Re: [time-nuts] f-multipliers from VHF to 10 GHz
> -Original Message- > From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of > Bruce Griffiths > Sent: Friday, May 15, 2020 4:32 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] f-multipliers from VHF to 10 GHz > > Indicative price: > https://www.richardsonrfpd.com/Products/Product/MLPNC-7103-SMT6 Marki Microwave is also selling a line of NLTL multipliers now: https://www.markimicrowave.com/multipliers/multipliers-products.aspx#multipl iers-nltls Pricing on these isn't bad at all, considering the low volumes involved. -- john ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Gravity, solid Earth tides
On Fri 2020-05-15T21:49:43-0700 Tom Van Baak hath writ: > Also, some of the very best pendulum clocks ever made were good enough that > their timekeeping was affected by lunar/solar tides. One is the English > Shortt-Synchronome and another is the Russian Fedchenko. Those are not measuring solid earth tides per se. They are measuring the failure of the earth to deform as much as, and in phase with, the changing potential, so the local acceleration of gravity changes. I have not found any papers which say that two distant chronometers have yet been tied together with a stable enough optical network to measure the changing difference in their potentials. -- Steve Allen WGS-84 (GPS) UCO/Lick Observatory--ISB 260 Natural Sciences II, Room 165 Lat +36.99855 1156 High Street Voice: +1 831 459 3046 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] Gravity, solid Earth tides
Hi Hal, Yes, both CERN, and especially LIGO, need to take the gravitational effects of the moon and sun into account. Also, some of the very best pendulum clocks ever made were good enough that their timekeeping was affected by lunar/solar tides. One is the English Shortt-Synchronome and another is the Russian Fedchenko. The way you "detect tides" is if your pendulum clock is so incredibly good at timekeeping that the only remaining error source(s) are random earthquakes or periodic variations correlated to the relative positions of the earth, moon, and sun. Sometimes you can see this in the phase (time) or frequency (rate) time series. Another way is to observe effects with stacking, FFT, PSD, or ADEV analysis. It's a particular interest of mine. A couple of links for you: http://leapsecond.com/pend/shortt/ http://leapsecond.com/pend/pdf/1985-Apr-NAWCC-Boucheron-Shortt.pdf http://leapsecond.com/pend/pdf/1986-Mar-AH-Boucheron-Shortt.pdf http://leapsecond.com/hsn2006/ http://leapsecond.com/pend/synchronome/quake.htm /tvb On 5/15/2020 9:22 PM, Hal Murray wrote: Are any clocks good enough to detect solid Earth tides? I remember a story about a CERN experiment that wasn't working until they corrected for the phase of the moon. It was extremely sensitive to the diameter of the ring which changed slightly with the tides. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Gravity, solid Earth tides
Are any clocks good enough to detect solid Earth tides? I remember a story about a CERN experiment that wasn't working until they corrected for the phase of the moon. It was extremely sensitive to the diameter of the ring which changed slightly with the tides. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] f-multipliers from VHF to 10 GHz
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 > > Wow, those are nice. I've studied and searched for NLTLs over the years, > and found all sorts of research papers about making monolithic ones, but > not such a finished piece that you can order up and go - even though > these may have been around for some time. I've even considered trying to > build some discretely and experiment, but got dissuaded when I found out > how many compression stages are needed for meaningful results. I think > that's why the research was all geared toward making them in integrated > form, where you can get lots of similar items repeated in tiny form. I'd > guess that these may have 20-100 stages, or maybe nowadays it can be one > continuous line with spatially variable characteristics.. > > It's cool to see, but probably quite spendy - I'd guess 2 grand or more. > I tried to find out the price looking at a distributor, but it's a > special order, call for quote type deal. I'm sure it's quite a few dB$ > above what I can justify for any of my projects. > > Ed > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] f-multipliers from VHF to 10 GHz
On 5/15/20 2:14 PM, Gerhard Hoffmann wrote: No, no, no, it's not that bad :-) I should not post here in the middle of the night. Sorry to cause that confusion. Minimum is -90 dBc @ 50 Hz, or let's say @100 Hz @ 10 GHz. that would equal -110 dBc@1 GHz, or -130 dBc @100 MHz, BTDT. That's much easier. Use one of the single chip synthesizers - they can probably do just what you want, with adequate performance. The question was really only about a _simple_ multiplier chain. The style used in ham radio 10 GHz transverters has too many stages, GaAS-Fets with 1/f and pipe cap filters. Too complicated. Yes, that would be an ordeal, and is completely unnecessary today. Macom still make a SRD diode, but probably it is easiest to phaselock a ceramic puck or an on-chip VCO to a 100+ MHz crystal. The offset- mixing removes the need for a low reference frequency or fractional voodoo. o Trivially easy to lock the onchip VCO to a 10 or 100 MHz oscillator. These days, dividing down from 10GHz isn't a chore, like it was 15 years ago. SRDs are a pain, they need huge drive power (100mW?) to work well, as do the Sampling Phase Detector/ harmonic mixer equivalents. It's hard to get a real low noise +20dBm signal . You'll spend as much time on that as the other stuff. Sampling phase detector and DRO from 2004 https://tmo.jpl.nasa.gov/progress_report/42-156/156C.pdf GaAs and PLL from 2006 https://tmo.jpl.nasa.gov/progress_report/42-166/166A.pdf You can probably do it with an off the shelf eval board. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] f-multipliers from VHF to 10 GHz
Bruce wrote Macom also do NLTL comb generators which are much quieter than SRDs: https://www.macom.com/products/product-detail/MLPNC-7100-SMA850 Wow, those are nice. I've studied and searched for NLTLs over the years, and found all sorts of research papers about making monolithic ones, but not such a finished piece that you can order up and go - even though these may have been around for some time. I've even considered trying to build some discretely and experiment, but got dissuaded when I found out how many compression stages are needed for meaningful results. I think that's why the research was all geared toward making them in integrated form, where you can get lots of similar items repeated in tiny form. I'd guess that these may have 20-100 stages, or maybe nowadays it can be one continuous line with spatially variable characteristics.. It's cool to see, but probably quite spendy - I'd guess 2 grand or more. I tried to find out the price looking at a distributor, but it's a special order, call for quote type deal. I'm sure it's quite a few dB$ above what I can justify for any of my projects. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] f-multipliers from VHF to 10 GHz
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 to cause that confusion. > > Minimum is -90 dBc @ 50 Hz, or let's say @100 Hz @ 10 GHz. > that would equal -110 dBc@1 GHz, or -130 dBc @100 MHz, BTDT. > > And then, the ~4 MHz difference between TX and RX frequency could be > done by a SSB mixer with a non-multiplied crystal. We would have some > common mode noise, but the RX-TX difference would be fairly constant. > It would not de-correlate over the 10 mm run length, not at low > offsets where it counts. > > The -110 was only meant for "Don't care about multiplied white noise > floor", not in the sense of a spec but in the sense of "guaranteed > harmless". It's not such a great relaxation after all, it could be > 20 dB looser. > > The question was really only about a _simple_ multiplier chain. The > style used in ham radio 10 GHz transverters has too many stages, > GaAS-Fets with 1/f and pipe cap filters. Too complicated. > > Macom still make a SRD diode, but probably it is easiest to phaselock > a ceramic puck or an on-chip VCO to a 100+ MHz crystal. The offset- > mixing removes the need for a low reference frequency or fractional > voodoo. > > cheers, Gerhard > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] f-multipliers from VHF to 10 GHz
No, no, no, it's not that bad :-) I should not post here in the middle of the night. Sorry to cause that confusion. Minimum is -90 dBc @ 50 Hz, or let's say @100 Hz @ 10 GHz. that would equal -110 dBc@1 GHz, or -130 dBc @100 MHz, BTDT. And then, the ~4 MHz difference between TX and RX frequency could be done by a SSB mixer with a non-multiplied crystal. We would have some common mode noise, but the RX-TX difference would be fairly constant. It would not de-correlate over the 10 mm run length, not at low offsets where it counts. The -110 was only meant for "Don't care about multiplied white noise floor", not in the sense of a spec but in the sense of "guaranteed harmless". It's not such a great relaxation after all, it could be 20 dB looser. The question was really only about a _simple_ multiplier chain. The style used in ham radio 10 GHz transverters has too many stages, GaAS-Fets with 1/f and pipe cap filters. Too complicated. Macom still make a SRD diode, but probably it is easiest to phaselock a ceramic puck or an on-chip VCO to a 100+ MHz crystal. The offset- mixing removes the need for a low reference frequency or fractional voodoo. cheers, Gerhard ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A tuning vs resonant peaks
I have tweaked mine to my satisfaction now. An offset of -768 gets it
as close as I can measure under sub-optimal conditions. See results at
bottom.
I am still curious as to whether Rubidium exhibits the same resonance
peaks that Cesium does, per Tom Van Baak's graph at
http://leapsecond.com/images/cfield.gif .
> Hi
>
> A few generic Rb information points:
>
> 1) All the telecom Rb’s need an external heatsink. To just mount them on
> a PC board, you need a lot of airflow (like fans …).
>
> 2) Heat sinking improves the lifespan of these devices. Without a heatsink,
> a year or two is doing pretty well. With a heatsink that gets the base to 40C
> (possibly heatsink + small fan) a decade or more is possible.
It sits on a square-foot slab of steel to the corner of which is mounted
a Panavise base.
>
> 3) If your Rb has a PPS output, cal is pretty easy. Just compare the pps
> to a < $20 GPS module with a scope. A day or three of tweaking should
> get you pretty close.
It does, but the generic problem with this technique is that there is an
arbitrary constant offset between the two pulses. The first time I did
this some years ago, I set an 8-digit counter to show the time
difference between the two pulses (~735ms that time), then took a
timestamped photo every ten minutes or so, did some math, and found the
Rb and the GPSDO were within 2e-10 of each other. You want the delta as
stable as possible.
There's also the Lissajous method.
I never run mine for more than a week, and often less than a day. It's
more of a Because I Can sort of thing...
>
> 4) With very few exceptions telecom Rb’s either have rotten phase noise /
> spurs
> or they have horrible phase noise / spurs. If you are going to do anything
> “fancy” (like microwaves) with one, you will need a cleanup loop.
Fortunately for me, I am not
>
> 5) Many outfits produced a wide range of parts, all with the same part number.
> What you have with a model number on it may be *very* different than
> what I have with the same … errr ... FE-5680 model number on it.
Basically, the two [non-]programmable units mentioned earlier. I have
the non- version. It has only the DE9 connector.
>
> 6) Most Rb’s have some sort of crystal oscillator in them. There often is an
> adjustment (re-centering) needed on surplus parts.
On tindie, there's also Nick Sayer's GPS disciplining board for the
FE-5680A.
>
> 7) Like OCXO’s Rb’s do have a warmup / retrace process that runs into
> days. They also are sensitive to temperature, voltage, pressure, and
> humidity. Compared to an OCXO, most of these sensitivities are pretty
> small.
>
> As mentioned in a number of posts, in a lot of ways, an Rb makes a pretty
> good basement lab standard. Compared to a GPSDO, there are a lot
> fewer things to go wrong.
>
Other than the lamp life... I've heard of ways to rejuvenate it. Mine
spends 99.44% of its time powered off, though.
==
Here's the output from a Python script I wrote to evaulate oscillator
performance (I'm too impatient to wait for ADEVs) using vxi11 to talk to
a LAN-connected GPIB controller. And while this counter does do
statistics, it doesn't do linear regression. This is from this morning;
it was behaving almost as well last night.
bash-4.3$ python count-one-adhoc.py 1e7
Given ideal 1e7
HEWLETT-PACKARD,53131A,0,3944
Reference is EXTERNAL at +1.0E+007 Hz
3.452 Previous gate time
Suggested gate time 1.79330192372
1.793 Gate time
1589572346.83 first time
0 bias
1000.0 expected value
12 readings to take
1 999.9998 Hz 1.93545103073 s 1.93545103073 delta s
2 1000.0 Hz 3.87260103226 s 1.93715000153 delta s
3 999.9998 Hz 5.80996990204 s 1.93736886978 delta s
4 1000.0002 Hz 7.74672698975 s 1.93675708771 delta s
5 1000.0002 Hz 9.68287706375 s 1.93615007401 delta s
6 999. Hz 11.6207020283 s 1.93782496452 delta s
7 1000.0004 Hz 13.5647189617 s 1.94401693344 delta s
8 1000.0 Hz 15.5021290779 s 1.9374101162 delta s
9 1000.0003 Hz 17.4395709038 s 1.93744182587 delta s
10 1000.0002 Hz 19.3772699833 s 1.93769907951 delta s
11 1000.0 Hz 21.3132119179 s 1.93594193459 delta s
12 999.9997 Hz 23.2543890476 s 1.94117712975 delta s
151.119617939 Sum s
2440.26380663 Sum s^2
12000.0 Sum y
1.201e+15 Sum y^2
23.2543890476 Sum ds
45.0639478477 Sum ds^2
1511196179.4 Sum ys
1000.0 Hz mean
0.150755672289 Hz std dev
12 readings in 23.2543890476 seconds, should be 21.516
1.93786575397 delta t mean, 0.144865753969 dead time, 0.144865753969 also,
8.07951778966 %
0.00240610675374 delta s std dev
1.50755672288e-08 stability? 15.0755672 ppb
4.16655598912e-12 accuracy? 4.1665560 ppt
second denominator 2.0
0.000215087265483 correlation
3.78864265201e-06 slope
999.9 intercept
1000.0 Hz hat in the middle
1000.0001 Hz hat # 17 at about 32.9437178175 s
bash-4.3$
--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight
Re: [time-nuts] f-multipliers from VHF to 10 GHz
On 5/14/20 5:58 PM, Gerhard Hoffmann wrote: I have a potential project in the electron spin spectroscopy sector and I need one or two clean signal sources in the 10 GHz range. Phase noise at, say, 50 Hz offset is important, but anything below 110 dBc does not care. That probably calls for a multiplied crystal. These Hittite PLLs from AD seem to be just not good enough, maybe they'd work if pushed, but no reserve left. Are there any known proven multipliers chains from VHF to 10 GHz? -110dBc @ 50 Hz offset at 10GHz? That's -170dBc @ 50Hz with a 10MHz ref. That's going to be a chore.. the Wenzel ULNs are -167dBc at 100Hz offset, and they're pretty good. But, as far as your synthesis approach, maybe not the Hittite PLL, but what about using the Hittite dividers and/or VCOs, and a different kind of PLL. You're talking about the noise "inside the loop" so the not so wonderful GaAs ring oscillator far out noise isn't an issue. We have used those VCOs and dividers for deep space transponder synthesizers, and that's a classic "gotta have really good close in noise" application. Compared to a DRO, which has microphonics, limited tuning range, etc. they're a lot easier. I notice that AD and TI both have a lot of new parts for <17GHz. Sure, most are targeting wideband high data rate kinds of applications, but they might fill the need. What about the LMX2595 or LMX2594 - I've not used them, but they might be interesting. The plot in the selection guide does show only -90dBc for the 2594 at 8GHz, but I don't know if that's the bare VCO, or locked to something, and then you'd ask what it's locked to. The divider noise is something like -150dBc at 10GHz, so that's probably not your dominant source. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
Re: [time-nuts] FE-5680A tuning vs resonant peaks
Hi A few generic Rb information points: 1) All the telecom Rb’s need an external heatsink. To just mount them on a PC board, you need a lot of airflow (like fans …). 2) Heat sinking improves the lifespan of these devices. Without a heatsink, a year or two is doing pretty well. With a heatsink that gets the base to 40C (possibly heatsink + small fan) a decade or more is possible. 3) If your Rb has a PPS output, cal is pretty easy. Just compare the pps to a < $20 GPS module with a scope. A day or three of tweaking should get you pretty close. 4) With very few exceptions telecom Rb’s either have rotten phase noise / spurs or they have horrible phase noise / spurs. If you are going to do anything “fancy” (like microwaves) with one, you will need a cleanup loop. 5) Many outfits produced a wide range of parts, all with the same part number. What you have with a model number on it may be *very* different than what I have with the same … errr ... FE-5680 model number on it. 6) Most Rb’s have some sort of crystal oscillator in them. There often is an adjustment (re-centering) needed on surplus parts. 7) Like OCXO’s Rb’s do have a warmup / retrace process that runs into days. They also are sensitive to temperature, voltage, pressure, and humidity. Compared to an OCXO, most of these sensitivities are pretty small. As mentioned in a number of posts, in a lot of ways, an Rb makes a pretty good basement lab standard. Compared to a GPSDO, there are a lot fewer things to go wrong. Bob > On May 15, 2020, at 12:19 AM, Jeff Woolsey wrote: > >> Hmmm... >> You mention varying suply voltage by 1.5V, but from where as a starting >> point? > > Sorry, that is a red herring. The regulator on the support board needs > enough headroom to regulate to 15V for the FE5680A. Thus anything less > than about 17V input will drag down the voltage into the unit, and the > frequency rises. I got down to 14V--the unit remains locked but 10MHz > doesn't. (It also doesn't help that the voltage display on the power > supply is about half a volt off.) On the other hand, the regulator has > a high-temp cutoff which I managed to hit at around 20V--there is no > real heat sink on the support card. Usually it's running around 80C; > cutoff at 125C. > > >> It's been a while since I calibrated an FE5680A but looking back through my >> notes, doing it "properly" is, or was for me anyway, a non trivial >> exercise.I'm not familiar with the Windows software mentioned but the >> approach I remember was first to determine what, if any, offset was >> programmed into the unit as received, > > > The software I'm using doesn't seem to be able to read and display the > previous offset Sigh. > > >> then to measure the frequency of the unit as received, then to calibrate the >> tuning itself by setting positive and negative tuning extremes and measuring >> the frequency range before interpolating to find an initial tuning word, >> followed by calculating a further approximation, and so on and so fifth, and >> of course eventually programming the FE5680A accordingly. > > > Which is what I should be doing instead of winging it > > >> At that time I was using a similar test setup of a 53132A referenced to a >> Thunderbolt, although I did use a second Thunderbolt feeding the second >> channel of the 53132A as a confidence check. > > > Somebody should push me to pulling the trigger on buying a little ublox > LEA M8F-based GPSDO (VCTCXO) (currently on that auction site). It > would replace a wireless cellphone eval kit (with ublox LEON chip) I > picked up MAD-magazine-cheap at a flea market that I managed to short > out the TIMEPULSE on... My tools are too big for soldering a wire to > surface-mount, let alone replacing the chip. > > >> Much as I love Lady Heather, hmmm just how kinky is that?:-), I don't rely >> too much on her reported offsets etc, > > The particular figure I think I'm looking at is straight out of the > TBolt. It's "10MHz offset" bytes 20-23 in the 0x8F-AC report packet. > All that LH does is multiply it by 1000 to report it as parts per > trillion. The TBolt is measuring the frequency offset of the 10MHz > output relative to GPS/UTC in parts per billion. Positive values > indicate the 10MHz clock is running slow relative to GPS/UTC. Watching > this value in LH shows a lot of jitter. I try to take measurements on > the counter when this value is closest to 0. This is impossible to > predict, of course. Next best would be to correlate this value with the > readings I take (via GPIB) from the counter. My impression is that the > Rb may be more stable over the short term than the GPSDO, but I'd like > to be more certain. > > >> preferring to trust hardware measurement for that, but would suggest that if >> she is showing your thunderbolt as locked and tracking a reasonable number >> of sats then experience suggests you should be able to trust your >> Thunderbolt as
Re: [time-nuts] Alfred Loomis - an early time nut
As well as the CSPAN interview on youtube there's also a printed transcript at... https://www.c-span.org/video/?169779-1/tuxedo-park That's a very good read in itself, and with a rather interesting observation 34 minutes and 17 seconds in:-)... Jennet Conant He bought three Shortt clocks. They were very famous astronomical clocks, the most exact clocks in the world. In fact, Big Ben is a Shortt clock. They were fabulously expensive. He bought no less than three for his laboratory.-- There is a CSPAN author interview on youtube. Not much about time-nuttery but lots of stories about the people involved. Her grandfather was president of Harvard during WW II and he was tangled up with much of the wartime research. A Wall Street Tycoon and the Secret Palace of Science: Finance, Investing (2002) https://www.youtube.com/watch?v=w6U2yUNQRY8 57 minutes. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] FE-5680A tuning vs resonant peaks
There is a lot of information in the Time-nuts archives relating to the FE5680, and all the commands you need for reading and programming the unit are in the manual, as best I remember I just used Hyperterminal. Just in case you're not aware of it, the Google site specific search string is.. Google site specific search for item "".. "space"site:http://www.febo.com/pipermail/time-nuts/ Below are a couple of posts repeated that might be of immediate interest. Firstly an important warning re power supplies from Skip Withrow, not saying it's relevant in this instance but well worth repeating anyway, and secondly Jose Camara's very useful notes on connections and programming. Hopefully neither will mind my reposting them, but they are in the archives anyway:-), and apologies if they come out a bit garbled, the list doesn't seem too keen at times on AOL's formatting, especially when copying and pasting. Note that some, but not all, FE5680As require an external +5V supply on Pin 4. Nigel GM8PZR - We recently had a customer that purchased an FEI FE-5650A (basically a repackage version of the FE-5680A) and reported that it worked for several hours, then died. We promptly sent another unit, and he reported that it died as well. He had nothing but power hooked to the unit. On return of the first unit, it was examined and found to have corrupted code. The corrupted code problem was thought to be associated with doing bad things to the serial port (like framing errors), and we still believe this to be the case. However, the customer said only power was connected to the unit. I was asking some questions about how he was powering the unit, when he said he turned on the power supply (a large HP variable supply) and turned the voltage up to +15V (our 5650's are single supply). Ah hah, slowly ramping the voltage up on these oscillators appears to be a no no. The second oscillator has now been examined and it too was confirmed to have corrupted code. So, the word of warning is - DO NOT slowly ramp the supply voltage of FE-5680A and FE-5650A oscillators. I can't say what slowly is, but this guy was good at killing them. If I get some time I may try to repeat the results. My advice was to set the supply at 15V and just turn it off and on. I have not heard from him since. Skip Withrow -- I recently bought a pair of FEI FE-5680A Rubidium Frequency Standard units on ebay (best offer of $150 for 2, free shipping from Hong Kong - seller tortlex2). It was relatively cheap (compared to EFRATOM units 10 years ago), compact and modern (programmable DDS), perhaps even useful to replace internal timebase in some test equipment. The first thing I found out is that it wasn't easy to find *reliable information on them. Many conflicting pinouts, different packaging, connectors all for the same FE-5680A model. One source (a seller on eBay) lists pin 3 as +5V, when in fact that is the lock indication output - I ran the unit like that initially, and it gave 10MHz out for a while (possibly the ACT240 buffer output diodes taking all the current to back feed the power) until the output buffer burned (if you get >100mA on the 5V, this is a good candidate for replacement - it right by the DB-9 connector, accessible by removing 4 bottom screws (the bottom plate only). I replaced it and used pin 4 instead, which is the correct one. Another difficulty was to get the unit to respond to serial commands, which was ultimately solved after finding the Rosetta stone (a technical manual for the unit in my configuration). This particular model, part number 217400-30352-1 doesn't respond to the trimpot on the side (at least not with any change in frequency) and uses the synthesizer for very fine adjustment of frequency around nominal 10MHz. 32-bit value adjusts in 7E-13 increments (way below the noise floor of the unit stability). After my little tribulation in getting to this point, I decided to post my verified findings, clearly identifying the model number of the unit, to help others that already have the unit or decide to spring $75 to join this nuthouse... er... community. 1. Manufacturer: FEI 2. Model FE-5680A, part number 217400-30352-1 3. Connector: DB-9M (male) with signals: pin 1: +15V input (1.7A max when cold starting, 0.6A typ steady state) pin 2: GND (15V return) pin 3: LOCKn (low=locked, high=unlocked) ACT240 output pin 4: +5V input (80mA typ.) pin 5: GND (signal) pin 6: 1pps (about 1us positive pulse each second) pin 7: 10MHz sinewave (~1Vpp on 50 ohm) pin 8: RS-232 RX (receive commands into unit) pin 9: RS-232 TX (unit sends responses to pc) 4. Trimpot with external access doesn't seem to do a thing - reportedly C-field on other models. 5. Instead of wide range
Re: [time-nuts] f-multipliers from VHF to 10 GHz
Gerhard, you didn't mention a budget number for this. You should be able to find a commercial synthesizer ready to go if you have enough money. If it's a one-off, DIY thing, then it's a different story. If this is the case, I'd recommend looking at the methods used in microwave counters. They often use synthesized VHF sources and SRD multipliers and YTFs to make and select sampling frequencies for down-converting microwave inputs. All I can say is that there are lots of ways, and the usual things apply. Start as high as possible. An XO may be good up to 200 MHz or so. A SAW resonator may be good to a GHz - noisier, but less multiplication needed. You may be able to PLL a DRO well enough directly at 10 GHz, and not need multiplication, with a high enough low-noise reference frequency for comparison. Going with a multiplier chain is reliable and straightforward, but can get complicated due to the number of stages and filters that may be needed. My favorite multiplier is the classic SRD. If you start with a high enough drive frequency, selecting the desired harmonic is fairly easy with a fixed or yig-tuned BPF. I always figure that if SRDs are good enough to multiply by hundreds of times in Cs and Rb standards, they're good enough for my simple needs. An alternative to the SRD is to use extremely fast logic or line or laser driver type parts running at VHF, that have edge speeds with enough juice at 10 GHz, then BP filtered and amplified. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
