Re: [Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Hi Pf, Most tone modes operate at an offset from carrier frequency, so that the audio frequencies of interest are more or less cenetered in the filter passband. I believe the JTx modes are already in the 1200 to 1500 Hz range so no offset is required. The crystal filter being used only restricts the bandwidth of the RX chain (1st IF). The DSP imposes its own audio filtering on the baseband, and that's what you're seeing as rolloff below ~300 and above ~3500 Hz. 73, matt W6NIA On Sun, 23 Aug 2015 19:03:21 +0200, you wrote: Hello, I'm dabbling with wsjtx, and I see that my rx audio has some definite roll off at 300 Hz and 3500 Hz. Selected filter is the 12 kHz one, and width is set to 4 kHz. Audio soundcard is the Numark studio-io, but I also saw this with an el-cheapo adapter. Also, I see the same roll-off in fldigi, so the final application should not matter. Am I doing something wrong? What should be the audio passband available at line out connector? Thanks Pf Matt Zilmer, W6NIA -- Always store beer in a dark place. -R. Heinlein __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Matt == Matt Zilmer mzil...@roadrunner.com writes: Matt Hi Pf, Matt Most tone modes operate at an offset from carrier frequency, so that Matt the audio frequencies of interest are more or less cenetered in the Matt filter passband. I believe the JTx modes are already in the 1200 to Matt 1500 Hz range so no offset is required. Hi Matt, actually, I'm seeing JT9 stations transmitting at 3400 Hz, and who knows if there are some even above that. JT65+JT9 uses quite a wide receive window. Matt The crystal filter being used only restricts the bandwidth of the RX Matt chain (1st IF). The DSP imposes its own audio filtering on the Matt baseband, and that's what you're seeing as rolloff below ~300 and Matt above ~3500 Hz. Yes, and that was what I wanted to know. I've read in this mailing list that the DSP limits the audio at 4 kHz. I'm seeing it roll off at little above 3400. The low end rolls off at around 300, so I'm getting an audio passband of ~3100 Hz. I wonder if this is normal, or if there's something else I can tweak in the settings. Pf -- Pierfrancesco Caci, ik5pvx __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Hello, I'm dabbling with wsjtx, and I see that my rx audio has some definite roll off at 300 Hz and 3500 Hz. Selected filter is the 12 kHz one, and width is set to 4 kHz. Audio soundcard is the Numark studio-io, but I also saw this with an el-cheapo adapter. Also, I see the same roll-off in fldigi, so the final application should not matter. Am I doing something wrong? What should be the audio passband available at line out connector? Thanks Pf -- Pierfrancesco Caci, ik5pvx __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Hi Guys, As an active WSJT-mode user, I'll attempt to clarify this set of issues. For a more complete answer, download the WSJT 10 and WSJT-X pdf documents. WSJT 10 and WSJT-X are designed for the rig to be set for the full USB bandwidth of an average radio. Each mode has an agreed upon slice of each of the HF and VHF bands. For JT65, WSJT-X includes as defaults the dial frequencies for those agreed upon slices, which are from about 400 Hz to about 3 kHz above the dial frequency. The 400 Hz and 3 kHz points are the result of the IF filters, and can be varied a bit from one radio to another. On 20M, for example, a dial frequency of 14,076 kHz puts JT65 between 14,076.4 and 14,079. The slice for JT9 is 2 kHz higher, with a dial frequency 2 kHz higher. This puts their operating slice between 14,078.4 and about 14,081 kHz. Note the overlap, which is intentional. WSJT-X can be set to decode BOTH JT65 and JT9. If, for example, you call CQ with a dial frequency of 14,076 and 2.2 kHz audio, it will be within the passband of other radios tuned to 14076, and they can decode you. Go higher than 3 kHz audio and you're taking your chances. :) This one for Matt: Joe Taylor, K1JT, the inventor of the WSJT modes, strongly recommends that the rig be set for full USB bandwidth, and that we allow his software to do the filtering to separate signals from each other. We talked about this at Pacificon several years ago. The reason is simple -- filters creates phase shift, and phase shift is the enemy of good decoding. Another thing -- WSJT-X is undergoing extensive development, and will eventually include most WSJT modes, not just JT65 and JT9. The latest versions of WSJT-X have added a feature that, if the rig supports it, will set the rig for split mode with different audio tones on the TX than the RX but setting the split so that they come out on the right frequency! Again, RTFM -- this time the WSJT-X manual. 73, Jim K9YC On Sun,8/23/2015 12:51 PM, Pierfrancesco Caci wrote: Matt == Matt Zilmer mzil...@roadrunner.com writes: Matt Hi Pf, Matt Most tone modes operate at an offset from carrier frequency, so that Matt the audio frequencies of interest are more or less cenetered in the Matt filter passband. I believe the JTx modes are already in the 1200 to Matt 1500 Hz range so no offset is required. Hi Matt, actually, I'm seeing JT9 stations transmitting at 3400 Hz, and who knows if there are some even above that. JT65+JT9 uses quite a wide receive window. Matt The crystal filter being used only restricts the bandwidth of the RX Matt chain (1st IF). The DSP imposes its own audio filtering on the Matt baseband, and that's what you're seeing as rolloff below ~300 and Matt above ~3500 Hz. Yes, and that was what I wanted to know. I've read in this mailing list that the DSP limits the audio at 4 kHz. I'm seeing it roll off at little above 3400. The low end rolls off at around 300, so I'm getting an audio passband of ~3100 Hz. I wonder if this is normal, or if there's something else I can tweak in the settings. Pf __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Yes, and that was what I wanted to know. I've read in this mailing list that the DSP limits the audio at 4 kHz. I'm seeing it roll off at little above 3400. The low end rolls off at around 300, so I'm getting an audio passband of ~3100 Hz. I wonder if this is normal, or if there's something else I can tweak in the settings. It depends on your roofing filter ... If you have an AM (6 KHz) or FM (13 KHz) filter, you will see 300 Hz to 4200 Hz with FC=2.20 and BW=4.00 (at -3dB). If you only have a 2.8 KHz filter, bandwidth will be around 2800 Hz (900 - 3700 with FC=2.20 and BW=4.00 or 400 - 3200 with FC=1.60 and BW=4.00). If you see roll-off at 3400 Hz you either have a narrow roofing filter or the DSP center frequency (FC) is set too low. 73, ... Joe, W4TV On 8/23/2015 3:51 PM, Pierfrancesco Caci wrote: Matt == Matt Zilmer mzil...@roadrunner.com writes: Matt Hi Pf, Matt Most tone modes operate at an offset from carrier frequency, so that Matt the audio frequencies of interest are more or less cenetered in the Matt filter passband. I believe the JTx modes are already in the 1200 to Matt 1500 Hz range so no offset is required. Hi Matt, actually, I'm seeing JT9 stations transmitting at 3400 Hz, and who knows if there are some even above that. JT65+JT9 uses quite a wide receive window. Matt The crystal filter being used only restricts the bandwidth of the RX Matt chain (1st IF). The DSP imposes its own audio filtering on the Matt baseband, and that's what you're seeing as rolloff below ~300 and Matt above ~3500 Hz. Yes, and that was what I wanted to know. I've read in this mailing list that the DSP limits the audio at 4 kHz. I'm seeing it roll off at little above 3400. The low end rolls off at around 300, so I'm getting an audio passband of ~3100 Hz. I wonder if this is normal, or if there's something else I can tweak in the settings. Pf __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] what audio passband should I expect in TX DATA/DATA A mode?
Joe == Joe Subich, W4TV li...@subich.com writes: Joe It depends on your roofing filter ... If you have an AM (6 KHz) or Joe FM (13 KHz) filter, you will see 300 Hz to 4200 Hz with FC=2.20 and Joe BW=4.00 (at -3dB). If you only have a 2.8 KHz filter, bandwidth Joe will be around 2800 Hz (900 - 3700 with FC=2.20 and BW=4.00 or 400 - Joe 3200 with FC=1.60 and BW=4.00). Joe If you see roll-off at 3400 Hz you either have a narrow roofing filter Joe or the DSP center frequency (FC) is set too low. Joe 73, Thanks Joe, this is exactly what I needed to know. I'm using the FM filter, and moving the passband up (by using SHIFT until FC=2.2), I can get the full 4 kHz, from slightly less than 300 Hz to slightly more than 4100. I've saved this as NORM2 for data mode. Pf -- Pierfrancesco Caci, ik5pvx __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
