L34 on K2 tuning question?
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Changes while tuning L34 on my K2 are very subtle.
Just barely hear L34 peak with the slug near the top of the can....is this normal? I'm just trying to determine if the receiver on my K2 is working as it should. Signals on the K2 with the Preamp switched in sound about the "same" as they do on my Ten Tec Argonaut V from 160 thru 10. With the preamp out, signals sound a little "softer" than the Argonaut, but I can still hear them. Is this normal as well? Serial number: 3349 Thanks for the help! 73..../ed ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs _______________________________________________ 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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Eddy,
I cannot answer about the comparison with the Argonaut, but I can say that the setting of L34 is very broad. If you cannot discern a peak, then set the slug 1 1/2 turns from the top of the can. One can usually set L34 for the best signal to noise ratio when using Spectrogram. Listen to the 7000 kHz birdie with the preamp on and no antenna attached. Use an IF filter between 500 and 400 Hz. Tune L34 so the Spectrogram display shows the 'signal' at a peak and then further refine the setting so the out of passband noise is at a minimum while still having the signal at the highest peak. 73, Don W3FPR Eddy Avila wrote: > Changes while tuning L34 on my K2 are very subtle. > Just barely hear L34 peak with the slug near the top > of the can....is this normal? > > I'm just trying to determine if the receiver on my K2 > is working as it should. Signals on the K2 with the > Preamp switched in sound about the "same" as they do > on my Ten Tec Argonaut V from 160 thru 10. With the > preamp out, signals sound a little "softer" than the > Argonaut, but I can still hear them. Is this normal as > well? > > Serial number: 3349 > > Thanks for the help! > > 73..../ed > > 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 Eddy
It's you guys on the forum and Gary and Scott at Elecraft that keep me coming back!! To all thanks for the email responses to my question.....I'm feeling a lot more confident my k2 is working 100%
73 all......./ed <quote author="k6sdw"> Changes while tuning L34 on my K2 are very subtle. Just barely hear L34 peak with the slug near the top of the can....is this normal? I'm just trying to determine if the receiver on my K2 is working as it should. Signals on the K2 with the Preamp switched in sound about the "same" as they do on my Ten Tec Argonaut V from 160 thru 10. With the preamp out, signals sound a little "softer" than the Argonaut, but I can still hear them. Is this normal as well? Serial number: 3349 Thanks for the help! 73..../ed |
Re: L34 on K2 tuning question?
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In reply to this post by Eddy
Eddy Avila wrote:
> Changes while tuning L34 on my K2 are very subtle. > Just barely hear L34 peak with the slug near the top > of the can....is this normal? > > I'm just trying to determine if the receiver on my K2 > is working as it should. I recently went through a similar situation where I felt my K2 was not hearing as well as it was supposed to be hearing. After checking for construction problems, I went back over the alignment including re-adjusting L34. I came up with a little tip on how to make adjusting L34 a little bit easier. As you are probably aware, adjusting L34 is best done with Spectogram. It is very difficult to tell when you have the maximum strength on the internal signal with the lowest noise just by ear. Take a look at the screen capture I made (http://www.ve3syb.ca/tmp/K2-L34.jpg) while adjusting L34 on my K2. You will notice there are two cross style cursors, one in red and the other in black. Once you have the K2 set up and Spectogram ready to go (ie. you see the internally generated signal), move the cursor so the horizontal part of the cursor is just at the top of the internal signal (the black cursor) and left click with the mouse to mark the level. Next, move the cursor to the top of the noise floor (red cursor) but do not click with the mouse. You can now easily watch for changes in the level of the internal signal while watching the noise floor. When adjusting L34, this set up made it easy to see when the internal signal was at its peak. You can left click with the mouse during the procedure to move the cursor that indicates the level of the internal signal as needed (ie. as it starts to get stronger) so you can tell when you have hit the peak remembering to move the cursor back to the top of the noise floor afterwards. When adjusting L34 on my machine, I was easily able to see when the internal signal was strongest. While adjusting L34 I never saw a change in the level of the noise to the left of the signal. After the internal signal peaked, adjusting L34 so it went further in to the can meant that the signal to the right of the internal signal began to drop off at a sharper angle. On my K2, the slug seems to have bottomed out and makes me wonder if a cap needs to be changed so the optimum setting of L34 will be with the slug somewhere in the middle of its range of travel. I hope the idea about positioning the cursors to aid in detecting changes in levels of the internal signal and the noise floor might be useful either to you or to other people. PS. I have discovered that Spectogram seems to work when run under Linux via Wine. -- Cheers! Kevin. http://www.ve3syb.ca/ |"What are we going to do today, Borg?" Owner of Elecraft K2 #2172 |"Same thing we always do, Pinkutus: | Try to assimilate the world!" #include <disclaimer/favourite> | -Pinkutus & the Borg _______________________________________________ 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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<quote author="Kevin Cozens-2"> Eddy Avila wrote: > Changes while tuning L34 on my K2 are very subtle. > Just barely hear L34 peak with the slug near the top > of the can....is this normal? > > I'm just trying to determine if the receiver on my K2 > is working as it should. I went through the same thing just today. We also used a spectogram but after failing to hear an apreciable change we followed the next suggestion, alligning the 40-meter band pass filter. Once this was aligned we were able to tune L-34 by ear. It did indeed occur near the top of the can, as stated in the text. Once done everything tested ok! Bill- KE5KWE |
Re: L34 on K2 tuning question?
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bill KE5KWE wrote:
> I went through the same thing just today. We also used a spectogram but > after failing to hear an apreciable change we followed the next suggestion, > alligning the 40-meter band pass filter. Once this was aligned we were able > to tune L-34 by ear. It did indeed occur near the top of the can, as stated > in the text. The internal signal on my K2 had peaked around the time that L34 was half-way down but the noise to the right of the internal signal didn't drop until about the time the slug hit the bottom of the can. Unless you use Spectogram to you may be close to the best position of the L34 slug but not at the ideal spot. One thing I'm interested in is the difference between the peak of the internal signal and the peak of the noise floor on K2 radios. On my radio I see a difference (between the black cross and red cross on the screen capture at http://www.ve3syb.ca/tmp/K2-L34.jpg) of about 17db as seen with Spectogram. Is this typical, above average, or below average of what other K2 owners have noticed? I'm still trying to convince myself that my K2 is hearing as well as it should. So far, it seems to be hearing everything I can hear on my shortwave radio. -- Cheers! Kevin. http://www.ve3syb.ca/ |"What are we going to do today, Borg?" Owner of Elecraft K2 #2172 |"Same thing we always do, Pinkutus: | Try to assimilate the world!" #include <disclaimer/favourite> | -Pinkutus & the Borg _______________________________________________ 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: L34 on K2 tuning question?
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In reply to this post by Eddy
Kevin,
When I first aligned my K2 I followed the instructions written in the manual for tuning L34 using the quote 'weak' 7 MHz birdie - more like a angry elephant. After doing some work to reduce the number of K2 receiver birdies, it struck me that the 7 MHz birdie signal is entering the receiver chain at not just one place, or could be perhaps two separate signals from different sources. If one 'birdie' signal had established itself in the receiver chain before L34 and another 'birdie' signal entered the chain AFTER L34, then tuning L34 as suggested in the manual using the birdie might not result in best overall receiver performance in terms of noise floor. Tuning L34 will have an effect on the combined level of the two birdie signals as seen by Spectrogram as a single signal (tuning birdie against birdie), and some effect on the observed noise floor, but not necessarily result in the overall noise figure which the receiver is capable of 'delivering' at 7 MHz and other bands. Tuning the 40m bandpass filter does affect the 'before L34 birdie', an effect noted by Bill KE5KWE. Using a signal generator connected to the antenna input running at a frequency further up the 40m band, to separate the observed signal from that wretched 7 MHz birdie, and setting the generator level so that the observed output signal was about 10db IIRC above noise, I found the optimum position of L34's slug to be near the top of the can but not at same place as when using the birdie, about 1/2 turn below IIRC. With L34 tuned this way, antenna noise can be heard on all bands 80m - 10m when using my K2 with a 400 Hz filter setting at this very quiet rural location. 73, Geoff GM4ESD Kevin Cozens <[hidden email]> wrote. > bill KE5KWE wrote: >> I went through the same thing just today. We also used a spectogram but >> after failing to hear an apreciable change we followed the next >> suggestion, >> alligning the 40-meter band pass filter. Once this was aligned we were >> able >> to tune L-34 by ear. It did indeed occur near the top of the can, as >> stated >> in the text. > > The internal signal on my K2 had peaked around the time that L34 was > half-way down but the noise to the right of the internal signal didn't > drop until about the time the slug hit the bottom of the can. Unless you > use Spectogram to you may be close to the best position of the L34 slug > but not at the ideal spot. > > One thing I'm interested in is the difference between the peak of the > internal signal and the peak of the noise floor on K2 radios. On my radio > I see a difference (between the black cross and red cross on the screen > capture at http://www.ve3syb.ca/tmp/K2-L34.jpg) of about 17db as seen with > Spectogram. > > Is this typical, above average, or below average of what other K2 owners > have noticed? I'm still trying to convince myself that my K2 is hearing as > well as it should. So far, it seems to be hearing everything I can hear on > my shortwave radio. > > -- > Cheers! > > Kevin. _______________________________________________ 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 Kevin Cozens-2
Kevin....great advice! Don't know why I didn't use the Spectrogram software in the first place instead of my "ears!" ....just checked and I was a ways off the peak, but using the PC and Spectrogram I've gained some sensitivity without raising any noise. Good call Kevin! 73
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Re: L34 on K2 tuning question?
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In reply to this post by Geoffrey Mackenzie-Kennedy
Geoffrey Mackenzie-Kennedy wrote:
> for tuning L34 using the quote 'weak' 7 MHz birdie - more like a angry > elephant. After doing some work to reduce the number of K2 receiver It's not all that strong compared with sky noise with even a small antenna. > birdies, it struck me that the 7 MHz birdie signal is entering the receiver > chain at not just one place, or could be perhaps two separate signals from > different sources. If one 'birdie' signal had established itself in the > receiver chain before L34 and another 'birdie' signal entered the chain I am pretty sure that the birdy is a harmonic of the main microcontroller instruction rate and is entering before the mixer. It's very unlikely that a post mixer birdy would move in the same way with tuning setting. > AFTER L34, then tuning L34 as suggested in the manual using the birdie > might > not result in best overall receiver performance in terms of noise floor. What I would have liked is an explanation of the theory behind the separate noise and signal peaks. The possibilities I can think of are: - some of the noise is coming in on the image frequency, but that would seem to be so far away as to be completely in the stop band for L34. - there is a close in gap in the crystal filter stop band and the noise is coming in there - possible, but I wouldn't have thought a filter weakness would be enough for just white noise to be an issue. - the combination of the L34 setting and reactance in one of the adjacent chips reduces the internal generated noise voltage at the the chip interface - I'm not sure why people should be saying that one should be specifically optimising for noise above the birdy. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ 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: L34 on K2 tuning question?
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David Woolley wrote:
> Geoffrey Mackenzie-Kennedy wrote: > >> for tuning L34 using the quote 'weak' 7 MHz birdie - more like a angry >> elephant. After doing some work to reduce the number of K2 receiver > > It's not all that strong compared with sky noise with even a small > antenna. To avoid any misunderstanding about my use of the term 'strong', the level of the internal spurious signal at 7 MHz in my K2's receiver was approximately 10db above the noise floor at the output of the product detector when viewed with a suitable spectrum analyzer, with the receiver connected to a 40m reference dipole at 70ft. The background noise here on 40m is usually 'below S1' with either dipole or beam, storm noise excepted. Receiver IF bandwidth was set to 400 Hz ,which is not, of course, the receiver's noise bandwidth because of the actual response of the K2's IF filter. In my book a receiver internal spurious signal of this magnitude is certainly not 'weak'!! > I am pretty sure that the birdy is a harmonic of the main > microcontroller instruction rate and is entering before the mixer. I agree that this is one source, and one point of entry for this signal.is K16 / K17. >It's very unlikely that a post mixer birdy would move in the same way with >tuning setting. Unfortunately there is evidence of multiple mixing due to the high level of signal from the various oscillators, VCO, BFO etc found right across the RF Board and elsewhere.This makes it highly likely that some products at IF will move in the same direction as the signal mixer's injection frequency. > What I would have liked is an explanation of the theory behind the > separate noise and signal peaks. The possibilities I can think of are: > - some of the noise is coming in on the image frequency, but that <snip> At the risk of oversimplifying, my thinking was as follows. If the birdy as observed was in fact the resultant of two signals, one of which had entered the signal chain before L34 and the other after L34, and the point at which the birdy was being observed was considered to be the summing point, then tuning L34 would result in a change in amplitude of the observed birdy. This change would be due not only to any change in the raw addition of signal power as L34 is tuned, but also due to the relative phase of the two signals at the summing point - which relationship would be changed to some extent as L34 is tuned. The noise power which determines the noise floor on the other hand is dominated by the 'legitimate' noise power coming down the receiver chain, and I have found no evidence that any part of this noise signal enters the receiver chain after L34. I should mention also that in my K2, the level of the VCO, 12.xxx MHz reference and spatially coupled BFO signals are high in the region of the two crystal filter The situation becomes quite different if a legitimate input signal is used to adjust L34 because the effect of phase change when tuning L34 is taken out of the equation. I have no evidence that any product produced by a signal introduced at the antenna finds its way into the signal chain after L34 when the applied signal level is useful for alignment purposes. However at high levels of input signal this is no longer true. > I'm not sure why people should be saying that > one should be specifically optimising for noise above the birdy. I believe that the birdy was being suggested in lieu of a signal generator. Elecraft's XG1 should do the job. 73, Geoff GM4ESD _______________________________________________ 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: L34 on K2 tuning question?
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In reply to this post by Eddy
Where I had written '--------will move in the same direction as the signal
mixer's injection frequency.' I should have written ' --------- will move in the same direction as the tuning. ' 73, Geoff GM4ESD ----- Original Message ----- From: "Geoffrey Mackenzie-Kennedy" <[hidden email]> To: "David Woolley (E.L)" <[hidden email]> Cc: "Elecraft Discussion List" <[hidden email]> Sent: Tuesday, January 22, 2008 12:06 PM Subject: Re: [Elecraft] L34 on K2 tuning question? <snip> >>It's very unlikely that a post mixer birdy would move in the same way with >>tuning setting. > > Unfortunately there is evidence of multiple mixing due to the high level > of signal from the various oscillators, VCO, BFO etc found right across > the RF Board and elsewhere.This makes it highly likely that some products > at IF will move in the same direction as the signal mixer's injection > frequency. <snip> _______________________________________________ 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: L34 on K2 tuning question?
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In reply to this post by Geoffrey Mackenzie-Kennedy
Geoffrey Mackenzie-Kennedy wrote:
> David Woolley wrote: > > I am pretty sure that the birdy is a harmonic of the main >> microcontroller instruction rate and is entering before the mixer. > > I agree that this is one source, and one point of entry for this > signal.is K16 / K17. Why do you say that. On my K2, the amplitude depends, in the expected way, on the settings of those two relays, indicating an earlier injection point. Note that the microcontroller to which they are adjacent is shut down during receive, so one should not be picking up anything from it's oscillator. (The relays are the attenuator and pre-amp bypass ones.) -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work. _______________________________________________ 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: L34 on K2 tuning question?
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David Wooley wrote:
> Geoffrey Mackenzie-Kennedy wrote: >> I agree that this is one source, and one point of entry for this >> signal.is K16 / K17. > > Why do you say that. On my K2, the amplitude depends, in the expected > way, on the settings of those two relays, indicating an earlier injection > point. Note that the microcontroller to which they are adjacent is shut > down during receive, so one should not be picking up anything from it's > oscillator. (The relays are the attenuator and pre-amp bypass ones.) In my K2 the amplitude of the 7MHz birdy behaves in a similar way. The source appears to be the MCU on the Control Board, because the birdy can still be detected below both K16 and K17 using a 'sniffer' whose exposed 'link' is approximately 1/8 inch in length, double shielded coax, when the VCO, Reference oscillator and BFO are shut down to eliminate a 7 MHz product from these sources. Changing the MCU's 4 MHz oscillator's frequency changes the birdy's frequency at the rate of 7/4 as seen on a spectrum analyzer. >From 'sniffing' the pcb trace connecting K16 pin 3 to D6 (via C53) I found maximum birdy amplitude to be at the K16 end, and removing D6 has little effect. Between K17 pin 8 and the mixer there is not much difference in the birdy's amplitude, the higher level being at the K17 end. The birdy can also be found in my K2 on the pcb traces which connect to the relay coils (pins 10) and in the nearby bundle of pcb traces, some of which eventually lead to the Control Board. Without destroying my K2's RF board, and with the test equipment that I have, I cannot be certain whether the birdy is being conducted all the way or whether spatial coupling is also present. However the existence of the birdy in the coil circuits K16 and K17 raises the possibility of the classic problem i.e. unwanted coupling between a relay's coil and its contacts. I had intended to take a look at the RF bypassing of the relay coils, or adding L-C filters, time permitting. Without further investigation I suspect that this 7MHz birdy is being introduced either via the relay coil circuits or by direct pick up by the pcb trace between D6 and K16, or both. If you would like to continue this discussion, I suggest that we do so off-list. I am leaving the house soon, but expect to be here tonight. 73, Geoff GM4ESD _______________________________________________ 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: L34 on K2 tuning question?
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In reply to this post by Geoffrey Mackenzie-Kennedy
Geoffrey Mackenzie-Kennedy wrote:
> > To avoid any misunderstanding about my use of the term 'strong', the > level of the internal spurious signal at 7 MHz in my K2's receiver was > approximately 10db above the noise floor at the output of the product > detector when viewed with a suitable spectrum analyzer, with the What's the analyzer bandwidth (resolution)? > receiver connected to a 40m reference dipole at 70ft. The background > noise here on 40m is usually 'below S1' with either dipole or beam, > storm noise excepted. Receiver IF bandwidth was set to 400 Hz ,which is > not, of course, the receiver's noise bandwidth because of the actual > response of the K2's IF filter. I get -21dB with an analyzer bin width of 10.8Hz, using spectrogram and an indoor doublet, consisting of about 20m of wire, but with only about 10m horizontal. Note that is 21 dB below the noise in 10.8 Hz, or about 37dB below the noise in 400Hz, and I cannot hear it. I did turn the AGC off. Using a 50 ohm dummy load at about 21 degrees C, I get about +28dB in the same bandwidth. Looking at last month's RadCom article on noise, it looks like a quiet 7MHz should generate about 35dB over a 25 degree resistor, which would give -7dB in 10.8Hz even in ideal conditions. My antenna noise, at 49dB over the resistor, is roughly in the middle of the range suggested in that article. Either you are misinterpreting the effective noise bandwidth of the analyzer, or you have a faulty K2. The birdy, itself, will have very little bandwidth. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ 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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