Re: [Elecraft] OT: Dayton New Equipment Show
These were my questions Friday based on the published data sheet: Questions for someone at Flex's Dayton booth: Except for the most demanding large signal conditions, Slice Receivers are free to operate in wide-band mode without the need for RF pre-selection filters. 1. What does most demanding mean? Further, the dual Spectral Capture Units can be optimally combined on the FLEX-6700 and FLEX-6700R to increase Blocking Dynamic Range up to 3 dB and IMD DR3 up to 2 dB. 2. Increase BDR 3 dB better than what? (nothing spec'd on Data Sheet) http://www.eham.net/ehamforum/smf/index.php/topic,82993.30.html No answers yet... 73, Bill W4ZV -- View this message in context: http://elecraft.365791.n2.nabble.com/OT-Dayton-New-Equipment-Show-tp7556083p7556134.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
It will be interesting to hear if the Flex 6000/6700 when used in Europe can deal with the European 40m BC stations. Some data. Over a period of several months when I was in Scotland, I measured the level of these 40m BC signals with which a receiver must cope. Using a 40m dipole at 70ft AGL firing N-S, not a beam, the level of the -carrier- of most of the European 40m BC stations at the shack end of the feeder would reach + 5 to +10 dbm under normal conditions of propagation. And there were many BC signals of similar strength on air at the same time. In this part of Europe the 40m BC signals are not as strong, probably due to being closer to the BC transmitters, which could benefit Flex's sales in Europe. 73, Geoff LX2AO On May 20, 2012 at 2:46 AM, Joe Subich, W4TV wrote: snip However, when one has five or six -33 dBm local signals (easy on 160 or 80 meters during a major contest ... or 40 meters in Europe with the superpower broadcasters just outside the band) the required signal handling is many orders of magnitude higher than just two -23 dBm (S9+60 dB) signals. Instantaneous peak voltages do not add linearly ... they add exponentially. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
Well, when Flex starts charging for software updates. That alone will kill future sales. With all the hype on how great their new lineup is,time will tell. We all know what is on paper and what happens in the real world can be completely different. They learned that you need a dedicated high performance PC to work the software. That was proven from their users with all those problems I have seen on their reflector. At least Elecraft has a proven record of great products. Charlie __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
But then, we may be witnessing another change in the evolution of ham radio where the added value to a rig is in the software and not the hardware. By licensing their SmartSDR, Flex may be realizing that the key factor separating them from the other emerging SDRs lies with their software and not the hardware components. In particular, their DSP as well as the visual user interface. So, the future SDR rig may indeed be the software you load on your computer and the hardware component is nothing but a mere commodity that you pick up from an SDR vendor or throw together yourself. After all, once the key parts of an SDR hardware are made available as various ADC ICs and other components then there is only the software to deal with. I submit that this is indeed the future of ham radio where your new rig is something you download from a software vendor rather then buy at HRO. My two-bits. 73, phil, K7PEH On May 20, 2012, at 9:33 AM, hq1...@aol.com wrote: Well, when Flex starts charging for software updates. That alone will kill future sales. With all the hype on how great their new lineup is,time will tell. We all know what is on paper and what happens in the real world can be completely different. They learned that you need a dedicated high performance PC to work the software. That was proven from their users with all those problems I have seen on their reflector. At least Elecraft has a proven record of great products. Charlie __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
On Sat, May 19, 2012 at 11:53 AM, Edward R. Cole kl...@acsalaska.netwrote: ...website now shows the Flex-6000/6700 newest entry into the SDR market === Said to be digital from antenna connector to output. Their hardware has long needed updating, so perhaps this will be it. However, Flex's really weak link has always been their software/systems integration, so it remains to be seen if this does anything to mitigate that. Tony KT0NY -- http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
The Flex 6000/6700 is an on frequency direct digital conversion radio - that is a 16 bit analog to digital converter operating at the front end of the radio with no intermediate conversion/IF and filtering stages. In addition, all of the DSP is contained in the radio (no more PowerSRD). The new software for the Flex 6000/6700 (reportedly PowerRX) is essentially a glass control panel). A general purpose computer is required for PowerRX but communication between the computer and transceiver is via TCP/IP which means the computer can be anywhere. Audio input and output will be available both on the transceiver and from PowerRX (interesting for remote operation scenarios). The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. The new Flex design is certainly interesting but may not truly be ready for critical real world use with the widely varying signal levels in amateur service. 73, ... Joe, W4TV On 5/19/2012 3:43 PM, Tony Estep wrote: On Sat, May 19, 2012 at 11:53 AM, Edward R. Colekl...@acsalaska.netwrote: ...website now shows the Flex-6000/6700 newest entry into the SDR market === Said to be digital from antenna connector to output. Their hardware has long needed updating, so perhaps this will be it. However, Flex's really weak link has always been their software/systems integration, so it remains to be seen if this does anything to mitigate that. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
decimation counts On 5/19/2012 7:29 PM, Joe Subich, W4TV wrote: The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
Joe, I'm not sure some of your suppositions are correct. First of all, the ADC samples at a significantly higher rate than the incoming RF (for HF), at 245.76MHz. Then, those samples go through decimation inside Digital DownConverter (DDC) in the FPGA, and the higher the decimation, the more the processing gain, and therefore added bits. I believe the typical assumption is that you gain the equivalent of approx. one-half bit (3dB) of dynamic range every time you decimate (divide) the sample rate by two. This is real gain, not some imaginary trick or magic. If you start with a 245.76MHz sample rate, and end up with 240kHz (example), you could achieve a processing gain of an additional five bits, or 30dB. If my quick math is correct. All without AGC or other games. Throw away at least one A/D bit, so 15 bits(ADC) plus five bits(proc gain) yields 20 bits, or about 120dB of dynamic range. I must be a little off, as I saw one note on the Flex reflector that they think 153dB or so of dynamic range. Maybe by lowering the final sample rate some more, or not tossing all of one bit of the ADC. I believe Mitola suggested that 130dB of dynamic range is adequate for HF, I'm not sure if that includes noise from storms, etc. BTW, the new software is called SmartSDR. I have been playing with DDC receivers for a couple of years now, and I firmly believe they will be the future. I suggest that thorough research of DDC-based receiver design will alter your perception. It did mine. I love my K3/P3, and do not plan to replace it anytime soon. It just works GREAT, and is a nice compact box without requiring a computer to use. But, I was very tempted to by a Flex 6500. That is, until I saw the $200 per year charge for the software. Technically, very leading edge. Marketing, you decide. Hope this isn't too off-topic. 73, Terry, WB4JFI -Original Message- From: Joe Subich, W4TV Sent: Saturday, May 19, 2012 7:29 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] OT: Dayton New Equipment Show The Flex 6000/6700 is an on frequency direct digital conversion radio - that is a 16 bit analog to digital converter operating at the front end of the radio with no intermediate conversion/IF and filtering stages. In addition, all of the DSP is contained in the radio (no more PowerSRD). The new software for the Flex 6000/6700 (reportedly PowerRX) is essentially a glass control panel). A general purpose computer is required for PowerRX but communication between the computer and transceiver is via TCP/IP which means the computer can be anywhere. Audio input and output will be available both on the transceiver and from PowerRX (interesting for remote operation scenarios). The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. The new Flex design is certainly interesting but may not truly be ready for critical real world use with the widely varying signal levels in amateur service. 73, ... Joe, W4TV On 5/19/2012 3:43 PM, Tony Estep wrote: On Sat, May 19, 2012 at 11:53 AM, Edward R. Colekl...@acsalaska.netwrote: ...website now shows the Flex-6000/6700 newest entry into the SDR market === Said to be digital from antenna connector to output. Their hardware has long needed updating, so perhaps this will be it. However, Flex's really weak link has always been their software/systems integration, so it remains to be seen if this does anything to mitigate that. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
Decimation can help but it is not a magic bullet that eliminates the effects of ADC overflow and/or blocking due to gain reduction. 73, ... Joe, W4TV On 5/19/2012 7:57 PM, Tom Azlin N4ZPT wrote: decimation counts On 5/19/2012 7:29 PM, Joe Subich, W4TV wrote: The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
Hi Joe, Guess we will have to await independent testing. The Flex folks seem to assert they have the equivalent of more than 24 bit when dealing with adjacent strong signals. From the Flex reflector... Just in rough numbers, you get a 1/2-bit for every divide-by-two decimation you do. If you are looking at dynamic range in a 500Hz bandwidth (this is what we typically do). The math I generally use to get there is log(f1/f2)/log(2)/2. I just think this way as a programmer (do everything in base 2). So if you take log(245.76E6/500)/log(2)/2 you get 9.4 extra bits when added to the 16 gives you 25.5 bits (152.7dB dynamic range). This assumes all 16-bits of the ADC are good which is probably not a good assumption. I'd have to pull out the notes and look at the data sheet again, but this should give you a rough idea. Hopefully I haven't made an additional duh today myself! Bottom line -- there's plenty of dynamic range. Also, if you are interested, we are using Xilinx DSP48E1 blocks which use an 18x25 multiplier and so Xilinx tools generate the on-board DDS as a 25-bit DDS by default --- again to preserve the SFDR of the receiver. We could add extra bits, but 25 are fine for the same reason. Steve Stephen Hicks, N5AC, AAR6AM VP Engineering FlexRadio Systems™ 4616 W Howard Ln Ste 1-150 Austin, TX 78728 Phone: 512-535-4713 x205 Email: steve at flexradio.com Web: www.flexradio.com On 5/19/2012 8:11 PM, Joe Subich, W4TV wrote: Decimation can help but it is not a magic bullet that eliminates the effects of ADC overflow and/or blocking due to gain reduction. 73, ... Joe, W4TV On 5/19/2012 7:57 PM, Tom Azlin N4ZPT wrote: decimation counts On 5/19/2012 7:29 PM, Joe Subich, W4TV wrote: The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
Direct digital conversion radio receivers rarely connect the A/D directly to the antenna input, the term direct referring to a lack of analog frequency conversion (mixing). The Flex 6000 series is no exception to this trend. There is a gain and filter stage ahead of the A/D, and presumably an AGC. This is how dynamic range is managed on this, and many similar receivers. Blocking is a concern, but not even the greatest concern. Analog signal levels should, regardless of the number of discrete measurement steps (bits), should be kept well above the minimum input level to avoid excessive quantization error levels. Mike Alexander - N8MSA amsct...@comcast.net - Original Message - From: Joe Subich, W4TV li...@subich.com To: elecraft@mailman.qth.net Sent: Saturday, May 19, 2012 7:29:24 PM Subject: Re: [Elecraft] OT: Dayton New Equipment Show The Flex 6000/6700 is an on frequency direct digital conversion radio - that is a 16 bit analog to digital converter operating at the front end of the radio with no intermediate conversion/IF and filtering stages. In addition, all of the DSP is contained in the radio (no more PowerSRD). The new software for the Flex 6000/6700 (reportedly PowerRX) is essentially a glass control panel). A general purpose computer is required for PowerRX but communication between the computer and transceiver is via TCP/IP which means the computer can be anywhere. Audio input and output will be available both on the transceiver and from PowerRX (interesting for remote operation scenarios). The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. The new Flex design is certainly interesting but may not truly be ready for critical real world use with the widely varying signal levels in amateur service. 73, ... Joe, W4TV On 5/19/2012 3:43 PM, Tony Estep wrote: On Sat, May 19, 2012 at 11:53 AM, Edward R. Colekl...@acsalaska.netwrote: ...website now shows the Flex-6000/6700 newest entry into the SDR market === Said to be digital from antenna connector to output. Their hardware has long needed updating, so perhaps this will be it. However, Flex's really weak link has always been their software/systems integration, so it remains to be seen if this does anything to mitigate that. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
On 5/19/2012 8:08 PM, wb4...@knology.net wrote: Joe, I'm not sure some of your suppositions are correct. Actually it depends on one's assumption of the number and strength of the signals applied to the front end. 120 dB of spurious free dynamic range is trivial if one is measuring it with *two tones*. However, when one has five or six -33 dBm local signals (easy on 160 or 80 meters during a major contest ... or 40 meters in Europe with the superpower broadcasters just outside the band) the required signal handling is many orders of magnitude higher than just two -23 dBm (S9+60 dB) signals. Instantaneous peak voltages do not add linearly ... they add exponentially. Even with decimation the peak voltage to the ADC can not be allowed to cause an overflow. In addition, one must be concerned about Herr Nyquist ... and minimum sample rates for the highest operating frequency. 73, ... Joe, W4TV On 5/19/2012 8:08 PM, wb4...@knology.net wrote: Joe, I'm not sure some of your suppositions are correct. First of all, the ADC samples at a significantly higher rate than the incoming RF (for HF), at 245.76MHz. Then, those samples go through decimation inside Digital DownConverter (DDC) in the FPGA, and the higher the decimation, the more the processing gain, and therefore added bits. I believe the typical assumption is that you gain the equivalent of approx. one-half bit (3dB) of dynamic range every time you decimate (divide) the sample rate by two. This is real gain, not some imaginary trick or magic. If you start with a 245.76MHz sample rate, and end up with 240kHz (example), you could achieve a processing gain of an additional five bits, or 30dB. If my quick math is correct. All without AGC or other games. Throw away at least one A/D bit, so 15 bits(ADC) plus five bits(proc gain) yields 20 bits, or about 120dB of dynamic range. I must be a little off, as I saw one note on the Flex reflector that they think 153dB or so of dynamic range. Maybe by lowering the final sample rate some more, or not tossing all of one bit of the ADC. I believe Mitola suggested that 130dB of dynamic range is adequate for HF, I'm not sure if that includes noise from storms, etc. BTW, the new software is called SmartSDR. I have been playing with DDC receivers for a couple of years now, and I firmly believe they will be the future. I suggest that thorough research of DDC-based receiver design will alter your perception. It did mine. I love my K3/P3, and do not plan to replace it anytime soon. It just works GREAT, and is a nice compact box without requiring a computer to use. But, I was very tempted to by a Flex 6500. That is, until I saw the $200 per year charge for the software. Technically, very leading edge. Marketing, you decide. Hope this isn't too off-topic. 73, Terry, WB4JFI -Original Message- From: Joe Subich, W4TV Sent: Saturday, May 19, 2012 7:29 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] OT: Dayton New Equipment Show The Flex 6000/6700 is an on frequency direct digital conversion radio - that is a 16 bit analog to digital converter operating at the front end of the radio with no intermediate conversion/IF and filtering stages. In addition, all of the DSP is contained in the radio (no more PowerSRD). The new software for the Flex 6000/6700 (reportedly PowerRX) is essentially a glass control panel). A general purpose computer is required for PowerRX but communication between the computer and transceiver is via TCP/IP which means the computer can be anywhere. Audio input and output will be available both on the transceiver and from PowerRX (interesting for remote operation scenarios). The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. The new Flex design is certainly interesting but may not truly be ready for critical real world use with the widely varying signal levels in amateur service. 73, ... Joe, W4TV On 5/19/2012 3:43 PM, Tony Estep wrote: On Sat, May 19, 2012 at 11:53 AM, Edward R. Colekl...@acsalaska.netwrote: ...website now shows the Flex-6000/6700 newest entry into the SDR market === Said to be digital from antenna connector to output. Their hardware has long needed updating, so perhaps this will be it. However, Flex's really weak link has always been their software/systems integration, so it remains to be seen if this does anything to mitigate that. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm
Re: [Elecraft] OT: Dayton New Equipment Show
Guess we will have to await independent testing. The Flex folks seem to assert they have the equivalent of more than 24 bit when dealing with adjacent strong signals. Yes we will need to wait for independent testing but given relatively wide filters (200 KHz or more), that testing can't be done with only two signals. The tests will need to be (notched) noise power tests or multiple tone tests that stress the *total* power handling capability of the system. It is the huge increase in instantaneous peak voltage when multiple signals are present that causes multi-channel (multiplexed) power amplifiers to be rated for peak powers as much as 20 dB higher that their average operating (output) power. The same problem of peak to average power (voltage) *will* impact the absolute voltage handling requirements of the ADC used in any DDC system. Decimation may improve resolution but not the absolute maximum and minimum signal levels. 73, ... Joe, W4TV On 5/19/2012 8:23 PM, Tom Azlin N4ZPT wrote: Hi Joe, Guess we will have to await independent testing. The Flex folks seem to assert they have the equivalent of more than 24 bit when dealing with adjacent strong signals. From the Flex reflector... Just in rough numbers, you get a 1/2-bit for every divide-by-two decimation you do. If you are looking at dynamic range in a 500Hz bandwidth (this is what we typically do). The math I generally use to get there is log(f1/f2)/log(2)/2. I just think this way as a programmer (do everything in base 2). So if you take log(245.76E6/500)/log(2)/2 you get 9.4 extra bits when added to the 16 gives you 25.5 bits (152.7dB dynamic range). This assumes all 16-bits of the ADC are good which is probably not a good assumption. I'd have to pull out the notes and look at the data sheet again, but this should give you a rough idea. Hopefully I haven't made an additional duh today myself! Bottom line -- there's plenty of dynamic range. Also, if you are interested, we are using Xilinx DSP48E1 blocks which use an 18x25 multiplier and so Xilinx tools generate the on-board DDS as a 25-bit DDS by default --- again to preserve the SFDR of the receiver. We could add extra bits, but 25 are fine for the same reason. Steve Stephen Hicks, N5AC, AAR6AM VP Engineering FlexRadio Systems™ 4616 W Howard Ln Ste 1-150 Austin, TX 78728 Phone: 512-535-4713 x205 Email: steve at flexradio.com Web: www.flexradio.com On 5/19/2012 8:11 PM, Joe Subich, W4TV wrote: Decimation can help but it is not a magic bullet that eliminates the effects of ADC overflow and/or blocking due to gain reduction. 73, ... Joe, W4TV On 5/19/2012 7:57 PM, Tom Azlin N4ZPT wrote: decimation counts On 5/19/2012 7:29 PM, Joe Subich, W4TV wrote: The issue will be the severely limited dynamic range of the 16 bit ADC. Without effective AGC ahead of the ADC there *will* be overload problems on crowded bands (e.g. 160/80/40) where any transceiver must deal with many extremely strong (local) signals while maintaining maximum sensitivity. With AGC, the strong local signals will cause blocking as the gain is reduced to prevent overflow of the ADC. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: Dayton New Equipment Show
I believe Joe is trying to say that traditional test methods fall short of reality when applied to direct sampling SDR receivers, and I would believe he is correct - there are too many other factors to be considered (and some of them are yet unknown to most of us). 73, Don W3FPR On 5/19/2012 8:57 PM, Joe Subich, W4TV wrote: Guess we will have to await independent testing. The Flex folks seem to assert they have the equivalent of more than 24 bit when dealing with adjacent strong signals. Yes we will need to wait for independent testing but given relatively wide filters (200 KHz or more), that testing can't be done with only two signals. The tests will need to be (notched) noise power tests or multiple tone tests that stress the *total* power handling capability of the system. It is the huge increase in instantaneous peak voltage when multiple signals are present that causes multi-channel (multiplexed) power amplifiers to be rated for peak powers as much as 20 dB higher that their average operating (output) power. The same problem of peak to average power (voltage) *will* impact the absolute voltage handling requirements of the ADC used in any DDC system. Decimation may improve resolution but not the absolute maximum and minimum signal levels. 73, ... Joe, W4TV __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
