Re: FW: Sherwood Engineering
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Barry,
Yes, remembering the pentode front end of my AN-ARC1 (modified for 2m AM) had a horrible Noise Figure (which impacted receive sensitivity). One could probably have a better NF with today's double balance mixers (which are commonly now the front end of HF receivers). This is done for best Blocking Dynamic performance. HF bands may often have -115 dBm noise levels (or higher) so sensitivity is not the main thing driving the design. Lower sideband noise of the new synthesizer will directly improve operating in a crowded band. For what I mainly do in ham radio, low noise figure is mandatory and sensitivity levels like -170 to -180 dBm are strived for. I am talking about eme (moonbounce). As frequency gets higher, sky noise drops rapidly so that receiver internally generated noise becomes the limiting factor. But low phase noise from the LO is also important. It is still somewhat controversial whether that is only in presence of strong adjacent frequency signals or even important for other reasons. I will update my K3 because its possible, so if that has potential of improving my weak-signal ability, my station will benefit. Synthesized PLL LO's are beginning to replace xtal LO's in microwave equipment and particular attention is given to low phase noise. I see the new synth as only good stuff, and spending a couple hundred bucks to keep my 5-year old radio up to current technology is pretty cheap, vs having to buy a brand new radio to get it. 73, Ed - KL7UW -------------------------------------------- From: [hidden email] To: "Burdick, Wayne" <[hidden email]> Cc: elecraft <[hidden email]> Subject: Re: [Elecraft] FW: Sherwood Engineering Tests Message-ID: <[hidden email]> Content-Type: text/plain; charset=utf-8 I'm old enough to remember that the most important characteristic of a receiver was sensitivity. Nothing else seemed to matter. Some receivers of the time had 2 RF amplifiers to make sure that they won the sensitivity battle. And, what would happened when a strong signal, not necessarily S9, would appear, bad things happened to your radio. At this point I won't define the date. This lunacy was being looked at by a number engineers, to include Dr. Ulrich Rhode, W2 something. I forget his call. He said in a series of papers in professional journals and Ham Radio Magazine that sensitivity was not the most important parameter at the time. It would turn out to be LO noise sidebands and dynamic range. That still holds today, and now, IMHO, ultimate rejection should be added. All of this is shown in Sherwood's data. What this all means is that all of the receiver parameters must be looked at to decide what makes a great radio. I suggest a review of some of Rhode's papers. His writings make extremely interesting reading as it addresses this discussion directly. 73, Barry K3NDM 73, Ed - KL7UW http://www.kl7uw.com "Kits made by KL7UW" Dubus Mag business: [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Ed,
I haven't checked but a few HF receivers. However, the ones I did showed noise figures of anywhere from 15 to 23 db, which is adequate for most HF work until you get up to the higher end. Pre-amps were invented for that. Before 2 db or better noise figure MOSFETS or eqiv. there was the parametric amplifier for those who wanted the best of noise figures for EME or other really low signal levels. I'm really glad technology makes life easier by replacing those evil little monsters. I, for one, never want to use a paramp again for the rest of my life. In my early years, there was CCIR-322 that defined the expected value of atmospheric noise by location, etc. I remember that 80 meters had an expected value of about 80 db Fa, or equivalent NF. and that tapered off until you hit galactic noise around 15-18 MHZ. All of which is/was below the average HF receiver noise figure. Where life gets interesting is that atmospheric noise in mostly lightning propagated from the tropics. Why is this important? because even on 10 meters the noise goes up when the band is open. This argument's premiss is that most receivers are over designed if sensitivity is the only parameter used to defined performance. If you find yourself in a position where your receiver noise figure at the moment is inadequate, having a pre-amp may help. Why the hedge? well, let's consider the last weekend's DX contest. 10 was crazy open with many very strong signals sitting side by side with weaker to much weaker signals. Had I turned on my pre-amp, and had I not owned a KX3, the result could have been that the strong signals might have hidden the weaker ones due to an apparent increase in the receiver noise floor caused by the mixing of strong signals with other noise. My receiver would have appeared to be less sensitive than it would have been with the pre-amp turned off. This was also the position that was written up by Rhode and others who stated that we were at a point where signal handling was as important or more important than just how sensitive the receiver was. And, ultimate filtering and shape factors have a place in this as it helps keep strong signals away from weak ones. However, there are other attributes of receiver design that help define just how good a radio will be. Unfortunately, some of them interact, and not always the best way. Bob Sherwood measures and publishes data that can help a perspective buyer make some guess what receiver would work best in a particular shack. The rankings are his opinion. Admittedly, buying a radio in his top rankings shouldn't disappoint, but all of the data should be looked at. And price is certainly a parameter that needs to be considered along with Bob's data. I still recommend that those not familiar with why receivers work and how they function in a real environment search out some of the work printed in the 60's and 70's on receivers design. They contain minimal math and are a good discussion of the real receiver issues. That should put Bob's work in perspective and help make sense of the data. And, IMHO, using a K3 or KX3 is the way to go. And for me, my requirement set drove me to the KX3, and I haven't been disappointed. 73, Barry K3NDM ----- Original Message ----- From: "Edward R Cole" <[hidden email]> To: "elecraft" <[hidden email]> Sent: Wednesday, February 25, 2015 9:27:32 AM Subject: Re: [Elecraft] FW: Sherwood Engineering Barry, Yes, remembering the pentode front end of my AN-ARC1 (modified for 2m AM) had a horrible Noise Figure (which impacted receive sensitivity). One could probably have a better NF with today's double balance mixers (which are commonly now the front end of HF receivers). This is done for best Blocking Dynamic performance. HF bands may often have -115 dBm noise levels (or higher) so sensitivity is not the main thing driving the design. Lower sideband noise of the new synthesizer will directly improve operating in a crowded band. For what I mainly do in ham radio, low noise figure is mandatory and sensitivity levels like -170 to -180 dBm are strived for. I am talking about eme (moonbounce). As frequency gets higher, sky noise drops rapidly so that receiver internally generated noise becomes the limiting factor. But low phase noise from the LO is also important. It is still somewhat controversial whether that is only in presence of strong adjacent frequency signals or even important for other reasons. I will update my K3 because its possible, so if that has potential of improving my weak-signal ability, my station will benefit. Synthesized PLL LO's are beginning to replace xtal LO's in microwave equipment and particular attention is given to low phase noise. I see the new synth as only good stuff, and spending a couple hundred bucks to keep my 5-year old radio up to current technology is pretty cheap, vs having to buy a brand new radio to get it. 73, Ed - KL7UW -------------------------------------------- From: [hidden email] To: "Burdick, Wayne" <[hidden email]> Cc: elecraft <[hidden email]> Subject: Re: [Elecraft] FW: Sherwood Engineering Tests Message-ID: <[hidden email]> Content-Type: text/plain; charset=utf-8 I'm old enough to remember that the most important characteristic of a receiver was sensitivity. Nothing else seemed to matter. Some receivers of the time had 2 RF amplifiers to make sure that they won the sensitivity battle. And, what would happened when a strong signal, not necessarily S9, would appear, bad things happened to your radio. At this point I won't define the date. This lunacy was being looked at by a number engineers, to include Dr. Ulrich Rhode, W2 something. I forget his call. He said in a series of papers in professional journals and Ham Radio Magazine that sensitivity was not the most important parameter at the time. It would turn out to be LO noise sidebands and dynamic range. That still holds today, and now, IMHO, ultimate rejection should be added. All of this is shown in Sherwood's data. What this all means is that all of the receiver parameters must be looked at to decide what makes a great radio. I suggest a review of some of Rhode's papers. His writings make extremely interesting reading as it addresses this discussion directly. 73, Barry K3NDM 73, Ed - KL7UW http://www.kl7uw.com "Kits made by KL7UW" Dubus Mag business: [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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If you want to better understand the receiver performance data that Rob publishes, he has given some very nice presentations that are conveniently captured here:
http://www.dj0ip.de/transceivers/sherwood-presentations/ 73, Matt VK2RQ > On 26 Feb 2015, at 3:31 am, [hidden email] wrote: > > ... > > Bob Sherwood measures and publishes data that can help a perspective buyer make some guess what receiver would work best in a particular shack. The rankings are his opinion. Admittedly, buying a radio in his top rankings shouldn't disappoint, but all of the data should be looked at. And price is certainly a parameter that needs to be considered along with Bob's data. > > I still recommend that those not familiar with why receivers work and how they function in a real environment search out some of the work printed in the 60's and 70's on receivers design. They contain minimal math and are a good discussion of the real receiver issues. That should put Bob's work in perspective and help make sense of the data. And, IMHO, using a K3 or KX3 is the way to go. And for me, my requirement set drove me to the KX3, and I haven't been disappointed. > > 73, > Barry Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: FW: Sherwood Engineering
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Also, please note that any comments by Rob regarding RX Audio and the K3 in
those presentations refers to K3s sold many years ago. We've made substantial changes to the audio to address his concerns. Eric elecraft.com On 2/25/2015 3:41 PM, Matt VK2RQ wrote: > If you want to better understand the receiver performance data that Rob publishes, he has given some very nice presentations that are conveniently captured here: > http://www.dj0ip.de/transceivers/sherwood-presentations/ > > 73, > Matt VK2RQ > >> On 26 Feb 2015, at 3:31 am, [hidden email] wrote: >> >> ... >> >> Bob Sherwood measures and publishes data that can help a perspective buyer make some guess what receiver would work best in a particular shack. The rankings are his opinion. Admittedly, buying a radio in his top rankings shouldn't disappoint, but all of the data should be looked at. And price is certainly a parameter that needs to be considered along with Bob's data. >> >> I still recommend that those not familiar with why receivers work and how they function in a real environment search out some of the work printed in the 60's and 70's on receivers design. They contain minimal math and are a good discussion of the real receiver issues. That should put Bob's work in perspective and help make sense of the data. And, IMHO, using a K3 or KX3 is the way to go. And for me, my requirement set drove me to the KX3, and I haven't been disappointed. >> >> 73, >> Barry > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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This raises an interesting point. In other venues (casual discussion, fests, on air discussions, etc), I’ve heard several times about the reputation of “bad receive audio” on the K3… and suspect since most of the kibitzers don’t actually own a K3, that it comes from early published sources — or those repeating what they got from the rumor mill started from these early sources. I’ve spent a whole lot of hours in front of my own K3 (fully updated serial 2091) and have yet to be “worn out” or become hearing impaired by the K3’s receive audio. It’s actually quite good.
Perhaps it’s time to encourage an update in some of these early reports and evaluations, since material (no matter how outdated) published to the internet and which pops up in Google search seems to live on forever as gospel … Grant NQ5T > On Feb 25, 2015, at 6:55 PM, Eric Swartz - WA6HHQ, Elecraft <[hidden email]> wrote: > > Also, please note that any comments by Rob regarding RX Audio and the K3 in those presentations refers to K3s sold many years ago. We've made substantial changes to the audio to address his concerns. > > Eric > elecraft.com <http://elecraft.com/> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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It's simple: The K3 has great audio on both RX and TX. And it now has one of the lowest-noise synthesizers and highest-dynamic range receivers on the planet--possibly all of Alpha quadrant. Please tell your friends. Maybe it'll go viral :)
73, Wayne N6KR On Feb 25, 2015, at 6:16 PM, GRANT YOUNGMAN <[hidden email]> wrote: > This raises an interesting point. In other venues (casual discussion, fests, on air discussions, etc), I’ve heard several times about the reputation of “bad receive audio” on the K3… and suspect since most of the kibitzers don’t actually own a K3, that it comes from early published sources — or those repeating what they got from the rumor mill started from these early sources. I’ve spent a whole lot of hours in front of my own K3 (fully updated serial 2091) and have yet to be “worn out” or become hearing impaired by the K3’s receive audio. It’s actually quite good. > > Perhaps it’s time to encourage an update in some of these early reports and evaluations, since material (no matter how outdated) published to the internet and which pops up in Google search seems to live on forever as gospel … > > Grant NQ5T > > >> On Feb 25, 2015, at 6:55 PM, Eric Swartz - WA6HHQ, Elecraft <[hidden email]> wrote: >> >> Also, please note that any comments by Rob regarding RX Audio and the K3 in those presentations refers to K3s sold many years ago. We've made substantial changes to the audio to address his concerns. >> >> Eric >> elecraft.com <http://elecraft.com/> >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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