Poor AM audio
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I just received and assembled my K3 about a week or so ago, I only have the 2.7Khz. filter that was shipped with the kit. I love the operation on SSB and digital modes BUT, when listening to the DX60 AM net the audio is quite distorted. I started out with the filter set to NORMAL and then made it as wide as possible untill the display reads 5.00. Is this normal to have the distorted audio untill I purchase the 6.00 Khz. filter? I quess I'm disapointed or am I doing something wrong? The operators manual does not say any thing about the distortion, only the fidelity will be increased with the 6.00 Khz. filter.
Dave Purola, N8NTA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Yes you need the 6.00 KHz filter for transmit and receive.
Fred -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Dave Purola Sent: Sunday, December 30, 2012 8:43 AM To: [hidden email] Subject: [Elecraft] Poor AM audio I just received and assembled my K3 about a week or so ago, I only have the 2.7Khz. filter that was shipped with the kit. I love the operation on SSB and digital modes BUT, when listening to the DX60 AM net the audio is quite distorted. I started out with the filter set to NORMAL and then made it as wide as possible untill the display reads 5.00. Is this normal to have the distorted audio untill I purchase the 6.00 Khz. filter? I quess I'm disapointed or am I doing something wrong? The operators manual does not say any thing about the distortion, only the fidelity will be increased with the 6.00 Khz. filter. Dave Purola, N8NTA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Dave Purola
Dave,
The fidelity will improve significantly with the wider filter. Regarding the distortion, try backing off on the RF Gain control a bit and see if that helps. It does here. You might also find that there is less distortion with Synchronous AM detection engaged. 73, Dale WA8SRA On 12/30/2012 9:42 AM, Dave Purola wrote: > I just received and assembled my K3 about a week or so ago, I only have the 2.7Khz. filter that was shipped with the kit. I love the operation on SSB and digital modes BUT, when listening to the DX60 AM net the audio is quite distorted. I started out with the filter set to NORMAL and then made it as wide as possible untill the display reads 5.00. Is this normal to have the distorted audio untill I purchase the 6.00 Khz. filter? I quess I'm disapointed or am I doing something wrong? The operators manual does not say any thing about the distortion, only the fidelity will be increased with the 6.00 Khz. filter. > > Dave Purola, > N8NTA > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Dave Purola
Dave,
AM is a double sideband signal, so the audio you receive will be only about half that of your filter setting. The 2.7 kHz roofing filter is limiting the demodulated audio to about half the width of that filter - 1.35 kHz - so you will not hear any high audio frequencies no matter how wide you set the DSP bandwidth. Even though the DSP bandwidth can be set higher, the internals of the DSP currently impose a 4.2 kHz limit on the audio response. You will not be able to transmit AM until you install the 6 kHz filter (or with the latest firmware the 13 kHz filter can be used). In the meantime, for reception only, you can use the 2.7 kHz filter to listen in synchronous AM mode. 73, Don W3FPR On 12/30/2012 9:42 AM, Dave Purola wrote: > I just received and assembled my K3 about a week or so ago, I only have the 2.7Khz. filter that was shipped with the kit. I love the operation on SSB and digital modes BUT, when listening to the DX60 AM net the audio is quite distorted. I started out with the filter set to NORMAL and then made it as wide as possible untill the display reads 5.00. Is this normal to have the distorted audio untill I purchase the 6.00 Khz. filter? I quess I'm disapointed or am I doing something wrong? The operators manual does not say any thing about the distortion, only the fidelity will be increased with the 6.00 Khz. filter. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hello,
Is it the same with the KX3? Thanks, Gil. -- PGP Key: http://keskydee.com/gil.asc On Dec 30, 2012, at 11:11 AM, Don Wilhelm wrote: > Dave, > > AM is a double sideband signal, so the audio you receive will be only about half that of your filter setting. The 2.7 kHz roofing filter is limiting the demodulated audio to about half the width of that filter - 1.35 kHz - so you will not hear any high audio frequencies no matter how wide you set the DSP bandwidth. Even though the DSP bandwidth can be set higher, the internals of the DSP currently impose a 4.2 kHz limit on the audio response. > > You will not be able to transmit AM until you install the 6 kHz filter (or with the latest firmware the 13 kHz filter can be used). > In the meantime, for reception only, you can use the 2.7 kHz filter to listen in synchronous AM mode. > > 73, > Don W3FPR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
This limitation of audio bandwidth of AM signals to 1.35 kHz is only true when the AM carrier is centered in the roofing filter passband. As Don says, AM is a double sideband signal, but you only need to receive one sideband to hear all the audio. You can use the big knob on the K3 to tune slightly above or below center to recover some of the higher modulation frequencies. The 'gotcha' is that the AM carrier must be in the passband for the audio to demodulate properly so if you tune too far off center, the carrier falls outside the filter skirt and the audio distorts. With a 2.7 kHz roofing filter, there isn't much room for error and the audio bandwidth is still pretty restricted. As Don points out, you can use AM Synchronous mode which lets the K3 reinsert the carrier and puts that carrier right at the filter skirt, so you get the maximum bandwidth possible with the filter. Even so, AM will sound better with a 6 or 13 kHz filter.
To digress, this issue has been around ever since narrow filters tailored to SSB appeared in ham receivers. Here's a snippet from the manual for my Collins 75A-3 (circa 1951) with its 3 kc mechanical filter: The tuning techniques used with a 75A-3 receiver differ somewhat from those used in tuning a conventional receiver. Because of the flat top and almost vertical sides of the pass band, it is possible to tune either sideband of an AM station and reject the opposite sideband. To get the most out of your 75A-3 take advantage of this unusual feature. Tuning "on the nose" results in loss of the high frequency audio components with, in most cases, a loss of intelligibility. Select the sideband that contains the least objectionable adjacent channel interference. ... Tune toward one side of the carrier being received until "S" meter reading drops sharply. Then carefully tune into the signal again until the "S" meter reading increases to its former value and the modulation is readable. The receiver is now tuned to one sideband plus the carrier of the AM station. So, what's old is new again! John, KU4AF Pittsboro, NC <quote author="Don Wilhelm-4"> Dave, AM is a double sideband signal, so the audio you receive will be only about half that of your filter setting. The 2.7 kHz roofing filter is limiting the demodulated audio to about half the width of that filter - 1.35 kHz - so you will not hear any high audio frequencies no matter how wide you set the DSP bandwidth. Even though the DSP bandwidth can be set higher, the internals of the DSP currently impose a 4.2 kHz limit on the audio response. You will not be able to transmit AM until you install the 6 kHz filter (or with the latest firmware the 13 kHz filter can be used). In the meantime, for reception only, you can use the 2.7 kHz filter to listen in synchronous AM mode. 73, Don W3FPR |
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Before MLB.com came up with their odd method of streaming HD (really very
good), I would listen to WCBS am out of New York for the nightYankees games. What actually worked the best, even though I had the 6 kHz filter, was 1.8 kHz filter SSB reception with the shift adjusted for best clarity, and usually with some noise blanking. This had no fading distortion, just missing content at the cancelling frequency. The K3 was good enough and stable enough to set the frequency and then hear music without shift artifacts in the tonality. When the signal is good enough on the various HF BC frequencies, I use synchronous AM detection and pick the best sounding sideband. Of course I'm just listening. Transmitting is another matter. On Sun, Dec 30, 2012 at 5:21 PM, KU4AF <[hidden email]> wrote: > This limitation of audio bandwidth of AM signals to 1.35 kHz is only true > when the AM carrier is centered in the roofing filter passband. As Don > says, > AM is a double sideband signal, but you only need to receive one sideband > to > hear all the audio. You can use the big knob on the K3 to tune slightly > above or below center to recover some of the higher modulation frequencies. > The 'gotcha' is that the AM carrier must be in the passband for the audio > to > demodulate properly so if you tune too far off center, the carrier falls > outside the filter skirt and the audio distorts. With a 2.7 kHz roofing > filter, there isn't much room for error and the audio bandwidth is still > pretty restricted. As Don points out, you can use AM Synchronous mode which > lets the K3 reinsert the carrier and puts that carrier right at the filter > skirt, so you get the maximum bandwidth possible with the filter. Even so, > AM will sound better with a 6 or 13 kHz filter. > > To digress, this issue has been around ever since narrow filters tailored > to > SSB appeared in ham receivers. Here's a snippet from the manual for my > Collins 75A-3 (circa 1951) with its 3 kc mechanical filter: > > The tuning techniques used with a 75A-3 receiver differ somewhat from those > used in tuning a conventional receiver. Because of the flat top and almost > vertical sides of the pass band, it is possible to tune either sideband of > an AM station and reject the opposite sideband. To get the most out of > your > 75A-3 take advantage of this unusual feature. Tuning "on the nose" results > in loss of the high frequency audio components with, in most cases, a loss > of intelligibility. Select the sideband that contains the least > objectionable adjacent channel interference. ... Tune toward one side of > the carrier being received until "S" meter reading drops sharply. Then > carefully tune into the signal again until the "S" meter reading increases > to its former value and the modulation is readable. The receiver is now > tuned to one sideband plus the carrier of the AM station. > > So, what's old is new again! > > John, KU4AF > Pittsboro, NC > > > > Dave, > > AM is a double sideband signal, so the audio you receive will be only > about half that of your filter setting. The 2.7 kHz roofing filter is > limiting the demodulated audio to about half the width of that filter - > 1.35 kHz - so you will not hear any high audio frequencies no matter how > wide you set the DSP bandwidth. Even though the DSP bandwidth can be > set higher, the internals of the DSP currently impose a 4.2 kHz limit on > the audio response. > > You will not be able to transmit AM until you install the 6 kHz filter > (or with the latest firmware the 13 kHz filter can be used). > In the meantime, for reception only, you can use the 2.7 kHz filter to > listen in synchronous AM mode. > > 73, > Don W3FPR > > > > > -- > View this message in context: > http://elecraft.365791.n2.nabble.com/Poor-AM-audio-tp7567914p7567946.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Gil G.
No Gil, the KX3 is a completely different radio.
Gil G. schreef: > Hello, > > Is it the same with the KX3? > > Thanks, > > Gil. > -- ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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