Hi There was a factor of two "oops" in the math. All the numbers are 2X reality.
Bob On Feb 28, 2010, at 10:58 PM, Bruce Griffiths wrote: > Unless Minicircuits have made significant changes to the RPD-1 there has to > be some kind of calibration error or an as yet poorly understood effect. > Did you try the load and filter shown in the attached application note? > > Replicating Minicircuits measurements within 10% or so is probably necessary > to correctly assess the effect of various termination networks. > > Bruce > > Bob Camp wrote: >> Hi >> >> Ok, RPD-1 #1 puts out 9.97 volts into a 500 ohm resistor to ground >> termination (no blocking capacitor). That's still well above the catalog >> spec. I'm running 25% more voltage than their 7 dbm. That still does not >> fully explain what I'm seeing. >> >> The scope does indeed indicate 15 volts when I hook it to a 15 volt supply. >> Given the number of broken pieces of test gear I seem to own that was worth >> checking. ... >> >> Bob >> >> >> On Feb 28, 2010, at 8:54 PM, Bob Camp wrote: >> >> >>> Hi >>> >>> The Minicircuits guys claim 800 to 1000 mv / radian. In my units that would >>> be 5 to 6.2 volts per cycle. I believe I'm getting ~ 3 X that mostly from >>> the open circuit termination at audio. It's certainly something I could >>> head back downstairs and check. >>> >>> The< 10% increase in slope between resistive and capacitive termination >>> has never really been enough with the RPD-1 to make it seem to be worth it. >>> It's certainly worth it with a ZAD-3. >>> >>> Bob >>> >>> >>> On Feb 28, 2010, at g8:39 PM, Bruce Griffiths wrote: >>> >>> >>>> The results for the RPD-1's are about what I expected: there's little >>>> difference in slope between either a 50 ohm +47nF termination or a 47nF >>>> termination. >>>> The slopes are about 6.5x greater than the values given by Minicircuits. >>>> (8mv/degree = 2.88V/cycle). I assume that they use 500 ohms connected >>>> directly to ground not via a capacitor. >>>> So there's something in NISTs claims of improved slope at least for the >>>> RPD-1. >>>> I suspect that NISTs original 50 ohm terminations were actually 50 ohms >>>> direct to ground not via a capacitor. >>>> Using a series capacitor increases the termination impedance at the beat >>>> frequency substantially over that when the resistor is connected directly >>>> to ground. >>>> >>>> Since its is also claimed by NIST and others that reactive termination >>>> reduces the noise, one also needs to measure the output noise spectral >>>> density for the various IF port terminations. >>>> >>>> Bruce >>>> >>>> Bob Camp wrote: >>>> >>>>> Hi >>>>> >>>>> Here's some data: >>>>> >>>>> The setup is very simple: >>>>> >>>>> Two oscillators at 10 MHz driving common base / 50 ohm output buffers. >>>>> The buffers ensure that the source impedance is really 50 ohms. One puts >>>>> out 9.3 dbm the other 9.5 dbm. They can be tuned for a beat note in the 0 >>>>> to 100 Hz range. >>>>> >>>>> The basic mixer termination filter is a pair cascaded / identical L >>>>> networks. Both have 10 uh in the series leg and 0.047 uf to ground in the >>>>> shunt leg. The "audio end" of the filter hooks straight into a digitizing >>>>> scope. >>>>> >>>>> The termination options for the mixer are: >>>>> >>>>> 1) inductive - just running into the 10 uh of the first L network. >>>>> 2) 50 ohms - drop a 57 ohm in series with 0.047 from the mixer output to >>>>> ground >>>>> 3) Capacitive - 0.047 uf to ground at the mixer output. >>>>> >>>>> The data is computed from the time to cross the center 50% of the output >>>>> waveform. If the output is 1V p-p then the data would cover the range >>>>> -.25 to +.25 volts. I've normalized it to "volts / cycle". Divide by 2* >>>>> pi if you want to get volts / radian. >>>>> >>>>> >>>>> mixer 50 ohms inductive >>>>> capacitive >>>>> >>>>> ZAD-3 3.51 2.96 9.98 >>>>> RPD-1 #1 17.77 10.50 18.85 >>>>> RPD-1 #2 17.40 10.058 18.53 >>>>> 10514A #1 5.796 4.396 10.31 >>>>> 10514A #2 5.826 4.406 10.33 >>>>> 10534A 5.402 4.078 10.88 >>>>> ZP3-MH 8.06 5.81 11.28 >>>>> ZAD-1H 7.73 5.93 9.38 >>>>> >>>>> Since not everybody has memorized mixer catalogs: >>>>> >>>>> ZAD-3 typical minicircuits 7 to 10 dbm mixer >>>>> RPD-1 500 ohm output phase detector (50 ohms is the "wrong" >>>>> termination for it) >>>>> 10514, 10534 HP products from a ways back >>>>> ZP3-MH a 13 dbm class mixer, 9 dbm should be under driving it >>>>> ZAD-1H a 17 dbm class mixer, should be 8 db under driven. >>>>> >>>>> Bottom line - Capacitive termination helps some parts more than others. >>>>> The RPD-1 does not get a real big boost, but the ZAD-1 certainly does. >>>>> There's no real way to know what it's going to do without checking your >>>>> mixer under your conditions. >>>>> >>>>> A few other notes: >>>>> >>>>> 1) The measurement technique slightly under states the slope for the 50 >>>>> ohm case. Since the beat note is approximately a sine wave in all cases, >>>>> the true slope at zero is a bit higher than this technique indicates. >>>>> >>>>> 2) The Inductive termination gives the widest linear region. The output >>>>> is very nearly an ideal triangle wave. It would make the best "wide >>>>> range" phase detector. >>>>> >>>>> 3) The terminations are not precise, but they are identical in all cases. >>>>> A more purely inductive load could be constructed. The parts are just >>>>> what I had lying around. >>>>> >>>>> 4) No strange bumps or peaks were detected in the beat notes of any of >>>>> the mixers. Never seen one, regardless of what NIST says they have seen. >>>>> >>>>> 5) Eventually I'll go back and check the RPD's with 500 ohms. I stuck >>>>> with 50 simply to keep everything as "same same" as I could. >>>>> >>>>> 6) Sweeping the beat note from 100 Hz to 1 Hz showed no change in the >>>>> output amplitude. >>>>> >>>>> 7) Contrary to my previous post the peak-peak output voltages are within >>>>> 10% for all terminations. Slope and peak to peak are different things..... >>>>> >>>>> 8) All mixers are running into essentially an open circuit load at audio. >>>>> The scope input is> 1 M ohm and the capacitive reactances are>100 K >>>>> ohms. >>>>> >>>>> 9) No attempt was made to set up directional couplers and figure out what >>>>> the "real" input to the mixers actually is. Ditto on playing with series >>>>> resistors to improve the match. >>>>> >>>>> So there it is. Anybody else got some data to compare to. >>>>> >>>>> Bob >>>>> >>>>> On Feb 28, 2010, at 3:53 PM, Bruce Griffiths wrote: >>>>> >>>>> >>>>> >>>>>> My simulations indicate that terminating the Mixer IF port in an RF >>>>>> short (with both RF and LO ports saturated) increases the beat frequency >>>>>> zero crossing slope by more than a factor of 2 (exact value depends on >>>>>> mixer component characteristics) but doesnt significantly increase the >>>>>> beat frequency amplitude over that with a high value resistive >>>>>> termination. To achieve this the IF port termination impedance needs to >>>>>> be high at the beat frequency and its significant harmonics. The value >>>>>> above which the impedance is considered high depends on mixer details >>>>>> such as transformer turns ratio, RF source impedance, diode >>>>>> characteristics and RF input levels, etc. >>>>>> >>>>>> Bruce >>>>>> >>>>>> Bob Camp wrote: >>>>>> >>>>>> >>>>>>> Hi >>>>>>> >>>>>>> Putting The C on the feedback R in a positive gain setup is only going >>>>>>> to take the "roll off" gain down to 1. Doing the same with an inverting >>>>>>> amp or using a series R / cap to ground will drop the gain a lot more >>>>>>> in the roll off region. >>>>>>> >>>>>>> I would worry about any resistor that's marked as 10K and reads 20K. >>>>>>> It's likely noisy. >>>>>>> >>>>>>> A typical DBM has a loss of 5 to 7 db when not in compression. With a >>>>>>> +7 to +10 dbm drive that should give you an output of 0 to 2 dbm . >>>>>>> The mixer output should be in the .6 to .8 V p-p range into 50 ohms. >>>>>>> You should get about twice that on the beat note running into a load> >>>>>>> 500 ohms. A gain of 20 should be plenty. That would give you .6 x 2 x >>>>>>> 20 = 24 V p-p out of the amp. >>>>>>> >>>>>>> If you "rf short" the output of the mixer you may double the beat note >>>>>>> again (total of 4X the 50 ohm value). Net would be a 2.4 to 3.2 V p-p >>>>>>> beat note. Anything much over a gain of 10 would be a problem then. >>>>>>> This is one of the cases where 2 X 2 probably does not = 4, so >>>>>>> measurements are indeed in order. >>>>>>> >>>>>>> >>>>>>> Bob >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Feb 28, 2010, at 1:01 AM, Brian Kirby wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>>> The values in the schematics are wrong for the op amp gain. The >>>>>>>> drawing was from an earlier drawing where I made a preamp to start >>>>>>>> checks on the mixers, and I sent it to you (Bruce G). Thats when you >>>>>>>> determined I did not have enough gain to get near the noise floor. >>>>>>>> The THAT1512/1646 ICs were ordered to make a new preamp for the future >>>>>>>> measurements on the mixers. >>>>>>>> >>>>>>>> When I use the scope and check the outputs of the IC, I have 20 volts >>>>>>>> peak to peak, sine-wave. I know from previous readings I see about >>>>>>>> 500 mv p-p out of the mixer. >>>>>>>> >>>>>>>> I went down to the bench and the resistors I used were still there (I >>>>>>>> bought several taped reels of Dale RN55D resistors when a local >>>>>>>> business went out). I used 294 ohms and 14.9 kilo-ohms, for a gain >>>>>>>> of 50 (the power rails are +/- 15 volts). Also not shown on the >>>>>>>> schematic is a 0.47 uF cap around the 14.9 kilo-ohm resistor. I think >>>>>>>> I was trying to limit the bandwidth to around 15 hertz. >>>>>>>> >>>>>>>> Also the resistor going between the op amp and the limiting diodes was >>>>>>>> marked 10K, its 20K. The diodes are 1N4148. Corrected drawing >>>>>>>> attached. >>>>>>>> >>>>>>>> This is what happens to time nuts who can only play on the weekend and >>>>>>>> stay up all night....and my employer just thinks I party too >>>>>>>> hard.....for Monday mornings. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Brian KD4FM >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Bruce Griffiths wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>> The LT1037 is shown with a gain of ~1690x, if this amplifier is used >>>>>>>>> to amplify the beat frequency signal, it will saturate. >>>>>>>>> Opamp recovery from saturation is poorly documented and may be very >>>>>>>>> slow. >>>>>>>>> It would be better to use some diodes in the amplifier feedback >>>>>>>>> network to limit the large signal gain to 5x (so that the LT1037 >>>>>>>>> remains stable as it isn't unity gain stable). >>>>>>>>> This will ensure a somewhat faster recovery from overload as the >>>>>>>>> LT1037 then avoids saturation and the opamp input stage remains in >>>>>>>>> the linear region. >>>>>>>>> >>>>>>>>> Bruce >>>>>>>>> >>>>>>>>> Bob Camp wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>>> Hi >>>>>>>>>> >>>>>>>>>> Assuming that the junction of the back to back diodes goes trough a >>>>>>>>>> chunk of coax to get to the counter: >>>>>>>>>> >>>>>>>>>> You are forming a low pass filter with the 10K resistor and the coax >>>>>>>>>> capacitance. The LT1037 is quite happy driving a 600 ohm load. You >>>>>>>>>> could easily drop the impedance at that point below 300 ohms. That >>>>>>>>>> should give you a faster edge into the counter. >>>>>>>>>> >>>>>>>>>> You also should check the slew rate performance of the 1037. You >>>>>>>>>> don't want the op amp to be slew rate limited. >>>>>>>>>> >>>>>>>>>> Bob >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Feb 27, 2010, at 12:41 PM, Brian Kirby wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>>> I am in the process of designing a DMTD system. As an experiment >>>>>>>>>>> to do basic measurements on the chosen mixer, I used a capacitor >>>>>>>>>>> (0.01 uF) in series to ground with a 47 ohm metal film resistor. >>>>>>>>>>> Where the capacitor and resistor meets, another resistor is >>>>>>>>>>> attached (390 ohms) that goes to ground. The idea is to provide a >>>>>>>>>>> 50 ohm termination at 20 Mhz and a lighter termination at audio >>>>>>>>>>> frequencies. I seen this is a NBS note and I can say, its a >>>>>>>>>>> starting point for my experiments. >>>>>>>>>>> >>>>>>>>>>> This (my) system is designed for 10 Mhz, using a 10 hertz beat. A >>>>>>>>>>> schematic is attached of what I am experimenting with at the >>>>>>>>>>> moment. A HP5370B is the recording instrument. The noise floor >>>>>>>>>>> from 1 days observations show 2x10-11 at 0.1 seconds, 2x10-12 at 1 >>>>>>>>>>> sec, 5x10-13 at 10 sec, 6x10-14 at 100 sec, 7x10-15 at 1000 sec, >>>>>>>>>>> and 7x10-16 at 10,000 secs. It will be interesting when the >>>>>>>>>>> project is completed to see how much improvement there will be. >>>>>>>>>>> >>>>>>>>>>> As I understand (or learning..) mixer performance is the key to the >>>>>>>>>>> DMTD system. It occurs to me that maybe a capacitor designed for >>>>>>>>>>> 50 ohms at 20 mhz may be a better termination (for the IF port) for >>>>>>>>>>> this mixer. A 16 pF capacitor is 50 ohms at 20 mhz, and for >>>>>>>>>>> comparison at 10 hertz, it would be 100 meg-ohms, which would give >>>>>>>>>>> maximum amplitude at 10 hertz. As I understand, a capacitor >>>>>>>>>>> terminated mixer will give a triangle wave output, which is very >>>>>>>>>>> beneficial to the design - as the end result is to get maximum >>>>>>>>>>> slope out of the mixer. I would say, unqualified as I am, the >>>>>>>>>>> capacitor termination matches the 20 mhz signal, and helps >>>>>>>>>>> attenuates the harmonics of the mixer, and has no , or very little >>>>>>>>>>> effect on the audio frequencies that we are interested in. >>>>>>>>>>> >>>>>>>>>>> And saying/rambling on... that if maximum slope is needed, its >>>>>>>>>>> needed on the 10 hertz beat signal - so maybe a capacitive >>>>>>>>>>> termination on the 10 hertz signal only and something resistive on >>>>>>>>>>> the 20 mhz signal........another idea use the 16 pF direct off the >>>>>>>>>>> mixer, then a series resistor for isolation and then a large >>>>>>>>>>> capacitor on the 10 hertz beat for maximum slope. >>>>>>>>>>> >>>>>>>>>>> At the present, I am awaiting parts to build a low noise preamp >>>>>>>>>>> base on the THAT1512 so I can make better measurements on the >>>>>>>>>>> mixer. Bruce has provided a lot of good suggestions and helpful >>>>>>>>>>> comments on my project and Ulrich has provided me quite a bit of >>>>>>>>>>> user support on his program, Plotter. Thanks to all. >>>>>>>>>>> >>>>>>>>>>> Comments ? Brian KD4FM >>>>>>>>>>> <DMTD_Plans.pdf>_______________________________________________ >>>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>>> To unsubscribe, go to >>>>>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>>> and follow the instructions there. >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>>> To unsubscribe, go to >>>>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>> and follow the instructions there. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>>> To unsubscribe, go to >>>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>> and follow the instructions there. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>> <DMTD_C_Plans.pdf>_______________________________________________ >>>>>>>> time-nuts mailing list -- [email protected] >>>>>>>> To unsubscribe, go to >>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- [email protected] >>>>>>> To unsubscribe, go to >>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>> and follow the instructions there. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- [email protected] >>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>>> >>>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > <phase12-3.pdf>_______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
