Re: Wha'ts Wrong With Our Radios (WAS:NewProducts, Building Demo, ...
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I know this is old, but I don't think I replied to it.
In a message dated 5/29/06 11:01:34 PM Eastern Daylight Time, [hidden email] writes: > On May 29, 2006, at 3:31 PM, [hidden email] wrote: > > > In a message dated 5/29/06 8:33:49 AM Eastern Daylight Time, > > [hidden email] writes: > > > >> Seems like the standard radios in my > >> youth all had 1/2" diameter knobs, and they were spaced at least 1 > >> 3/4" inches apart or more. So, the ones on the K2 are probably too > >> small, and too close together. > > > > I'd go even bigger, because I have big hands. Tuning knob should be > > in excess of 2". other knobs in excess of 1". Say 2-1/2" for the > > tuning and 1" for everything else. Yes, that's big! > > 2 1/2" tuning knobs are moderately small. 3" is more like it. > There should be lots of room around the knob, too. That means lots of panel space. > But 1" knobs are pretty big, actually. Perhaps 3/4" ? > > I find 1" to be small... ;-) >> What other knobs would you have on a K2-like radio? > > > > Some form of dedicated bandswitch > > I disagree here. I don't rotary bandswitches are beneficial. (They > certainly are traditional) Pushbuttons work great, and if you don't > like the single band-up/band-down, we could always expand this to > have a dedicated button for each band. > The thing is the idea that you can just glance at the knob and know what band you are on. Note that the knob/pushbutton is just the interface; the actual switching would be done by relays. > > Some form of dedicated filter selector > > Same issue here -- I actually prefer the buttons to the rotary > switch. It would be REALLY nice to have a series of buttons for this > though -- that way we could directly access the filter setting we want. > Same issue. > > Some form of dedicated AGC selector > > Again, I'm not sold on the rotary switch. You just need more buttons. > > And again the same issue. Of course there may be button designs that tell you which option is selected. The problem, of course, is that all this stuff uses up panel space like mad and you wind up with a much larger rig. 73 de Jim, N2EY _______________________________________________ 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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Bit by bit I learn K2 is loaded with quality not commonly found in other HF
ham gear. Why no ( real.. ) IF shift ? ( common in all " other " rigs , even my cheap FT-100's ). Peter, PE1E _______________________________________________ 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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Being single conversion may have something to do with it. But I imagine one
could shift the bfo frequency along with the tuning to give the effect of IF shift, if one had a place to put another knob. 73/72 - Mike WA8BXN _______________________________________________ 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 PE1E
In a message dated 8/7/06 7:03:01 PM Eastern Daylight Time,
[hidden email] writes: > I imagine one > could shift the bfo frequency along with the tuning to give the effect of IF > shift, if one had a place to put another knob. > The venerable Collins 75A-4 of a half-century ago, possibly the first receiver to have the feature, implemented the feature that way - mechanically! When you turned the knob, the PTO assembly rotated one way, changing the LO frequency and the BFO pitch control rotated to change the BFO frequency the same amount, but in the opposite direction. The method's success depended on the absolute linearity of the Collins PTO and BFO tuning. Quite a challenge even though the PTO and BFO tuned only single ranges for all bands. btw, Collins called it "bandpass tuning" IIRC. The same concept could be employed in the K-2, but it would require software that would figure out how to move the LO one way and the BFO the other way by exactly the same amount. And the software would have to do it on all bands and all frequencies on those bands! Most "other" rigs implement IF shift by an extra conversion step after the first fixed IF. This means there's a lot of gain and stages between the antenna and the sharp selectivity "knothole". No thanks. IMHO, IF shift is of limited use in a CW receiver, and not worth giving up having the filter right up against the first mixer. 73 de Jim, N2EY _______________________________________________ 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 PE1E
Others pointed out the reason - single conversion design. That
single-conversion design is also what helps the K2's performance excel compared to those with multiple-conversions that allow for an "IF Shift" knob. Frequency conversions in receivers are like making copies in photography. You can go to great extremes to make each copy very high quality, but each generation degrades the image, just the same. In a receiver, every conversion degrades the performance, no matter how hard the engineers try to avoid it. But all is not lost. You CAN do IF Shift with a K2 to a limited extent: I do. I assume you're talking about SSB since IF shift on CW is pretty meaningless. On SSB you have only one filter setting, so you have three more positions to play with. Select OPT1 for your filter for each FL setting, but adjust the BFO frequency as you desire to alter the position of the passband with respect to the carrier as you want. Then, if you want to shift the passband around, just punch the FILTER button so move to a different position. It will affect ONLY the received signal, since the K2 reverts to FL1 for transmit, no matter which FL position you're using for receive. Ron AC7AC -----Original Message----- Bit by bit I learn K2 is loaded with quality not commonly found in other HF ham gear. Why no ( real.. ) IF shift ? ( common in all " other " rigs , even my cheap FT-100's ). Peter, PE1E _______________________________________________ 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: Why no IF shift ?
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Ron AC7AC wrote:
Others pointed out the reason - single conversion design. That single-conversion design is also what helps the K2's performance excel compared to those with multiple-conversions that allow for an "IF Shift" knob. Frequency conversions in receivers are like making copies in photography. You can go to great extremes to make each copy very high quality, but each generation degrades the image, just the same. In a receiver, every conversion degrades the performance, no matter how hard the engineers try to avoid it. ----------------------------------------------------------------- Hang on <g>. One problem with single down conversion receivers is that their "stronger" spurious responses which, depending on the IF used, can be close to or even in one or more of the frequency bands covered by the receiver. If bandpass filters are used between the antenna connector and the mixer, their selectivity might offer some degree of protection against signals coming in at spurious response frequencies outside but close to the bands covered but obviously no protection against anything coming in at an "in-band" spurious response frequency. The choice of IF that reduces this problem in a single down conversion receiver is quite limited. In a double conversion receiver, up and then down, assuming that sensible design and construction practices are followed, the close or in-band spurious responses (if they exist) are considerably reduced. Then there is the internal birdie problem, usually created by one or more of the receiver's oscillators and /or their harmonics getting together to produce a signal at some spurious response frequency of the receiver. If the Front End, LO and IF are not properly shielded in separate "boxes" with all associated DC and control lines filtered, then expect birdies in a single down conversion receiver. The same method of construction should be used in a double conversion receiver. I suspect that commercial double conversion amateur receivers have received a bad press because for reasons of cost this is usually not done. It is true that every conversion degrades the performance, but for several years the technology has been available that allows a double conversion receiver to be built which exhibits an IIP3 of +40dbm at an offset of 2 kHz while running at full gain, Noise Figure of 8db on 10m. I have one here. The downside is that each one of the three VHF roofing filters / embedded amplifiers selected draws 240 mA. With double conversion, in addition to true "IF Shift" a form of continuous bandwidth control can also be introduced. 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 |
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In reply to this post by PE1E
In a message dated 8/8/06 6:41:46 AM Eastern Daylight Time,
[hidden email] writes: > One problem with single down conversion receivers is that their > "stronger" spurious responses which, depending on the IF used, can be close > to or even in one or more of the frequency bands covered by the receiver. How? In a single conversion superhet, the most important spurs are the image and IF feedthrough. In the case of a K2, the image is always about 9.830 MHz from the desired signal, and the IF is around 4.915 MHz. The bandpass filters take care of those spurs very well, in my experience. If > > bandpass filters are used between the antenna connector and the mixer, their > > selectivity might offer some degree of protection against signals coming in > at spurious response frequencies outside but close to the bands covered but > obviously no protection against anything coming in at an "in-band" spurious > response frequency. What in band spurs exist in the K2? The choice of IF that reduces this problem in a single > > down conversion receiver is quite limited. > > In a double conversion receiver, up and then down, assuming that sensible > design and construction practices are followed, the close or in-band > spurious responses (if they exist) are considerably reduced. > That may be the case in a general-coverage receiver, but in a ham-bands-only design, the spurious responses are easily handled by good input filters. > Then there is the internal birdie problem, usually created by one or more > of > the receiver's oscillators and /or their harmonics getting together to > produce a signal at some spurious response frequency of the receiver. Again, this is dependent on the design. For a ham-bands-only receiver, the birdies can be placed outside the ham bands. If the > > Front End, LO and IF are not properly shielded in separate "boxes" with all > associated DC and control lines filtered, then expect birdies in a single > down conversion receiver. The same method of construction should be used in > a double conversion receiver. I suspect that commercial double conversion > amateur receivers have received a bad press because for reasons of cost this > > is usually not done. > There are some very good up/down double conversion amateur receivers. But they all suffer from the same problem: The signal has to go through several stages and conversions before it gets to the sharp filters. In a single conversion design like the K2, the number of stages and conversions between antenna and sharp filter is minimized. > It is true that every conversion degrades the performance, but for several > years the technology has been available that allows a double conversion > receiver to be built which exhibits an IIP3 of +40dbm > at an offset of 2 kHz while running at full gain, Noise Figure of 8db on > 10m. I have one here. The downside is that each one of the three VHF roofing > > filters / embedded amplifiers selected draws 240 mA. > There's also the issue of price.... > With double conversion, in addition to true "IF Shift" a form of continuous > > bandwidth control can also be introduced. > 73 de Jim, N2EY _______________________________________________ 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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Folks, (long philosophical response - delete if not interested in my
opinion). Some very good points mentioned in this thread, but the reality of all of it is compromise. For any given price target, some tradeoffs must be made. If I can interpret the K2 design goals loosely, the dynamic range was considered uppermost, and good sensitivity and IP3 performance running a close second. To achieve that in a kit product, single conversion IMHO is the only realistic way to go. Yes, there ae very good designs out there for multi-conversion receivers and they have their costs and limitations, but the K2 is a compromise of all that. It is single conversion because that is the way to contain the dynamic range and good IP3 characteristics within the chosen price range. It is well known that one must get into the $3K+++ transceivers to achieve those receive parameters that K2/100 owners have achieved for less than half that price. Certainly, IF shift is not an easy acomplishment with a single conversion transceiver. Answering one question posed in the thread which asked why a BFO frequency knob would not do the deed - the answer is YES, BUT - if only the BFO frequency is changed, the displayed frequency would no longer be correct - the firmware currently corrects for both the BFO and VFO frequencies and displays the correct carrier frequency, so while passband tuning might be accomplished simply by changing the BFO, the VFO would have to be altered manually to compensate for the BFO shift, and the resulting frequency on the dial would be incorrect. We used to do exactly that on receivers with a variable BFO, but then we did not have digital dials that were good to the nearest 10 Hz (but I digress). When CAL FIL is run, all that is taken into consideration in the firmware, and the EEPROM values contain the result of that calibration run which produces correct carrier frequency dial readings - you have to give up one thing to gain another in any design process unless 'price is no object'. If the world were perfect, we would all have receivers with a 120+ dB dynamic range, straight sided selectivity curves (with perfectly flat pass band shapes and no change in group delay across the passband), MDS figures in the -160 dB range and all that at a cost of less than $100 - of course I am dreaming based on today's technology and price/performance criteria that would be within the budget of the majority of hams. There is no sense in developing a superior design for production that would sell only one unit because of the cost involved - that is the stuff that extreme designs can produce, but those are currently the stuff of advanced homebrewers - they are the designs of tomorrow when the price of such designs comes down to an affordable level suitable for production. 73, Don W3FPR > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of [hidden email] > Sent: Tuesday, August 08, 2006 7:27 PM > To: [hidden email]; [hidden email] > Subject: Re: [Elecraft] Why no IF shift ? > > > In a message dated 8/8/06 6:41:46 AM Eastern Daylight Time, > [hidden email] writes: > > > > One problem with single down conversion receivers is that their > > "stronger" spurious responses which, depending on the IF used, > can be close > > to or even in one or more of the frequency bands covered by the > receiver. > > How? > > In a single conversion superhet, the most important spurs are the > image and > IF feedthrough. In the case of a K2, the image is always about > 9.830 MHz from > the desired signal, and the IF is around 4.915 MHz. The bandpass > filters take > care of those spurs very well, in my experience. > > If > > > > bandpass filters are used between the antenna connector and the > mixer, their > > > > selectivity might offer some degree of protection against > signals coming in > > at spurious response frequencies outside but close to the bands > covered but > > obviously no protection against anything coming in at an > "in-band" spurious > > response frequency. > > What in band spurs exist in the K2? > > The choice of IF that reduces this problem in a single > > > > down conversion receiver is quite limited. > > > > In a double conversion receiver, up and then down, assuming > that sensible > > design and construction practices are followed, the close or in-band > > spurious responses (if they exist) are considerably reduced. > > > > That may be the case in a general-coverage receiver, but in a > ham-bands-only > design, the spurious responses are easily handled by good input filters. > > > Then there is the internal birdie problem, usually created by > one or more > > of > > the receiver's oscillators and /or their harmonics getting together to > > produce a signal at some spurious response frequency of the receiver. > > Again, this is dependent on the design. For a ham-bands-only > receiver, the > birdies can be placed outside the ham bands. > > If the > > > > Front End, LO and IF are not properly shielded in separate > "boxes" with all > > associated DC and control lines filtered, then expect birdies > in a single > > down conversion receiver. The same method of construction > should be used in > > a double conversion receiver. I suspect that commercial double > conversion > > amateur receivers have received a bad press because for reasons > of cost this > > > > is usually not done. > > > > There are some very good up/down double conversion amateur receivers. But > they all suffer from the same problem: The signal has to go > through several > stages and conversions before it gets to the sharp filters. In a > single conversion > design like the K2, the number of stages and conversions between > antenna and > sharp filter is minimized. > > > > It is true that every conversion degrades the performance, but > for several > > years the technology has been available that allows a double conversion > > receiver to be built which exhibits an IIP3 of +40dbm > > at an offset of 2 kHz while running at full gain, Noise Figure > of 8db on > > 10m. I have one here. The downside is that each one of the > three VHF roofing > > > > filters / embedded amplifiers selected draws 240 mA. > > > > There's also the issue of price.... > > > With double conversion, in addition to true "IF Shift" a form > of continuous > > > > bandwidth control can also be introduced. > > > _______________________________________________ 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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Wow. Thanks Don!!
john-n4dsp ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: <[hidden email]>; <[hidden email]>; <[hidden email]> Sent: Tuesday, August 08, 2006 8:39 PM Subject: RE: [Elecraft] Why no IF shift ? > Folks, (long philosophical response - delete if not interested in my > opinion). > > Some very good points mentioned in this thread, but the reality of all of > it > is compromise. > For any given price target, some tradeoffs must be made. If I can > interpret > the K2 design goals loosely, the dynamic range was considered uppermost, > and > good sensitivity and IP3 performance running a close second. To achieve > that in a kit product, single conversion IMHO is the only realistic way to > go. > > Yes, there ae very good designs out there for multi-conversion receivers > and > they have their costs and limitations, but the K2 is a compromise of all > that. It is single conversion because that is the way to contain the > dynamic range and good IP3 characteristics within the chosen price range. > It is well known that one must get into the $3K+++ transceivers to achieve > those receive parameters that K2/100 owners have achieved for less than > half > that price. > > Certainly, IF shift is not an easy acomplishment with a single conversion > transceiver. Answering one question posed in the thread which asked why a > BFO frequency knob would not do the deed - the answer is YES, BUT - if > only > the BFO frequency is changed, the displayed frequency would no longer be > correct - the firmware currently corrects for both the BFO and VFO > frequencies and displays the correct carrier frequency, so while passband > tuning might be accomplished simply by changing the BFO, the VFO would > have > to be altered manually to compensate for the BFO shift, and the resulting > frequency on the dial would be incorrect. We used to do exactly that on > receivers with a variable BFO, but then we did not have digital dials that > were good to the nearest 10 Hz (but I digress). When CAL FIL is run, all > that is taken into consideration in the firmware, and the EEPROM values > contain the result of that calibration run which produces correct carrier > frequency dial readings - you have to give up one thing to gain another in > any design process unless 'price is no object'. > > If the world were perfect, we would all have receivers with a 120+ dB > dynamic range, straight sided selectivity curves (with perfectly flat pass > band shapes and no change in group delay across the passband), MDS figures > in the -160 dB range and all that at a cost of less than $100 - of course > I > am dreaming based on today's technology and price/performance criteria > that > would be within the budget of the majority of hams. There is no sense in > developing a superior design for production that would sell only one unit > because of the cost involved - that is the stuff that extreme designs can > produce, but those are currently the stuff of advanced homebrewers - they > are the designs of tomorrow when the price of such designs comes down to > an > affordable level suitable for production. > > > 73, > Don W3FPR > > >> -----Original Message----- >> From: [hidden email] >> [mailto:[hidden email]]On Behalf Of [hidden email] >> Sent: Tuesday, August 08, 2006 7:27 PM >> To: [hidden email]; [hidden email] >> Subject: Re: [Elecraft] Why no IF shift ? >> >> >> In a message dated 8/8/06 6:41:46 AM Eastern Daylight Time, >> [hidden email] writes: >> >> >> > One problem with single down conversion receivers is that their >> > "stronger" spurious responses which, depending on the IF used, >> can be close >> > to or even in one or more of the frequency bands covered by the >> receiver. >> >> How? >> >> In a single conversion superhet, the most important spurs are the >> image and >> IF feedthrough. In the case of a K2, the image is always about >> 9.830 MHz from >> the desired signal, and the IF is around 4.915 MHz. The bandpass >> filters take >> care of those spurs very well, in my experience. >> >> If >> > >> > bandpass filters are used between the antenna connector and the >> mixer, their >> > >> > selectivity might offer some degree of protection against >> signals coming in >> > at spurious response frequencies outside but close to the bands >> covered but >> > obviously no protection against anything coming in at an >> "in-band" spurious >> > response frequency. >> >> What in band spurs exist in the K2? >> >> The choice of IF that reduces this problem in a single >> > >> > down conversion receiver is quite limited. >> > >> > In a double conversion receiver, up and then down, assuming >> that sensible >> > design and construction practices are followed, the close or in-band >> > spurious responses (if they exist) are considerably reduced. >> > >> >> That may be the case in a general-coverage receiver, but in a >> ham-bands-only >> design, the spurious responses are easily handled by good input filters. >> >> > Then there is the internal birdie problem, usually created by >> one or more >> > of >> > the receiver's oscillators and /or their harmonics getting together to >> > produce a signal at some spurious response frequency of the receiver. >> >> Again, this is dependent on the design. For a ham-bands-only >> receiver, the >> birdies can be placed outside the ham bands. >> >> If the >> > >> > Front End, LO and IF are not properly shielded in separate >> "boxes" with all >> > associated DC and control lines filtered, then expect birdies >> in a single >> > down conversion receiver. The same method of construction >> should be used in >> > a double conversion receiver. I suspect that commercial double >> conversion >> > amateur receivers have received a bad press because for reasons >> of cost this >> > >> > is usually not done. >> > >> >> There are some very good up/down double conversion amateur receivers. But >> they all suffer from the same problem: The signal has to go >> through several >> stages and conversions before it gets to the sharp filters. In a >> single conversion >> design like the K2, the number of stages and conversions between >> antenna and >> sharp filter is minimized. >> >> >> > It is true that every conversion degrades the performance, but >> for several >> > years the technology has been available that allows a double conversion >> > receiver to be built which exhibits an IIP3 of +40dbm >> > at an offset of 2 kHz while running at full gain, Noise Figure >> of 8db on >> > 10m. I have one here. The downside is that each one of the >> three VHF roofing >> > >> > filters / embedded amplifiers selected draws 240 mA. >> > >> >> There's also the issue of price.... >> >> > With double conversion, in addition to true "IF Shift" a form >> of continuous >> > >> > bandwidth control can also be introduced. >> > >> > > _______________________________________________ > 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 Free Edition. > Version: 7.1.405 / Virus Database: 268.10.7/411 - Release Date: 8/7/2006 > > _______________________________________________ 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 Wilhelm-3
Hi Group,
PRESS your delete button now if you don't like long winded arguement. For the price paid for K2, we have the chance to enjoy exceptionally RX performance near the top end transceivers. Naturally, we have to give up something e.g. band scope specturm, manual notch within AGC loop, IF shift, band pass tuning, FM mode and general TX/RX coverage etc Part of the price paid for K2 is for customer services and support. Elecraft has to be profitable in their business in order to survive. Bearing in mind, quite a portion of the ham population is fond of multiband multifunction all mode rigs. It is nothing wrong for them but competition in the ham rig market is keen. If we are NOT prepared to give up something for such a high performance K2, the price for K2 could be much higher and not affordable by most of the hams. Just taking IC7800 as an example, only 25% of the sale goes to the ham market whereas 75% goes to the institutional users. ICOM earn most of their profit from corporate users. Therefore, you can imagine how many hams can afford high end rigs at high price. For what we got from the K2 is quite a good balance among performance, functions and pricing. Clearly, if there were a new K3 with all the missing functions mentioned in para. 1 above and at similar price tag, I would be delighted to jump into it. However, we have to be realisitc and Eleraft has to make his profit to survive. I share the 'miss' of IF shift and did ask similar question about 4 years ago when I first built my s/n1146. Eventually, I accepted it as a compromise. I have the luck to own / play around most of the top end rigs but I still love my K2. 73 Johnny Siu VR2XMC From: "Don Wilhelm" <[hidden email]> Reply-To: [hidden email] To: <[hidden email]>, <[hidden email]>,<[hidden email]> Subject: RE: [Elecraft] Why no IF shift ? Date: Tue, 8 Aug 2006 20:39:34 -0400 Folks, (long philosophical response - delete if not interested in my opinion). Some very good points mentioned in this thread, but the reality of all of it is compromise. For any given price target, some tradeoffs must be made. If I can interpret the K2 design goals loosely, the dynamic range was considered uppermost, and good sensitivity and IP3 performance running a close second. To achieve that in a kit product, single conversion IMHO is the only realistic way to go. Yes, there ae very good designs out there for multi-conversion receivers and they have their costs and limitations, but the K2 is a compromise of all that. It is single conversion because that is the way to contain the dynamic range and good IP3 characteristics within the chosen price range. It is well known that one must get into the $3K+++ transceivers to achieve those receive parameters that K2/100 owners have achieved for less than half that price. Certainly, IF shift is not an easy acomplishment with a single conversion transceiver. Answering one question posed in the thread which asked why a BFO frequency knob would not do the deed - the answer is YES, BUT - if only the BFO frequency is changed, the displayed frequency would no longer be correct - the firmware currently corrects for both the BFO and VFO frequencies and displays the correct carrier frequency, so while passband tuning might be accomplished simply by changing the BFO, the VFO would have to be altered manually to compensate for the BFO shift, and the resulting frequency on the dial would be incorrect. We used to do exactly that on receivers with a variable BFO, but then we did not have digital dials that were good to the nearest 10 Hz (but I digress). When CAL FIL is run, all that is taken into consideration in the firmware, and the EEPROM values contain the result of that calibration run which produces correct carrier frequency dial readings - you have to give up one thing to gain another in any design process unless 'price is no object'. If the world were perfect, we would all have receivers with a 120+ dB dynamic range, straight sided selectivity curves (with perfectly flat pass band shapes and no change in group delay across the passband), MDS figures in the -160 dB range and all that at a cost of less than $100 - of course I am dreaming based on today's technology and price/performance criteria that would be within the budget of the majority of hams. There is no sense in developing a superior design for production that would sell only one unit because of the cost involved - that is the stuff that extreme designs can produce, but those are currently the stuff of advanced homebrewers - they are the designs of tomorrow when the price of such designs comes down to an affordable level suitable for production. 73, Don W3FPR _______________________________________________ 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: Why no IF shift ?
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In reply to this post by N2EY
Jim,
Have just been able to get to read your e-mail. Will answer in full later today - 02:50 am at the moment - probably direct to avoid using Discussion List bandwidth. 73, Geoff GM4ESD ----- Original Message ----- From: [hidden email] To: [hidden email] ; [hidden email] Sent: Wednesday, August 09, 2006 12:27 AM Subject: Re: [Elecraft] Why no IF shift ? In a message dated 8/8/06 6:41:46 AM Eastern Daylight Time, [hidden email] writes: One problem with single down conversion receivers is that their "stronger" spurious responses which, depending on the IF used, can be close to or even in one or more of the frequency bands covered by the receiver. How? <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 |
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In reply to this post by PE1E
In a message dated 8/8/06 9:53:06 PM Eastern Daylight Time,
[hidden email] writes: > Have just been able to get to read your e-mail. Will answer in full later > today - 02:50 am at the moment - probably direct to avoid using Discussion > List bandwidth. > Greetings, I strongly suggest replying to the Elecraft reflector too, because it's important to the Elecraft product line. I'm pretty sure the moderators would like to see all sides of the issue. Who knows - it might influence the design of a future Elecraft rig. 73 de Jim, N2EY _______________________________________________ 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 PE1E
In a message dated 8/8/06 8:41:15 PM Eastern Daylight Time,
[hidden email] writes: > but the reality of all of it is compromise. > For any given price target, some tradeoffs must be made. If I can interpret > the K2 design goals loosely, the dynamic range was considered uppermost, and > good sensitivity and IP3 performance running a close second. (snip of excellent discussion) I agree with all that, but would add a bit more: *All* rig designs are compromises/tradeoffs - just different ones. Besides the above criteria, Elecraft designs focus on low power requirement, low complexity, minimal use of custom parts, user constructability and serviceability, and small size/weight without going all surface mount. Many other designs, including some considered "portable", accept massive increases in complexity, power requirement, and use of special parts to achieve their design goals. User serviceability is usually minimal - beyond a certain very basic point, you either have to be a skilled technician with lots of test gear, or you send the rig to one. That's not to say either approach is "right" or "wrong", just that they accept very different tradeoffs. 73 de Jim, N2EY _______________________________________________ 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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[hidden email] wrote:
> User serviceability is usually minimal - beyond a certain > very basic point, you either have to be a skilled technician with lots of test > gear, or you send the rig to one. > > That's not to say either approach is "right" or "wrong", just that they > accept very different tradeoffs. > You said a mouthful there Jim -- GB & 73's KA5OAI Sam Morgan _______________________________________________ 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 PE1E
The TS-820 is single conversion & has IF shift, does it not?
IF shift is handiest I find for CW, as chance to move passband such that unwanted signal outside or down the skirt. IF shift on SSB tends to result in moving passband on to another signal. Much prefer the good skirts from cascaded filters on CW, rather than upper skirt of one filter & lower skirt of other with variable bandwidth tuning. And much prefer VBT on SSB, as can cut down to just enough to understand what is being said if need be. The K2 is a nice rig, but really wasn't intended for something demanding like (c-word deleted). I have yet to turn in a top ten world score in a (c-word deleted) with the K2, but can do so with TS-950/IC-765. K2 only used as substitute if one of those dies. I find IF gymnastics indispensable even for (d-word deleted), as well as well as good IF filtering - something in mainstream rigs now for decades. Neither really needed for something with say backpacking in mind - K2 rather lacking in latter, but more than adequate for more pedestrian-like operation & therefore many will not agree at all. Hopefully one day Elecraft will come up with a product that is something like an all solid-state kit form of a modernized TS-820, provided it has decent IF filters or chance to put something better (preferably plural) in that would make it possible to not need VBT. 73, VU/VR2BrettGraham _______________________________________________ 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 PE1E
In a message dated 8/10/06 1:39:55 PM Eastern Daylight Time,
[hidden email] writes: > The TS-820 is single conversion & has IF shift, does it not? The TS-820 is not single conversion. It is either double or triple conversion. 73 de Jim, N2EY _______________________________________________ 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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Incorrect - it is definitely single conversion, using an analogue PLL
local oscillator and 8.83Mhz IF 73, Dave G3VGR [hidden email] wrote: > In a message dated 8/10/06 1:39:55 PM Eastern Daylight Time, > [hidden email] writes: > > > >>The TS-820 is single conversion & has IF shift, does it not? > > > The TS-820 is not single conversion. It is either double or triple > conversion. > > 73 de Jim, N2EY > _______________________________________________ > 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 PE1E
In a message dated 8/10/06 7:03:23 PM Eastern Daylight Time, [hidden email]
writes: > Incorrect - it is definitely single conversion, using an analogue PLL > local oscillator and 8.83Mhz IF > > Right you are - I was thinking of the 520. Sorry for the confusion! 73 de Jim, N2EY _______________________________________________ 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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