The result is clipping at an early stage within the radio. Most analog radios can tolerate a bit of clipping at an early stage. The result is minor compression of the peaks and a minor increase in distortion. In fact, for SSB operation this might even provide just a bit more punch to the signal. In the case of an SDR, the clipping is hard flat-topping, usually from exceeding the range of the A:D converter at the audio input. The rise in distortion is very rapid. So in order to ensure that all the stages are operating linearly, one must be sure to keep the input level below that which produces any clipping at all. Fortunately for us the Flex radios have an indicator of input level. If that is indicating less than 0dB, you are not clipping the signal in the radio. With the input signal at 0dB and the drive level set for 100, the output is 100W. If you want to reduce the output and still make sure you have some headroom to prevent clipping, it is easier to turn down the input level. Setting the input to -3dB will produce 50W output. Reducing the input to -6dB will reduce the output to 25W. BTW, if you are operating PSK you need to realize that PSK31 is not pure PSK but has envelope shaping in order to minimize the sidebands. This means that there is amplitude variation along with the phase shift in the carrier. It is a good idea to include some headroom so that the amplitude peaks are not clipping. Setting the input to something less than -3dB is probably safe but that does limit your average power output to 50W. I hope this helps. 73 de Brian, WB6RQN ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
On Oct 30, 2008, at 8:18 PM, Eddy Van de Velde wrote: Tim, Can you give some information why it is preffered to leave the Drive at 100 Watts and turn the RF output down with the TX Audio Gain ? I use to set the Drive to 30 Watts in PSK on my SDR-1000 and leave the TX Audio Gain unchanged. I understand this is not the best way, is it ? What Tim told you is correct but I haven't seen anyone tell you why so I thought I would chime in. In the olden days, the mic gain was how you controlled power output from your radio so to those of us who grew up with older radios, this approach seems natural. You would just advance the mic gain until just below the level where you actuated the ALC (onset of clipping) and you were all done. If you wanted less power you just turned down the mic gain. Now most radios have a separate output level control so newer hams are used to using this control to set power output. What typically happens is that people set the mic gain control a bit too high and then compensate by turning down the drive level. The result is clipping at an early stage within the radio. Most analog radios can tolerate a bit of clipping at an early stage. The result is minor compression of the peaks and a minor increase in distortion. In fact, for SSB operation this might even provide just a bit more punch to the signal. In the case of an SDR, the clipping is hard flat-topping, usually from exceeding the range of the A:D converter at the audio input. The rise in distortion is very rapid. So in order to ensure that all the stages are operating linearly, one must be sure to keep the input level below that which produces any clipping at all. Fortunately for us the Flex radios have an indicator of input level. If that is indicating less than 0dB, you are not clipping the signal in the radio. With the input signal at 0dB and the drive level set for 100, the output is 100W. If you want to reduce the output and still make sure you have some headroom to prevent clipping, it is easier to turn down the input level. Setting the input to -3dB will produce 50W output. Reducing the input to -6dB will reduce the output to 25W. BTW, if you are operating PSK you need to realize that PSK31 is not pure PSK but has envelope shaping in order to minimize the sidebands. This means that there is amplitude variation along with the phase shift in the carrier. It is a good idea to include some headroom so that the amplitude peaks are not clipping. Setting the input to something less than -3dB is probably safe but that does limit your average power output to 50W. I hope this helps. 73 de Brian, WB6RQN ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
Excellent explanation, Brian. I hope you don't mind that I used your description below for a KC article. I did give you the appropriate credit, so it isn't technically plagiarism :-) -Tim -Original Message- From: Brian Lloyd [mailto:[EMAIL PROTECTED] Sent: Thursday, October 30, 2008 6:29 PM To: Eddy Van de Velde Cc: flexradio@flex-radio.biz; Tim Ellison Subject: Re: [Flexradio] TX in Digital Mode On Oct 30, 2008, at 8:18 PM, Eddy Van de Velde wrote: Tim, Can you give some information why it is preffered to leave the Drive at 100 Watts and turn the RF output down with the TX Audio Gain ? I use to set the Drive to 30 Watts in PSK on my SDR-1000 and leave the TX Audio Gain unchanged. I understand this is not the best way, is it ? What Tim told you is correct but I haven't seen anyone tell you why so I thought I would chime in. In the olden days, the mic gain was how you controlled power output from your radio so to those of us who grew up with older radios, this approach seems natural. You would just advance the mic gain until just below the level where you actuated the ALC (onset of clipping) and you were all done. If you wanted less power you just turned down the mic gain. Now most radios have a separate output level control so newer hams are used to using this control to set power output. What typically happens is that people set the mic gain control a bit too high and then compensate by turning down the drive level. The result is clipping at an early stage within the radio. Most analog radios can tolerate a bit of clipping at an early stage. The result is minor compression of the peaks and a minor increase in distortion. In fact, for SSB operation this might even provide just a bit more punch to the signal. In the case of an SDR, the clipping is hard flat-topping, usually from exceeding the range of the A:D converter at the audio input. The rise in distortion is very rapid. So in order to ensure that all the stages are operating linearly, one must be sure to keep the input level below that which produces any clipping at all. Fortunately for us the Flex radios have an indicator of input level. If that is indicating less than 0dB, you are not clipping the signal in the radio. With the input signal at 0dB and the drive level set for 100, the output is 100W. If you want to reduce the output and still make sure you have some headroom to prevent clipping, it is easier to turn down the input level. Setting the input to -3dB will produce 50W output. Reducing the input to -6dB will reduce the output to 25W. BTW, if you are operating PSK you need to realize that PSK31 is not pure PSK but has envelope shaping in order to minimize the sidebands. This means that there is amplitude variation along with the phase shift in the carrier. It is a good idea to include some headroom so that the amplitude peaks are not clipping. Setting the input to something less than -3dB is probably safe but that does limit your average power output to 50W. I hope this helps. 73 de Brian, WB6RQN ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
On Oct 30, 2008, at 4:19 PM, FireBrick wrote:
Brian
this scares meI 'Think' I understand what you said...
but
one thing confuses me
usually I'm too dense to be confused
And that is my fault because I wasn't careful to make sure I was
naming things correctly. (I was at school and didn't have PSDR in
front of me.) Hopefully I am being more clear with this posting. (I am
sitting at PSDR while writing this so as to be 100% accurate.)
As there is nothing on my PWSDR console labeled 'INPUT' I have to
assume (this is where I go out on a limb) that you mean TX Gain.
Yes, if you are using DIGU or DIGL, the 'TX Gain' slider controls the
input level to the transmitter. Don't forget that you also have to
consider the mixer. Open the mixer and you will find input level
sliders for Mic, Line-In, Bal Line, and Flexwire. These also affect
the input level depending on source. If you are using an external
source that comes in via the Line In (I'm thinking PACTOR right now)
then you need to set the Line-In level too. And then the digital mode
program, e.g. MixW or DM780, has its own output level control.
(Hmm, I just realized that I am assuming that I can run audio in on
Line-In when operating in the digital modes. I haven't yet moved my
PACTOR controller over to the F5K to try it out so if I am in error,
someone please correct me. TNX!)
So there are many ways to change the gain coming in. The key is to set
the TX Meter to read 'Mic'. That is how you actually set the level at
the input to the transmitter. Fiddle with TX Gain, mixer levels, and
output level of your digital mode program to produce something less
than 0dB on the 'Mic' level meter.
So, set the drive to 100 and adjust the other level controls to
produce something like -3dB of 'Mic' level. That will be about 50W
out. Set it for -6dB for 25W out.
As I usually keep my TX Gain at -1
Are you saying that when operating PSK (a couple times a day), I
should keep the TX Gain at -3 and just up the Drive (normally kept
at 50 watts) 10 or 15?
Drive should be set to 100 and then control the power output with TX
Gain. Check by looking at 'Mic' in the TX Meter. Do this for all the
digital modes.
It's far too cumbersome to control 'Input' to PSK via the sound card
controller.
Well, once you get everything set you don't need to change anything.
FWIW, I have my TX Gain set at -3 which produces a mic input level
('Mic' on the TX Meter) of -4dB. That should be just a skosh under 40W
out. That works just peachy for me and I have gotten good IMD reports
that way.
--
73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
___
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/
Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
On Oct 30, 2008, at 6:00 PM, Tim Ellison wrote: Excellent explanation, Brian. I hope you don't mind that I used your description below for a KC article. I did give you the appropriate credit, so it isn't technically plagiarism :-) You are welcome and no worries, Tim. Please use it as you see fit (or not :-). -- 73 de Brian, WB6RQN Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
On Oct 30, 2008, at 6:00 PM, Tim Ellison wrote: Excellent explanation, Brian. I hope you don't mind that I used your description below for a KC article. I did give you the appropriate credit, so it isn't technically plagiarism :-) BTW Tim, I looked in the PSDR manual to see what it says about the mixer when sending audio to the radio in DIGU and DIGL modes. It is surprisingly vague on this point (or I just didn't see it). I would recommend that the manual be updated to clearly define the function of the mixer when using these modes. -- 73 de Brian, WB6RQN Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
I just adjusted the mic according to your suggestions. Drive 90 watts TX Gain set to -4 Mic reads -6dBm results in 40 watts output. But trying to adjust the Master Volume of the transmission portion of WinWarbler could NOT lower the MIC reading. - Original Message - From: Brian Lloyd [EMAIL PROTECTED] To: Tim Ellison [EMAIL PROTECTED] Cc: flexradio@flex-radio.biz Sent: Thursday, October 30, 2008 9:20 PM Subject: Re: [Flexradio] TX in Digital Mode On Oct 30, 2008, at 6:00 PM, Tim Ellison wrote: Excellent explanation, Brian. I hope you don't mind that I used your description below for a KC article. I did give you the appropriate credit, so it isn't technically plagiarism :-) BTW Tim, I looked in the PSDR manual to see what it says about the mixer when sending audio to the radio in DIGU and DIGL modes. It is surprisingly vague on this point (or I just didn't see it). I would recommend that the manual be updated to clearly define the function of the mixer when using these modes. -- 73 de Brian, WB6RQN Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
[Flexradio] TX in Digital Mode
I am having problem with PSK and RTTY TX. When set to DIGU and I go by the manual to set the TX Meter to ALC and VAC TX Gain to I get a TX Meter ALC value of 0 or less, I get no Power out (Drive set to 45). Now, if I assume the manual is wrong or I am reading it wrong and set TX Gain to 6, all is good and my TX on the spectrum and scope look good (my monitored IMD on a second receiver is -25 or better at idle). I am using MixW for my CW, PSK and RTTY. I know with my ICOM-756Pro2 and Rigblaster Pro, which is my second Transceiver, you set the TX for an ALC of 0 or less (and that all works fine). However, I don't think there is a correlation of ALC on the FLEX and my pro. How should I adjust the VAC TX Gain on my Flex for PSK and RTTY? Adjust the TX Meter for ALC or TX Fwd Pwr? Thanks for the help, Still Love my Flex, Val - N0QW + + \/ \/ + \ / \ /\ / + \/ \/ \/ + Val Walker - N0QW + ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
You didn't indicate what radio you are using. This is the way I have my FLEX-5000 setup and I have no problems and the signals are clean. First off, don't set your RF output in the manner you described for digital modes when using VAC. You need not look at the ALC. This is one area where setting up a traditional radio is not 100% analogous with that of a SDR. Set the PA gain to 100. Adjust you RF output with the TX audio gain and not by turning down the PA. Set the TX meter for Forward Power. For PSK31, adjust the VAC TX gain until you hit 35 watts output. On my setup that is about -5. Now change your TX meter to MIC and you should be well below 0 dB. If you run the VAC TX gain up to 0, you should be very close to 0 db on the MIC TX meter reading and consequently putting out about 100 watts PEP. You never want to exceed 0 dB on the TX MIC meter or your signal will be distorting. Also, if you are using PowerSDR 1.14.0, there is a VAC gain bug that shows up when running at 192 KHz. It is fixed in the test branch (I am not sure about the trunk version). Here are some of the settings you should use as a starting point for a digital setup. Change the PowerSDR sampling rate to 96 KHz with a 1024 buffer size (if you are using a FLEX-5000, make sure the buffer size is 1024 and the operating mode is SafeMode1) In PowerSDR, the VAC buffer should be 1024 to match the PowerSDR/Firewire audio buffer size and set the VAC sampling rate 48 KHz. Your PSK31 IMD for this configuration should be between -30 and -32 dB when measured with an external device. -Tim -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Val Walker Sent: Wednesday, October 29, 2008 10:15 PM To: Flex Reflector Subject: [Flexradio] TX in Digital Mode I am having problem with PSK and RTTY TX. When set to DIGU and I go by the manual to set the TX Meter to ALC and VAC TX Gain to I get a TX Meter ALC value of 0 or less, I get no Power out (Drive set to 45). Now, if I assume the manual is wrong or I am reading it wrong and set TX Gain to 6, all is good and my TX on the spectrum and scope look good (my monitored IMD on a second receiver is -25 or better at idle). I am using MixW for my CW, PSK and RTTY. I know with my ICOM-756Pro2 and Rigblaster Pro, which is my second Transceiver, you set the TX for an ALC of 0 or less (and that all works fine). However, I don't think there is a correlation of ALC on the FLEX and my pro. How should I adjust the VAC TX Gain on my Flex for PSK and RTTY? Adjust the TX Meter for ALC or TX Fwd Pwr? Thanks for the help, Still Love my Flex, Val - N0QW + + \/ \/ + \ / \ /\ / + \/ \/ \/ + Val Walker - N0QW + ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
Re: [Flexradio] TX in Digital Mode
There was a bug fix (1903)that corrected this problem. It was fixed on 10/2/2008 The problem fixed only occurred when using a 192k sample rate. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Val Walker Sent: Wednesday, October 29, 2008 8:15 PM To: Flex Reflector Subject: [Flexradio] TX in Digital Mode I am having problem with PSK and RTTY TX. When set to DIGU and I go by the manual to set the TX Meter to ALC and VAC TX Gain to I get a TX Meter ALC value of 0 or less, I get no Power out (Drive set to 45). Now, if I assume the manual is wrong or I am reading it wrong and set TX Gain to 6, all is good and my TX on the spectrum and scope look good (my monitored IMD on a second receiver is -25 or better at idle). I am using MixW for my CW, PSK and RTTY. I know with my ICOM-756Pro2 and Rigblaster Pro, which is my second Transceiver, you set the TX for an ALC of 0 or less (and that all works fine). However, I don't think there is a correlation of ALC on the FLEX and my pro. How should I adjust the VAC TX Gain on my Flex for PSK and RTTY? Adjust the TX Meter for ALC or TX Fwd Pwr? Thanks for the help, Still Love my Flex, Val - N0QW + + \/ \/ + \ / \ /\ / + \/ \/ \/ + Val Walker - N0QW ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ ___ FlexRadio Systems Mailing List FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/
