Re: [time-nuts] Cutler NAA on 24.0kHz....
Nat Semi App Note 72 page 18, par. 6.4 shows the configuration for bandpass active filter. This matches the last LM3900 stage, so you would seem to be correct. The shift in filter frequency for 200bps is because the higher modulation rate results in a greater frequency shift. It's like 50hz instead of the 25hz of the 100bps rate. Paul On Aug 17, 2014, at 4:35 PM, Robert LaJeunesse lajeune...@mail.com wrote: It's simple, but not obvious. The LM3900 is a Norton amplifier, and while it has differential inputs they are current driven. (Most older op amps are voltage driven.) The LM3900 is powered from 10V, so I think of that as just above the maximimum output voltage. Both the upper amplifier and the second lower amplifier have 1M feedback resistors, and + inputs fed 10V by 1M bias resistors. That would bias the output at near the supply rail, turning these stages into something like half-wave rectifiers. Since the first lower stage has a 2M bias resistor it idles at about half supply, and behaves as a simple inverter. If my analysis is correct (and I worked at National when the LM3900 came out, a friend did apps for this odd new part) then the combining of the two outputs produces a negative going full wave rectification of the signal. The fourth LM3900 stage looks like an inverting bandpass filter, but I'd have to dig out some reference books to determine its behavior in more detail. As f or the 100-200 switch I'm confused, why would the bandpass frequency be lowered for the higher modulation rate? Bob LaJeunesse Sent: Saturday, August 16, 2014 at 2:56 PM From: Kenneth G. Gordon kgordon2...@frontier.com To: paul swed paulsw...@gmail.com Cc: time-nuts@febo.com Subject: Re: [time-nuts] Cutler NAA on 24.0kHz On 16 Aug 2014 at 13:35, paul swed wrote: Kenneth on the opamps that is correct. But I put little U's to indicate phase. They actually represent the top half of the input cycle. Yes, I saw those, but unless I am mistaken, you didn't add a U after the second opamp, which would have returned the phase to the input's. In the top path it inverts once. I see twice: once through the first op amp and again through the second one. The second one then outputs to the IF. Anyway, to me, it is a very interesting and simple circuit. I LIKE simple. I am a great believer in the KISS principle. Ken W7EKB ___ 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] Mc Coy OCXO in HP equipment.
I am presently downsizing and that has also resulted in shrinking my HP 70 000 series spectrum analyzer. Out with the 70310A OCXO reference. The unit has a McCoy OSC92-13B OCXO. The original price was $ 5000 and the option with out OCXO was a $ 2500 saving. Some OCXO. Does any one have any information on the unit and is it used in other equipment. Thank you Bert Kehren ___ 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] Cutler NAA on 24.0kHz....
I may build up the d-msk-r tracor circuit. I seriously speculate it works as follows. Tracor down converts NAA's signal to a 100 Hz IF. The NAA signal is plus and minus 50 Hz msk or FSK Making the mark 50 Hz and space 150 Hz. (Really don't know whats mark or space nor does it matter) The tracor d-msk-r acts as a doubler so 50 Hz becomes 100 Hz only for the mark condition. The space goes to 300 Hz and the last stage bandpass filter only passes the doubled mark signal at 100 Hz the signal that the Tracor can lock to. I believe the 300 Hz simply leaves gaps in the signal. Purest of a guess. When I looked at NAA in spectrum lab it did not appear as a traditional FSK signal. Instead it was a clearly random signal without clearly defined mark and space carriers. Kind of pointing to a OPSK like signal. If the theory is true the d-msk-r only works on an IF of 100 Hz. The reason tracor selected this IF over the others that could have been used. Regards Paul WB8TSL On Mon, Aug 18, 2014 at 11:17 AM, Paul Davis ziggy9+time-n...@pumpkinbrook.com wrote: Nat Semi App Note 72 page 18, par. 6.4 shows the configuration for bandpass active filter. This matches the last LM3900 stage, so you would seem to be correct. The shift in filter frequency for 200bps is because the higher modulation rate results in a greater frequency shift. It's like 50hz instead of the 25hz of the 100bps rate. Paul On Aug 17, 2014, at 4:35 PM, Robert LaJeunesse lajeune...@mail.com wrote: It's simple, but not obvious. The LM3900 is a Norton amplifier, and while it has differential inputs they are current driven. (Most older op amps are voltage driven.) The LM3900 is powered from 10V, so I think of that as just above the maximimum output voltage. Both the upper amplifier and the second lower amplifier have 1M feedback resistors, and + inputs fed 10V by 1M bias resistors. That would bias the output at near the supply rail, turning these stages into something like half-wave rectifiers. Since the first lower stage has a 2M bias resistor it idles at about half supply, and behaves as a simple inverter. If my analysis is correct (and I worked at National when the LM3900 came out, a friend did apps for this odd new part) then the combining of the two outputs produces a negative going full wave rectification of the signal. The fourth LM3900 stage looks like an inverting bandpass filter, but I'd have to dig out some reference books to determine its behavior in more detail. As f or the 100-200 switch I'm confused, why would the bandpass frequency be lowered for the higher modulation rate? Bob LaJeunesse Sent: Saturday, August 16, 2014 at 2:56 PM From: Kenneth G. Gordon kgordon2...@frontier.com To: paul swed paulsw...@gmail.com Cc: time-nuts@febo.com Subject: Re: [time-nuts] Cutler NAA on 24.0kHz On 16 Aug 2014 at 13:35, paul swed wrote: Kenneth on the opamps that is correct. But I put little U's to indicate phase. They actually represent the top half of the input cycle. Yes, I saw those, but unless I am mistaken, you didn't add a U after the second opamp, which would have returned the phase to the input's. In the top path it inverts once. I see twice: once through the first op amp and again through the second one. The second one then outputs to the IF. Anyway, to me, it is a very interesting and simple circuit. I LIKE simple. I am a great believer in the KISS principle. Ken W7EKB ___ 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] Cutler NAA on 24.0kHz....
Paul wrote: Nat Semi App Note 72 page 18, par. 6.4 shows the configuration for bandpass active filter. This matches the last LM3900 stage, so you would seem to be correct. The shift in filter frequency for 200bps is because the higher modulation rate results in a greater frequency shift. It's like 50hz instead of the 25hz of the 100bps rate. Robert wrote: It's simple, but not obvious. The LM3900 is a Norton amplifier, and while it has differential inputs they are current driven. * * * Both the upper amplifier and the second lower amplifier have 1M feedback resistors, and + inputs fed 10V by 1M bias resistors. That would bias the output at near the supply rail, turning these stages into something like half-wave rectifiers. Since the first lower stage has a 2M bias resistor it idles at about half supply, and behaves as a simple inverter. * * * combining the two outputs produces a negative going full wave rectification of the signal. The fourth LM3900 stage looks like an inverting bandpass filter, but I'd have to dig out some reference books to determine its behavior in more detail. As f or the 100-200 switch I'm confused, why would the bandpass frequency be lowered for the higher modulation rate? The circuit as a whole operates as a frequency doubler using full-wave rectification and filtering. The rx LO is 100Hz below the nominal carrier frequency, so in normal (non-MSK) mode, the IF frequency is 100Hz. Referring to the MSK addendum, a received 200 baud MSK signal is 50Hz below nominal, and a 100 baud MSK signal is 25Hz below nominal. With the LO 100 Hz below nominal, this makes the IF frequency 50Hz when receiving a 200 baud MSK signal, and 75 Hz when receiving a 100 baud MSK signal. After doubling, these become 100 Hz (200 baud) and 150 Hz (100 baud), so the BPF is switchable between 100Hz and 150Hz. They used a FET to chop the 150Hz (100 baud) signal with a 50Hz square wave. I can't say I'm impressed with the design, even for the era. The whole instrument is built mostly with LM3900s, which makes it thousands (maybe even millions) of times noisier than it would be if it had been properly designed with standard op-amps. It may work more or less, but it's a fugly way to get there. There are other questionable choices (like the FET chopper, an overall design that depends on lots of one-shots, etc.). The designers knew about the LM301 (there is one in the unit), so there was really no excuse for using LM3900s. Yeah, the 301 was more expensive -- but this was supposed to be a state-of-the-art measuring device for characterizing good OCXOs down to PPB or below. I simulated the MSK board in LTspice. Let me know (OFFLIST ONLY, please) if you would like the files to play with (662kB ZIP file). (Note that these won't do you any good if you're not an LTspice user.) Again, please do not clutter the list with requests for files -- OFFLIST ONLY, please (check your headers carefully before you hit Send). 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.
[time-nuts] MH370 Doppler
Is anyone paying attention to all the chatter about the lost aircraft MH370, Inmarsat's supposed flight tracks based on 6 or 7 pings (1 per hour), the Doppler shift (BFO) and transaction timing (BTO) etc?? Basically from my perspective they are putting too much stock into the Doppler which relies in part upon the stability of the satellite terminal in the 777 aircraft. My question is how stable an oscillator (reported OCXO - not confirmed) would be under the extremes of either or both a cabin fire or decompression event. There is a website (Duncan Steel Blog) where some math brains are trying to sort out the raw data provided by Inmarsat. They have made assumptions about the stability of the local oscillator in the satellite, but I think the aircraft satellite terminal's master oscillator is a variable they have pushed aside. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.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] MH370 Doppler
I thought that Inmarsat terminals had AFC to the sat's down-link. Not to the degree of true phase-lock like DSN has but enough so that the sat's abillity to do doppler correction on the uplink is valid to help with BER, etc... Otherwise the doppler correction would be of no help and not be needed. -Brian, WA1ZMS/4 iPhone On Aug 18, 2014, at 12:53 PM, Joe Leikhim jleik...@leikhim.com wrote: Is anyone paying attention to all the chatter about the lost aircraft MH370, Inmarsat's supposed flight tracks based on 6 or 7 pings (1 per hour), the Doppler shift (BFO) and transaction timing (BTO) etc?? Basically from my perspective they are putting too much stock into the Doppler which relies in part upon the stability of the satellite terminal in the 777 aircraft. My question is how stable an oscillator (reported OCXO - not confirmed) would be under the extremes of either or both a cabin fire or decompression event. There is a website (Duncan Steel Blog) where some math brains are trying to sort out the raw data provided by Inmarsat. They have made assumptions about the stability of the local oscillator in the satellite, but I think the aircraft satellite terminal's master oscillator is a variable they have pushed aside. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.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. ___ 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] Fwd: Re: Fwd: MH370 Doppler
Because of the bent pipe transponder there is a doppler shift on the uplink from the terminal in the aircraft and doppler on the downlink from the satellite. Each has to be calculated differently because of the relative motion of the satellite (to ground station and aircraft) and the gross difference in UL and DL frequency bands. The local oscillator in the satellite is subject to drift due to solar temperature changes as the satellite drifts in and out of eclipse. This is apparently being considered. However, the Doppler parameter called burst frequency offset is a value reported by the satellite terminal to the ground station. My point is that, all of the discussion I have read ignores the possibility that the master oscillator aboard the aircraft is also subjsect to drift due to thermal effects and those effects could be quite significant if a fire on board. . Remember this Doppler shift is not being tracked (observed) continuously, rather as a periodic data point reported from the aircraft terminal on hourly intervals. Not like averaging the tone from a train whistle to get a baseline. On 8/18/2014 4:13 PM, Brian, WA1ZMS wrote: Joe- My understanding is that the Inmarsat link has doppler correction as one of the parameters that the bird calculates from each ping heard. So it matters not much if the LO on the sat drifts. So long as you have the previous data you can plot a trend line. The trend is the sat LO drift and the delta from that trend is the dopler. At least that's how I read the raw Inmarsat data. I may be wrong. Need to think about it more. -Brian, WA1ZMS/4 iPhone Begin forwarded message: *From:* Joe Leikhim jleik...@leikhim.com mailto:jleik...@leikhim.com *Date:* August 18, 2014 at 12:53:24 PM EDT *To:* time-nuts@febo.com mailto:time-nuts@febo.com *Subject:* *[time-nuts] MH370 Doppler* *Reply-To:* Discussion of precise time and frequency measurement time-nuts@febo.com mailto:time-nuts@febo.com Is anyone paying attention to all the chatter about the lost aircraft MH370, Inmarsat's supposed flight tracks based on 6 or 7 pings (1 per hour), the Doppler shift (BFO) and transaction timing (BTO) etc?? Basically from my perspective they are putting too much stock into the Doppler which relies in part upon the stability of the satellite terminal in the 777 aircraft. My question is how stable an oscillator (reported OCXO - not confirmed) would be under the extremes of either or both a cabin fire or decompression event. There is a website (Duncan Steel Blog) where some math brains are trying to sort out the raw data provided by Inmarsat. They have made assumptions about the stability of the local oscillator in the satellite, but I think the aircraft satellite terminal's master oscillator is a variable they have pushed aside. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com mailto:jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM http://WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com mailto:time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.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] Fwd: Re: Fwd: MH370 Doppler
In message 53f268cf.80...@leikhim.com, Joe Leikhim writes: My point is that, all of the discussion I have read ignores the possibility that [...] The major point being ignored is that the terminal in the plane does a signon after approx 45-60 minutes (can't remember exact duration -- it's in the data released.) That means that the terminal was powered on. That implies it was previously powered off. The terminal doesn't power on by it's on, somebody is in the plane at that point, messing with circuit breakers. The hopeful interpretation is that somebody in the cockpit is heroically fighting to reconfigure the plane so he can call mayday and/or gain control. The conspiratorical interpretation is that in the time interval between the previous ping and the sign on, there plenty of time to land the plane at some marginally suitable strip, do what what you came for, take off, reconfigure the plane and autopilot and leave by parachute via the back door. The quick detour into the extreme high corner of the planes envelope which seems perfectly designed to incapacitate the passengers makes me lean towards the latter. -- 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] MH370 Doppler
On Mon, Aug 18, 2014 at 04:18:30PM -0400, Brian, WA1ZMS wrote: I thought that Inmarsat terminals had AFC to the sat's down-link. Not to the degree of true phase-lock like DSN has but enough so that the sat's abillity to do doppler correction on the uplink is valid to help with BER, etc... Otherwise the doppler correction would be of no help and not be needed. I beleive most Aero Classic terminals use a fairly good OCXO. Somewhere I may have a limit spec on stability, but those docs are not immediately handy. Normally a demod in the terminal is kept tuned to one of the continuous L band control channels which I believe may be Doppler compensated in the ground uplink transmitter for the 6 Ghz C band uplink Doppler and LO drift on the satellite so it is correctly on frequency as radiated on the L band downlink. This could supply a frequency reference to the terminal that could be used to AFC the terminal frequency standard so it is close to right on. Doing this would require terminal firmware to determine estimated Doppler at the L band control channel downlink frequency from the satellite based on some estimate of the planes position, satellite position and relative velocities. The QPSK DSP modems used at both ends would be easily able to supply estimated frequency offset, both on the ground at ground earth station and in the plane. It is presumably true that this measurement is corrected on the ground end for the Doppler due to movement of the satellite relative to the ground station on the C band downlink relaying the L band uplinks from the plane so it reflects frequency error as seen at the satellite on the L band uplink with the downlink and satellite LO drift terms removed. I presume this is what INMARSAT is reporting, but am not sure. IIRC the plane is expected to adjust its burst uplink frequency and timing to come out right at the satellite receive antenna... thus compensating for the uplink Doppler at L band and the time delay too. But I do remember that the ground supplies feedback on the control channel as to how much the plane is off so it can adjust... Guess it might be time to dig out the docs again. -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ 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] Mc Coy OCXO in HP equipment.
I am just speculating that this oscillator was used instead of the 10811 because the 10811 would not fit. Therefore, it would NOT be used in other equipment. I would guess the specs would be similar to the 10811. The 70,000 series had some general purpose power bus that the McCoy would have to run off of. It might use different voltages than the 10811. Rick On 8/18/2014 8:55 AM, ewkeh...@aol.com wrote: I am presently downsizing and that has also resulted in shrinking my HP 70 000 series spectrum analyzer. Out with the 70310A OCXO reference. The unit has a McCoy OSC92-13B OCXO. The original price was $ 5000 and the option with out OCXO was a $ 2500 saving. Some OCXO. Does any one have any information on the unit and is it used in other equipment. Thank you Bert Kehren ___ 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] DIY FE-5680A lobotomy (disable temp compensation)
On Fri, 04 Jul 2014 02:35:41 +0100, you wrote: Hi Bert, I am thinking about testing a heat pipe on a fan cooled setup I use. The first temp controlled chassis I did used a peltier and works very well, but was a lot more work to do and is much more power hungry. The main problem I find is not the temp controller itself, but rather the change in the temperature across the chassis as the ambient changes. However good the temp controller is, it only controls a single point, but other points further away from the sensing thermistor can vary a lot. I noticed you posted a picture of a heat pipe cooler a couple of weeks ago - did you happen to compare the temperature across the unit with direct fan cooling and the heat pipe cooler, or with different heat pipes? Angus. I finally got around to playing with a couple of laptop heat pipes, fixed to a 25x50x75mm block of aluminium which is fixed to the 12mm thick baseplate. On a quick test of it, a sensor near the end of the baseplate showed 1.5-2x greater variation with temperature compared with just having a fan blow directly onto the baseplate. The oscillator also had to be allowed to run a few degrees C hotter for the heatpipe coolers to work to the same max ambient temp. One cooler had two heatpipes with about 12cm between the aluminium block and the heatsink fins (cast in this case) The other had a single, wider heat pipe with about 5cm between the block and the heatsink (this time with a lot more fine fins) The second cooler was rather more efficient, allowing a extra degreee of cooling at the top end, but more problematic was that it entered 'bang-bang' mode with the analogue temperature controller even sooner, and the temperature fluctuations there were greater. Both were rather worse than with the fan just blowing onto the baseplate. Using a PWM fan controller would help a good bit, but getting more creative with a microcontroller would be better. That way you can give the fan a minimum of a small kick every so often, and vary the repetition rate as well as the duty cycle as more cooling is needed. With feedback from the fan and even air temperature monitoring, you could get a good idea of exactly how much cooling was being applied. Another problem is that the overall temp control range is lower with the coolers - barely 8-9 DegC compared with 12+ DegC with the fan blowing directly on the baseplate. That's mainly the result of the poorer cooling at the top end of the range. The Rb osc fitted during this test was a SA.22c which takes a good bit less power than a 5680A, and the fan blowing onto the baseplate was normally a 60mm one fitted about 50mm away from it. The baseplate was horizontal with the fan blowing onto it from below. Maybe fitting a heatsink directly onto the base would help further with the maximum temp, but it would increase the convection cooling at the minimum temp, reducing the overall benefit. It could also be more susceptible to drafts, and would make the fan control much more delicate. Anyway, that's the results I got with my setup. Other setups and more fine tuning could change things a good bit, but I just wanted to get an idea of how the two cooling methods compared on the same setup. Angus On Sat, 28 Jun 2014 12:37:37 -0400 (EDT), you wrote: Will someone beside us use heat pipe. Would love to have an impendent input. What does it take to get a test going. Scott has done a lot of work, how about some one else step up to the plate. There are a lot of time nuts out there with the 5680A,many for the first time will have a very good reference and some of our experts with proper equipment can make a big difference. Bert Kehren In a message dated 6/28/2014 12:20:12 P.M. Eastern Daylight Time, newell+timen...@n5tnl.com writes: At 04:32 AM 6/28/2014, wb6bnq wrote: monitoring process ? In other words have you traced out the connections to see what is driving the pin you think is the temperature input ? No. I've only traced back from the ADC input to the voltage divider. The next big question is have you monitored the frequency and its stability, externally, to observe what effects are taking place when you disable this input to the A/D ? I have not. That sounds complicated and messy but may be easier than it appears. An appropriate container would be: It does sound messy. I don't think I'm willing to dunk one of my units. ___ 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.
