K3 & ADAT ADT-200A by HB9CBU
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Hi,
has anybody done a serious test of the ADT-200A transceiver yet? <http://www.adat.ch/index_e.html> <http://www.adat.ch/pub/Presentation_Hamfest_22-09-07.pdf> <http://www.adat.ch/pub/ADT-200A_Messresultate_V10.pdf> It would be rather interesting to see how the concept used by the K3 (24 bit digitalization after IF) compares in the real world to the early 14 bit digitalization as used by the ADT-200A (and afaik by the Perseus RX from Microtelecom), especially with the chips available currently. The adaptive predistortion transmitter linearization used by HB9CBU in the ADT-200A would be cool in the K3... vy 73 de toby _______________________________________________ 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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Hi,
I, too, would be very interested in seeing how "entire HF spectrum digitized at once" receivers would fare in the real world. I am *very* skeptical. Although the Perseus (with that architecture) receiver fares relatively well in the recent ARRL test, the testing completely ignores what happens when there are not *two* but thousands of strong signals in the passband. With this new architecture, it's imperative that ARRL and other labs find other ways of evaluating real world performance as a simple two-tone test becomes completely irrelevant.
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re: K3 & ADAT ADT-200A by HB9CBU
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In reply to this post by dj7mgq
AB2TC wrote:
>Hi, > >I, too, would be very interested in seeing how "entire HF spectrum digitized >at once" receivers would fare in the real world. I am *very* skeptical. >Although the Perseus (with that architecture) receiver fares relatively well >in the recent ARRL test, the testing completely ignores what happens when >there are not *two* but thousands of strong signals in the passband. With >this new architecture, it's imperative that ARRL and other labs find other >ways of evaluating real world performance as a simple two-tone test becomes >completely irrelevant. Toby Deinhardt wrote: > > Hi, > > has anybody done a serious test of the ADT-200A transceiver yet? > > <http://www.adat.ch/index_e.html> > <http://www.adat.ch/pub/Presentation_Hamfest_22-09-07.pdf> > <http://www.adat.ch/pub/ADT-200A_Messresultate_V10.pdf> > > It would be rather interesting to see how the concept used by the K3 (24 > bit digitalization after IF) compares in the real world to the early 14 > bit digitalization as used by the ADT-200A (and afaik by the Perseus RX > from Microtelecom), especially with the chips available currently. > <snip> > > The Perseus actually out performs the K3 receiver regardless of what the recent ARRL test reports. I agree that the ARRL needs to come up with valid tests to evaluate real world performance of digital receivers such as the Perseus, ADT-200A, and QS1R. -- Phil Covington Software Radio Laboratory LLC Columbus, Ohio http://www.srl-llc.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 ab2tc
On Mon, 2008-12-01 at 06:35, ab2tc wrote:
> Hi, > > I, too, would be very interested in seeing how "entire HF spectrum digitized > at once" receivers would fare in the real world. I am *very* skeptical. > Although the Perseus (with that architecture) receiver fares relatively well > in the recent ARRL test, It compares well for third-order intermodulation distortion, but not for blocking dynamic range. The A/D converter is very linear within its range, so you can get some fantastic TOI (third-order intercept) numbers if you measure with signals near the top of the ADC range. However the ADC full-scale signal level is less than a conventional mixer can handle. > the testing completely ignores what happens when > there are not *two* but thousands of strong signals in the passband. Exactly. > With > this new architecture, it's imperative that ARRL and other labs find other > ways of evaluating real world performance as a simple two-tone test becomes > completely irrelevant. > > Toby Deinhardt wrote: > > > > Hi, > > > > has anybody done a serious test of the ADT-200A transceiver yet? > > > > <http://www.adat.ch/index_e.html> > > <http://www.adat.ch/pub/Presentation_Hamfest_22-09-07.pdf> > > <http://www.adat.ch/pub/ADT-200A_Messresultate_V10.pdf> > > > > It would be rather interesting to see how the concept used by the K3 (24 > > bit digitalization after IF) compares in the real world to the early 14 > > bit digitalization as used by the ADT-200A (and afaik by the Perseus RX > > from Microtelecom), especially with the chips available currently. > > <snip> > > > > > > > ----- > AB2TC - Knut Al N1AL _______________________________________________ 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 & ADAT ADT-200A by HB9CBU
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In reply to this post by Philip Covington
Philip Covington wrote on Monday, December 01, 2008 at 3:13 PM
> The Perseus actually out performs the K3 receiver regardless of what > the recent ARRL test reports. I agree that the ARRL needs to come up > with valid tests to evaluate real world performance of digital > receivers such as the Perseus, ADT-200A, and QS1R. ------------------------------------------------------------- Perhaps some test similar to the wideband 'noise loading' tests performed on multichannel microwave systems would be useful. A problem that might arise is IMD generated by the test equipment's bandstop filter used to prevent noise input within the tested receiver's ultimate passband. 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 Alan Bloom
Correct. I believe the Perseus only has a 14-bit ADC so it's more limited in dynamic range than the 24-bit ADCs commonly used by other SDR rigs. Its dynamic range may be OK for IMD but today's SDRs cannot approach the BDR of rigs like the K3 until even higher resolution ADCs become available. I believe the best BDR I've seen for any SDR is the Flex 5000, which has just over 120 dB...the K3 is better by about 20 dB. 73, Bill W4ZV P.S. How many hits for "1000 " or "5000 " in the contest soapbox so far? ZERO. (Which says something about SDRs in use by real contesters). |
Re: K3 & ADAT ADT-200A by HB9CBU
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On Mon, Dec 1, 2008 at 1:29 PM, Bill W4ZV <[hidden email]> wrote:
> > > > Alan Bloom wrote: >> >> On Mon, 2008-12-01 at 06:35, ab2tc wrote: >>> Hi, >>> >>> I, too, would be very interested in seeing how "entire HF spectrum >>> digitized >>> at once" receivers would fare in the real world. I am *very* skeptical. >>> Although the Perseus (with that architecture) receiver fares relatively >>> well >>> in the recent ARRL test, >> >> It compares well for third-order intermodulation distortion, but not for >> blocking dynamic range. The A/D converter is very linear within its >> range, so you can get some fantastic TOI (third-order intercept) numbers >> if you measure with signals near the top of the ADC range. However the >> ADC full-scale signal level is less than a conventional mixer can >> handle. >> > > Correct. I believe the Perseus only has a 14-bit ADC so it's more limited > in dynamic range than the 24-bit ADCs commonly used by other SDR rigs. Its > dynamic range may be OK for IMD but today's SDRs cannot approach the BDR of > rigs like the K3 until even higher resolution ADCs become available. > > I believe the best BDR I've seen for any SDR is the Flex 5000, which has > just over 120 dB...the K3 is better by about 20 dB. > > 73, Bill W4ZV > > P.S. How many hits for "1000 " or "5000 " in the contest soapbox so far? > ZERO. (Which says something about SDRs in use by real contesters). This is not correct. You can't just compare the number of bits without taking into consideration the ADC sampling rate and signal bandwidth. Please see the concept of "signal processing gain" or "process gain". A SDR such as the Perseus with a 14 bit ADC gains dynamic range by the process of decimation/filtering. If a 14 bit ADC is sampling at 80 MSPS and you are decimating to common filter bandwidths used for CW signals, ex. 500 Hz, there is an increase of dynamic range by 10 log(80e6/500) = 52 dB. The 14 bit ADC used in Perseus is rated at ~77 dB SNR at 15 MHz. With decimation the dynamic range is increased to approx. 77 dB + 52 dB = 129 dB. Another example is the QS1R's 16 bit ADC rated at ~77 dB SNR at 30 MHz. The ADC samples at 125 MSPS. 10 log(125e6/500) = 54 dB, so dynamic range after decimation is approx. 77 dB + 54 dB = 131 dB. Many of the better 24 bit audio ADCs used in SDRs are capable of 120 - 124 dB of dynamic range at *best*. I believe the K3's PCM1804 24 bit ADC is rated at 112 dB SNR. The AK5394A 24 bit ADC used in the Flex-5000 series radios has a rated SNR of 123 dB. For ADCs the SNR is pretty much the same as dynamic range. 73 Phil N8VB -- Phil Covington Software Radio Laboratory LLC Columbus, Ohio http://www.srl-llc.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 & ADAT ADT-200A by HB9CBU
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> This is not correct. You can't just compare the number of > bits without taking into consideration the ADC sampling rate > and signal bandwidth. Please see the concept of "signal > processing gain" or "process gain". The concept of processing gain is completely different than blocking dynamic range. The maximum large signal capability of any DAC has an absolute limit based on the largest integer the DAC can resolve and the DAC reference voltage. When more than one signal is present within the "window" (DC to maximum frequency) of the DAC the DAC needs to be able to handle the sum of the instantaneous peak (vector maximum) voltages not their average levels. No amount of decimation and processing will reduce the instantaneous peak voltage that the ADC must handle to prevent overload. The clipping (overload) level results in distortion (IMD) or imposes an operating condition that must be prevented by the application of hardware AGC (gain reduction) ahead of the ADC (blocking). Decimation and processing gain are only of value as long as he hardware is operating within its linear range. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Philip > Covington > Sent: Monday, December 01, 2008 3:21 PM > To: Bill W4ZV > Cc: [hidden email] > Subject: Re: [Elecraft] K3 & ADAT ADT-200A by HB9CBU > > > On Mon, Dec 1, 2008 at 1:29 PM, Bill W4ZV > <[hidden email]> wrote: > > > > > > > > Alan Bloom wrote: > >> > >> On Mon, 2008-12-01 at 06:35, ab2tc wrote: > >>> Hi, > >>> > >>> I, too, would be very interested in seeing how "entire HF > spectrum > >>> digitized at once" receivers would fare in the real world. I am > >>> *very* skeptical. Although the Perseus (with that architecture) > >>> receiver fares relatively well > >>> in the recent ARRL test, > >> > >> It compares well for third-order intermodulation > distortion, but not > >> for blocking dynamic range. The A/D converter is very > linear within > >> its range, so you can get some fantastic TOI (third-order > intercept) > >> numbers if you measure with signals near the top of the > ADC range. > >> However the ADC full-scale signal level is less than a > conventional > >> mixer can handle. > >> > > > > Correct. I believe the Perseus only has a 14-bit ADC so it's more > > limited in dynamic range than the 24-bit ADCs commonly used > by other > > SDR rigs. Its dynamic range may be OK for IMD but today's > SDRs cannot > > approach the BDR of rigs like the K3 until even higher > resolution ADCs > > become available. > > > > I believe the best BDR I've seen for any SDR is the Flex > 5000, which > > has just over 120 dB...the K3 is better by about 20 dB. > > > > 73, Bill W4ZV > > > > P.S. How many hits for "1000 " or "5000 " in the contest > soapbox so > > far? ZERO. (Which says something about SDRs in use by real > > contesters). > > This is not correct. You can't just compare the number of > bits without taking into consideration the ADC sampling rate > and signal bandwidth. Please see the concept of "signal > processing gain" or "process gain". A SDR such as the > Perseus with a 14 bit ADC gains dynamic range by the process > of decimation/filtering. If a 14 bit ADC is sampling at 80 > MSPS and you are decimating to common filter bandwidths used > for CW signals, ex. 500 Hz, there is an increase of dynamic > range by 10 log(80e6/500) = 52 dB. The 14 bit ADC used in > Perseus is rated at ~77 dB SNR at 15 MHz. With decimation > the dynamic range is increased to approx. 77 dB + 52 dB = 129 dB. > > Another example is the QS1R's 16 bit ADC rated at ~77 dB SNR > at 30 MHz. The ADC samples at 125 MSPS. 10 log(125e6/500) = > 54 dB, so dynamic range after decimation is approx. 77 dB + > 54 dB = 131 dB. > > Many of the better 24 bit audio ADCs used in SDRs are capable > of 120 - 124 dB of dynamic range at *best*. I believe the > K3's PCM1804 24 bit ADC is rated at 112 dB SNR. The AK5394A > 24 bit ADC used in the Flex-5000 series radios has a rated > SNR of 123 dB. For ADCs the SNR is pretty much the same as > dynamic range. > > 73 Phil N8VB > -- > Phil Covington > Software Radio Laboratory LLC > Columbus, Ohio > http://www.srl-llc.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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...which is why the hybrid approach of a narrow roofing filter before the ADC works so well in Orion and the K3. The narrow roofing filters limit extremely strong signals outside the passband which would otherwise kick in ADC protection AGC. I don't think there's a way around the fundamental limitation of ADC resolution in the direct conversion designs. Phil, on the QS-1R specifications webpage, I see BDR is specified at 125 dB...very similar to the Flex 5000's 123 dB. I haven't seen any independent measurements of the QS-1R yet, but hope one will be forthcoming by ARRL. Until SDR receivers are in the same >140 dB league of the K3, I'm not sure the contest community will bite this apple. When higher resolution ADCs eventually become available at a reasonable price, I'm sure the situation will change. 73, Bill |
Re: K3 & ADAT ADT-200A by HB9CBU
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In reply to this post by Joe Subich, W4TV-3
On Mon, Dec 1, 2008 at 3:56 PM, Joe Subich, W4TV <[hidden email]> wrote:
> >> This is not correct. You can't just compare the number of >> bits without taking into consideration the ADC sampling rate >> and signal bandwidth. Please see the concept of "signal >> processing gain" or "process gain". > > The concept of processing gain is completely different than > blocking dynamic range. The maximum large signal capability > of any DAC has an absolute limit based on the largest integer > the DAC can resolve and the DAC reference voltage. When more > than one signal is present within the "window" (DC to maximum > frequency) of the DAC the DAC needs to be able to handle the > sum of the instantaneous peak (vector maximum) voltages not > their average levels. > > No amount of decimation and processing will reduce the > instantaneous peak voltage that the ADC must handle to > prevent overload. The clipping (overload) level results > in distortion (IMD) or imposes an operating condition that > must be prevented by the application of hardware AGC (gain > reduction) ahead of the ADC (blocking). Decimation and > processing gain are only of value as long as he hardware > is operating within its linear range. > > 73, > > ... Joe, W4TV I assume you mean ADC above and not DAC... You are right that if you exceed the maximum voltage level into the ADC no amount of processing gain will change this fact. What the processing gain does give you is the ability to hear weak signals that are much lower than the 14 or 16 bit ADC without decimation would be capable of hearing. The weakest signal that can be resolved plays just as important a part in the calculation of the blocking dynamic range of a receiver as its strong signal handling capability - and this is true whether we are talking about ADCs or analog receivers. -- Phil Covington Software Radio Laboratory LLC Columbus, Ohio http://www.srl-llc.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 dj7mgq
On Monday, December 01, 2008, at 01:16PM, "Bill W4ZV" <[hidden email]> wrote: >...which is why the hybrid approach of a narrow roofing filter before the >ADC works so well in Orion and the K3. Bill is correct. Think of this this way: the clipping level of a codec does not change, but the noise floor of the processed passband falls. You gain nothing anymore only after the Nyquist rate of the signal of interest has exceeded (think energy density) the decimated sampling rate. 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 |
Re: K3 & ADAT ADT-200A by HB9CBU
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In reply to this post by Bill W4ZV
On Mon, Dec 1, 2008 at 4:16 PM, Bill W4ZV <[hidden email]> wrote:
> > > > Joe Subich, W4TV-3 wrote: >> >> >>> This is not correct. You can't just compare the number of >>> bits without taking into consideration the ADC sampling rate >>> and signal bandwidth. Please see the concept of "signal >>> processing gain" or "process gain". >> >> The concept of processing gain is completely different than >> blocking dynamic range. The maximum large signal capability >> of any DAC has an absolute limit based on the largest integer >> the DAC can resolve and the DAC reference voltage. When more >> than one signal is present within the "window" (DC to maximum >> frequency) of the DAC the DAC needs to be able to handle the >> sum of the instantaneous peak (vector maximum) voltages not >> their average levels. >> >> No amount of decimation and processing will reduce the >> instantaneous peak voltage that the ADC must handle to >> prevent overload. The clipping (overload) level results >> in distortion (IMD) or imposes an operating condition that >> must be prevented by the application of hardware AGC (gain >> reduction) ahead of the ADC (blocking). Decimation and >> processing gain are only of value as long as he hardware >> is operating within its linear range. >> > > ...which is why the hybrid approach of a narrow roofing filter before the > ADC works so well in Orion and the K3. The narrow roofing filters limit > extremely strong signals outside the passband which would otherwise kick in > ADC protection AGC. I don't think there's a way around the fundamental > limitation of ADC resolution in the direct conversion designs. > > Phil, on the QS-1R specifications webpage, I see BDR is specified at 125 > dB...very similar to the Flex 5000's 123 dB. I haven't seen any independent > measurements of the QS-1R yet, but hope one will be forthcoming by ARRL. > Until SDR receivers are in the same >140 dB league of the K3, I'm not sure > the contest community will bite this apple. When higher resolution ADCs > eventually become available at a reasonable price, I'm sure the situation > will change. > > 73, Bill > There is no "ADC protection AGC" in the Perseus or the QS1R. Perseus ADC begins clipping somewhere around -3 dBm without attenuation. QS1R begins clipping at +9 dBm. Perseus already outperforms the K3's receiver regardless of the ARRL's claimed 140 dB BDR of the K3. The ARRL test of the Perseus was in error (which has been pointed out) and hopefully they will be publishing a correction soon. As more ops get experience with these direct sampling receivers, there will be many more converts. Unfortunately there is a huge amount of misinformation out there regarding SDR hardware and this is a contributing problem. None of this is meant to disparage the excellent K3. I am eying one myself. -- Phil Covington Software Radio Laboratory LLC Columbus, Ohio http://www.srl-llc.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 & ADAT ADT-200A by HB9CBU
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In reply to this post by dj7mgq
Forward on behalf of Leif SM5BSZ:
_______________________________ Hi All, I am not a member on the Elecraft list, but I did work quite some time on this issue: > I, too, would be very interested in seeing how "entire HF spectrum digitized > at once" receivers would fare in the real world. I am *very* skeptical. > Although the Perseus (with that architecture) receiver fares relatively well > in the recent ARRL test, the testing completely ignores what happens when > there are not *two* but thousands of strong signals in the passband. With > this new architecture, it's imperative that ARRL and other labs find other > ways of evaluating real world performance as a simple two-tone test becomes > completely irrelevant. You are right. The "simple two-tone" test is irrelevant for units like the Perseus or the SDR-14. Have a look here (QEX Nov/Dec 2006): http://www.sm5bsz.com/dynrange/qex/digital-imd.pdf and here (for real life testing on 7MHz): http://www.sm5bsz.com/digdynam/practical.htm There are two properties one has to characterize when testing the dynamic range of a radio receiver. 1) The ability to receive a small signal in the presence of a single dominating interference. What has been published by ARRL is totally wrong and should just be discarded. The procedure adopted by the ARRL is intended to measure the point where the front-end goes 1 dB into saturation (or rather any stage preceeding the bandwidth-defining final filter.) The FT1000D is not at -154 dB for example: (QEX Mar/Apr 2006): http://www.sm5bsz.com/dynrange/qex/bdr.pdf Even in those cases where the ARRL Lab BDR is correctly measured (to give 1 dB gain compression) the result is not at all the blocking dynamic range as understood in the professional world where it refers to the ratio (difference in dB) between the strongest and the weakest signals that can be simultaneously present without loss of readability of the weakest signal. Surely the bandwidth, modulation type, frequency separation and other things have to be specified, but generally the mechanism is reciprocal mixing at narrow frequency separations (or some other phenomrnon that behaves in a similar fashion. e.g. AM modulation in preamplifiers.) I like to call this the "two-signal dynamic range" (one strong and one weak.) 2) The linearity of stages preceeding the bandwidth-limiting filter. Conventionally this is measured with "a simple two-tone test" Such measurements are often incorrect for various reasons, but in recent years they are generally more reliable since a better understanding for the problems is now widespread in the ham community. I prefer to call this test "the three-signal dynamic range" One weak plus two (equall) strong signals. The point of 1 dB compression is closely related to IP3 in those cases (large separations) where the attenuation for all the test tones would be the same. There is yet another way to measure the same thing and that is by measurement of cross modulation. (How strong can a 60% modulated AM signal be before it modulates the desired weak signal with x% AM modulation?) As it turns out, worst case is with only two signals so the best measurement is a two-tone test. One has to follow the interference all the way to the noise floor. (And below in case the modulation mode is operated below the noise floor of the main filter. As an example, CW is typically operated down to 15 dB below the noise floor since the human ear has an effective bandwidth of less than 50Hz) The link above, QEX Nov/Dec 2006, shows that the level of the interference at the frequency of third order intermodulation is independent of the signal level. It stays constant at about -100 dBm for a SDR-14 which is high above the intrinsic noise floor. There are also signals at a similar level corresponding to IM5, IM7, IM9, IM11, ... The mechanism is feedback from the 3 volt p-p signals at the digital side. Linear has cips LTC2207 and others that reduce this feedback by 15dB according to their own information if I remember correctly. What I can measure on the Perseus is that IM3 flattens out at about -125 dBm: http://www.sm5bsz.com/perseus/perseus.htm The Perseus has NF=22 dB while the SDR-14 has NF=12 dB. The intermodulation-free dynamic range is 104 dB for the Perseus, but only when the A/D converter is operated at the largest possible signal level. For the SDR-14 it is 82 dB. In real life there are more than two strong signals and that improves the performance drastically since the phase-stability of the signals on the digital side is destroyed (dithering.) A radio like the Perseus would probably outperform a conventional radio like the IC-7800 in a A/B test on e.g. 7 MHz with real antennas and many BC stations provided a location can be found where many BC stations are strong enough to produce false signals on any of the receivers. The IC7800 has a dynamic range of 104 dB according to ARRL but it would not be as favourably affected by a large number of strong signals. For close range intermodulation (5 kHz and below) the Perseus would outperform the IC-7800 with a large margin. Provided, of course, that the antenna signal is strong enough. For optimum performance, the operator must know how to place a suitable attenuator or amplifier between the antenna and the receiver to place the dynamic range at the correct posuition. In a real life blocking test, the Perseus outperforms the IC-7800 with a wide margin. Someone actually tested and wrote about it on the Perseus mailing list. > > It would be rather interesting to see how the concept used by the K3 (24 > > bit digitalization after IF) compares in the real world to the early 14 > > bit digitalization as used by the ADT-200A (and afaik by the Perseus RX > > from Microtelecom), especially with the chips available currently. The K3 strategy should not have any problems with noise pick-up from the digital side so the level where "intermodulation" flattens out should be very low. My own design, WSE2500+Delta44 with NF=17 dB flattens out at -140dBm (QEX JanFeb 2004): http://www.sm5bsz.com/linuxdsp/qex/040102qex020.pdf On the other hand, the blocking or rather reciprocal mixing test on the K3 will be limited by the VCO which is -120dBc/Hz at 2 kHz and 141dBc/Hz at 20 kHz (QST April 2008) This converts to blocking dynamic ranges of 93 and 114 dB respectively for K3. The Perseus is MUCH better, 115 and 123 respectively. (ARRL Lab made a mistake in the December issue which I expect they will correct in a coming issue.) In real life, better reciprocal mixing is not yet important because ALL amateur transmitters have too much sideband noise, keying clicks and other impurities that dominate over the performance of a really good modern receiver. Soon someone will start to sell the inverse of Perseus for our transmitters and they will allow drastical improvements on the transmit side. Same band, multi-transmitter operations from field-days and other activities will become much easier in the future:-) 73 Leif / SM5BSZ _______________________________________________ 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 & ADAT ADT-200A by HB9CBU
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In reply to this post by Bill W4ZV
On Mon, Dec 1, 2008 at 1:29 PM, Bill W4ZV <[hidden email]> wrote:
> 73, Bill W4ZV > > P.S. How many hits for "1000 " or "5000 " in the contest soapbox so far? > ZERO. (Which says something about SDRs in use by real contesters). Not from the contest soapbox, but... "GI4NKB Awarded First Place for Northern Ireland in the CQ WW CW 2007 Contest using a FLEX-5000" 73 Phil N8VB _______________________________________________ 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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Isn't the K3 an SDR???
GM4FDM Philip Covington wrote: > On Mon, Dec 1, 2008 at 1:29 PM, Bill W4ZV <[hidden email]> wrote: > > >> 73, Bill W4ZV >> >> P.S. How many hits for "1000 " or "5000 " in the contest soapbox so far? >> ZERO. (Which says something about SDRs in use by real contesters). >> > > Not from the contest soapbox, but... > > "GI4NKB Awarded First Place for Northern Ireland in the CQ WW CW 2007 > Contest using a FLEX-5000" > > 73 Phil N8VB > _______________________________________________ > 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 > > > --- > avast! Antivirus: Inbound message clean. > Virus Database (VPS): 081130-0, 30/11/2008 > Tested on: 01/12/2008 22:25:55 > avast! - copyright (c) 1988-2008 ALWIL Software. > http://www.avast.com > > > > > -- So I met the bloke who invented crosswords today. I can't remember his name, it's P something T something R. --- avast! Antivirus: Outbound message clean. Virus Database (VPS): 081130-0, 30/11/2008 Tested on: 01/12/2008 22:27:29 avast! - copyright (c) 1988-2008 ALWIL Software. http://www.avast.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 Philip Covington
I found GI4NKB in the Assisted Category results on page 20 of CQ's online results pdf: GI4NKB A 431,673 986 63 246 He was also the *only* entrant from Northern Ireland in that category. ;-) 73, Bill |
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Hi,
Also note that the Flex5000 does not have the "digitize the entire HF band at once" architecture but rather uses a I/Q direct conversion approach followed by a pair of audio A/D converters sampling at 192kHz. The OP and my follow-up question was really on how well the convert all of it at once type receiver would fare in the real world.
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In reply to this post by Tom Wylie
Not according to Flex Systems..."Real radios don't need knobs". Maybe not, but so far they don't win HF contests either...unless there are no other entrants in the category. ;-) Technically you're correct. The K3 and most high-end transceivers introduced in the past ~10 years are technically SDRs (but they hide it well). :-) There are at least 3 different variants of SDRs: 1. Hybrid superhet/DSP. Roofing filter front-end followed by DSP (e. g. Orion, K3, IC-7800, etc). 2. Quadrature Sampling Detector (QSD) front-end (e.g. Flex 1000, 5000, etc). 3. Direct Conversion (high speed ADC) front-end (Perseus, QS-1R, HPSDR, etc). 73, Bill |
Re: K3 & ADAT ADT-200A by HB9CBU
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In reply to this post by dj7mgq
Bill W4ZV wrote:
> Correct. I believe the Perseus only has a 14-bit ADC so it's more limited > in dynamic range than the 24-bit ADCs commonly used by other SDR rigs. You probably are unaware that an ADC dynamic range in a given bandwidth does not depend just on its ENOB (effective number of bits) but also on the sampling frequency. > Its dynamic range may be OK for IMD but today's SDRs cannot approach the BDR of > rigs like the K3 until even higher resolution ADCs become available. Sorry to tell you a bad new: you are wrong! Direct sampling receivers have a TRUE dynamic range, at least at small spacings, which is much higher than that of rigs which use IF sampling. This has nothing to do with ADC themselves, but with the receiver LOs. Modern SDRs use crystal grade LOs and digital tuners. IF sampling receivers don't and they ALWAYS suffer the phase noise of their synthesizers. > I believe the best BDR I've seen for any SDR is the Flex 5000, which has > just over 120 dB...the K3 is better by about 20 dB. If we follow the definition of BDR as made by ARRL tests you are right. Unfortunately this definition does not give an exact idea of the true dynamic range of a receiver. I can demonstrate, and I think that Phil can do it as well with his QS1R, that if you feed a so called SDR with a + 7 dBm (S 9+80) carrier interferer, you can comfortably listen to a - 104 dBm (S 4) signal which is 2 kHz apart the interferer. Demonstrate that you can do the same with a receiver which uses a 24-bit ADC at the IF level and I will publicly apologize with you. In the case you can't I will be glad to accept your apologies. "Conventional" radios begins to behave a little better than direct sampling platforms when carrier interferers are at least 100 kHz apart. But please don't say that the close spacing blocking dynamic range of "analog" platforms is 20 dB better than that of good RF sampling radios. This is a really amazing assertion. >...which is why the hybrid approach of a narrow roofing filter before the >ADC works so well in Orion and the K3. The narrow roofing filters limit >extremely strong signals outside the passband which would otherwise kick in >ADC protection AGC. I don't think there's a way around the fundamental >limitation of ADC resolution in the direct conversion designs. This could be true if your receiver LO phase noise were negligible. Unfortuntately it isn't. >Phil, on the QS-1R specifications webpage, I see BDR is specified at 125 >dB...very similar to the Flex 5000's 123 dB. I haven't seen any independent >measurements of the QS-1R yet, but hope one will be forthcoming by ARRL. If they will deserve QS1R the same treatment Perseus had on QST, I wish Phil a very good luck. >Until SDR receivers are in the same >140 dB league of the K3, I'm not sure >the contest community will bite this apple. When higher resolution ADCs >eventually become available at a reasonable price, I'm sure the situation >will change. You are still wrong. The situation is already changed but you are not aware of it yet. You are confusing a figure which is the Blocking Gain Compression with the true dynamic range of a receiver. > P.S. How many hits for "1000 " or "5000 " in the contest soapbox so far? > ZERO. (Which says something about SDRs in use by real contesters). This reasoning is a little bit amazing, I think. Probably in the fourties you had no television set but this did not prevented a television set to enter the home of everyone and yours too. Don't confuse what people knows with what people don't because they haven't seen yet. It takes time for news to be widely accepted, but sooner or later they are. (Doesn't matter if pioneers died meanwhile, life is this way). 73 Nico Palermo, IV3NWV _______________________________________________ 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 that case the BDR would be 111 dB, would it not? I believe the K3 was measured at BDR of 140 dB at 2 kHz spacing on 14 MHz in the most recent ARRL test. Not that we would actually try to operate so close to such a strong signal on CW due to key clicks, etc, but BDR results at wider spacings are very important if there are other stations on the same band (e.g. one on SSB and one on CW in Field Day or during a DXpedition like VP6DX, or if you had a close neighbor on the same band). Can you briefly explain why you feel ARRL's definition of BDR below is not correct? 5.7.1 The purpose of the Blocking Dynamic Range Test is to determine the level of gain compression, or desensitization, that occurs as a result of another signal on a nearby frequency. The blocking dynamic range is the difference between the level of the noise floor from the level of undesired signal that produces a 1 dB decrease in a weak desired signal. Frequencies of 3.520 MHz, 14.020 MHz, 50.020 MHz, 144.020 MHz and 432.020 MHz are used for this test as appropriate for the DUT. The calculation is as follows: Blocking Dynamic Range = Blocking Level - Noise Floor (expressed in dBm) 73, Bill W4ZV |
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