K3 Buffer Mod
Locked
 
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Tony,
I have the LP-Pan with recommended Creative Labs E-MU 0202 and find this to be optimal, I mean no reason to make a mod of any type to K3. If someone told you that this must be done, I'd want to see why with my own eyes before doing this job. IMO (in my opinion) you don't "work" with SMD on K3, they fly around like little fleas even if you use a pair of 15w irons to remove them. They are just that small. But you can get them off without any major damage, find them, and carefully replace them - *when necessary*. YMMV... de wb8yqj Previous message: [Elecraft] K3 Buffer Mod Next message: [Elecraft] K2/100 LOCKUP THOUGHTS? Should I expect any negative impacts if I used regular resistors in place of SM resistors for this mod? N2TK, Tony _______________________________________________ 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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It sounds like Tony should leave the K3 as is. Dont screw it up unless
your qualified to make the mods. Jim K4JAF ----- Original Message ----- From: "Don Rasmussen" <[hidden email]> To: <[hidden email]> Sent: Thursday, August 21, 2008 7:06 PM Subject: [Elecraft] K3 Buffer Mod > Tony, > > I have the LP-Pan with recommended Creative Labs E-MU > 0202 and find this to be optimal, I mean no reason to > make a mod of any type to K3. If someone told you that > this must be done, I'd want to see why with my own > eyes before doing this job. > > IMO (in my opinion) you don't "work" with SMD on K3, > they fly around like little fleas even if you use a > pair of 15w irons to remove them. They are just that > small. But you can get them off without any major > damage, find them, and carefully replace them - *when > necessary*. YMMV... > > de wb8yqj > > Previous message: [Elecraft] K3 Buffer Mod > Next message: [Elecraft] K2/100 LOCKUP THOUGHTS? > > > Should I expect any negative impacts if I used > regular resistors in place > of SM resistors for this mod? > > N2TK, Tony > > > _______________________________________________ > 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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Jim,
The reason I ask about using regular resistors instead of SM resistors is that I don't have the correct value SM resistors. If there is a degradation in performance with film axial lead resistors I will get the SM resistors. It is not a question of qualification of mounting SM components. 73, N2TK, Tony -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Jim Cox Sent: Thursday, August 21, 2008 8:55 PM To: Don Rasmussen; [hidden email] Subject: Re: [Elecraft] K3 Buffer Mod It sounds like Tony should leave the K3 as is. Dont screw it up unless your qualified to make the mods. Jim K4JAF ----- Original Message ----- From: "Don Rasmussen" <[hidden email]> To: <[hidden email]> Sent: Thursday, August 21, 2008 7:06 PM Subject: [Elecraft] K3 Buffer Mod > Tony, > > I have the LP-Pan with recommended Creative Labs E-MU > 0202 and find this to be optimal, I mean no reason to > make a mod of any type to K3. If someone told you that > this must be done, I'd want to see why with my own > eyes before doing this job. > > IMO (in my opinion) you don't "work" with SMD on K3, > they fly around like little fleas even if you use a > pair of 15w irons to remove them. They are just that > small. But you can get them off without any major > damage, find them, and carefully replace them - *when > necessary*. YMMV... > > de wb8yqj > > Previous message: [Elecraft] K3 Buffer Mod > Next message: [Elecraft] K2/100 LOCKUP THOUGHTS? > > > Should I expect any negative impacts if I used > regular resistors in place > of SM resistors for this mod? > > N2TK, Tony > > > _______________________________________________ > 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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Tony,
Since this is not a high frequency area, there should be little performance difference (if any) between SMD parts and axial leaded parts. The more relevant consideration is physical fit. If you have 1/8 watt resistors it would be easier than 1/4 watt, but you should be able to get the 1/4 watt parts in there. 73, Don W3FPR N2TK wrote: > Jim, > The reason I ask about using regular resistors instead of SM resistors is > that I don't have the correct value SM resistors. If there is a degradation > in performance with film axial lead resistors I will get the SM resistors. > It is not a question of qualification of mounting SM components. > > 73, > N2TK, Tony > > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Jim Cox > Sent: Thursday, August 21, 2008 8:55 PM > To: Don Rasmussen; [hidden email] > Subject: Re: [Elecraft] K3 Buffer Mod > > It sounds like Tony should leave the K3 as is. Dont screw it up unless > your qualified to make the mods. Jim K4JAF > > > ----- Original Message ----- > From: "Don Rasmussen" <[hidden email]> > To: <[hidden email]> > Sent: Thursday, August 21, 2008 7:06 PM > Subject: [Elecraft] K3 Buffer Mod > > >> Tony, >> >> I have the LP-Pan with recommended Creative Labs E-MU >> 0202 and find this to be optimal, I mean no reason to >> make a mod of any type to K3. If someone told you that >> this must be done, I'd want to see why with my own >> eyes before doing this job. >> >> IMO (in my opinion) you don't "work" with SMD on K3, >> they fly around like little fleas even if you use a >> pair of 15w irons to remove them. They are just that >> small. But you can get them off without any major >> damage, find them, and carefully replace them - *when >> necessary*. YMMV... >> >> de wb8yqj >> >> Previous message: [Elecraft] K3 Buffer Mod >> Next message: [Elecraft] K2/100 LOCKUP THOUGHTS? >> >> >> Should I expect any negative impacts if I used >> regular resistors in place >> of SM resistors for this mod? >> >> N2TK, Tony >> >> >> _______________________________________________ >> 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 > > No virus found in this incoming message. > Checked by AVG - http://www.avg.com > Version: 8.0.138 / Virus Database: 270.6.6/1626 - Release Date: 8/21/2008 6:54 PM > > > 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 Don Rasmussen
17.7 dB transfer loss from RF IN to IF OUT is why... http://www.cliftonlaboratories.com/elecraft_k3_and_panadapters.htm#What_then_is_the_transfer_gain_of_the_K3_ |
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In reply to this post by Don Wilhelm-4
Tnx Don,
I do have the correct values in 1/8w. I wouldn't think there would be a difference, but I like to ask first, just in case. Finally should get some time over the next week to get beyond page 25 of the assembly manual for my second K3. 73, N2TK, Tony -----Original Message----- From: Don Wilhelm [mailto:[hidden email]] Sent: Friday, August 22, 2008 8:10 AM To: N2TK Cc: 'Jim Cox'; 'Don Rasmussen'; [hidden email] Subject: Re: [Elecraft] K3 Buffer Mod Tony, Since this is not a high frequency area, there should be little performance difference (if any) between SMD parts and axial leaded parts. The more relevant consideration is physical fit. If you have 1/8 watt resistors it would be easier than 1/4 watt, but you should be able to get the 1/4 watt parts in there. 73, Don W3FPR N2TK wrote: > Jim, > The reason I ask about using regular resistors instead of SM resistors is > that I don't have the correct value SM resistors. If there is a degradation > in performance with film axial lead resistors I will get the SM resistors. > It is not a question of qualification of mounting SM components. > > 73, > N2TK, Tony > > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Jim Cox > Sent: Thursday, August 21, 2008 8:55 PM > To: Don Rasmussen; [hidden email] > Subject: Re: [Elecraft] K3 Buffer Mod > > It sounds like Tony should leave the K3 as is. Dont screw it up unless > your qualified to make the mods. Jim K4JAF > > > ----- Original Message ----- > From: "Don Rasmussen" <[hidden email]> > To: <[hidden email]> > Sent: Thursday, August 21, 2008 7:06 PM > Subject: [Elecraft] K3 Buffer Mod > > >> Tony, >> >> I have the LP-Pan with recommended Creative Labs E-MU >> 0202 and find this to be optimal, I mean no reason to >> make a mod of any type to K3. If someone told you that >> this must be done, I'd want to see why with my own >> eyes before doing this job. >> >> IMO (in my opinion) you don't "work" with SMD on K3, >> they fly around like little fleas even if you use a >> pair of 15w irons to remove them. They are just that >> small. But you can get them off without any major >> damage, find them, and carefully replace them - *when >> necessary*. YMMV... >> >> de wb8yqj >> >> Previous message: [Elecraft] K3 Buffer Mod >> Next message: [Elecraft] K2/100 LOCKUP THOUGHTS? >> >> >> Should I expect any negative impacts if I used >> regular resistors in place >> of SM resistors for this mod? >> >> N2TK, Tony >> >> >> _______________________________________________ >> 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 > > No virus found in this incoming message. > Checked by AVG - http://www.avg.com > Version: 8.0.138 / Virus Database: 270.6.6/1626 - Release Date: 8/21/2008 > > > _______________________________________________ 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 Bill W4ZV
> >Don Rasmussen wrote: > > > > > > I have the LP-Pan with recommended Creative Labs E-MU > > 0202 and find this to be optimal, I mean no reason to > > make a mod of any type to K3. If someone told you that > > this must be done, I'd want to see why with my own > > eyes before doing this job. > > >At 08:16 AM 8/22/2008, Bill W4ZV wrote: >17.7 dB transfer loss from RF IN to IF OUT is why... But isn't that just an engineering design decision made by the Elecraft team? Since that decision was (hopefully) made with regard to the entire radio system, isn't that decision likely to be a good one? As one data point, my K3 is not modified, yet the IF panadaptor works extremely well, and PowerSDR gives peak heights approximating the true signal strengths seen at the input of the K3. When I feed in a 1 uV signal from my KG-2 signal generator, I see a definite distinct peak on the panadaptor, and when I feed in a 50 uV (S9) signal, I see a large S9 signal on the panadaptor. I am a loss to understand why you guys are quarreling with the Elecraft design in this instance. I am beginning to suspect that it is simply because it does not agree with the usual designs provided by some military contractors who are probably using an _arbitrary_ "standard" anyway. I would think twice before possibly damaging my radio or lowering its resale value with non-factory authorized modifications. YMMV. Jerry W4UK _______________________________________________ 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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The sensitivity may be adequate as a panadapter (but really only with the preamp on), but if you have ever tried to listen to a moderately weak signal with the audio output from PowerSDR-IF, it will be abundantly clear that more sensitivity is needed. PowerSDR has a very good synchronous AM detector, for example, so the combination offers listening opportunities the K3 does not yet have. I have also listened to DRM using the "Dream" decoder and finding that only the strongest of signals will decode properly.
Knut - AB2TC
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In reply to this post by Jerry Flanders
1uV (-107 dBm) is ~30 dB above the K3's noise floor. One of the primary reasons I wanted LP-PAN was to use either PowerSDR or CW Skimmer's waterfall to help detect very weak (i.e. noise floor) signals. Why would I want to limit myself to signals 30 dB above the noise floor? Answer: I wouldn't! Elecraft is well aware of N8LP's mod, Wayne saw no problems with it at first glance and is now considering whether to make it a production mod. Both N8LP and K8ZOA seem to feel it is not "damaging the radio, etc". Begging your pardon Jerry but Elecraft does not always get everything right the first time (e.g. the HAGC mod) but fortunately they are willing to listen to data and rational arguments for potential improvements. Thankfully Elecraft is much more open-minded to improvements than most manufacturers! 73, Bill |
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> Elecraft is well aware of N8LP's mod, Wayne saw no problems with it at first
> glance and is now considering whether to make it a production mod. Both > N8LP and K8ZOA seem to feel it is not "damaging the radio, etc". Remember to make the measurements Jack points out on his web page if you do the mod. This is to be sure the buffer transistor does not exceed its thermal ratings. 73, Lyle KK7P _______________________________________________ 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 Jerry Flanders
> >Don Rasmussen wrote:
> > > > > > > > > I have the LP-Pan with recommended Creative Labs E-MU > > > 0202 and find this to be optimal, I mean no reason to > make a mod of > > > any type to K3. If someone told you that this must be > done, I'd want > > > to see why with my own eyes before doing this job. > > > > > > >At 08:16 AM 8/22/2008, Bill W4ZV wrote: > >17.7 dB transfer loss from RF IN to IF OUT is why... > > >At 07:38 AM 8/22/2008, Jerry Flanders wrote: > But isn't that just an engineering design decision made by > the Elecraft team? Of course. A primary design criteria was limiting the IF output level to minimize spurious emissions. > Since that decision was (hopefully) made > with regard to the entire radio system, isn't that decision > likely to be a good one? It was a good decision based on the information available at the time. Now that LP-Pan is created and a bit more IF output signal is needed, it has been determined that the small increment in IF output will not impact the original goal of minimizing the IF output. It's a potential production mod that Elecraft might even make. Your confidence in Elecraft is reinforced by this example. The K3 is extremely well-designed as a system component where there are countless other system components it might be connected with. Some system components such as LP-Pan didn't even exist when the K3 was released and there are far too many system components for Elecraft or anyone to fully validate. The fact that the K3 works so well with all these variables is evidence of exceptional design. 73, Ed - W0YK _______________________________________________ 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 KK7P
Yes, here are the details: http://cliftonlaboratories.com/elecraft_k3_and_panadapters.htm#Alternative_to_increasing_K3_IF_sample_port_output ********************************************************** "If you make this modification, I suggest measuring the voltage across the new R9. Q10's drain current is set by a combination of the voltage drop across R9 and the individual characteristics of the J310 part in your K3. FETs have a notoriously wide part-to-part spread in parameters and it's possible that the J310 device in your K3 has parameters sufficiently far from the mean that Q10's power dissipation limits will be reached or exceeded. The surface mount J310 has a maximum power dissipation rating of 350 mw, and for reliability a safe operating value is 200 mw or so. Q10's current can be easily determined by measuring the voltage drop across R9. If changed to 49.9 ohms, Q10's drain current Id is 1000*Vs/50 (in milliamperes) where Vs is the voltage measured from ground to Q10's source pin. To calculate the power dissipated in Q10, measure its drain voltage. The power is then (Vd-Vs)*Id in milliwatts, where Id is in milliamperes. An example. After replacing R9 with a 49.9 ohm resistor, the following voltage readings are found: Vs = 2 volts, Vd = 12 volts. The idle current through Q10 is thus 2 / 49.9 = 40 mA. The power dissipated in Q10 is (12-2) * 40 = 400 milliwatts. This exceeds the J310's maximum permissible power dissipation and would not be a good design practice." ********************************************************** In my unit the voltage across R9 was 460 mV, which resulted in 0.46/51 = 9 mA and power of 90 mW, well below the maximum rating of 350 mW and below Jack's recommendation of 200 mW. 73, Bill |
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In reply to this post by Don Rasmussen
I am scratching my head wondering whether any of this applies to the LP-PAN,
or whether it is only relevant to other panadaptors such as the Softrock and the Z90. K8ZOA's web page (the same one everyone is quoting) says: "I looked at two potential panadapters; a Softrock and my Z90. (Telepostinc's LP-PAN has a built-in amplifier to overcome the transfer gain problem.)" and in the recommendations near the bottom of the page, refering to the mod, "These steps are not necessary with an LP-PAN panadapter as it has a built-in isolation amplifier." That same web page also suggests that an alternative to the mod would be to use an external buffer amplifier. So, I have two questions: 1. Is the mod necessary with the LP-PAN, or is it only needed with other panadapters? That is, is the noise figure of the LP-PAN's internal amplifier sufficient, or is the mod to the K3 required to lift weak signals above the noise floor of the LP-PAN? 2. Would the external buffer amplifier solution be a viable alternative to the mod? 73, Rich VE3KI _______________________________________________ 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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Larry's LP-PAN uses my Z10000 amplifier design in its front end, with a
couple of modifications to provide variable gain. The AD8007 amplifier chip in both my Z10000 and the LP-PAN is a decent amplifier with a respectable noise figure. If the K3's IF sample circuit had been built with closer to 0 dB transfer gain, then the composite noise figure would be closer to the K3's noise figure. To answer the two questions directly (I don't have an LP-PAN, so Larry might wish to modify my answers): 1. Is the mod necessary with the LP-PAN, or is it only needed with other panadapters? That is, is the noise figure of the LP-PAN's internal amplifier sufficient, or is the mod to the K3 required to lift weak signals above the noise floor of the LP-PAN? I believe you will see a small improvement in composite K3-LP-PAN noise figure if the changes are made to the K3's IF sample circuitry. However, I doubt that under most band conditions you will observe a difference as there is sufficient external noise to mask the improvement. 2. Would the external buffer amplifier solution be a viable alternative to the mod? Yes, I believe it is if you are using something other than the LP-PAN as the panadapter. Panadapters are not normally designed to be as sensitive as a receiver. There are many reasons for that that I won't bother to go over now. The consequence is that designers of receivers that provide a pan scope RF sample have the levels set so that there is at least a net 0 gain, and positive gains of 10 dB or more are not uncommon. I'm speaking mostly of commercial and military grade equipment, but my Kenwood TS-940 has reasonable transfer gain as well. Jack K8ZOA www.cliftonlaboratories.com Richard Ferch wrote: > I am scratching my head wondering whether any of this applies to the LP-PAN, > or whether it is only relevant to other panadaptors such as the Softrock and > the Z90. > > K8ZOA's web page (the same one everyone is quoting) says: > > "I looked at two potential panadapters; a Softrock and my Z90. > (Telepostinc's LP-PAN has a built-in amplifier to overcome the transfer gain > problem.)" > > and in the recommendations near the bottom of the page, refering to the mod, > > > "These steps are not necessary with an LP-PAN panadapter as it has a > built-in isolation amplifier." > > That same web page also suggests that an alternative to the mod would be to > use an external buffer amplifier. > > So, I have two questions: > > 1. Is the mod necessary with the LP-PAN, or is it only needed with other > panadapters? That is, is the noise figure of the LP-PAN's internal amplifier > sufficient, or is the mod to the K3 required to lift weak signals above the > noise floor of the LP-PAN? > > 2. Would the external buffer amplifier solution be a viable alternative to > the mod? > > 73, > Rich VE3KI > > _______________________________________________ > 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 Don Rasmussen
Thanks for the interesting info Chen. Your post did not make it to
the list for some reason so I'm leaving it attached below for any (including Elecraft) that may be interested. 73, Bill W4ZV On Fri, Aug 22, 2008 at 12:31 PM, Kok Chen <[hidden email]> wrote: > All sound cards that are connected to a QSD-based SDR have an absolute noise > floor. If a signal that is being > converted is weaker than this A/D noise floor, it will not move the least > significant bit of the A/D converter; > i.e., the software demodulator receives no signal. Indeed, the signal needs > to be a couple of bits stronger > than the noise floor, or you are going to get unwanted spectral byproducts > that degrades the demodulation > capabilities of the SDR. > > Thus, you want the noise floor of the K3's I.F. output to be at least as > strong as the noise floor of the SDR. If the > K3's noise floor is stronger, you can always use a pad in between. It is > only when the two noise floors are matched > that you will get the maximum dynamic range out of an SDR based system. > > The only time you can use an A/D converter down to, and below, the least > significant bit of the A/D is if the input > noise to the A/D converter is Gaussian (i.e., there are no other strong > signals anywhere in the passband). You > will then be able to use "noise linearization" to obtain a perfectly > undistorted spectrum. This is known as the > Van Vleck theorem, which also appears in Probability books as the "Arcsine > law" of joint Gaussian processes. > However, you will need some software to apply a correction, plus you always > lose 2.1 dB in recovered SNR. The > noise linearization technique had been put to good use by Van Vleck in WWII > radar and Sandy Weinreb's > "autocorrelation receiver" in radio astronomy, but I am not sure it will > work well in H.F. radios, and certainly > not when listening to a pileup. > > 73, > Chen, W7AY > > 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 Jack Smith-6
I have addressed this on my reflector, but for the benefit of those on
the Elecraft reflector... 95% of LP-PAN users will be happy with the NF and sensitivity without any modifications to the K3. On most bands, the resulting NF caused by the loss in the K3 buffer will be masked by atmospheric noise. On the higher bands, keeping the K3 preamp on will help a lot. This is usually OK at most locations because the K3 preamp is quite strong. The reason I came up with the mod is because a couple users were trying to use CW Skimmer for weak signal detection with LP-PAN feeding it. The mod improves the NF of the IF output by up to 10dB (K3 preamp off, somewhat less with the K3 preamp ON). Even though the NF of LP-PAN itself is quite good, it can't do anything to improve the system NF since it's downstream of the loss. My advice is to try it without modifying the K3 first. You will most likely be quite happy with the result. Be sure to read all the instructions before attempting the mod. It is comparable in complexity to the HAGC mod that Elecraft offers... but still requires reworking SMT parts. 73, Larry N8LP Jack Smith wrote: > Larry's LP-PAN uses my Z10000 amplifier design in its front end, with > a couple of modifications to provide variable gain. > > The AD8007 amplifier chip in both my Z10000 and the LP-PAN is a decent > amplifier with a respectable noise figure. > > If the K3's IF sample circuit had been built with closer to 0 dB > transfer gain, then the composite noise figure would be closer to the > K3's noise figure. > > To answer the two questions directly (I don't have an LP-PAN, so Larry > might wish to modify my answers): > > 1. Is the mod necessary with the LP-PAN, or is it only needed with other > panadapters? That is, is the noise figure of the LP-PAN's internal > amplifier > sufficient, or is the mod to the K3 required to lift weak signals > above the > noise floor of the LP-PAN? > > I believe you will see a small improvement in composite K3-LP-PAN > noise figure if the changes are made to the K3's IF sample circuitry. > However, I doubt that under most band conditions you will observe a > difference as there is sufficient external noise to mask the improvement. > > 2. Would the external buffer amplifier solution be a viable > alternative to > the mod? > > Yes, I believe it is if you are using something other than the LP-PAN > as the panadapter. Panadapters are not normally designed to be as > sensitive as a receiver. There are many reasons for that that I won't > bother to go over now. The consequence is that designers of receivers > that provide a pan scope RF sample have the levels set so that there > is at least a net 0 gain, and positive gains of 10 dB or more are not > uncommon. I'm speaking mostly of commercial and military grade > equipment, but my Kenwood TS-940 has reasonable transfer gain as well. > > > Jack K8ZOA > www.cliftonlaboratories.com > > > Richard Ferch wrote: >> I am scratching my head wondering whether any of this applies to the >> LP-PAN, >> or whether it is only relevant to other panadaptors such as the >> Softrock and >> the Z90. >> >> K8ZOA's web page (the same one everyone is quoting) says: >> >> "I looked at two potential panadapters; a Softrock and my Z90. >> (Telepostinc's LP-PAN has a built-in amplifier to overcome the >> transfer gain >> problem.)" >> >> and in the recommendations near the bottom of the page, refering to >> the mod, >> >> >> "These steps are not necessary with an LP-PAN panadapter as it has a >> built-in isolation amplifier." >> >> That same web page also suggests that an alternative to the mod would >> be to >> use an external buffer amplifier. >> >> So, I have two questions: >> >> 1. Is the mod necessary with the LP-PAN, or is it only needed with other >> panadapters? That is, is the noise figure of the LP-PAN's internal >> amplifier >> sufficient, or is the mod to the K3 required to lift weak signals >> above the >> noise floor of the LP-PAN? >> >> 2. Would the external buffer amplifier solution be a viable >> alternative to >> the mod? >> >> 73, >> Rich VE3KI >> >> _______________________________________________ >> 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 Jerry Flanders
Jerry,
I do agree with you. There is a requirement for an isolation amplifier anyhow, so I do not understand why the -17.7 dB cannot be made up in the isolation amplifier if the device to be driven needs input at the same level as the antenna signal. Should Elecraft ever come out with a device (Panadapter?) that is designed to connect to the IF out at the level it currently is designed for, any K3 that has been modified will require that the modification be removed. 73, Don W3FPR Jerry Flanders wrote: > >> >> Don Rasmussen wrote: >> > >> > >> > I have the LP-Pan with recommended Creative Labs E-MU >> > 0202 and find this to be optimal, I mean no reason to >> > make a mod of any type to K3. If someone told you that >> > this must be done, I'd want to see why with my own >> > eyes before doing this job. >> > > > >> At 08:16 AM 8/22/2008, Bill W4ZV wrote: >> 17.7 dB transfer loss from RF IN to IF OUT is why... > > But isn't that just an engineering design decision made by the Elecraft > team? Since that decision was (hopefully) made with regard to the entire > radio system, isn't that decision likely to be a good one? > > As one data point, my K3 is not modified, yet the IF panadaptor works > extremely well, and PowerSDR gives peak heights approximating the true > signal strengths seen at the input of the K3. When I feed in a 1 uV > signal from my KG-2 signal generator, I see a definite distinct peak on > the panadaptor, and when I feed in a 50 uV (S9) signal, I see a large S9 > signal on the panadaptor. > > I am a loss to understand why you guys are quarreling with the Elecraft > design in this instance. I am beginning to suspect that it is simply > because it does not agree with the usual designs provided by some > military contractors who are probably using an _arbitrary_ "standard" > anyway. > > I would think twice before possibly damaging my radio or lowering its > resale value with non-factory authorized modifications. > > YMMV. > > Jerry W4UK 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 Buffer Mod
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Date: Fri, 22 Aug 2008 16:50:46 -0400 From: Don Wilhelm <[hidden email]> Should Elecraft ever come out with a device (Panadapter?) that is designed to connect to the IF out at the level it currently is designed for, any K3 that has been modified will require that the modification be removed. No, they're clever about things like that- unless there's a good reason not to, any device they would design would be able to cope with either signal level. Unless they decide the mod (or a version of it) has a distinct advantage, in which it will be blessed and incorporated into future production. 73, doug _______________________________________________ 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 |
K3 Noise Blanker, Filter and DSP Measurements
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In reply to this post by N8LP
I've added a third page of K3 performance measurements to my web site
this evening. http://www.cliftonlaboratories.com/elecraft_k3_noise_blanker_and_crystal_dsp_filtering.htm Four topics are covered: 1. IF noise blanker 2. Linearity of DBV function 3. Frequency domain filter measurements 4. Time domain filter measurements 73 de Jack K8ZOA www.cliftonlaboratories.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 Noise Blanker, Filter and DSP Measurements
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Jack,
Thanks for posting all this data. Very interesting. (At least to a data-junkie engineer. ;=) Al N1AL On Fri, 2008-08-22 at 16:14, Jack Smith wrote: > I've added a third page of K3 performance measurements to my web site > this evening. > http://www.cliftonlaboratories.com/elecraft_k3_noise_blanker_and_crystal_dsp_filtering.htm > > Four topics are covered: > 1. IF noise blanker > 2. Linearity of DBV function > 3. Frequency domain filter measurements > 4. Time domain filter measurements > > 73 de Jack K8ZOA > www.cliftonlaboratories.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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