K3 and AM mode: using the DSP bandwidth controls
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K3 and AM mode: using the DSP bandwidth controls
 
Administrator
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A few of you have asked how to use and interpret the settings of the
receiver's DSP controls when in AM mode (SHIFT/WIDTH and HICUT/LOCUT functions). I'll be improving the associated Owner's Manual section soon, but I thought I'd try to get the word out more quickly. What the DSP controls are adjusting is the final audio passband: what you hear. This is true in all modes, and is immediately reflected in the DSP "graphic" on the LCD. When you rotate WIDTH and see "2.80", that means that the audio bandwidth is 2.80 kHz. When you rotate SHIFT and see "1.60", that means the center of the audio passband is 1.60 kHz. Of course there isn't just audio filtering in the K3. As you rotate these controls, we internally adjust the 1st and 2nd I.F. passbands optimally to match the audio passband. For example, in SSB mode, if you set WIDTH to "2.80", and have a 2.80 kHz crystal filter, then you have three filters all cascaded at this same bandwidth: a 2.8 kHz 1st-IF crystal filter (centered at 8.215 MHz); a 2.8 kHz 2nd-IF DSP filter (centered at 15 kHz); and finally, a 2.8 kHz DSP audio filter (centered at 1.6 kHz). We do all the math to make this as seamless as possible, selecting the ideal crystal filter as you cut the highs or lows or reduce the audio bandwidth. With this in mind, I can now explain what happens in AM mode, which has to be handled differently. An AM signal is comprised of a carrier and both sidebands. So it's much wider than an SSB signal, and this is why you need a 6-kHz crystal filter for best fidelity. But this filter bandwidth is only required ahead of the AM demodulator, that is, at the first and second I.F.s. After the demodulator, we're back to the audio passband -- what you hear. So, when you rotate the DSP controls in AM mode, even though you'll typically see the 6-kHz filter selected ("FL1" on my rig), you won't see "6.00" shown on the LCD. Instead, you'll see the audio bandwidth ("2.80", etc.), just like you do in other modes. And this is what makes sense, given that the controls are linked the AF passband. This will be even more apparent when using FM (coming soon!). FM requires a filter around 13 kHz wide. As you can see, having the DSP controls show something like "13.00" when WIDTH is rotated wouldn't be very useful. You'll want to know how they affect what you hear, not the underlying IF filter selection. Note: For now, I suggest that you enable only the 6-kHz crystal filter for AM. A future firmware revision will also properly handle the 2.8 or 2.7 kHz crystal filters when DSP controls are rotated in AM mode. This will be most useful when doing hicut/locut. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 and AM mode: using the DSP bandwidth controls
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Nice explanation, thanks.
- David Wilburn [hidden email] K4DGW K2 S/N 5982 On Mon, 2007-12-17 at 13:06 -0800, wayne burdick wrote: > A few of you have asked how to use and interpret the settings of the > receiver's DSP controls when in AM mode (SHIFT/WIDTH and HICUT/LOCUT > functions). I'll be improving the associated Owner's Manual section > soon, but I thought I'd try to get the word out more quickly. > > What the DSP controls are adjusting is the final audio passband: what > you hear. This is true in all modes, and is immediately reflected in > the DSP "graphic" on the LCD. When you rotate WIDTH and see "2.80", > that means that the audio bandwidth is 2.80 kHz. When you rotate SHIFT > and see "1.60", that means the center of the audio passband is 1.60 > kHz. > > Of course there isn't just audio filtering in the K3. As you rotate > these controls, we internally adjust the 1st and 2nd I.F. passbands > optimally to match the audio passband. For example, in SSB mode, if you > set WIDTH to "2.80", and have a 2.80 kHz crystal filter, then you have > three filters all cascaded at this same bandwidth: a 2.8 kHz 1st-IF > crystal filter (centered at 8.215 MHz); a 2.8 kHz 2nd-IF DSP filter > (centered at 15 kHz); and finally, a 2.8 kHz DSP audio filter (centered > at 1.6 kHz). We do all the math to make this as seamless as possible, > selecting the ideal crystal filter as you cut the highs or lows or > reduce the audio bandwidth. > > With this in mind, I can now explain what happens in AM mode, which has > to be handled differently. > > An AM signal is comprised of a carrier and both sidebands. So it's much > wider than an SSB signal, and this is why you need a 6-kHz crystal > filter for best fidelity. But this filter bandwidth is only required > ahead of the AM demodulator, that is, at the first and second I.F.s. > After the demodulator, we're back to the audio passband -- what you > hear. > > So, when you rotate the DSP controls in AM mode, even though you'll > typically see the 6-kHz filter selected ("FL1" on my rig), you won't > see "6.00" shown on the LCD. Instead, you'll see the audio bandwidth > ("2.80", etc.), just like you do in other modes. And this is what makes > sense, given that the controls are linked the AF passband. > > This will be even more apparent when using FM (coming soon!). FM > requires a filter around 13 kHz wide. As you can see, having the DSP > controls show something like "13.00" when WIDTH is rotated wouldn't be > very useful. You'll want to know how they affect what you hear, not the > underlying IF filter selection. > > Note: For now, I suggest that you enable only the 6-kHz crystal filter > for AM. A future firmware revision will also properly handle the 2.8 or > 2.7 kHz crystal filters when DSP controls are rotated in AM mode. This > will be most useful when doing hicut/locut. > > 73, > Wayne > N6KR > > > --- > > http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 and AM mode: using the DSP bandwidth controls
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In reply to this post by wayne burdick
I'm sure my fogginess on this is due to my own understanding deficit, but I
would like some more explanation on this in order to compare how the K3 will be used to how I use GC receivers now to listen to AM SWBC in congested bands. I've found the best way to reduce QRM while using a typical "dumb" AM/SSB GC receiver is to put the carrier in the center of the IF passband, then switch to either USB or LSB mode (with the carrier zero-beat) and listen to either the upper or the lower sideband. That way, if adjacent-channel QRM is worse on the high side, listening only to the lower sideband eliminates it, and vice-versa. Will something equivalent to this mode of reception be possible on the K3? Bill / W5WVO wayne burdick wrote: > A few of you have asked how to use and interpret the settings of the > receiver's DSP controls when in AM mode (SHIFT/WIDTH and HICUT/LOCUT > functions). I'll be improving the associated Owner's Manual section > soon, but I thought I'd try to get the word out more quickly. > > What the DSP controls are adjusting is the final audio passband: what > you hear. This is true in all modes, and is immediately reflected in > the DSP "graphic" on the LCD. When you rotate WIDTH and see "2.80", > that means that the audio bandwidth is 2.80 kHz. When you rotate SHIFT > and see "1.60", that means the center of the audio passband is 1.60 > kHz. > > Of course there isn't just audio filtering in the K3. As you rotate > these controls, we internally adjust the 1st and 2nd I.F. passbands > optimally to match the audio passband. For example, in SSB mode, if > you set WIDTH to "2.80", and have a 2.80 kHz crystal filter, then you > have three filters all cascaded at this same bandwidth: a 2.8 kHz > 1st-IF crystal filter (centered at 8.215 MHz); a 2.8 kHz 2nd-IF DSP > filter (centered at 15 kHz); and finally, a 2.8 kHz DSP audio filter > (centered at 1.6 kHz). We do all the math to make this as seamless as > possible, selecting the ideal crystal filter as you cut the highs or > lows or reduce the audio bandwidth. > > With this in mind, I can now explain what happens in AM mode, which > has to be handled differently. > > An AM signal is comprised of a carrier and both sidebands. So it's > much wider than an SSB signal, and this is why you need a 6-kHz > crystal filter for best fidelity. But this filter bandwidth is only > required ahead of the AM demodulator, that is, at the first and > second I.F.s. After the demodulator, we're back to the audio passband > -- what you hear. > > So, when you rotate the DSP controls in AM mode, even though you'll > typically see the 6-kHz filter selected ("FL1" on my rig), you won't > see "6.00" shown on the LCD. Instead, you'll see the audio bandwidth > ("2.80", etc.), just like you do in other modes. And this is what > makes sense, given that the controls are linked the AF passband. > > This will be even more apparent when using FM (coming soon!). FM > requires a filter around 13 kHz wide. As you can see, having the DSP > controls show something like "13.00" when WIDTH is rotated wouldn't be > very useful. You'll want to know how they affect what you hear, not > the underlying IF filter selection. > > Note: For now, I suggest that you enable only the 6-kHz crystal filter > for AM. A future firmware revision will also properly handle the 2.8 > or 2.7 kHz crystal filters when DSP controls are rotated in AM mode. This > will be most useful when doing hicut/locut. > > 73, > Wayne > N6KR > > > --- > > http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 and AM mode: using the DSP bandwidth controls
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To clarify -- Will something equivalent to this mode be possible on the K3
>>IN AM MODE<< -- i.e., without having to absorb the carrier energy, as when listening in USB/LSB mode? Can I shift the IF passband in AM mode and listen to just one sideband or the other? Bill / W5WVO Bill W5WVO wrote: > I'm sure my fogginess on this is due to my own understanding deficit, > but I would like some more explanation on this in order to compare > how the K3 will be used to how I use GC receivers now to listen to AM > SWBC in congested bands. > I've found the best way to reduce QRM while using a typical "dumb" > AM/SSB GC receiver is to put the carrier in the center of the IF > passband, then switch to either USB or LSB mode (with the carrier > zero-beat) and listen to either the upper or the lower sideband. That > way, if adjacent-channel QRM is worse on the high side, listening > only to the lower sideband eliminates it, and vice-versa. > > Will something equivalent to this mode of reception be possible on > the K3? > Bill / W5WVO > > > wayne burdick wrote: >> A few of you have asked how to use and interpret the settings of the >> receiver's DSP controls when in AM mode (SHIFT/WIDTH and HICUT/LOCUT >> functions). I'll be improving the associated Owner's Manual section >> soon, but I thought I'd try to get the word out more quickly. >> >> What the DSP controls are adjusting is the final audio passband: what >> you hear. This is true in all modes, and is immediately reflected in >> the DSP "graphic" on the LCD. When you rotate WIDTH and see "2.80", >> that means that the audio bandwidth is 2.80 kHz. When you rotate >> SHIFT and see "1.60", that means the center of the audio passband is >> 1.60 kHz. >> >> Of course there isn't just audio filtering in the K3. As you rotate >> these controls, we internally adjust the 1st and 2nd I.F. passbands >> optimally to match the audio passband. For example, in SSB mode, if >> you set WIDTH to "2.80", and have a 2.80 kHz crystal filter, then you >> have three filters all cascaded at this same bandwidth: a 2.8 kHz >> 1st-IF crystal filter (centered at 8.215 MHz); a 2.8 kHz 2nd-IF DSP >> filter (centered at 15 kHz); and finally, a 2.8 kHz DSP audio filter >> (centered at 1.6 kHz). We do all the math to make this as seamless as >> possible, selecting the ideal crystal filter as you cut the highs or >> lows or reduce the audio bandwidth. >> >> With this in mind, I can now explain what happens in AM mode, which >> has to be handled differently. >> >> An AM signal is comprised of a carrier and both sidebands. So it's >> much wider than an SSB signal, and this is why you need a 6-kHz >> crystal filter for best fidelity. But this filter bandwidth is only >> required ahead of the AM demodulator, that is, at the first and >> second I.F.s. After the demodulator, we're back to the audio passband >> -- what you hear. >> >> So, when you rotate the DSP controls in AM mode, even though you'll >> typically see the 6-kHz filter selected ("FL1" on my rig), you won't >> see "6.00" shown on the LCD. Instead, you'll see the audio bandwidth >> ("2.80", etc.), just like you do in other modes. And this is what >> makes sense, given that the controls are linked the AF passband. >> >> This will be even more apparent when using FM (coming soon!). FM >> requires a filter around 13 kHz wide. As you can see, having the DSP >> controls show something like "13.00" when WIDTH is rotated wouldn't >> be very useful. You'll want to know how they affect what you hear, >> not the underlying IF filter selection. >> >> Note: For now, I suggest that you enable only the 6-kHz crystal >> filter for AM. A future firmware revision will also properly handle >> the 2.8 or 2.7 kHz crystal filters when DSP controls are rotated in AM >> mode. >> This will be most useful when doing hicut/locut. >> >> 73, >> Wayne >> N6KR >> >> >> --- >> >> http://www.elecraft.com >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by wayne burdick
wayne burdick wrote:
> A few of you have asked how to use and interpret the settings of the > receiver's DSP controls when in AM mode (SHIFT/WIDTH and HICUT/LOCUT > functions). I'll be improving the associated Owner's Manual section > soon, but I thought I'd try to get the word out more quickly. > It makes so much sense when the K3's "Dad" explains it. Too bad Wayne couldn't have talked to my Dad before he tried to explain to me where babies come quite a few years ago. Fortunately, I already knew. :-) DIFFERENT SUBJECT: My KAT100 seems to have lost it's tuning brains. Is there something I can do to reboot it? Feeding a dummy load, it rattles relays like mad, finally gives up at 9:1 SWR. 73, Fred K6DGW - Northern California Contest Club - CU in the 2008 Cal QSO Party 4-5 Oct 08 - www.cqp.org _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 and AM mode: using the DSP bandwidth controls
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On Mon, 17 Dec 2007, Fred Jensen wrote:
> > It makes so much sense when the K3's "Dad" explains it. Too bad Wayne > couldn't have talked to my Dad before he tried to explain to me where babies > come quite a few years ago. I believe that is True Mojo. Thom,EIEIO Email, Internet, Electronic Information Officer www.baltimorehon.com/ Home of the Baltimore Lexicon www.tlchost.net/hosting/ Web Hosting as low as 3.49/month _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by k6dgw
Fred,
There is no 'reboot' possible with the KAT100. Either you have a really bad load on the KAT100 (like a short or open circuit), or the 1N5711 diodes have been zapped by a static surge of some type (like lightning). Replacing the diodes usually cures that behavior. 73, Don W3FPR Fred Jensen wrote: > > DIFFERENT SUBJECT: My KAT100 seems to have lost it's tuning brains. > Is there something I can do to reboot it? Feeding a dummy load, it > rattles relays like mad, finally gives up at 9:1 SWR. > > 73, > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3 and AM mode: using the DSP bandwidth controls
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Administrator
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In reply to this post by Bill VanAlstyne W5WVO
Bill W5WVO wrote:
> To clarify -- Will something equivalent to this mode be possible on > the K3 >>IN AM MODE<< -- i.e., without having to absorb the carrier > energy, as when listening in USB/LSB mode? Can I shift the IF passband > in AM mode and listen to just one sideband or the other? Bill, In AM mode, if you tap XFIL to select a 2.8 or 2.7 kHz filter, then SHIFT the passband down (counterclockwise), you'll be removing one sideband. The narrower crystal filter passband results in a loss of fidelity from the high-precision I-Q AM demodulator, but the signal will still be intelligible. If you want to control which sideband you remove, you can always use LSB or USB. This provides excellent fidelity on AM signals, and you don't have to touch the VFO -- just changes modes. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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