[time-nuts] Bob Pease
From Dave Jones: Word has just filtered through Twitter that Bob Pease was killed in a car accident. This one by the sounds of it: http://www.mercurynews.com/bay-area-news/ci_18310586?source=rssnclick_check=1 In a sad twist, it is reported that he was returning from Jim Willam's memorial. A sad week indeed. RIP Bob Pease. Dave Regards, David Partridge ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
It is confirmed by one of the magazines. EDN I think. Other than reading his columns, my only connection to Bob Pease was seeing him at Foothill selling his books out of the trunk of his beetle. -Original Message- From: David C. Partridge david.partri...@perdrix.co.uk Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 09:45:51 To: 'Discussion of precise time and frequency measurement'time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] Bob Pease From Dave Jones: Word has just filtered through Twitter that Bob Pease was killed in a car accident. This one by the sounds of it: http://www.mercurynews.com/bay-area-news/ci_18310586?source=rssnclick_check=1 In a sad twist, it is reported that he was returning from Jim Willam's memorial. A sad week indeed. RIP Bob Pease. Dave Regards, David Partridge ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] PEMCO 50a Info
Anyone have info or schematic for this counter? it has 5 seven segment filament display tubes plus OVEN and OVER lights. The logic board uses an oven holding a hc6 type 10 mHz crystal. One of the divider chips is a 74s112 so I presume the counter goes to 50 mHz or so. I got it for free from a junkbox. It appears to count but the time base isn't working - the count just keeps increasing every time the display updates. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
One of his books was something like: Driving into an accident.!!! N0UU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
More or less ... http://www.amazon.com/How-Drive-into-Accidents-Not/dp/0965564819 Very sad that two great analog designers had passed away in the same week. Best regards, Javier El 20/06/2011 15:52, lstosk...@cox.net escribió: One of his books was something like: Driving into an accident.!!! N0UU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
One important thing to note is he wasn't wearing his seat belts. All you old codgers, and immortal young bucks, that think not wearing seat belts will allow you to fly free and live in an accident need to take your blinders off and pay attention: Flying free and living after an accident only happens in Hollywood. In the real world, YOU DIE! I have lost too many otherwise intelligent friends from this same idiotic act of insanity. Most in accidents under 25MPH. Most within a couple miles of their homes. The only one that didn't die had serious brain damage that left her with a stammer, crutches for life, and took away her brilliant musical talent. Several that did die left behind spouses, and a host of children. Several were childhood friends, that were children at the time of their deaths. Buckle up! Wear your seat belts! PLEASE! -Chuck Harris Javier Herrero wrote: More or less ... http://www.amazon.com/How-Drive-into-Accidents-Not/dp/0965564819 Very sad that two great analog designers had passed away in the same week. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] DDS'ery
Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
In message 4dff5d29.2070...@mail.ua.pt, Luis Cupido writes: Isn't it the very same thing as just using the most significant bit of the accumulator. Indeed it is, and that's how programmable digital clocks often work. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Forgot the sine table... I meant obviously ...an accumulator 'sine table' and DAC... lc. On 6/20/2011 3:46 PM, Luis Cupido wrote: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Hello, No, it is not the same. If you just use the MSB of the accumulator, it has a lot of period jitter. It can be unnoticeable if the ration between reference frequency and output frequency is very high. Think on the process inversely: draw a sine wave, and sample it at for example 4.3 samples per period, and look when the sample becames positive and when it is negative (that would be the same to take only the MSB). Best regards Javier El 20/06/2011 16:46, Luis Cupido escribió: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
In message 4dff5f2f.7050...@hvsistemas.es, Javier Herrero writes: No, it is not the same. If you just use the MSB of the accumulator, it = has a lot of period jitter. It can be unnoticeable if the ration between = reference frequency and output frequency is very high. In practice, this jitter is a lot lower than you get from squaring the sinewave. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
In message 4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Does a 1969 VW Beetle even have them ? A casual check via Google indicates that, yes indeed, the 1969 Beetle came with seat belts. Peter K1PGV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Luis: No, not the same. The most significant bit out of the accumulator has the alias information on it (Fs +/- Fo), so it still needs to be run through the low pass filter to clean off the alias signals. The alias signals manifest themselves as jitter, so no amount of just clipping will remove them. If your application is not sensitive to the alias frequencies, then OK to drive out of the DDS directly. If you are driving something like a mixer in a wide band radio, then you still need to use the low pass filters. They don't call them anti-alias filters for no reason. --- Graham / KE9H == On 6/20/2011 9:46 AM, Luis Cupido wrote: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Indeed it does. At least, the model I drove did. *** REPLY SEPARATOR *** On 20-Jun-11 at 15:05 Poul-Henning Kamp wrote: In message 4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. __ Information from ESET Smart Security, version of virus signature database 6223 (20110620) __ The message was checked by ESET Smart Security. http://www.eset.com Bruce Lane, Owner Head Hardware Heavy, Blue Feather Technologies (http://www.bluefeathertech.com) Assoc. member, AZA AAZK for many moons. Salvadore Dali's computer has surreal ports... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
All US cars since 1963 have seat belts. Poul-Henning Kamp wrote: In message4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
The jitter when taking only the MSB is same as the DDS clock period. I don't think that squaring the filtered sinewave you will get that jitter (of course, if you square the sinewave with no filtering, you will get the same jitter that taking only the MSB). In fact, it is the reason that AD9850/AD9851 include a comparator instead of just an MSB output. Regards, Javier El 20/06/2011 17:04, Poul-Henning Kamp escribió: In message4dff5f2f.7050...@hvsistemas.es, Javier Herrero writes: No, it is not the same. If you just use the MSB of the accumulator, it = has a lot of period jitter. It can be unnoticeable if the ration between = reference frequency and output frequency is very high. In practice, this jitter is a lot lower than you get from squaring the sinewave. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Yes. My convertible Super-Beetle did for sure. Rustproofing- not so much. :) -John === In message 4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
After 42 years, I suspect that the rust-proof warranty is also rusty ;) I think that in Europe (at least in Spain) seat-belts became mandatory a bit after that in US, around 1970, so perhaps european MY1969 Beetle's did not have them. Regards, Javier El 20/06/2011 17:17, J. Forster escribió: Yes. My convertible Super-Beetle did for sure. Rustproofing- not so much. :) -John === In message4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Thanks for the comments... Yes the key is obviously the low pass filtering one has the other doesn't. I had mainly in my mind a PLL following that ACC. so actually driving a phase comparator of a PLL (narrow enough loop bw) that problem would not exist. Ok great. Good point on the mixer we got to have nothing in the alias region for it to be ok. (not my application at the moment but will keep that in mind) Thanks guys... Luis Cupido. ct1dmk. On 6/20/2011 4:11 PM, Graham / KE9H wrote: Luis: No, not the same. The most significant bit out of the accumulator has the alias information on it (Fs +/- Fo), so it still needs to be run through the low pass filter to clean off the alias signals. The alias signals manifest themselves as jitter, so no amount of just clipping will remove them. If your application is not sensitive to the alias frequencies, then OK to drive out of the DDS directly. If you are driving something like a mixer in a wide band radio, then you still need to use the low pass filters. They don't call them anti-alias filters for no reason. --- Graham / KE9H == On 6/20/2011 9:46 AM, Luis Cupido wrote: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
To reduce the spurii due to quantization distortion. Here is an explanation, in Section 4 http://www.analog.com/static/imported-files/tutorials/450968421DDS_Tutorial_rev12-2-99.pdf Regards, Javier El 20/06/2011 17:39, Luis Cupido escribió: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Actually it is (n*Fs +/-Fo), however, they do go down in amplitude as a SinX/X. Theoretically, they would also be there after the Sin ROM, and the only one really of concern in the real world is the Fs - Fo, hence the LPF. When I used to design DDSs in the early 70's, we typically tried to use an Fs that was about 2.5 times the max desired Fo, to make filtering easier. We also used discrete parts then :). Now, with the higher speed devices available a real high Fs can be selected to meet a desired Fmax. Of course the limit is always being pushed, and, the devices are never fast enough. Regards - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Graham / KE9H Sent: Monday, June 20, 2011 11:12 AM To: time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery Luis: No, not the same. The most significant bit out of the accumulator has the alias information on it (Fs +/- Fo), so it still needs to be run through the low pass filter to clean off the alias signals. The alias signals manifest themselves as jitter, so no amount of just clipping will remove them. If your application is not sensitive to the alias frequencies, then OK to drive out of the DDS directly. If you are driving something like a mixer in a wide band radio, then you still need to use the low pass filters. They don't call them anti-alias filters for no reason. --- Graham / KE9H == On 6/20/2011 9:46 AM, Luis Cupido wrote: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. Or am I missing something here ? Comments appreciated. thanks. Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Hi: Google maps shows that address 14831 pierce road Saratoga as Mountain Winery and a very twisty road. Have Fun, Brooke Clarke http://www.PRC68.com David C. Partridge wrote: From Dave Jones: Word has just filtered through Twitter that Bob Pease was killed in a car accident. This one by the sounds of it: http://www.mercurynews.com/bay-area-news/ci_18310586?source=rssnclick_check=1 In a sad twist, it is reported that he was returning from Jim Willam's memorial. A sad week indeed. RIP Bob Pease. Dave Regards, David Partridge ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] OT: Bob Pease died
http://www.eetimes.com/electronics-news/4217077/Analog-expert-Bob-Pease-dies-in-tragic-accident ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Thanks. Luis cupido. ct1dmk. On 6/20/2011 4:52 PM, Javier Herrero wrote: To reduce the spurii due to quantization distortion. Here is an explanation, in Section 4 http://www.analog.com/static/imported-files/tutorials/450968421DDS_Tutorial_rev12-2-99.pdf Regards, Javier El 20/06/2011 17:39, Luis Cupido escribió: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On Mon, 20 Jun 2011 16:39:16 +0100 Luis Cupido cup...@mail.ua.pt wrote: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? If you filter a square wave, you have a lot more harmonics than if you filter a signal that is already nearly sine. Hence the DAC stage gives you a higher signal purity. And as filters are never optimal, you'd rather go with a more pure signal :-) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
De nada, Luis :) I've been playing around a bit with Altera NCO IP (in fact, I need to implement a digital NCO quite shortly for a project, although in this case close-in spurs are more tolerable than in other applications). A lot of information in the application note for ADI is also applicable to the purely digital side. I've not yet played on the practical side - this will be after summer :) Quartus software (for Altera FPGAs) enables to customize several parameters of their NCO IP, and plots an expected spectrum of the output signal. It is fun to explore the effect of different sin/cos algorithms (ROM-based, CORDIC, multiplier-based), phase accumulator and magnitude precision, and angular resolution. Although the IP is not free (but can be used for evaluation), Quartus Web Edition (that it is free) enables to play a bit around - and at least it is illustrative :) I forgot that Section 7 shows what occurs taking only the MSB (it shows it using a comparator after the DAC, without filtering and also after filtering). Best regards, Javier El 20/06/2011 18:46, Luis Cupido escribió: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Thanks. Luis cupido. ct1dmk. On 6/20/2011 4:52 PM, Javier Herrero wrote: To reduce the spurii due to quantization distortion. Here is an explanation, in Section 4 http://www.analog.com/static/imported-files/tutorials/450968421DDS_Tutorial_rev12-2-99.pdf Regards, Javier El 20/06/2011 17:39, Luis Cupido escribió: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On 6/20/11 7:46 AM, Luis Cupido wrote: Folks, a quick one... A DDS, that is an accumulator with a DAC followed by a low pass filter and comparator (zero crossing) to produce a square wave to drive a PLL or a MIXER or else (at logic levels). Isn't it the very same thing as just using the most significant bit of the accumulator. The zero crossing using just the MSB will have jitter, compared to making a sign wave and then letting the zero crossing occur between samples. Depending on your application, MSB only might work well enough. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On 6/20/11 8:39 AM, Luis Cupido wrote: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Spur content heading into the filter.. the sine table and DAC greatly reduces the harmonic content of the output, which makes filtering easier. You could think of the cos table and DAC as a specialized filter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On 6/20/11 9:46 AM, Luis Cupido wrote: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Tons.. Jouko Vankka wrote whole books about it. Direct Digital Synthesizers and transmitters for software radio Direct Digital Synthesizers: Theory, Design and Applications You might want to look at various Error Feedback/Error Filtering schemes which allow you to use a smaller cosine table and/or smaller DAC and have better spur performance. Vankka, J, A direct digital synthesizer with a tunable error feedback structure, IEEE Trans on Comm, V45, #4, pp416-420, 1997 Vankka's EF technique works quite well at suppressing spurs close to the carrier (at the expense of pushing them farther out). Reinhardt, V, Spur Reduction Techniques in Direct Digital Synthesizers, Proc Intl Freq Control Symp, 1993 Flanagan, M., Zimmerman, G., Spur-reduced digital sinusoid synthesis IEEE Trans on Comm, V43, #7, pp2254-2262, 1995 (this one is about using dither to spread the spurs out) O'Leary, P., Maloberti, F., A direct-digital synthesizer with improved spectral performance, IEEE Trans on Comm, V39, #7, 1991 You might also look at some of the spur cancellation things, such as the one implemented in some of AD's DDS parts.. Basically, it's a second NCO that generates a coherent signal that is subtracted/added to the primary signal to notch out the spur. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Bob Pease died
I think Bob died out of grief for Jim Williams. Jim's death came as a shock alredy. now Bob. I don't think Bob could stand it. I had the great fortune to meet Jim about a year ago and to work with him since then, and he was such a joy to be around. A mentor and teacher par excellence. Both of them had such impact on me and all we do here over the last two decades. Here is a letter Bob wrote about Jim shortly before his death as posted by one of the commentators from the below link: From: Robert Pease Date: 06/18/11 05:05:08 I worked for him as a kid at Philbrick on band gap reference development. The impact this guy had on me as a kid are deeply ingrained. He was bigger than life,untamed, invincible, an analog hero. An icon. A showman. A Czar. They came from around the world to see him. His office, his breadboards,It was non stop fun and excitement. Then he calls us to an awards meeting. I was only 19. He gives the new CEO the triple humper award.He pulls a three cup bra from a shopping cart. I was in awe.Incredible entertainment.Justice served. Under the first cup a V/$ converter. Under the third cup a F/$ converter. I thought this was the most incredible event I had ever witnessed.Until he unveils the third cup contents. He reaches into his pants and pulls out his letter of resigation. He quit,efffective immediately to go to National. I was in shock! Betrayed.When he left there was a vacuum.I feel it again. I feel so fortunate I was able to experience him, and so many other talented and interesting people in the industry. He will be missed by all. Ralph In a message dated 6/20/2011 09:45:11 Pacific Daylight Time, p...@petelancashire.com writes: http://www.eetimes.com/electronics-news/4217077/Analog-expert-Bob-Pease-dies -in-tragic-accident ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. -Original Message- From: Jim Lux jim...@earthlink.net Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 12:04:24 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery On 6/20/11 9:46 AM, Luis Cupido wrote: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Tons.. Jouko Vankka wrote whole books about it. Direct Digital Synthesizers and transmitters for software radio Direct Digital Synthesizers: Theory, Design and Applications You might want to look at various Error Feedback/Error Filtering schemes which allow you to use a smaller cosine table and/or smaller DAC and have better spur performance. Vankka, J, A direct digital synthesizer with a tunable error feedback structure, IEEE Trans on Comm, V45, #4, pp416-420, 1997 Vankka's EF technique works quite well at suppressing spurs close to the carrier (at the expense of pushing them farther out). Reinhardt, V, Spur Reduction Techniques in Direct Digital Synthesizers, Proc Intl Freq Control Symp, 1993 Flanagan, M., Zimmerman, G., Spur-reduced digital sinusoid synthesis IEEE Trans on Comm, V43, #7, pp2254-2262, 1995 (this one is about using dither to spread the spurs out) O'Leary, P., Maloberti, F., A direct-digital synthesizer with improved spectral performance, IEEE Trans on Comm, V39, #7, 1991 You might also look at some of the spur cancellation things, such as the one implemented in some of AD's DDS parts.. Basically, it's a second NCO that generates a coherent signal that is subtracted/added to the primary signal to notch out the spur. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Jim Lux wrote: On 6/20/11 9:46 AM, Luis Cupido wrote: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Tons.. Jouko Vankka wrote whole books about it. Direct Digital Synthesizers and transmitters for software radio Direct Digital Synthesizers: Theory, Design and Applications You might want to look at various Error Feedback/Error Filtering schemes which allow you to use a smaller cosine table and/or smaller DAC and have better spur performance. Vankka, J, A direct digital synthesizer with a tunable error feedback structure, IEEE Trans on Comm, V45, #4, pp416-420, 1997 Vankka's EF technique works quite well at suppressing spurs close to the carrier (at the expense of pushing them farther out). Reinhardt, V, Spur Reduction Techniques in Direct Digital Synthesizers, Proc Intl Freq Control Symp, 1993 Flanagan, M., Zimmerman, G., Spur-reduced digital sinusoid synthesis IEEE Trans on Comm, V43, #7, pp2254-2262, 1995 (this one is about using dither to spread the spurs out) O'Leary, P., Maloberti, F., A direct-digital synthesizer with improved spectral performance, IEEE Trans on Comm, V39, #7, 1991 You might also look at some of the spur cancellation things, such as the one implemented in some of AD's DDS parts.. Basically, it's a second NCO that generates a coherent signal that is subtracted/added to the primary signal to notch out the spur. See also: http://www.iro.umontreal.ca/~mignotte/IFT3205/Documents/TipsAndTricks/UltraLowPhaseNoiseDSPOscillator.pdf http://www.iro.umontreal.ca/%7Emignotte/IFT3205/Documents/TipsAndTricks/UltraLowPhaseNoiseDSPOscillator.pdf Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Bob Pease died
Here is a letter Bob wrote about Jim shortly before his death as posted by one of the commentators from the below link: Then he calls us to an awards meeting. I was only 19. He gives the new CEO the triple humper award.He pulls a three cup bra from a shopping cart. I saw that too, but the age thing didn't make sense. If Bob was 70 and Jim was 63, how could Bob be the 19 year old kid working with Jim (at age 12?!) at Philbrick? What a sad week in the analog world. -- newell N5TNL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Inside an FPGA, CORDIC can be implemented performing quite fast. An open-source implementation of CORDIC algorithm and a DDS using look-up table or CORDIC can be found in OpenCores, gh_vhdl_lib. Jim, thank you very much for all the excellent references, and particularly the last one about the CORDIC variation. The Altera simulations of its NCO showns significant more spurii for CORDIC (traditional one) than the other alternatives for same phase accumulator and magnitude precisions, and angular same angular resolution, but it is by far the most effective in terms of FPGA usage. Probably I will use the CORDIC approach in the implementation of my digital down-converter, but the OpenCores core instead of the Altera IP, if it is clean enough (the signal I need to downconvert is 8-bit quantized and with poor S/N ratio, so some -40dB spurious will not have significance). Regards, Javier El 20/06/2011 21:17, li...@lazygranch.com escribió: Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. -Original Message- From: Jim Luxjim...@earthlink.net Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 12:04:24 To:time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery On 6/20/11 9:46 AM, Luis Cupido wrote: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Tons.. Jouko Vankka wrote whole books about it. Direct Digital Synthesizers and transmitters for software radio Direct Digital Synthesizers: Theory, Design and Applications You might want to look at various Error Feedback/Error Filtering schemes which allow you to use a smaller cosine table and/or smaller DAC and have better spur performance. Vankka, J, A direct digital synthesizer with a tunable error feedback structure, IEEE Trans on Comm, V45, #4, pp416-420, 1997 Vankka's EF technique works quite well at suppressing spurs close to the carrier (at the expense of pushing them farther out). Reinhardt, V, Spur Reduction Techniques in Direct Digital Synthesizers, Proc Intl Freq Control Symp, 1993 Flanagan, M., Zimmerman, G., Spur-reduced digital sinusoid synthesis IEEE Trans on Comm, V43, #7, pp2254-2262, 1995 (this one is about using dither to spread the spurs out) O'Leary, P., Maloberti, F., A direct-digital synthesizer with improved spectral performance, IEEE Trans on Comm, V39, #7, 1991 You might also look at some of the spur cancellation things, such as the one implemented in some of AD's DDS parts.. Basically, it's a second NCO that generates a coherent signal that is subtracted/added to the primary signal to notch out the spur. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Bob Pease died
El 20/06/2011 21:45, Scott Newell escribió: Here is a letter Bob wrote about Jim shortly before his death as posted by one of the commentators from the below link: Then he calls us to an awards meeting. I was only 19. He gives the new CEO the triple humper award.He pulls a three cup bra from a shopping cart. I saw that too, but the age thing didn't make sense. If Bob was 70 and Jim was 63, how could Bob be the 19 year old kid working with Jim (at age 12?!) at Philbrick? I was thinking the same... and also that Pease name was Robert A., not Ralph (and its usually signature was RAP) Regards, Javier -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
With the coordic (yeah, sometimes cordic), you need to build it a few more bits wider than the DAC. Then it closely matches the lookup table. One of the best references for the coordic I found was a PhD dissertation at Stanford. The author's last name was Ahmed IIRC. It is a very versatile algorithm. You can vary the magnitude of the initial vector to AM the signal. PM is done by directly. The coordic can also multiply, divide, and compute inverse trig functions. It was used (and might still be) in scientific calculators. We did a FSK demod with the coordic. Basically unwrap the phase of the signal and least mean square fit the phase to a straight line, where the slope of the line relates to the frequency. -Original Message- From: Javier Herrero jherr...@hvsistemas.es Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 21:46:11 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery Inside an FPGA, CORDIC can be implemented performing quite fast. An open-source implementation of CORDIC algorithm and a DDS using look-up table or CORDIC can be found in OpenCores, gh_vhdl_lib. Jim, thank you very much for all the excellent references, and particularly the last one about the CORDIC variation. The Altera simulations of its NCO showns significant more spurii for CORDIC (traditional one) than the other alternatives for same phase accumulator and magnitude precisions, and angular same angular resolution, but it is by far the most effective in terms of FPGA usage. Probably I will use the CORDIC approach in the implementation of my digital down-converter, but the OpenCores core instead of the Altera IP, if it is clean enough (the signal I need to downconvert is 8-bit quantized and with poor S/N ratio, so some -40dB spurious will not have significance). Regards, Javier El 20/06/2011 21:17, li...@lazygranch.com escribió: Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. -Original Message- From: Jim Luxjim...@earthlink.net Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 12:04:24 To:time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery On 6/20/11 9:46 AM, Luis Cupido wrote: Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. ... Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Tons.. Jouko Vankka wrote whole books about it. Direct Digital Synthesizers and transmitters for software radio Direct Digital Synthesizers: Theory, Design and Applications You might want to look at various Error Feedback/Error Filtering schemes which allow you to use a smaller cosine table and/or smaller DAC and have better spur performance. Vankka, J, A direct digital synthesizer with a tunable error feedback structure, IEEE Trans on Comm, V45, #4, pp416-420, 1997 Vankka's EF technique works quite well at suppressing spurs close to the carrier (at the expense of pushing them farther out). Reinhardt, V, Spur Reduction Techniques in Direct Digital Synthesizers, Proc Intl Freq Control Symp, 1993 Flanagan, M., Zimmerman, G., Spur-reduced digital sinusoid synthesis IEEE Trans on Comm, V43, #7, pp2254-2262, 1995 (this one is about using dither to spread the spurs out) O'Leary, P., Maloberti, F., A direct-digital synthesizer with improved spectral performance, IEEE Trans on Comm, V39, #7, 1991 You might also look at some of the spur cancellation things, such as the one implemented in some of AD's DDS parts.. Basically, it's a second NCO that generates a coherent signal that is subtracted/added to the primary signal to notch out the spur. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list
Re: [time-nuts] OT: Bob Pease died
Very sad news to hear. Though I have never emailed Robert Pease. I sure did read much of what he had to print over many many years. Enjoyed his humor and approach to communicating technology realities. A very sad ending. Regards Paul WB8TSL On Mon, Jun 20, 2011 at 3:51 PM, Javier Herrero jherr...@hvsistemas.eswrote: El 20/06/2011 21:45, Scott Newell escribió: Here is a letter Bob wrote about Jim shortly before his death as posted by one of the commentators from the below link: Then he calls us to an awards meeting. I was only 19. He gives the new CEO the triple humper award.He pulls a three cup bra from a shopping cart. I saw that too, but the age thing didn't make sense. If Bob was 70 and Jim was 63, how could Bob be the 19 year old kid working with Jim (at age 12?!) at Philbrick? I was thinking the same... and also that Pease name was Robert A., not Ralph (and its usually signature was RAP) Regards, Javier -- --**--** Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: Bob Pease died
At 02:51 PM 6/20/2011, Javier Herrero wrote: I was thinking the same... and also that Pease name was Robert A., not Ralph (and its usually signature was RAP) How's this: Ralph had two stories to tell in that post. The first was that he received an email from Bob Pease the night of the accident (he provided the timestamp of RAP's email). The second story was not the email from RAP, but instead was of Ralph's personal experience at Philbrick, remembering either RAP or JW. That makes more sense to me. -- newell N5TNL ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Thank you. A good friend of mine is a huge Bob Pease fan and also a devout non-wearer of seat belts. He's already used-up one of his nine lives on an accident where he wasn't belted-in. Hopefully this unfortunate reminder will cause him to change his mind about belt use. -John -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris Sent: Monday, June 20, 2011 9:42 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Bob Pease One important thing to note is he wasn't wearing his seat belts. All you old codgers, and immortal young bucks, that think not wearing seat belts will allow you to fly free and live in an accident need to take your blinders off and pay attention: Flying free and living after an accident only happens in Hollywood. In the real world, YOU DIE! I have lost too many otherwise intelligent friends from this same idiotic act of insanity. Most in accidents under 25MPH. Most within a couple miles of their homes. The only one that didn't die had serious brain damage that left her with a stammer, crutches for life, and took away her brilliant musical talent. Several that did die left behind spouses, and a host of children. Several were childhood friends, that were children at the time of their deaths. Buckle up! Wear your seat belts! PLEASE! -Chuck Harris Javier Herrero wrote: More or less ... http://www.amazon.com/How-Drive-into-Accidents-Not/dp/0965564819 Very sad that two great analog designers had passed away in the same week. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Replacing electrolytics - any disadvantages of high temp ones?
I'm sure many of you with old equipment must have considered the fact that electrolytic caps have a finite life and considered replacing them. I have a few that look suspect (bulging) on a transceiver, and decided to replace them. I'm tempted to do all of them in the PSU, as: * It runs hot * PSU could destory other bits * Two of the 15 or so caps on the PSU board show signs of bulging. For the PSU I used all 105 deg C caps, apart from one which was rated at 125 deg C. These are higher spec than the originals. I also replaced another cap (not in a hot region) with a 105 deg C rated cap. I've made my capacitor choice based on assuming. 1) Higher temperature devices (like 105 deg C) will be more relieable than low temperature ones like the standard 85 deg C cap. I'm sure at high temperatures, that must be true, but I've no idea if it would be beneficial if the cap does not get very warm. 2) There are no disadvantage of the higher temperature caps, other than cost. Are these true? I've ruled out the idea of replacing all electrolytics with new ones. That would be a LOT of work, and cost a lot of money. Dave -- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On Mon, 20 Jun 2011 20:26:46 + li...@lazygranch.com wrote: With the coordic (yeah, sometimes cordic), you need to build it a few more bits wider than the DAC. Then it closely matches the lookup table. One of the best references for the coordic I found was a PhD dissertation at Stanford. The author's last name was Ahmed IIRC. This seems to be Signal processing algorithms and architectures by Hassan Masud Ahmed, 1982. Unfortunately, my google skills fail me to locate a digital copy of this dissertation. I'm even unable to locate a paper version in any of the university libraries. Does anyone have this as PS or PDF? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Replacing electrolytics - any disadvantages of high temp ones?
In message 4dffbaf4.4070...@onetel.net, Dr. David Kirkby writes: 1) Higher temperature devices (like 105 deg C) will be more relieable than low temperature ones like the standard 85 deg C cap. I'm sure at high temperatures, You should check both temperature and lifetime rating of the capactors. There are many capacitors on the market these days with 5000h or even 2000h rated life. That is 7 or 3 months respectively. And yes, it should be criminal to manufacture and sell those. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Not even remotely. Try it. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Monday, June 20, 2011 8:04 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DDS'ery In message 4dff5f2f.7050...@hvsistemas.es, Javier Herrero writes: No, it is not the same. If you just use the MSB of the accumulator, it = has a lot of period jitter. It can be unnoticeable if the ration between = reference frequency and output frequency is very high. In practice, this jitter is a lot lower than you get from squaring the sinewave. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
You did a good job just finding the title. Socrates search? I looked at it in the flesh in the Terman library. I suppose the dissertation can be purchased. I left out hyperbolic functions. I'm not sure if it can compute logs. I had need once to compute a log and found an old paper from IBM for a log algorithm. We did a DTMF with a coordic. This was all part of a DSP based modem, unique for its time, routine to the point of boredom today. The DTMF accuracy was of course spot on. Basically once you have the algorithm in the box, you might as well use it, even if the quality is overkill. I don't have Marvin's Frerking's book on DSP comms because I left that field before it was published, but I am told it covers cordic and similar algorithms. If you google Marvin Frerking cordic, some of his book is digitized in google books. --Original Message-- From: Attila Kinali To: li...@lazygranch.com To: Discussion of precise time and frequencymeasurement Subject: Re: [time-nuts] DDS'ery Sent: Jun 20, 2011 2:35 PM On Mon, 20 Jun 2011 20:26:46 + li...@lazygranch.com wrote: With the coordic (yeah, sometimes cordic), you need to build it a few more bits wider than the DAC. Then it closely matches the lookup table. One of the best references for the coordic I found was a PhD dissertation at Stanford. The author's last name was Ahmed IIRC. This seems to be Signal processing algorithms and architectures by Hassan Masud Ahmed, 1982. Unfortunately, my google skills fail me to locate a digital copy of this dissertation. I'm even unable to locate a paper version in any of the university libraries. Does anyone have this as PS or PDF? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
I'm not familiar with Altera's DDS options, but I will say that Xilinx's DDS compiler is superb. It can be configured to provide SFDR up to 150 dB (and I'd notice it if I were getting much less than that in practice.) As Javier hinted, the reason you can't use the MSB directly is that its transition point is not necessarily stationary between cycles of the frequency you're trying to synthesize. It will flop around all over the place. You need at least a few more bits in most applications -- remember that in an n-bit word, the magnitude represented by the n-1 LSBs is almost as much as the bit-n MSB. When DDS technology was first becoming popular in the 1980s, Qualcomm was one of the main vendors, and they required external DACs. High-speed DACs were pricy and used a lot of power, so I imagine that a great many people tried feeding the MSB directly to the filter, as I did. It could be feasible at some selected frequencies or at very high clock/output ratios, but in the general case the output signal is just comically awful. You would need a truly massive filter to provide the needed flywheel effect to make up for those missing bits. And it would need to be a BPF, not just an LPF, because not all of the artifacts associated with output quantization are above the desired carrier frequency. Sometimes the MSB's toggle period is going to be shorter than it should be, and sometimes it's going to be longer. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of Luis Cupido Sent: Monday, June 20, 2011 9:46 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DDS'ery Gracias, Javier. As you read in my previous email I'm basically worried about close-in spurs (those that will pass through the PLL loop filter). will digest that 4th section... tks. Since I'm inside an FPGA... I'm eager to get spurs down without leaving the digital world... Anyone knows any literature covering that ? Thanks. Luis cupido. ct1dmk. On 6/20/2011 4:52 PM, Javier Herrero wrote: To reduce the spurii due to quantization distortion. Here is an explanation, in Section 4 http://www.analog.com/static/imported- files/tutorials/450968421DDS_Tutorial_rev12-2-99.pdf Regards, Javier El 20/06/2011 17:39, Luis Cupido escribió: Well, if we really need to filter it out we better filter the MSB and square it again... Why having a DAC for ??? Right ? Luis Cupido. ct1dmk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
A good friend of mine is a huge Bob Pease fan and also a devout non-wearer of seat belts. He's already used-up one of his nine lives on an accident where he wasn't belted-in. Hopefully this unfortunate reminder will cause him to change his mind about belt use. Buckle up! Wear your seat belts! PLEASE! At the risk of being OT, I'll add my experience as a first responder. It was VERY easy to tell who was and was not belted when we arrived. The unbelted victims had much worse injuries in general, high speed impact with windshield etc, and occasionally were ejected. The interesting thing about being ejected is that you get ejected generally into the path of the vehicle. Unless you get very lucky. I went through a 55mph collision with a telephone pole in my explorer with only a seat belt (no bags on that model/year) I had only a belt bruise. The impact was severe enough that my front plate bonded itself to the phone pole, and had to be peeled off after we towed the truck. Black ice sucks. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Replacing electrolytics - any disadvantages of high temp ones?
On 06/20/11 10:44 PM, Poul-Henning Kamp wrote: In message4dffbaf4.4070...@onetel.net, Dr. David Kirkby writes: 1) Higher temperature devices (like 105 deg C) will be more relieable than low temperature ones like the standard 85 deg C cap. I'm sure at high temperatures, You should check both temperature and lifetime rating of the capactors. I have, but I would assume one rated at 6000 hours at 125 deg C would be at least as good as one rated at 7000 hours at 105 deg C. There are many capacitors on the market these days with 5000h or even 2000h rated life. That is 7 or 3 months respectively. Even 1000 hours I've seen. But these are of course at the maximum temperature, which few would use them at. Otherwise failure rates would be a lot higher than they are. I've not seen any electrolytics rated more than 10,000 hours (14 months), but they last a lot longer if the temperature is lower. My PC is already more than 14 months old, and has been on 24/7. Hopefully it is not dying on me. And yes, it should be criminal to manufacture and sell those. Well, I think the MTBF will be a lot more than that in practical use, as few would design equipment to run at 85 deg C, which is the lowest maximum temperature rating I've seen on any cap. -- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Unfortunately, my google skills fail me to locate a digital copy of this dissertation. My Google-fu is pretty decent. You can apparently order a PDF for web download for $37 from: http://proquest.umi.com/pqdlink?did=753152421Fmt=7clientId =79356RQT=309VName=PQD I say apparently because I haven't actually TRIED it... but there it is. Peter K1PGV ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bob Pease
Mine did! Sad to hear of his departure, Neville Michie On 21/06/2011, at 1:05 AM, Poul-Henning Kamp wrote: In message 4dff5c52.4070...@erols.com, Chuck Harris writes: One important thing to note is he wasn't wearing his seat belts. Does a 1969 VW Beetle even have them ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Replacing electrolytics - any disadvantages of high temp ones?
David Another important factor when considering power supply caps is ripple current rating. It is generally the ripple current that makes them get warm. I think the usual thumbnail calculation still work for caps if you can reduce the temperature by 20 degrees they will last at least 4 times as long. That is an activation energy (Arrhenius eqn) of about 1ev. I also believe though I cant quote that they are best run at about 75% of their specified working voltage. I have always wonderd about this but it would seem to be a mistake to have too low a voltage on electrolytics ...maybe something to do with the strength of the instulating layer formed. Alan G3NYK - Original Message - From: Dr. David Kirkby david.kir...@onetel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, June 21, 2011 12:40 AM Subject: Re: [time-nuts] Replacing electrolytics - any disadvantages of high temp ones? On 06/20/11 10:44 PM, Poul-Henning Kamp wrote: In message4dffbaf4.4070...@onetel.net, Dr. David Kirkby writes: 1) Higher temperature devices (like 105 deg C) will be more relieable than low temperature ones like the standard 85 deg C cap. I'm sure at high temperatures, You should check both temperature and lifetime rating of the capactors. I have, but I would assume one rated at 6000 hours at 125 deg C would be at least as good as one rated at 7000 hours at 105 deg C. There are many capacitors on the market these days with 5000h or even 2000h rated life. That is 7 or 3 months respectively. Even 1000 hours I've seen. But these are of course at the maximum temperature, which few would use them at. Otherwise failure rates would be a lot higher than they are. I've not seen any electrolytics rated more than 10,000 hours (14 months), but they last a lot longer if the temperature is lower. My PC is already more than 14 months old, and has been on 24/7. Hopefully it is not dying on me. And yes, it should be criminal to manufacture and sell those. Well, I think the MTBF will be a lot more than that in practical use, as few would design equipment to run at 85 deg C, which is the lowest maximum temperature rating I've seen on any cap. -- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
On 6/20/11 12:17 PM, li...@lazygranch.com wrote: Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. It's a tradeoff.. To do CORDIC you need four multiplies and 2 adds, which might be a lot of gates, if you have a fair number of bits, compared to an adder and some lookup tables. If you have a fast multiply instruction on a processor, then CORDIC gets very attractive. The other problem with CORDIC is that roundoff errors accumulate, the longer you run the generator for, because it's basically a difference equation/numerical integration sort of scheme. That said, some of AD's latest DDSes use a monolithic CORDIC generator. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] DDS'ery narrow scoped.
Folks, Many thanks to you all, for the info. This is indeed a great forum. My aplic. is a DDS signal that will serve as reference for a pll with a relatively narrow loop filter. As I said before. Most replies presume the analog world with DAC filters etc etc. But that I know ;-) I'm digging out the possibilities in the digital side not involving going back to analog and back to digital. this is how this started :-) Now that you all have been so kind in the great comments you gave, please let me just be very very very specific. Imagine an FPGA and a square wave coming out. Just that. Nothing more. (That is what I had in mind when querying about the MSB usage in the first place.) My first approach was the ACC MSB (and that is working already on the bench.) So I'm researching a way to have that digital output cleaner (spurs) without leaving the digital(FPGA) world sticking to the block diagram of one FPGA one digital output. Specially worried about close in spurs (the far away ones won't bother me much). That is really scenario I'm trying to picture if there is any hope to generate a cleaner digital output out of an FPGA (dds with whatever processing required to be done after and producing a square wave). Thanks for your patience. Luis Cupido. ct1dmk P.S. At the moment I'm testing on the bench with a real FPGA cyclone III with a 48bit dds at 100MHz fclock and at circa 6 and 18MHz output and it is not that bad. I got better than -60dBc in the desired ranges. So not too unhappy for a start ;-) PLL cleans 99% of it... but the close in spurs are annoying. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
I don't have the algorithm in front of me, but I don't recall any multiplication, just addition and magnitude comparison. -Original Message- From: Jim Lux jim...@earthlink.net Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 17:14:44 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery On 6/20/11 12:17 PM, li...@lazygranch.com wrote: Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. It's a tradeoff.. To do CORDIC you need four multiplies and 2 adds, which might be a lot of gates, if you have a fair number of bits, compared to an adder and some lookup tables. If you have a fast multiply instruction on a processor, then CORDIC gets very attractive. The other problem with CORDIC is that roundoff errors accumulate, the longer you run the generator for, because it's basically a difference equation/numerical integration sort of scheme. That said, some of AD's latest DDSes use a monolithic CORDIC generator. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery
Correct, CORDIC doesn't require a multiplier, only adds and shifts. That's the whole idea. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts- boun...@febo.com] On Behalf Of li...@lazygranch.com Sent: Monday, June 20, 2011 5:24 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] DDS'ery I don't have the algorithm in front of me, but I don't recall any multiplication, just addition and magnitude comparison. -Original Message- From: Jim Lux jim...@earthlink.net Sender: time-nuts-boun...@febo.com Date: Mon, 20 Jun 2011 17:14:44 To: Discussion of precise time and frequency measurementtime- n...@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] DDS'ery On 6/20/11 12:17 PM, li...@lazygranch.com wrote: Just a FYI, you don't have to use sine lookup tables. You can generate sine and cosine on the fly with a coordic. Perhaps not easy at RF speed, but very common in audio DSP. It's a tradeoff.. To do CORDIC you need four multiplies and 2 adds, which might be a lot of gates, if you have a fair number of bits, compared to an adder and some lookup tables. If you have a fast multiply instruction on a processor, then CORDIC gets very attractive. The other problem with CORDIC is that roundoff errors accumulate, the longer you run the generator for, because it's basically a difference equation/numerical integration sort of scheme. That said, some of AD's latest DDSes use a monolithic CORDIC generator. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] DDS'ery narrow scoped.
That is maybe interesting to you: http://www.holmea.demon.co.uk/Projects.htm#Frac - Henry -- ehydra.dyndns.info Luis Cupido schrieb: P.S. At the moment I'm testing on the bench with a real FPGA cyclone III with a 48bit dds at 100MHz fclock and at circa 6 and 18MHz output and it is not that bad. I got better than -60dBc in the desired ranges. So not too unhappy for a start ;-) PLL cleans 99% of it... but the close in spurs are annoying. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Update re light squared
http://www.pcworld.com/businesscenter/article/230780/lightsquared_may_change_bands_to_save_gps.html#tk.mod_rel Regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
