K2 AF noise level?
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Hey 'Crafters,
I'm debating between the KAF2 or an outboard audio filter for my K2. Possible choices are the SCAF-1 and an Autek QF1A. My goal is to greatly reduce the hiss that is there in the headphones when the narrow CW filters are engaged. I'd also like to add some CW selectivity. A notch would be great too. KAF2 has the benefit of being integrated into the rig but doesn't offer lots of flexibility. The others are external but give you more control over the filtering. How well does the KAF2 kill the hiss? I assume it does great for that. Does it add any noise back in? - Keith KD1E - - K2 5411 - _______________________________________________ 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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Keith:
I also enjoy the flexibility of an external AF filter, and have used an Autek QF1 for over 20 years. However, my K2 has such a quiet AF output compared to my previous rigs that the hum from the QF1s internal power supply becomes quite noticeable and very annoying when I use it with the K2. Maybe the QF1A is quieter, 73, Steve Kercel AA4AK At 09:45 AM 5/16/2006, Darwin, Keith wrote: >Hey 'Crafters, > >I'm debating between the KAF2 or an outboard audio filter for my K2. >Possible choices are the SCAF-1 and an Autek QF1A. > >My goal is to greatly reduce the hiss that is there in the headphones >when the narrow CW filters are engaged. I'd also like to add some CW >selectivity. A notch would be great too. > >KAF2 has the benefit of being integrated into the rig but doesn't offer >lots of flexibility. The others are external but give you more control >over the filtering. > >How well does the KAF2 kill the hiss? I assume it does great for that. >Does it add any noise back in? > >- Keith KD1E - >- K2 5411 - >_______________________________________________ >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 Darwin, Keith
I just built a SCAF-1 and while it turns my IC-706MKIIG into a new radio it doesn't offer any improvement on the K2 with the KDSP2. I've also used the KAF2 and I don't think it would be much of an improvement over that either.
Doug W6JD -------------- Original message -------------- From: "Darwin, Keith" <[hidden email]> > Hey 'Crafters, > > I'm debating between the KAF2 or an outboard audio filter for my K2. > Possible choices are the SCAF-1 and an Autek QF1A. > > My goal is to greatly reduce the hiss that is there in the headphones > when the narrow CW filters are engaged. I'd also like to add some CW > selectivity. A notch would be great too. > > KAF2 has the benefit of being integrated into the rig but doesn't offer > lots of flexibility. The others are external but give you more control > over the filtering. > > How well does the KAF2 kill the hiss? I assume it does great for that. > Does it add any noise back in? > > - Keith KD1E - > - K2 5411 - > _______________________________________________ > 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 Darwin, Keith
One source of noise is in the K2 audio amplifier. It isn't much of a problem with the standard speaker since there is a built-in high frequency roll off. However, if you use very good quality earbuds that were designed for music, the hiss comes through loud and clear. I like to use the buds because they block out virtually all ambient noise and let me concentrate on CW. (I need all the help I can get).
I have ordered some sample chips from National Semiconductor to see if a low noise headphone amp will improve the situation. I probably won't get the chips for another two weeks and will have to spend some time experimenting, so I probably won't be able to report for a while, but will report back when I do. Howard W. Ashcraft, Jr. W1WF Hanson, Bridgett, Marcus, Vlahos & Rudy 425 Market Street, 26th Fl. San Francisco, CA 94105 ph: 415.995.5073 fax: 415.541.9366 e: [hidden email] ________________________________ From: Darwin, Keith [mailto:[hidden email]] Sent: Tue 5/16/2006 6:45 AM To: [hidden email] Subject: [Elecraft] K2 AF noise level? Hey 'Crafters, I'm debating between the KAF2 or an outboard audio filter for my K2. Possible choices are the SCAF-1 and an Autek QF1A. My goal is to greatly reduce the hiss that is there in the headphones when the narrow CW filters are engaged. I'd also like to add some CW selectivity. A notch would be great too. KAF2 has the benefit of being integrated into the rig but doesn't offer lots of flexibility. The others are external but give you more control over the filtering. How well does the KAF2 kill the hiss? I assume it does great for that. Does it add any noise back in? - Keith KD1E - - K2 5411 - ***************************** This communication, including any attachments, is confidential and may be protected by privilege. If you are not the intended recipient, any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by telephone or email, and permanently delete all copies, electronic or other, you may have. To ensure compliance with requirements imposed by the IRS, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein. The foregoing applies even if this notice is imbedded in a message that is forwarded or attached. ***************************** _______________________________________________ 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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Why not build yourself a simple low-pass audio filter? Even a
simple capacitor across the earbud leads will do quite a bit. Try 10mf or 20mf or even 50mf. If that isn't satisfactory, a slightly more sophisticated single-section LC filter would sure do what you want. Check the Handbook for needed values. best wishes, dave belsley, w1euy On May 17, 2006, at 4:43 PM, Howard W. Ashcraft wrote: > One source of noise is in the K2 audio amplifier. It isn't much of > a problem with the standard speaker since there is a built-in high > frequency roll off. However, if you use very good quality earbuds > that were designed for music, the hiss comes through loud and > clear. I like to use the buds because they block out virtually all > ambient noise and let me concentrate on CW. (I need all the help I > can get). > > I have ordered some sample chips from National Semiconductor to see > if a low noise headphone amp will improve the situation. I > probably won't get the chips for another two weeks and will have to > spend some time experimenting, so I probably won't be able to > report for a while, but will report back when I do. > > Howard W. Ashcraft, Jr. W1WF > Hanson, Bridgett, Marcus, Vlahos & Rudy > 425 Market Street, 26th Fl. > San Francisco, CA 94105 > > ph: 415.995.5073 > fax: 415.541.9366 > e: [hidden email] > > ________________________________ > > From: Darwin, Keith [mailto:[hidden email]] > Sent: Tue 5/16/2006 6:45 AM > To: [hidden email] > Subject: [Elecraft] K2 AF noise level? > > > > Hey 'Crafters, > > I'm debating between the KAF2 or an outboard audio filter for my K2. > Possible choices are the SCAF-1 and an Autek QF1A. > > My goal is to greatly reduce the hiss that is there in the headphones > when the narrow CW filters are engaged. I'd also like to add some CW > selectivity. A notch would be great too. > > KAF2 has the benefit of being integrated into the rig but doesn't > offer > lots of flexibility. The others are external but give you more > control > over the filtering. > > How well does the KAF2 kill the hiss? I assume it does great for > that. > Does it add any noise back in? > > - Keith KD1E - > - K2 5411 - > > > > > > > > ***************************** > This communication, including any attachments, is confidential and > may be protected by privilege. If you are not the intended > recipient, any use, dissemination, distribution, or copying of this > communication is strictly prohibited. If you have received this > communication in error, please immediately notify the sender by > telephone or email, and permanently delete all copies, electronic > or other, you may have. > > To ensure compliance with requirements imposed by the IRS, we > inform you that any tax advice contained in this communication > (including any attachments) was not intended or written to be used, > and cannot be used, for the purpose of (i) avoiding penalties under > the Internal Revenue Code or (ii) promoting, marketing or > recommending to another party any transaction or matter addressed > herein. > > The foregoing applies even if this notice is imbedded in a message > that is forwarded or attached. > ***************************** > > _______________________________________________ > 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 ------------------------------------- david a. belsley professor of economics _______________________________________________ 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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I thought of that, too. However, I would like to see whether clean, full range audio works better on ssb. Also, passive filtration results in some insertion loss. Anyway, the point is to experiment, which is what I will be doing. It would be interesting to compare the approaches. Thanks.
Howard W. Ashcraft, Jr. Hanson, Bridgett, Marcus, Vlahos & Rudy 425 Market Street, 26th Fl. San Francisco, CA 94105 ph: 415.995.5073 fax: 415.541.9366 e: [hidden email] -----Original Message----- From: David A. Belsley [mailto:[hidden email]] Sent: Wed 5/17/2006 3:15 PM To: Howard W. Ashcraft Cc: Darwin, Keith; [hidden email] Subject: Re: [Elecraft] K2 AF noise level? Why not build yourself a simple low-pass audio filter? Even a simple capacitor across the earbud leads will do quite a bit. Try 10mf or 20mf or even 50mf. If that isn't satisfactory, a slightly more sophisticated single-section LC filter would sure do what you want. Check the Handbook for needed values. best wishes, dave belsley, w1euy On May 17, 2006, at 4:43 PM, Howard W. Ashcraft wrote: > One source of noise is in the K2 audio amplifier. It isn't much of > a problem with the standard speaker since there is a built-in high > frequency roll off. However, if you use very good quality earbuds > that were designed for music, the hiss comes through loud and > clear. I like to use the buds because they block out virtually all > ambient noise and let me concentrate on CW. (I need all the help I > can get). > > I have ordered some sample chips from National Semiconductor to see > if a low noise headphone amp will improve the situation. I > probably won't get the chips for another two weeks and will have to > spend some time experimenting, so I probably won't be able to > report for a while, but will report back when I do. > > Howard W. Ashcraft, Jr. W1WF > Hanson, Bridgett, Marcus, Vlahos & Rudy > 425 Market Street, 26th Fl. > San Francisco, CA 94105 > > ph: 415.995.5073 > fax: 415.541.9366 > e: [hidden email] > > ________________________________ > > From: Darwin, Keith [mailto:[hidden email]] > Sent: Tue 5/16/2006 6:45 AM > To: [hidden email] > Subject: [Elecraft] K2 AF noise level? > > > > Hey 'Crafters, > > I'm debating between the KAF2 or an outboard audio filter for my K2. > Possible choices are the SCAF-1 and an Autek QF1A. > > My goal is to greatly reduce the hiss that is there in the headphones > when the narrow CW filters are engaged. I'd also like to add some CW > selectivity. A notch would be great too. > > KAF2 has the benefit of being integrated into the rig but doesn't > offer > lots of flexibility. The others are external but give you more > control > over the filtering. > > How well does the KAF2 kill the hiss? I assume it does great for > that. > Does it add any noise back in? > > - Keith KD1E - > - K2 5411 - > > > > > > > > ***************************** > This communication, including any attachments, is confidential and > may be protected by privilege. If you are not the intended > recipient, any use, dissemination, distribution, or copying of this > communication is strictly prohibited. If you have received this > communication in error, please immediately notify the sender by > telephone or email, and permanently delete all copies, electronic > or other, you may have. > > To ensure compliance with requirements imposed by the IRS, we > inform you that any tax advice contained in this communication > (including any attachments) was not intended or written to be used, > and cannot be used, for the purpose of (i) avoiding penalties under > the Internal Revenue Code or (ii) promoting, marketing or > recommending to another party any transaction or matter addressed > herein. > > The foregoing applies even if this notice is imbedded in a message > that is forwarded or attached. > ***************************** > > _______________________________________________ > 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 ------------------------------------- david a. belsley professor of economics ***************************** This communication, including any attachments, is confidential and may be protected by privilege. If you are not the intended recipient, any use, dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by telephone or email, and permanently delete all copies, electronic or other, you may have. To ensure compliance with requirements imposed by the IRS, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein. The foregoing applies even if this notice is imbedded in a message that is forwarded or attached. ***************************** _______________________________________________ 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: K2 AF noise level?
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Howard,
Come on down to AmTech day some month...there's usually a few K2s there and you can hear the various options. I am there about half the time and have the DSP. 73, Leigh/WA5ZNU Howard W. Ashcraft wrote: > I thought of that, too. However, I would like to see whether clean, full range audio works better on ssb. Also, passive filtration results in some insertion loss. Anyway, the point is to experiment, which is what I will be doing. It would be interesting to compare the approaches. Thanks. > > > _______________________________________________ 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 Darwin, Keith
But is it the AF amp? I *think* (not sure) that I did a test with my K2. Listen to a dummy load and hear the hiss. Turn down the RF gain and the hiss goes away. I KNOW that was the case with my Omni V and I *think* that's the case with the K2 as well. If that's true, then the hiss is from the IF stages and changing the audio amp will do little. Of course, I could be wrong. Wouldn't be the first time :-) After you've done your mod, please post your results. 73 / 72! - Keith KD1E - - K2 5411 - -----Original Message----- From: Howard W. Ashcraft [mailto:[hidden email]] Sent: Wednesday, May 17, 2006 4:44 PM To: Darwin, Keith; [hidden email] Subject: RE: [Elecraft] K2 AF noise level? One source of noise is in the K2 audio amplifier. It isn't much of a problem with the standard _______________________________________________ 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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Keith KD1E wrote:
But is it the AF amp? I *think* (not sure) that I did a test with my K2. Listen to a dummy load and hear the hiss. Turn down the RF gain and the hiss goes away. I KNOW that was the case with my Omni V and I *think* that's the case with the K2 as well. If that's true, then the hiss is from the IF stages and changing the audio amp will do little. --------------------------- True, but you must turn down both the RF and AF gains controls. The "RF" gain control (actually it controls the gain of the I.F. amplifier) has a finite range. It won't silence the receiver. The AF gain control is also at the *input* to the audio amp, so turn it all the way down as well to hear the real noise output of the audio amplifier. On my K2, using sensitive headphones, there's no background hiss from the audio amp. It's all coming from the I.F and RF stages. I can hear the background noise increase when enabling the Preamp with a dummy load connected to the antenna port, so some of the background is originating all they way back in the RF stage. Of course, that noise level is way below the band noise even up on 10 meters, so it's not limiting the sensitivity of the receiver. But with the RF and AF gain controls at minimum, so I'll I'd hear is the noise from the audio amplifier, my K2 is completely quiet. Ron AC7AC _______________________________________________ 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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What am I hearing on my K2/100 when on exactly 7.000 plus or minus a few KC's I hear a steady tone when switched to the dummy load? At first I thought it was coming from my computer monitor but it's not. When I switch back to the antenna system the tone is gone or at least so attenuated I can't hear it.
k3ey Ron D'Eau Claire <[hidden email]> wrote: Keith KD1E wrote: But is it the AF amp? I *think* (not sure) that I did a test with my K2. Listen to a dummy load and hear the hiss. Turn down the RF gain and the hiss goes away. I KNOW that was the case with my Omni V and I *think* that's the case with the K2 as well. If that's true, then the hiss is from the IF stages and changing the audio amp will do little. --------------------------- True, but you must turn down both the RF and AF gains controls. The "RF" gain control (actually it controls the gain of the I.F. amplifier) has a finite range. It won't silence the receiver. The AF gain control is also at the *input* to the audio amp, so turn it all the way down as well to hear the real noise output of the audio amplifier. On my K2, using sensitive headphones, there's no background hiss from the audio amp. It's all coming from the I.F and RF stages. I can hear the background noise increase when enabling the Preamp with a dummy load connected to the antenna port, so some of the background is originating all they way back in the RF stage. Of course, that noise level is way below the band noise even up on 10 meters, so it's not limiting the sensitivity of the receiver. But with the RF and AF gain controls at minimum, so I'll I'd hear is the noise from the audio amplifier, my K2 is completely quiet. Ron AC7AC _______________________________________________ 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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Curt, K3EY asked:
What am I hearing on my K2/100 when on exactly 7.000 plus or minus a few KC's I hear a steady tone when switched to the dummy load? At first I thought it was coming from my computer monitor but it's not. When I switch back to the antenna system the tone is gone or at least so attenuated I can't hear it. ----------------------- That's a known "birdie" generated internally within the K2 receiver. One disadvantage of a superhet receiver is that *all* superhets have birdies and spurious responses produced by the multiple oscillators and mixing schemes involved in the design. The trick is to work out a design using frequencies that avoids birdies in the normal tuning range. With nine bands covering the HF spectrum, that's a pretty formidable task. One of the advantages of the single-conversion design used in the K2 is that is produces a minimum of such signals, but there are a few and that one at 7 MHz is one of them. Offhand, I'm not sure which combination of oscillators mixing together is producing it, but it is perfectly normal. Indeed, that's the signal the manual recommends you use to adjust L34 in the Alignment and Test procedure, Part II. As you noticed, it's a very weak birdie that is normally audible only if there's no antenna connected to the receiver. Normal off-air background noise at 7 MHz is much stronger than the birdie, so it's not audible in normal operation. Ron AC7AC _______________________________________________ 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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