Its a form of CE with a resistor in series with the emitter coupled with
transformer feedback from collector to base.
Production scheduling likely prevents substitution of alternatives to achieve a
faster delivery.
Assembly costs would likely increase if leaded parts are substituted.
Initial
In principle DDS spurs due to phase truncation can be largely suppressed using
well known techniques when an FPGA is used just leaving spurs due to the DAC.
Bruce
> On 25 June 2018 at 06:00 Attila Kinali mailto:att...@kinali.ch > wrote:
>
>
> On Sun, 24 Jun 2018 17:29:43 +
>
The PN of the output amplifier in the thunderbolt will limit the PN nois of the
10Mhz output to a value significantly higher than the actual PN at the output
of a low PN OCXO.
Bruce
> On 21 June 2018 at 09:26 Attila Kinali wrote:
>
>
> On Wed, 20 Jun 2018 14:27:35 +
> Ethan Waldo
Surely all that's required is a simplistic worst case analysis.
Just assume that the value of Tau is always the worst possible so the full
effect of the modulation is always seen.
If the worst case phase modulation is say phi
then the worst case ADEV (Tau) will be proportional to phi*T/Tau
There are some NIR sensitive photodiodes that take advantage of the NIR
transparency of some black epoxies.
Bruce
> On 20 August 2018 at 02:48 Dana Whitlow wrote:
>
>
> Be watchful about the black epoxy. It may just be a dyed (otherwise
> clear) epoxy,
> and some of the black dyes in common
LED noise and its quality / aging
degradation.
http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p10.pdf
Bruce
> On 20 August 2018 at 03:42 Gerhard Hoffmann wrote:
>
>
>
>
> Am 19.08.2018 um 14:43 schrieb Bruce Griffiths:
> > Yes, I looked at the plots and I see
take a look at the plots, did you?
>
> It is seldom to find these data taken all in an identical setup.
>
>
> Am 19.08.2018 um 14:07 schrieb Bruce Griffiths:
> > The LT3042 is still inherently very noisy at ultra low frequencies
> > approaching and below th
Use the phase detector output to drive the tristate control input of a fast
CMOS tristate state buffer (eg 74HC126 or faster) which in turn drives the RC
network eliminating the diode.
Then correct for the exponential charging characteristics using the micro.
For best results increase ADC
A low phase noise method is to use a dual conjugate regenerative divider with
6MHz and 16Mhz bandpass filters in the feedback loop to produce 16Mhz output.
For 12MHz output use 2MHz and 12MHz bandpass filters in the feedback loop.
Bruce
> On 01 October 2018 at 09:05 Bob kb8tq wrote:
>
>
>
-2 regen dividers (both worked very well) but
> nothing else.
>
> -Brian
>
>
> > On Sep 30, 2018, at 4:25 PM, Bruce Griffiths
> > wrote:
> >
> > A low phase noise method is to use a dual conjugate regenerative divider
> > with 6MHz and 16Mhz b
https://www.arl.wustl.edu/~jst/cse/260/glitchChaney.pdf
suggests metastability was noticed in the 1940's but not taken seriously for
decades thereafter.
Bruce
> On 21 January 2019 at 19:10 Hal Murray wrote:
>
>
>
> When did people designing counter/timers start paying attention to
>
NIST used off the shelf RF transformers in their mixers based on diode
connected (collector connected directly to base) 2N. The transformer
impedance ratios (!:5 IIRC) are specified in the papers on the mixer
performance.
Suitable transformers are made by Minicircuits and others.
Bruce
John
http://adsabs.harvard.edu/full/1968JRASC..62..205T
indicates a timing accuracy of a few milliseconds was typical for the Calgary
PZT.
Bruce
> On 26 March 2019 at 11:44 John Ackermann N8UR wrote:
>
>
> Does anyone have a pointer to information about the absolute time
> accuracy (not
:15 Bruce Griffiths wrote:
>
>
> John
> http://adsabs.harvard.edu/full/1968JRASC..62..205T
> indicates a timing accuracy of a few milliseconds was typical for the Calgary
> PZT.
>
> Bruce
> > On 26 March 2019 at 11:44 John Ackermann N8UR wrote:
> &g
rch 2019 at 17:41 Bruce Griffiths wrote:
>
>
> These light curves for a star being occulted by the moon should give some
> idea of the effects of diffraction:
>
> http://tdc-www.harvard.edu/occultations/moon/vb141occa.html
>
> Bruce
> > On 27 March
Brooke
Yes but the accuracy would suffer due to observer related effects.
However when used with a CCD camera or equivalent the accuracy should improve
somewhat much as adding a TV camera to a transit circle improved its accuracy.
I had a personal tour of the USNO setup on Black-
In principle one could time tag each individual photon with subnanosecond
resolution.
Bruce
> On 29 March 2019 at 09:00 Poul-Henning Kamp wrote:
>
>
>
> In message <236772484.9174006.1553757616...@webmail.xtra.co.nz>, Bruce
> Griffith
> s writes:
>
> >However when used with a CCD
The Danjon impersonal astrolabe is perhaps better suited to accurate
measurements:
https://www.nzmuseums.co.nz/collections/3267/objects/3380/astrolabe
Bruce
> On 27 March 2019 at 15:48 Tom Van Baak wrote:
>
>
> BobH wrote:
> >> This would be an excellent project for time-nuts to verify.
These light curves for a star being occulted by the moon should give some idea
of the effects of diffraction:
http://tdc-www.harvard.edu/occultations/moon/vb141occa.html
Bruce
> On 27 March 2019 at 15:48 Tom Van Baak wrote:
>
>
> BobH wrote:
> >> This would be an excellent project for
2.4/0.1 = 24 not 240 !!!
Bruce
> On 06 March 2019 at 17:36 jimlux wrote:
>
>
> On 3/5/19 3:05 PM, Charles Steinmetz wrote:
> > Ho, hum, yet another fantastical claim for magical gain from a
> > tiny-for-wavelength antenna.
> >
> > See the many discussions of same by Kurt N. Sterba over the
3/8" (nominal bore) NPT thread has an outer diameter near 5/8" and has 18
threads/inch somewhat finer than the 5/8 11 TPI used for most surveying antennae
Bruce
> On 23 February 2019 at 11:06 David Witten wrote:
>
>
> FWIW
>
> I just poked around my shop and found something that fit
NPT or BSPT pipe thread perhaps?
Bruce
> On 15 February 2019 at 14:08 Bob kb8tq wrote:
>
>
> Hi
>
> Indeed for an antenna that is going on a mount one time and one time only a
> “tapered” thread
> might make sense. Crank it down and it locks in place …..
>
> Bob
>
> > On Feb 14, 2019, at
Mica is a sheet silicate mineral little or no carbon present.
Bruce
> On 11 February 2019 at 11:15 Bob Bownes wrote:
>
>
> >
> > Yes, those brown roughly 1" square caps used intact sheets of mica as
> > dielectric. You can easily split the mineral into uniform, thin,
> > transparent sheets.
Try:
https://www.researchgate.net/publication/235103340_Estimating_Frequency_Stability_and_Cross-Correlations
Bruce
> On 16 June 2019 at 10:54 jimlux wrote:
>
>
> I found a lot of references to estimating the uncertainties in
> measurements derived with three cornered hat. What about for
CANVAS is apparently northern hemisphere specific.
I just asked and was allowed to download CANVAS including source code
Bruce
> On 28 April 2019 at 01:21 Bob kb8tq wrote:
>
>
> Hi
>
> Just to confirm - it seems to be broken from here as well.
>
> Bob
>
> > On Apr 27, 2019, at 7:31 AM,
As expected the seller doesn't know, but offered 2 cells for the price of one
if further info on the cells he's offering can be provided.
Determining the cell filling would likely be somewhat interesting/challenging.
Absorption spectroscopy using a tunable ECDL comes to mind to sort out the
I asked the seller which cell. We'll see what the response is.
If its filled with RB87 and buffer gas it may be usable with a suitably tuned
ECDL locked to the correct line.
Bruce
> On 06 May 2019 at 14:04 Bob kb8tq wrote:
>
>
> Hi
>
> I’m sure they are good cells. The gotcha is “which one is
or lower cutoff
frequencies are usually impractical.
Bruce
> On 10 July 2019 at 22:58 Gerhard Hoffmann wrote:
>
>
>
> Am 10.07.19 um 11:27 schrieb Bruce Griffiths:
> > Like virtually all low dropout regulator ICs the LT3042 is quite noisy at
> > frequencies below it
The HP Journal article (page 20 March 1981 issue) on the 10811A agrees with Bob.
It also points out that the lack of activity dips due to coupled modes and a
much smaller dependence of the frequency on the signal level are advantages of
the SC cut compared to the AT and BT cuts.
Bruce
> On 13
Figure 5 in http://www.wenzel.com/wp-content/uploads/Sub-pico-Multiplier.pdf
??
Bruce
> On 13 July 2019 at 05:23 Bob kb8tq wrote:
>
>
> Hi
>
> If you do go the TEC route, plan on a fairly big power source :). There is a
> Wenzel doc on doing a TEC based enclosure using a couple of die cast
>
The mention of deglitching after the mixers perhaps indicates that the mixers
may be flipflops and that the device is perhaps a DDMTD. Alternatively the
block diagram is intentionally misleading.
Bruce
> On 23 April 2019 at 03:11 cdel...@juno.com wrote:
>
>
> Hi,
>
> A friend directed me
Probably only worth the effort if one were considering a higher resolution
device intended to surpass that of the venerable HP5370A/B or equivalent.
Doable with off the TDC shelf parts but is there any demand?
Bruce
> On 15 August 2019 at 11:18 John Ackermann N8UR wrote:
>
>
> In theory,
Actually the leakage of at least some standard electrolytic capacitors can be
quite low if one waits long enough. I've seen a leakage as small as a few
nanoamps after several minutes at room temperature with randomly selected 100uF
capacitors.
Bruce
> On 30 August 2019 at 18:53 ed breya
Am 26.08.19 um 04:47 schrieb Bruce Griffiths:
> > I've only used an ultra low esr 33F supercap made in Korea in the source
> > circuit of the input JFET on a preamp.
> > Down to 10Hz at least it didn't appear to add significant noise to the
> > 4nV/rtHz @10Hz preamp.
&g
I've only used an ultra low esr 33F supercap made in Korea in the source
circuit of the input JFET on a preamp.
Down to 10Hz at least it didn't appear to add significant noise to the 4nV/rtHz
@10Hz preamp.
Bruce
> On 26 August 2019 at 13:52 Didier Juges wrote:
>
>
> How do SuperCaps compare
That should have been:
Its only necessary (as NIST have shown) to cool the splitters to reduce the
correlated or anti-correlated thermal noise between splitter outputs.
Everything else can run at ambient temperature.
Bruce
> On 21 August 2019 at 21:13 Bruce Griffiths wrote:
>
>
&
Its only necessary (as NIST have shown) to cool the splitters to reduce the
correlated or anti-correlated noise between the outputs. Everything else can
run at ambient temperature.
Bruce
> On 21 August 2019 at 18:49 ed breya wrote:
>
>
> That's quite an impressive system. I guess it's a few
With hot and cold noise sources perhaps?
Bruce
> On 24 August 2019 at 07:07 Perry Sandeen via time-nuts
> wrote:
>
>
> Gentlemen,
> A question for my curiosity and education. Traditionally, the standard was
> 10X better than what was being calibrated.
>
> Since this is at the theoretical
A frequency doubler and a frequency quintupler will be needed.
Options for the quintupler:
1) Convert to square wave and isolate the desired 25MHz output using filters. A
bandpass filter is a poor choice if high phase stability is required. A high
pass filter supplemented with series tuned
Dual JK flipflop configured as divide by 3 producing a 33% duty cycle 5MHz
output which is filtered to extract the 10MHz second harmonic component.
Bruce
> On 18 September 2019 at 21:08 "David C. Partridge"
> wrote:
>
>
> Having seen the recent discussion of the NB3N502 and other PLLs for
>
Electro-optic samplers are about the closest but they typically transform from
time to spatial domain and have multibit resolution. The storage isnt atomic
but in an image sensor attached to a spectroscometer.
http://beamdocs.fnal.gov/AD/DocDB/0025/002555/001/eos1.pdf
Bruce
> On 28 July 2019
The LTC6957 is a better choice for squaring up sinewaves:
http://www.ko4bb.com/getsimple/index.php?id=phase-noise-and-other-measurements-with-a-timepod
CERN amongst others use it. The pin programmable filtering allows its bandwidth
to be optimised to suit the input signal frequency and amplitude.
Like virtually all low dropout regulator ICs the LT3042 is quite noisy at
frequencies below its reference low pass filter high frequency cutoff. Some
zener based references are considerably quieter in this region.
Bruce
> On 10 July 2019 at 18:18 Perry Sandeen via time-nuts
> wrote:
>
>
Merely selecting every 100th sample throws away the opportunity to reduce the
effective ADC noise by digital filtering before decimation.
Bruce
> On 05 November 2019 at 10:08 Jan-Derk Bakker wrote:
>
>
> Dear Scott,
>
> You are entirely correct, sampling at 100ksps is mathematically the same
There are a number of NIST papers on this:
https://tf.nist.gov/general/publications.htm
You can also simulate the effect of a capacitive IF port load.
However a capacitive load can also degrade the isolation and RF and LO port
mismatch.
One can also use diode connected BJTs instead if lower
Cross Correlation methods are commonly used with analog mixers.
Most of the high end commercial offerings use it (Holzworth, Anapico, Rhohde &
Schwarz, etc.)
Bruce
> On 12 December 2019 at 18:53 Gerhard Hoffmann
> wrote:
>
>
> It seems the mixer noise cannot be ignored.
>
>
> I wonder then
Consistency of the glitch independent of DAC output is more important than its
size. A constant amplitude glitch occurring at the dac update rate is more
benign in its effect than a glitch whose amplitude varies with DAC output.
Brruce
> On 16 October 2019 at 08:02 Attila Kinali wrote:
>
>
>
Its measured noise floor is consistent with that expected from the noise
specifications for the opamps employed.
Bruce
> On 24 October 2019 at 08:46 Tom Knox wrote:
>
>
> Hi John;
> Amazing product, I did not realize you could use the TADD-1 for 100MHz
> distribution.
> I do have a
If the DAC update rate isn't excessive a 2nV-sec glitch is unlikely to produce
a significant perturbation at the output of the lowpass filter following the
DAC.
Bruce
> On 16 October 2019 at 21:01 Attila Kinali wrote:
>
>
> On Wed, 16 Oct 2019 15:04:31 +1300 (NZDT)
> Bruce G
Detecting the steep drop in oven heater current when the temperature regulator
loop assumes control shouldn't require an extremely low tempco sensing resistor.
In principle PWM DACs can offer high resolution at relatively low cost, one
tradeoff being the settling time of the low pass filter
e I think I am fine with a DAC8501 or DAC8560, which are both based on a
> resistor string, and therefore are also monotonic by design.
>
> Tobias
>
>
> From: time-nuts [time-nuts-boun...@lists.febo.com] on behalf of Bruce
> Griffiths [b
IIRC Tolansky obtained some interferograms illustrating the surface deflections
of these acoustic resonators.
I'll unearth my copy of Tolansky's book on optical interferometry and check.
Bruce
> On 01 March 2020 at 13:41 "John Moran, Scawby Design"
> wrote:
>
>
> Wow, that provoked an
Interferogram showing vibration nodes etc for quartz ring resonator frequency
standard attached.
Bruce
> On 01 March 2020 at 14:27 Bob kb8tq wrote:
>
>
> Hi
>
> It’s also the size of the 2.5 MHz 5th’s and similar parts made “way back”.
> They went into glass packages
> the size of door
hic interferometry, mostly related to
> identifying
> resonances and vibratory modes of blades on jet turbine rotors, and it's
> hard to
> break the habit of trying to interpret interference patters.
>
> Dana
>
>
> On Sat, Feb 29, 2020 at 7:34 PM Bruce Griffiths
>
That's not relevant.
The idea is to see what frequency the crystal oscillates at not to build a high
stability oscillator.
If can be made to oscillate at a frequency somewhere around 5MHz/3 then its
likely a third overtone crystal.
Bruce
> On 28 February 2020 at 23:34 Attila Kinali wrote:
>
>
Magnus
You need a linear polariser plus a quarter waveplate to produce circularly
polarised light from unpolarised light. A quarter waveplate alone wont suffice.
So called circular polarisers used with modern digital cameras comprise a
polariser with the linear polariser oriented correctly
The wavelength of a laser diode can be tuned by varying its temperature and/or
bias current.
Mode hopping during tuning can be an issue with standard FP laser diodes.
Single transverse and longitudinal mode operation is also desirable.
The laser wavelength has to be within a few picometers of the
behind the option-K22 amplifiers that
> > were sold by HP for use with the 3048A. I've got one of those but I needed
> > a couple more of them at one point, so I built some (literally) quick and
> > dirty copies with BFG591 transistors with good results.
> >
> > I've m
Simulation indicates that the required C value depends on the transformer turns
ratios and the RC product sets the notch frequency.
Large signal modulation of the transistor parameters results in a distorted
signal at the base when a large signal is applied to the output.
the RC product is
PSOF fiber has a much lower tempco:
https://accelconf.web.cern.ch/accelconf/p01/PAPERS/MPPH011.PDF
Bruce
> On 17 January 2020 at 00:08 Bruce Griffiths
> wrote:
>
>
> Except for some low tempco single mode fibers the delay tempco is on the
> order of 10ppm/K:
> https://li
Except for some low tempco single mode fibers the delay tempco is on the order
of 10ppm/K:
https://library.nrao.edu/public/memos/edtn/EDTN_168.pdf
Bruce
> On 16 January 2020 at 23:29 Magnus Danielson wrote:
>
>
> Hi,
>
> On 2020-01-15 23:34, Attila Kinali wrote:
> > On Wed, 4 Dec 2019
That's not possible at room temperature since thermal noise will limit the
residual PN to -180DbC/Hz with a noiseless amplifier and a +3dBm input.
Bruce
> On 10 January 2020 at 14:38 Lifespeed wrote:
>
>
> Hi Time Nuts,
>
>
>
> I have a need for a low phase noise, noise floor and noise
An OP37 may not function well as a diode clamped limiter since the loop gain
is <5 during limiting.
A unity gain stable opamp would likely be better.
Bruce
> On 17 April 2020 at 09:26 Bob kb8tq wrote:
>
>
> Hi
>
> The OP-37 is fine as long as the gain is over 5X. Under that gain level, you
The PN floor is somewhat lower with a 15dBm rather than a 4dBm input
http://www.ko4bb.com/getsimple/index.php?id=phase-noise-and-other-measurements-with-a-timepod
Bruce
> On 27 March 2020 at 06:11 kb...@n1k.org mailto:kb...@n1k.org wrote:
>
>
> Hi
>
> Ok so here's a "new" part as
A constant temperature oven for the crystal filter may be required to minimise
the crystal filter phase shift tempco contribution to the output phase
stability.
Bruce
> On 27 March 2020 at 11:03 Perry Sandeen via time-nuts
> wrote:
>
>
> Learned Gentlemen,
> Both the HP 106 and 107 have a
One can merely add diodes to the opamp feedback network form a feedback limiter
and maintain the opamp outputs within the range for which the opamp is well
behaved whilst maintaining the increase in slew rate for the output.
Bruce
> On 04 April 2020 at 04:26 Tobias Pluess wrote:
>
>
> Jup,
phase noise
> measurement) and which ones should be used as actual mixers (like in this
> case).
>
>
> Tobias
> HB9FSX
>
> On Fri., 3 Apr. 2020, 23:09 Bruce Griffiths,
> wrote:
>
> > One can merely add diodes to the opamp feedback network form a feedback
> &g
e RPD vs. TUF mixers - what is the actual property which makes
> the RPD "better" than the TUF?
>
> Thanks,
> Tobias
>
> On Sat., 4 Apr. 2020, 02:01 Bruce Griffiths,
> wrote:
>
> > Tobias
> >
> > That would certainly work for a start and
Macom also do NLTL comb generators which are much quieter than SRDs:
https://www.macom.com/products/product-detail/MLPNC-7100-SMA850
Bruce
> On 16 May 2020 at 09:14 Gerhard Hoffmann
> wrote:
>
>
> No, no, no, it's not that bad :-) I should not post here in the middle
> of the night. Sorry
Indicative price:
https://www.richardsonrfpd.com/Products/Product/MLPNC-7103-SMT6
Bruce
> On 16 May 2020 at 10:54 ed breya wrote:
>
>
> Bruce wrote
>
> Macom also do NLTL comb generators which are much quieter than SRDs:
> https://www.macom.com/products/product-detail/MLPNC-7100-SMA850
>
>
For sine to square wave conversion use LTC6957 (select variant to suit
following logic).
Bruce
> On 02 September 2020 at 17:24 Manfred Bartz mailto:vk3...@gmail.com > wrote:
>
>
> Hi all,
>
> I bought 2 x 10811 OCXOs for a 10MHz GPSDO project I am working on.
> The OCXOs came
You could use either the NIST CG JFET doubler or its bipolar CB equivalent.
Bruce
> On 11 September 2020 at 08:43 Tobias Pluess wrote:
>
>
> Dear colleagues
>
> I recently got a FTS1000 oscillator. (Not FTS1000A or B, but just FTS1000,
> I assume it is the first version). It is a very nice
undation.
> John Ponsonby
>
>
> Do we know what this ?Long Term Aging Process? is or is it proprietary?
>
>
>
> On Sat, Sep 26, 2020 at 5:03 PM Bruce Griffiths <mailto:bruce.griffi...@xtra.co.nz>>
> wrote:
>
> > Drift ~1-2mK per year for su
Drift ~1-2mK per year for suitably conditioned thermistors at 25C:
https://www.littelfuse.com/technical-resources/technical-centers/temperature-sensors/thermistor-info/thermistor-terminology/stability.aspx
Bruce
> On 27 September 2020 at 11:15 Bob kb8tq wrote:
>
>
> Hi
>
> Roughly speaking
If one does a ratiometric measurement comparing the voltage drop across the RTD
with the voltage drop across a stable low Tc resistor connected in series with
the RTD the excitation source only needs to be quiet with good short term
stability.
Bruce
> On 29 September 2020 at 07:48 "John
> On 04 August 2020 at 10:32 Poul-Henning Kamp wrote:
>
>
>
> Attila Kinali writes:
>
> >> The main reason I dont just repair/replace the A15 is that
> >> I want to find out how much instability the PSU contributes.
> >
> >There are very few points where supply voltage
For fixed frequency operation there's always Wenzel's divider using a D FF with
LC feedback:
http://www.wenzel.com/wp-content/uploads/dividers.pdf
At least the power consumption is low.
Bruce
> On 03 July 2020 at 12:35 Bob kb8tq wrote:
>
>
> Hi
>
> > On Jul 2, 2020, at 6:38 PM, jimlux
When simulating the Wenzel divider its important to include the input
protection diodes or the input signal at the D input of the FF becomes
unrealistically large even with a finite Q inductor.
Bruce
> On 03 July 2020 at 20:18 glenlist wrote:
>
>
> Bravo Microchip for extending the ECL
There is no universal circuit that minimises jitter for all signals without
some tuning to suit the input frequency and threshold crossing slew rate. The
LTC6957 works well for higher frequency sine waves. The low frequency sine wave
outputs of a DMTD require a set of cascaded lowpass filtered
https://tf.nist.gov/general/pdf/3093.pdf
is likely more accessible than the sciencemag link
Bruce
> On 05 June 2020 at 11:15 Bill Byrom wrote:
>
>
> This was published in the 22 May 2020 issue of Science (AAAS journal). For
> AAAS members, the direct link is:
>
ote:
>
>
> Thanks, Bruce! That's a copy of that same Science article. I guess that NIST
> got permission to post it on their website, since they were the sponsor of
> the study.
> --
> Bill N5BB
>
>
> On Thu, Jun 4, 2020, at 6:32 PM, Bruce Griffiths wrote:
> > h
The Hydrogen plasma emission is dominated in the visible dominated by Halpha
emission at 656.3 nm. Other Balmer series lines will also be present.
Bruce
> On 26 December 2020 at 09:12 Magnus Danielson wrote:
>
>
> Dana,
>
> The glow is a side-effect of the plasma. The primary use in H-maser
Original source about TEC lifetime reduction when the TEC ripple cureent is
high:
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1991-02.pdf
Page 74
I suspect that someone there may have been bitten by the short TEC life
experienced without the LC filter.
Although they used relatively small
You could always use a TEC as the heart of a dewpoint sensor by optically
sensing the temperature required for dew to form on a cooled mirror.
In practice the temperature at which the dew vanishes is typically used.
A collimated light beam together with a photodiode is typically used to sense
this complication when I was working with
> this thing,
> however, or I would have asked. Oh, well, an opportunity missed. Sigh!
>
> Dana
>
>
> On Wed, Dec 23, 2020 at 6:53 PM Bruce Griffiths
> wrote:
>
> > You could always use a TEC as the heart o
Its just another variation on the principle of the Dicke radiometer.
In their case the amplifier input device is turned off periodically by
modulating its gate bias.
https://www.engr.colostate.edu/ece/faculty/reising/pdf/journals/Ogut_et_al_T-TST_2020.pdf
Bruce
> On 19 November 2020 at 12:38
Attached is the block diagram of the receiver in essence an amplifier for which
the effective input is gated/chopped on and off by turning the amplifier input
FET on and off.
Bruce
> On 19 November 2020 at 16:15 "Richard (Rick) Karlquist"
> wrote:
>
>
>
> On 11/18/2020 5:27 PM, jimlux
Not true
The Wiedemann-Franz gives the ratio of the thermal conductivity to electrical
conductivity of a metal:
( pi^2 / 3 ) * ( (k/e)^2 ) * T
Bruce
> On 31 October 2020 at 12:49 "Dr. David Kirkby"
> wrote:
>
>
> On Fri, 30 Oct 2020 at 22:17, Luiz Alberto Saba wrote:
>
> > My bad...
If the drive current ripple is too high fatigue failure from cyclic
thermomechanical stress can be significant.
Bruce
> On 23 October 2020 at 10:37 ed breya wrote:
>
>
> Regarding TEC life, in my experience, what wrecks them the most is
> cooling applications where the cold side is below the
Poseidon Scientific Instruments (acquired by Raytheon) make a room temperature
10.24GHz Sapphire loaded cavity oscillator with a low PN floor:
https://www.rdi.uwa.edu.au/__data/assets/pdf_file/0012/3447669/Raytheon-TechnologyToday-20141-Extract.pdf
Bruce
> On 02 April 2021 at 05:06 Chris Caudle
The oscillator circuit consists of an SSM2210 supermatch npn pair configured as
a long-tailed differential pair with a 12mA tail current and 51 ohm collector
loads. One output feeds the output buffer whilst the other provides feedback to
the crystal via an LC network that is series resonant at
An interferogram showing the nodes etc. of such a resonating quartz crystal
ring was posted by me in either February or March 2020.
Bruce
> On 01 April 2021 at 15:16 Bob kb8tq wrote:
>
>
> Hi
>
> Some of the early 100 KHz resonators were ring shaped. The British really
> pioneered
> this
Unless something akin to VLBI or pulsar timing is involved millisecond accuracy
will usually suffice for amateur astronomy.
Bruce
> On 11 March 2021 at 06:31 Bob kb8tq wrote:
>
>
> Hi
>
> > On Mar 10, 2021, at 12:17 PM, Attila Kinali wrote:
> >
> > On Wed, 10 Mar 2021 06:39:46 -0800
> >
Surely Polaris is a spectacularly poor choice for obtaining accurate Sidereal
time via a meridian transit of a known star?
A theodolite suited to high altitude observations like the Wild T4 was is
desirable.
Otherwise a prism and a mercury mirror 9or equivalent) can be used to covert a
The Danjon astrolabe typically achieved a timing precision of around 25millisec
or so.
Manually timing transits with a stopwatch will be better than a second but
somewhat worse than the Danjon astrolabe.
Bruce
> On 28/12/2021 22:42 David Taylor via time-nuts
> wrote:
>
>
> On 27/12/2021
Was it related to the cause of the hump in the PN plot vs offset frequency that
the E1938A exhibits?
Bruce
> On 26/12/2021 17:56 Richard (Rick) Karlquist wrote:
>
>
> I'm sure I said that ... a long time ago. I can't remember now what the
> fix was, but I am fairly sure it would only apply
Yes, that post is full of misleading information.
The TI document is irrelevant as the PIC based divider doesn't have non
harmonically related signals using the same chip.
All internal signals within the PIC are harmonics of the divided output signal.
The post did not distinguish between random
ghtly longer when 2
> > outputs switch when compared to when only one is switching.
> >
> > Has anybody measured that on a PIC? (or similar chip)
> >
> > I think one of tvb's picDEVs has several outputs.
> >
>
> On 1/7/2022 5:00 PM, Bruce Griffiths wrote:
>
That entire thread is full of misinformation and should be ignored unless one
understands the difference between random and data dependent jitter.
For a well designed divider with a single output frequency only the random
jitter spec is significant.
One doesn't need a bunch of expensive
Modern CPLDs often have an internal state machine that configures the chip on
power up. Not all of these shutdown the internal state machine clock after
configuration is complete. Crosstalk from the internal clock/oscillator will
modulate the output of a divider.
IIRC the Coolrunner II chips
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