Re: [time-nuts] HP-3586B SSB L.O. Mods...
Hi Deep dips in WWVB can be from several sources. One is the sunrise / sunset thing that seems to happen on a fairly regular basis. Once you take that out, I suspect that great big storms like the one between you and Colorado just might have some influence. Any antenna, even VLF is going to be sensitive to local disruption. The issue could be quite local. Never rule out alien invasion unless you have already checked the appropriate topic related web sites Bob On Mar 22, 2011, at 9:54 PM, paul swed wrote: I did indeed get spectrum lab to work. Its a new install on the bench laptop and I just reset everything to factory on spec lab. Then changed the FFT sample length to higher values like 500K and filter to rectangle. I'm easily reading the errors that I could see on the scope. Ref signal is wwvb at 60KC. Perfect is 1.8500 KC I read 1.849922 and 1.850370. Pretty much the errors are lining up with the expected DDS errors. This gets addicting. Do like when the stuff works and the theory fits. Though will say WWVB is going through some deep dips tonight. Wonder whats cooking in the ether? Regards Paul WB8TSL On Tue, Mar 22, 2011 at 9:29 PM, Bob Camp li...@rtty.us wrote: Hi That's what I used to do for the FMT stuff. I just used a simple divider to get a 1 KHz tone. Bob On Mar 22, 2011, at 9:12 PM, paul swed wrote: Thanks Bob On Tue, Mar 22, 2011 at 9:09 PM, Bob Camp li...@rtty.us wrote: Hi If you have a stereo sound card, you could digitize both the synthesizer output and the BFO. Mix them both down digitally. Do the angle conversion and compare the phase records. The sound card clock should pretty much drop out that way. Bob On Mar 22, 2011, at 9:05 PM, paul swed wrote: Welll I sort of went past this and have a reasonable answer. All system locked to a rb ref. A HP8660 as source gen and set to 3 MC. The 3586 if is 15.625KC. Set a HP 3335 to the IF frequency and on a scope the signals lined right up and are stable. Bob I think you or someone else mentioned this fact and I verified it. Then I went to the audio out on the 3586. That signal should be 1.850KC. Set the 3335 to 1.85 KC and watched the drift rate for USB and LSB. The answer is for 1 cycle drift rate is; 2.68 seconds for lsb or 2.0X10-4 (This will bring responses) 9.97 seconds for usb or 5.4X10-5 Have to say that drift is way below what my ears can hear these days. So though I could change the DDS for FMT use and drive the decimal point at least 3 more digits to the left. I really have to say good enough and a success from just two weeks ago. Regards Paul WB8TSL On Tue, Mar 22, 2011 at 8:45 PM, Bob Camp li...@rtty.us wrote: Hi My assumption is that to do any of this, some sort of calibrated clock on the sound card would be needed. Either a mod to the card, or some luck with the built in clock source. It's going to be needed weather you use an FFT or some other DSP process. For a fully locked system, mod the sound card for an external clock and whip up a phase locked loop to drive it. The mix down source would likely be purely digital. Inserted after you had the sample stream. My first choice would be to use a 2 KHz stupid clock (0 1 0 -1) with an 8 KHz sample rate. Pretty simple math. Bob On Mar 22, 2011, at 6:23 PM, Alberto di Bene wrote: On 3/22/2011 5:24 PM, Bob Camp wrote: The other approach would be to simply take the samples, do a mix down, and get the phase from an ATAN calculation on the I/Q results. That would give you pure phase and thus frequency. How do you intend to generate the numeric LO stream to use for the mix down ? It must have a sampling rate with a precision comparable to what you intend to measure... 73 Alberto I2PHD ___ 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. ___ 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
Re: [time-nuts] HP-3586B SSB L.O. Mods...
Indeed you left out one other. Congress will tax the ionosphere so some times there simply is less of it. Need to close the budget gap somehow. On Wed, Mar 23, 2011 at 7:38 AM, Bob Camp li...@rtty.us wrote: Hi Deep dips in WWVB can be from several sources. One is the sunrise / sunset thing that seems to happen on a fairly regular basis. Once you take that out, I suspect that great big storms like the one between you and Colorado just might have some influence. Any antenna, even VLF is going to be sensitive to local disruption. The issue could be quite local. Never rule out alien invasion unless you have already checked the appropriate topic related web sites Bob On Mar 22, 2011, at 9:54 PM, paul swed wrote: I did indeed get spectrum lab to work. Its a new install on the bench laptop and I just reset everything to factory on spec lab. Then changed the FFT sample length to higher values like 500K and filter to rectangle. I'm easily reading the errors that I could see on the scope. Ref signal is wwvb at 60KC. Perfect is 1.8500 KC I read 1.849922 and 1.850370. Pretty much the errors are lining up with the expected DDS errors. This gets addicting. Do like when the stuff works and the theory fits. Though will say WWVB is going through some deep dips tonight. Wonder whats cooking in the ether? Regards Paul WB8TSL On Tue, Mar 22, 2011 at 9:29 PM, Bob Camp li...@rtty.us wrote: Hi That's what I used to do for the FMT stuff. I just used a simple divider to get a 1 KHz tone. Bob On Mar 22, 2011, at 9:12 PM, paul swed wrote: Thanks Bob On Tue, Mar 22, 2011 at 9:09 PM, Bob Camp li...@rtty.us wrote: Hi If you have a stereo sound card, you could digitize both the synthesizer output and the BFO. Mix them both down digitally. Do the angle conversion and compare the phase records. The sound card clock should pretty much drop out that way. Bob On Mar 22, 2011, at 9:05 PM, paul swed wrote: Welll I sort of went past this and have a reasonable answer. All system locked to a rb ref. A HP8660 as source gen and set to 3 MC. The 3586 if is 15.625KC. Set a HP 3335 to the IF frequency and on a scope the signals lined right up and are stable. Bob I think you or someone else mentioned this fact and I verified it. Then I went to the audio out on the 3586. That signal should be 1.850KC. Set the 3335 to 1.85 KC and watched the drift rate for USB and LSB. The answer is for 1 cycle drift rate is; 2.68 seconds for lsb or 2.0X10-4 (This will bring responses) 9.97 seconds for usb or 5.4X10-5 Have to say that drift is way below what my ears can hear these days. So though I could change the DDS for FMT use and drive the decimal point at least 3 more digits to the left. I really have to say good enough and a success from just two weeks ago. Regards Paul WB8TSL On Tue, Mar 22, 2011 at 8:45 PM, Bob Camp li...@rtty.us wrote: Hi My assumption is that to do any of this, some sort of calibrated clock on the sound card would be needed. Either a mod to the card, or some luck with the built in clock source. It's going to be needed weather you use an FFT or some other DSP process. For a fully locked system, mod the sound card for an external clock and whip up a phase locked loop to drive it. The mix down source would likely be purely digital. Inserted after you had the sample stream. My first choice would be to use a 2 KHz stupid clock (0 1 0 -1) with an 8 KHz sample rate. Pretty simple math. Bob On Mar 22, 2011, at 6:23 PM, Alberto di Bene wrote: On 3/22/2011 5:24 PM, Bob Camp wrote: The other approach would be to simply take the samples, do a mix down, and get the phase from an ATAN calculation on the I/Q results. That would give you pure phase and thus frequency. How do you intend to generate the numeric LO stream to use for the mix down ? It must have a sampling rate with a precision comparable to what you intend to measure... 73 Alberto I2PHD ___ 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. ___ 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
Re: [time-nuts] 50/60 Hz clocks
On 03/22/2011 11:45 PM, Hal Murray wrote: mag...@rubidium.dyndns.org said: On the other hand, it would not be difficult to make a DDS which hit 60/ 1000 exactly. Reducing it by 20 on each side you get 3/50 so a 19 bit accumulator (mod 50) incrementing with 3 on every 100 ns period would do it. Neat. Thanks. I'd noticed that adding in decimal rather than binary would make exact target frequencies in some cases, but I hadn't generalized to adding modulo N. Using N of 10,000,000 with a 10 MHz clock gets you all exact integer frequencies in the audio range. Which was my main point... it doesn't have to be THAT complex. A 50 entry LUT is however expensive. A LUT for sine would be possible. Playing a few tricks with the LUT table (realizing that the LUT would be walked through three times with three different start-alignments) converts it into a LUT of the same size and a increment by one or decrement by one counter modulus 50. A decrement by one counter allows wrap-around loading with 49 easy. CPLD or CMOS/TTL implementations would be trivial for the counter. The LUT will be large... More neat. Thanks again. It's just a simple state machine cycling through some collection of states. Exactly. It really helps when trying to understand spurious response. A DDS has a large number of states and for most frequencies, all states will be visited before looping. A 32-bit DDS clocked at 10 MHz wraps in 429.4967296 s. Half the possible settings will wrap quicker (at various power of 2 variants). If we are willing to rearrange the LUT/ROM, we can simplify the next state calculation from a modulo adder to a re-loadable counter. Which is what I propose above. Cheers, Magnus ___ 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] 50/60 Hz clocks, start at 60M0 Hz
Just thinking here about making a 60M0 Hz oscillator and phase locking it to the 10M0 reference. Then divide the 60M0 by 1e6. Youve got a perfectly locked 60 Hz square wave. For low harmonic 60 Hz sine wave one can go for 480 Hz to start a Walsh -Hadamard converter. Take 60M0 divide by 125 (easy with a binary counter) then divide by 1000. Result is 480 Hz. Take the 480 Hz and build the output stage with a DG201 CMOS switches (or similar) and a couple of opamps. Result is very low harmonic perfectly locked 60 Hz signal ready to drive an audio amplifier. Greg On 3/23/2011 1:03 PM, Magnus Danielson wrote: On 03/22/2011 11:45 PM, Hal Murray wrote: mag...@rubidium.dyndns.org said: On the other hand, it would not be difficult to make a DDS which hit 60/ 1000 exactly. Reducing it by 20 on each side you get 3/50 so a 19 bit accumulator (mod 50) incrementing with 3 on every 100 ns period would do it. Neat. Thanks. I'd noticed that adding in decimal rather than binary would make exact target frequencies in some cases, but I hadn't generalized to adding modulo N. Using N of 10,000,000 with a 10 MHz clock gets you all exact integer frequencies in the audio range. Which was my main point... it doesn't have to be THAT complex. A 50 entry LUT is however expensive. A LUT for sine would be possible. Playing a few tricks with the LUT table (realizing that the LUT would be walked through three times with three different start-alignments) converts it into a LUT of the same size and a increment by one or decrement by one counter modulus 50. A decrement by one counter allows wrap-around loading with 49 easy. CPLD or CMOS/TTL implementations would be trivial for the counter. The LUT will be large... More neat. Thanks again. It's just a simple state machine cycling through some collection of states. Exactly. It really helps when trying to understand spurious response. A DDS has a large number of states and for most frequencies, all states will be visited before looping. A 32-bit DDS clocked at 10 MHz wraps in 429.4967296 s. Half the possible settings will wrap quicker (at various power of 2 variants). If we are willing to rearrange the LUT/ROM, we can simplify the next state calculation from a modulo adder to a re-loadable counter. Which is what I propose above. Cheers, Magnus ___ 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] 50/60 Hz clocks
On 03/10/2011 11:41 PM, Robert LaJeunesse wrote:
Poor man's solution: Use an Arduino to read the Thunderbolt 1PPS and lock a 50Hz
(or 60Hz) square wave to the 1PPS. Any resulting jitter can likely be kept in
Here is an even poorer man's solution (and plug):
A DDS using both compare outputs of an 8 pin part to get
a phase-centered PWM with half the usual ripple.
With PPS input as a bonus so the zero crossing occurs where
you want it to.
http://n1.taur.dk/gen60a.jpg
Output 5Vpp@60Hz +1.1mVpp@39kHz. Very pretty sinewave.
//
TinyAWG.c
// 60Hz generator - 2011 Kasper Pedersen - Beerware license
//
// This is an arbirtrary waveform generator set up to produce 60Hz sine
// Compile with GCC -Os
//
//
// 2-5V ---+-+
// | |
// |__ |
// | __|* |__|
// | | |__| VCC |__|---+--||--+
// 3k| | | | 1u |
// | __| |_ _|_
// 10MHz ---||--+|__| CLK LOCK|__| GND
// 1n | | |
// | |__| |_____ ___
// 3k| | |__| PPS PWM1|__|---___--+---___---+
// | | | 2k2 | 3k3 |
// | __| |_____ | |
// GND ---+|__| GND PWM0|__|---___--+--||--+--||--+-
// | |__| 2k2100n | 100n
// | ATTINY13V |60Hz out
// | |
// +-+
//
//
// Rising edge on PPS input (optional) will steer the output
// so that, after 128 edges, the positive zero crossing
// of the output will coincide with PPS.
// When this happens, LOCK will go high.
//
// PWM frequency is 39kHz
// first filter stage attenuates 27x
// second filter stage attenuates 81x and pulls phase 1 deg.
#includeavr/io.h
#includeavr/interrupt.h
#includeavr/pgmspace.h
#define DCBIAS 127
PROGMEM unsigned char table[256]={
127,130,133,136,139,142,145,149,152,155,158,161,164,167,169,172,
175,178,181,184,186,189,192,194,197,200,202,205,207,209,212,214,
216,218,220,222,224,226,228,230,232,233,235,237,238,240,241,242,
243,245,246,247,248,248,249,250,251,251,252,252,252,253,253,253,
253,253,253,253,252,252,252,251,251,250,249,248,248,247,246,245,
243,242,241,240,238,237,235,233,232,230,228,226,224,222,220,218,
216,214,212,209,207,205,202,200,197,194,192,189,186,184,181,178,
175,172,169,167,164,161,158,155,152,149,145,142,139,136,133,130,
127,124,121,118,115,112,109,105,102,99,96,93,90,87,85,82,
79,76,73,70,68,65,62,60,57,54,52,49,47,45,42,40,
38,36,34,32,30,28,26,24,22,21,19,17,16,14,13,12,
11,9,8,7,6,6,5,4,3,3,2,2,2,1,1,1,
1,1,1,1,2,2,2,3,3,4,5,6,6,7,8,9,
11,12,13,14,16,17,19,21,22,24,26,28,30,32,34,36,
38,40,42,45,47,49,52,54,57,60,62,65,68,70,73,76,
79,82,85,87,90,93,96,99,102,105,109,112,115,118,121,124};
unsigned char phase;
signed acc;
unsigned char lastp=1;
ISR(SIG_OVERFLOW0)
{
signed s;
unsigned char v;
//60Hz*256=15360Hz increment rate.
//irq rate is 10MHz/256=39062.5Hz.
//we need to increment at: 60*256*256 / 10M
//split into primes and eliminate common factors:
//10MHz = 2^7 * 5* 5^6
//60*256 *256 = 2^7 *2 * 5 *2*2*3 * 2^8
//scaler = 2*2*2*3*256 / 5*5*5*5*5*5
// = 6144 / 15625
v=__LPM(table[phase]); //generate output
OCR0A=v;
OCR0B=(2*DCBIAS)-v;
s=acc; //generate phase
s-=6144;
if (s0) {
acc= s+15625;
++phase;
} else {
acc= s;
}
if (PINB16) { //on rising edge: adjust phase so this conincides with
the positive zero crossing.
if (!lastp) { //we need 128 pulses to become adjusted
lastp=1;
if (!phase) {
//phase is 0. At 15kHz we are within 65us
PORTB|=4;
} else
if (phase0x80) {
++phase; // 65us adjustments
PORTB=~4;
} else {
--phase;
PORTB=~4;
}
}
} else {
lastp=0;
}
}
void main(void)
{
TCCR0A=0xB3; //A is clear on match, positive output when bigger
TCCR0B=0x01;
TIMSK0=0x02;
DDRB|=1; //output
DDRB|=2;
DDRB|=4; //locked output
PORTB|=16; //~50uA pullup on PPS pin.
sei();
for (;;);
}
[time-nuts] 50/60 Hz clocks
it doesn't have to be THAT complex. A 50 entry LUT is however expensive. Yeah, might even cost as much as a whole US dollar (ragged as they are these days). 512 kbyte EPROMs can be had for under $1... connect the outputs to a resistor ladder (might need an output latch), filter, voila rather nice sine wave. ___ 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] Fluke 203A Distribution Amplifier Manual?
Date: Tue, 22 Mar 2011 18:29:33 -0700 From: Dan Rae dan...@verizon.net Subject: [time-nuts] Fluke 203A Distribution Amplifier Manual? Does anyone know of a source for this one? It is a sort of functional clone of the -hp- 5087; mine is modified for 1 in and 9 10 MHz outputs. I have tried all the usual suspects... Dan Hi Dan, I have an original copy of the Fluke 203A manual. If you can wait for a few days till I can get to a better scanner, I can scan it for you. It doesn't have a large number of pages, but there are a number of B-size foldouts in it. Cheers, David dgminala at mediacombb dot net ___ 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] 50/60 Hz clocks
Hi You can do the drop / add pulse thing with a sub 50 cent micro. The only real sorting function is that you rule out the ones that won't take an external 10 MHz clock. If you want pseudo sine wave with PWM that likely will fit. We're only driving a motor here, low distortion is hardly a requirement. Bob On Mar 23, 2011, at 7:20 PM, Chris Albertson wrote: On Wed, Mar 23, 2011 at 3:18 PM, Mark Sims hol...@hotmail.com wrote: it doesn't have to be THAT complex. A 50 entry LUT is however expensive. Yeah, might even cost as much as a whole US dollar (ragged as they are these days). 512 kbyte EPROMs can be had for under $1... connect the outputs to a resistor ladder (might need an output latch), filter, voila rather nice sine wave. I think if you really needed a 500K entry LUT then each entry would need to be 3 bytes wide or you loose the point of having a large table.So you are up to a 1.5 Mbyte table. That said a sine wave can be compressed. First off you only need to store 1/4 of the wave. Then because the function is monotonic you only need the deltas from the last sample and we assume the first sample is zero. The wide table could easy be compressed to 512K But even so, one can buy a small micro controller with way more than 1.5MB for only a few dollars. Or for that matter AD will give you sample DDS chips for free if you ask. -- = Chris Albertson Redondo Beach, California ___ 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] Fluke 203A Distribution Amplifier Manual?
Hi David, Is it possible for you to upload your scan to KO4BB (once it is done)? I am also looking for this manual and I am sure there are more people lurking. Stijn Date: Tue, 22 Mar 2011 18:29:33 -0700 From: Dan Rae dan...@verizon.net Subject: [time-nuts] Fluke 203A Distribution Amplifier Manual? Does anyone know of a source for this one? It is a sort of functional clone of the -hp- 5087; mine is modified for 1 in and 9 10 MHz outputs. I have tried all the usual suspects... Dan Hi Dan, I have an original copy of the Fluke 203A manual. If you can wait for a few days till I can get to a better scanner, I can scan it for you. It doesn't have a large number of pages, but there are a number of B-size foldouts in it. Cheers, David dgminala at mediacombb dot net ___ 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] 50/60 Hz clocks
On Wed, Mar 23, 2011 at 4:23 PM, Bob Camp li...@rtty.us wrote: Hi We're only driving a motor here, low distortion is hardly a requirement. You mean this is for a mechanical clock? Then telk of a 512K LUT is pointless. You need only 8-bit samples and to shore 90 degrees of the sine function takes 64 bytes. Yes the entire sine wave generators would go into an 80 cent uP. that fits in an 8-pin package.. I've seen examples of this in higher-end battery backup supplies and power inverters. I think I had a desktop computer in about 1980 that I used for word processing mostly. Itwas far less then what now can fit into an 8pin dip and sell for under a buck. I remember it had a 4Mhz 8-bit CPU with about 32MB RAM -- = Chris Albertson Redondo Beach, California ___ 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] Squaring Tbolt 10Mhz output
Hello All, I'm trying to square the 10Mhz output from a Thunderbolt GPSDO, and failing miserably. I'm still very new at this so please forgive my ignorance. I thought it was going to be easy. I have tried diodes, comparators, op-amps, Schmidt trigger buffers,regular buffers, inverters, and differential amplifier circuits. I must be missing something simple because i just can't shape the wave into a square wave. Has any one done this? Any hints or tips for a struggling newbie? Many thanks! -- Best Regards, James Fournier ___ 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] Squaring Tbolt 10Mhz output
Feed it through a 10M0 Hz crystal filter (easy to make out of one crystal) then put the output of the filter into a fast comparator. It is commonly done in certain types of DDS synthesizers. Is that clear enough or do you need a picture? Greg On 3/23/2011 6:57 PM, James Fournier wrote: Hello All, I'm trying to square the 10Mhz output from a Thunderbolt GPSDO, and failing miserably. I'm still very new at this so please forgive my ignorance. I thought it was going to be easy. I have tried diodes, comparators, op-amps, Schmidt trigger buffers,regular buffers, inverters, and differential amplifier circuits. I must be missing something simple because i just can't shape the wave into a square wave. Has any one done this? Any hints or tips for a struggling newbie? Many thanks! ___ 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] Squaring Tbolt 10Mhz output
James Fournier wrote: Hello All, I'm trying to square the 10Mhz output from a Thunderbolt GPSDO, and failing miserably. I'm still very new at this so please forgive my ignorance. I thought it was going to be easy. I have tried diodes, comparators, op-amps, Schmidt trigger buffers,regular buffers, inverters, and differential amplifier circuits. I must be missing something simple because i just can't shape the wave into a square wave. Has any one done this? Any hints or tips for a struggling newbie? Many thanks! Almost all of the above should work provided they are correctly biased. What exactly is the problem? No output? An output duty cycle other than 50%? Please provide circuit diagrams so that we can spot your errors. 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.
[time-nuts] Upgrade project, Odetics 325/425
Fellow clock-tickers, Just a point of interest. I have successfully upgraded my Odetics 425 by replacing its original quartz OCXO with an Efratom (Ball) FRS-C series rubidium oscillator. The process was pretty simple: Wire the FRS-C in, with practically identical wiring to the OCXO, and (since the bottom of the case is already drilled and countersunk for an FRS-C) mount the thing. The only other steps were to flip switch #2 on the MPU board's pack to ON, and (as a purely cosmetic touch) to add a 'lock indicator' LED, driven by the FRS-C's 'Lock Indicator' line. Reassemble, power on, wait about fifteen minutes, and everything locked up and behaved beautifully. It was ticking happily along even as I left work this afternoon. I see no reason why this trick should not work on any other Odetics 325 or 425. If anyone needs more details, let me know. Happy tweaking. -=-=-=-=-=-=-=-=-=-=-=- Bruce Lane, Owner Head Hardware Heavy, Blue Feather Technologies -- http://www.bluefeathertech.com kyrrin (at) bluefeathertech do/t c=o=m Quid Malmborg in Plano... ___ 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] Squaring Tbolt 10Mhz output
James wrote: I'm trying to square the 10Mhz output from a Thunderbolt GPSDO, and failing miserably. I'm still very new at this so please forgive my ignorance. I thought it was going to be easy. I have tried diodes, comparators, op-amps, Schmidt trigger buffers,regular buffers, inverters, and differential amplifier circuits. I must be missing something simple because i just can't shape the wave into a square wave. Has any one done this? I concur with Bruce that most of these should work. More details about what you have tried (i.e., schematics), and what results you have gotten, will be necessary for us to be able to help you. (The list accepts small attachments.) Meanwhile, here are two links you can peruse that give several shaping circuits (the second link is Bruce's work): http://www.wenzel.com/documents/waveform.html http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:clock_shapers Best regards, Charles ___ 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] Squaring Tbolt 10Mhz output
One problem that is evident when a simple longtailed pair (differential amplifier) is used to convert a sine wave to a square wave is the tilt that is evident in the waveform when the output transistor is conducting. This is due to feedthrough from the input signal via the emitter base capacitance of the input transistor to the emitter of the output transistor. The attached circuit schematic illustrates one classical method of minimising this tilt. The value of C5 is selected/adjusted to achieve nominally zero tilt. Compensation isn't perfect due to the voltage dependence of the emitter base capacitance but the tilt can be significantly reduced, Using transistors with lower emitter base capacitances also helps as does reducing the value of the output collector load resistor. This requires increasing the tail current to maintain the output swing. The attached circuit produces a 3.3V pp output signal. For lower amplitude input signals capacitively coupling the emitters of the differential amplifier and splitting the current source so that each transistor has its own current source can be useful in minimising the effects of Vbe mismatches between the transistors. Bruce Charles P. Steinmetz wrote: James wrote: I'm trying to square the 10Mhz output from a Thunderbolt GPSDO, and failing miserably. I'm still very new at this so please forgive my ignorance. I thought it was going to be easy. I have tried diodes, comparators, op-amps, Schmidt trigger buffers,regular buffers, inverters, and differential amplifier circuits. I must be missing something simple because i just can't shape the wave into a square wave. Has any one done this? I concur with Bruce that most of these should work. More details about what you have tried (i.e., schematics), and what results you have gotten, will be necessary for us to be able to help you. (The list accepts small attachments.) Meanwhile, here are two links you can peruse that give several shaping circuits (the second link is Bruce's work): http://www.wenzel.com/documents/waveform.html http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:clock_shapers Best regards, Charles ___ 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. attachment: EnhancedLTPShaper.PNG___ 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.
