Re: [time-nuts] 10 MHz 'failover' switch?

Getting great isolation at 10 MHz is the easy part, given enough switching elements and control. One question is whether the switchover needs to be transparent (glitchless), without adding or losing any clock cycles, and ideally with no phase shift. This would involve a much more sophisticated

[time-nuts] Need info: Spectrum Instruments brand GPSDO

I recently picked up some old cell base station units, and retrieved two of what appear to be this unit, from Spectrum Instruments: http://www.spectruminstruments.net/products/custom2/custom2.html I have asked them if any info is available, but no response yet. If anyone knows anything about

Re: [time-nuts] HP5065A Step Recovery Diode, what part#?

Most of my SRD stock resides on old junked PLO brick boards - that way they won't get lost, and I can possibly use some of the associated circuitry. I have quite a few good PLOs, and have used a number of them in various projects. The ones that I have from the 1960s -1980s seldom run the

Re: [time-nuts] WTS: Efratom PTB-100 Precision Timebase

It's not necessarily a fault in the Rb physics - sometimes "regular" circuit or component problems cause the grief. I have three units kind of like this - "SPTB-100/LN-001," to be exact, with 5 MHz out. As I recall, it's similar to the M-100, so close enough to use some of its available

Re: [time-nuts] 10 MHz -> 16 MHz

I agree with Alex - injection-locking would be the simplest of all, if the slight correction signal added every 16 cycles is acceptable. Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to

Re: [time-nuts] Still looking for a schematic drawing for Oscilloquartz 8600-3 (945.860.011.03 S/N 422)

It seems rather drastic to scrap a basically working unit for lack of info. If you can't find anything, then there's a wide range of possibilities - you've got nothing to loose then, so try tweaking the circuit design a little. It should be evident where the coarse tuning and oscillator

Re: [time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

Yes Paul, LEDs wear out over time. By the late 70s and into the 80s, I think they were improved and perfected to the point where wearout is very slow and barely noticeable visually, and efficiency is much higher compared to the oldies. Even opto-couplers are sometimes specified for LED

Re: [time-nuts] VHF-UHF Frequency Calibrator

That's an interesting unit. You may want to take a close look at the small axial-leaded component going from the tube socket pin 7, to the B+ feed-through cap adjacent the "C18" label on the chassis. It appears you have it as a choke in the schematic, but I believe it's a diode - specifically,

Re: [time-nuts] VHF-UHF Frequency Calibrator

I'd recommend just tacking in a temporary line cord on old stuff like this - no point in putting in anything fancy, if it may turn out to be junk anyway. If it checks out OK, cool, impressive, or promising, then you can decide on refinement and restoration. Good luck. Ed

Re: [time-nuts] VHF-UHF Frequency Calibrator

Brooke wrote: "I checked optically, using an Ohmmeter and using the Diode Test function of a Fluke 87 DMM. It's an inductor. I share your concern as to how 11 GHz signals come from tube equipment with point to point wiring." OK, so much for that idea. The appearance of the part threw me off

Re: [time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

That's an interesting story and history about the clocks. I happen to have the original type digital one, used in a 5065A. I don't have an actual 5065A, but many years ago acquired a carcass of one - it was missing the Rb physics and a few other things, but was a nice box for re-use. I

Re: [time-nuts] Atomic Clocks: It is important that they keep good time, Part 1

Paul, what do you mean by the display "looking pretty ratty?" As I recall, the original buck regulator had regulated output voltage around 5V for the LEDs. and the PMOS clock IC needed something around 12V. Whatever the LEDs run from, it should be regulated and well filtered. If the LEDs are

Re: [time-nuts] Programmable clock for BFO use....noise

Those programmable oscillators look interesting. I went to Cardinal the website to learn more, but they're pretty sparse on details. It looks like they make all sorts of crystals, OC, TC, and VT XO modules, etc, and these programmable ones, which are apparently PLL-based oscillators locked to

Re: [time-nuts] Programmable clock for BFO use....noise

Rick said: "The trouble with a DDS is that you need a microcontroller with software just to baby sit the thing." Yes, I know what you mean. I wouldn't want to go through all that. I'm picturing more like the small, cheap DDS boards that show up on ebay. Maybe the right stuff could be found

[time-nuts] 8 kHz problem in Wavetek/Rockland 5135A synthesizer

My (formerly) trusty 5135A crapped out a while back, and I've been trying to fix it recently. I have tried in vain to find some particular details on the remaining problem circuit. I haven't found any kind of manual for it, but found one for the 5120A, an apparently similar, older model. The

Re: [time-nuts] Noise of digital frequency circuits (was: Programmable clock for BFO use....noise)

Atilla wrote: "Yes. This effect has been known for a few decades at least. What kind of puzzles me is, that I have not seen a mathematically sound explanation of it, so far. People talk of aliasing and sampling, but do not describe where the sampling happens in the first place. After all, it's

Re: [time-nuts] 8 kHz problem in Wavetek/Rockland 5135A synthesizer

Thank you so much, Nigel - I shall go and get all of those files. It's good to have as much info as possible on anything related to these synthesizers. I just had a breakthrough - or more a stroke of luck - on the 5135A. I'll explain later. Ed

Re: [time-nuts] 8 kHz problem in Wavetek/Rockland 5135A synthesizer

Alan, if you want some detailed info regarding my 5135A repair, let me know. I still have to get my head around what's going on in there, and organize my documents and notes. I did some experimenting last night, and tacked some wires to the output latch in this section, to bring the results

Re: [time-nuts] new op amp for distribution amplifiers

I'd suggest that if you wish to use a DIP or SO-8 version of a single CFA, and attain maximum BW and flatness, on a regular board, it should be mounted on the ground plane side, and the feedback resistor should be underneath on the opposite surface, directly between the output and inverting

Re: [time-nuts] 4.19 MHz xtal

I forgot to add that there's nothing remarkable about 4.194304 MHz in terms of stability - it's just high enough to fit in reasonably small packaging for clock use, and not take too-too much power. Lower frequencies can work just fine, but the crystal tends to get way bigger. The 32,768 kHz

Re: [time-nuts] 4.19 MHz xtal

Your crystal doesn't show enough digits to see why it's a common value. The "exact" number should be 4.194304 MHz, which is 2^22. It can be divided by this base-2 integer conveniently to make 1 Hz for clock use. The crystal marking, especially on small, common parts is often rounded or

Re: [time-nuts] Lars GPSDO

I'd recommend that once you get things figured out and tuned up to nominal running conditions, you should narrow the offset pot range, and use good low-TC resistors to make up most of the network R, with the pot having as small an effect as practical. BTW I don't see the pot in the pictures,

Re: [time-nuts] injection locking crystal oscillator

In this case, it appears what you want is choice of two 10 MHz reference sources, and not any frequency conversion. Instead of injection locking, why not just switch between one or the other? It's quite simple to externally drive the built-in oscillator in most ICs. You can make the circuits

Re: [time-nuts] Power supply for OCXO using "USB power blocks"

Jim said: The question is really more one of "how much filtering do I need to design into the downstream power supply circuits" The answer of course depends on the source and receiver of the noise. Common USB type systems and accessories are built to maximize cheapness, pass EMC testing well

Re: [time-nuts] Helium leaks

Jim, The He and H2 can depart from inside the device just as easily as they entered, so if put back in a normal environment, the diffusion will reverse and eventually stop at a new equilibrium point. If the parts are exposed to the nice high vacuum of free space, they should ultimately be

Re: [time-nuts] inexpensive fiber optic distribution

I'd recommend that fiber-optic transmission should be used where it has definite advantages, such as long distance, for galvanic isolation, or in serious EMC situations. It's fun to experiment with for all kinds of things, but it has no advantage over traditional wiring/cable for signal

Re: [time-nuts] GPS 1PPS, phase lock vs frequency lock, design (Bob kb8tq) (life speed)

I think I have a setup that exemplifies this situation, and some anecdotes. A while back, I acquired two "identical" GPSDO boards, and boxed them up together, with common environment, power supply, and GPS signal via a splitter. I've mentioned this thing a couple of times here, and had planned

Re: [time-nuts] Z3801 Power Supply Schematic?

Hi Dave, I would appreciate the Z3801A schematic too, if possible. I recall looking for any schematics for this unit years ago, and found some info about various aspects, but not a complete PS schematic. That would be great if one exists now. Ed

Re: [time-nuts] Building a DMTD/phase noise set in the 21st century

I think there may be some confusion over the "super-capacitor" term. Over the years, I've seen two types. The most commonly encountered are the ones in consumer gear, for storing charge to keep CMOS RAM alive during power outage and such, for a reasonable amount of time. These may be from 47

Re: [time-nuts] Keysight N5511A - phase noise measurements down to theoretical-177 dBm/Hz

That's quite an impressive system. I guess it's a few generations beyond my 11729C. One way to get overall performance to the limits of room temperature kT noise level, is to lower the T where you work. I wouldn't be surprised if some parts are TE-cooled, easily affordable in a big budget

Re: [time-nuts] Building a DMTD/phase noise set in the 21st century

You can also try capacitance multiplication with an active (power gain) device - of course, it needs to have commensurately low noise too. I had a few schemes sketched out years ago, for extra filtering a low noise voltage reference I intend (some day) to build, using some of the 2SK160 (as I

[time-nuts] Need info on MC24P and MC36P microwave mixers

I've been gathering up and organizing parts for my DMTD project, and also am revisiting my differential frequency counter that will go with it. I had started the counter project years ago, and had most of the big stuff mounted and ready to start building. This was to be a cascade of frequency

Re: [time-nuts] Dead 5061B

Yes, I've heard of this method before. It may help to study the internal structure of the filament and its support, and orient the tube to get some gravity assistance while trying the procedure. I recall that someone here put up a nice pictorial of the innards of a shot, dissected Cs beam tube

Re: [time-nuts] Question for my new GPSDO

I think the main need for the overall DAC system in these is not linearity, but monotonicity - an increasing digital input always causes an output change in one direction only, and never reverses. The linearity and other characteristics of the sub-parts comes into play when you need to combine

Re: [time-nuts] GPS Antennas

Attila wrote: "Bob kb8tq > wrote: /There are a lot of 3D printers out there that happily print ABS …. / I am not sure that's a good idea. The way how filament printers work will lead to lots of pores where humidity can

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

I have a Hitachi VD-1000 video distribution unit that's been sitting unused for years, waiting until I finally get around to making it into a reference unit. I just dug it out and looked inside. It is full of RCA jack cables for jumping the signals around in different ways. I apparently had

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

I think there may be some confusion due to similarity of names. Extron apparently makes or made video gear. Efratom made Rb sources and precision frequency distribution stuff. I'd like to find info on the Efratom distribution system, and specifically the "MBF" modules. Ed

Re: [time-nuts] 100 MHz decade divider advice needed

I'd recommend good old ECL and related families for these sorts of things. It's a lot more RF-friendly. 116/216 type receivers and small RF transformers can work for I/O, the signals are reasonably-sized (<1 V pp), can be all differential, can operate over a wide impedance range, and is quiet,

Re: [time-nuts] gpsdo 10MHz steering resolution

One more thing - this is less likely, but possible. Depending on the physical setup, it's possible to have magnetic coupling from transformers and wiring interfering with sensitive circuitry. This can be internal to a piece of equipment (the way it's built), or external, like if one piece of

Re: [time-nuts] gpsdo 10MHz steering resolution

From the picture, I'd guess the spurs are due to excessive line frequency ripple from your 50 Hz mains (full-wave rectified = 100 Hz spurs) - it could be internal to the reference source or other gear in the system, or ground loops. Check the specs for residual line noise on the various

Re: [time-nuts] DC distribution

Larry and Bill have hit the nails on the heads. For crimping, it's important to achieve a gas-tight connection, by essentially cold-welding enough Cu of the wire to the Cu or alloy of the crimp device. Too much of the wrong other materials present, or insufficient crimping force, may produce

Re: [time-nuts] FA-2 questions

Hal wrote: "dickw1ksz at gmail.com said: >/provide frequencies at 72.5, 725 and 7,975 MHz that are / What's interesting about 72.5, 725, or 7975 MHz?" Nothing, unless you're using those frequencies. But, if you want to

Re: [time-nuts] HP105B HP 105B 1 amp fuse blowing

I'd take Taka's suggestions regarding the actual battery and charger characteristics. A gross over-current means something's wrong, but a random fuse blowout after many years shouldn't be too surprising either, presuming everything seems normal otherwise. If it's not a battery/charger issue,

[time-nuts] Time nuts access

Did something happen to change access to this group? I keep getting 404 errors when I try to view the group discussions. It was working just fine and normally up to a few days ago, then nothing. Ed ___ time-nuts mailing list --

Re: [time-nuts] digital pots Part 2

Helipots are wonderful, old-school parts that are hard to beat - except for being quite expensive (but, they always were, relatively). As others have mentioned, there are many advantages of these over digital ones, for manually-adjusted functions. I would never use anything but a wirewound

Re: [time-nuts] OCXO and fluctuations after EFC adjustment

Rick said: "In the case of the 10811, I have already posted about the reference diode of special characteristics. I don't remember all the exact details of how it was chosen, but it was based on proprietary knowledge." This reminds me of something unusual I found in a Vectron 10 MHz OCXO

Re: [time-nuts] OCXO and fluctuations after EFC adjustment

This sort of behavior shouldn't be surprising at all. When you change the EFC (especially by a fairly large amount to move it a few Hz), you change the (transient and steady-state) operating points of the circuitry, so it has to drift gradually to stabilize at the new conditions. The effects

Re: [time-nuts] What to do with your dead cesium

I did a similar thing with an HP5065A carcass, by repackaging the guts of a Z3801A inside. Actually, I should say doing, rather than did - I started this over ten years ago, getting only to the point where the Z3801A was functional again. All the bells and whistles are in various states of

Re: [time-nuts] What to do with your dead cesium

Sorry Bob, but in my case, it was long ago, and the few unnecessary 5065A boards are long gone. The carcass I got had no Rb tube, and a number of boards/modules were missing. I kept the power supply guts for redesign, the front panel ass'y, digital clock, mechanical parts, and a few odds and

Re: [time-nuts] power supplies

Power supplies are indeed mostly commodity items, but absolutely essential. I have a large collection of OEM open-frame units, in linear and SMPS, and a small collection of commercial bench supplies, and some home-made ones. You can of course get a bunch of bench units and set them up for

Re: [time-nuts] Power Supplies

If you have a supply with something north of 15V, and you'd like to make 12V battery type voltage, it's easy to add an external solution with a low dropout three-terminal regulator to take it down a bit and still get good regulation. Look at LT1085 family, for example. Ed

Re: [time-nuts] GPS antenna splitter recommendation?

Having more ports than you need will incur some extra loss, since the signal power has to be divvied up (usually equally) between them all. On the other hand, there's a pretty good chance that you'll want another port or more in the future - especially in time-nuts type pursuits, so it's good

Re: [time-nuts] What to do with a dead Cesium...

Ulf wrote: "You can be pretty sure that the week after scrapping/modifying/found other uses for itsomeone offers a "Look what I found on a shelf" brand new unused tube for next to nothing. I would tuck tthe dead unit away for some time." Yes, I'm sure many of us have had that sort of thing

Re: [time-nuts] potential low-RFI power supply

Trying to look at the junk on the output voltage won't tell the story you need. Just connect a scope (1 meg) input to the DC output ground, and you'll begin to see the common-mode current situation. The actual LF and HF ripple on the DC out can be dealt with by sufficient filtering or

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

Re: [time-nuts] potential low-RFI power supply

Taka, You can set up a mini conducted-EMC lab with a few additional items that can be purchased, and some that you can make yourself, if you have the right parts. The most important item is a wideband AC current probe or transformer. A commercial clip-on type is most convenient, and ideally

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

Re: [time-nuts] HP 106B on Ebay

Speaking of antique OCXO references, I picked up two different ones for cheap over the last couple of years. One is a GenRad 1115A, and the other is a Vectron FS-323. Unbeknownst to me, the GenRad was totally shot. I brought it home from a flea market carefully, but upon flipping it around to

Re: [time-nuts] HP-10811AB-OCXO interface questions

Look in the HP5328A counter manual for the circuit - that's what this came from, indicated by the board marking. Seems like an awful lot of extra circuitry to support the OCXO. The only thing I can think of offhand is it may be a PLL circuit to allow locking to an external reference. You'll

Re: [time-nuts] Need help phase locking with small offset

I totally agree with the others warning to avoid processing too many different signals within a FPGA or any kind of part with multiple functions. There will always be some amount of crosstalk, so any device should be used only for one frequency chain, and only that frequency's related

Re: [time-nuts] ! PPS Source

Thanks all, for the info on this issue. It does indeed look doable to experiment with phase-locking the GPS RX module's internal clock to the ultimate 10 MHz GPSDO output. That is, doable, but not necessarily easy or without problems. I dug up my old notes and info from about ten years ago,

Re: [time-nuts] Looking for specs for a Matsushita CCA532ST02 GPS antenna

Don't forget to check the current draw spec if available - or measure it - and make sure the GPS RX is spec'd about the same range. Some RX units monitor the draw and may report an error (no antenna) if it's too low, or may not provide enough current if too high. Ed

Re: [time-nuts] distribution amps for 200 MHz

The answer lies somewhere between lots and lots of small amplifiers and associated parts, and one big one driving a tree of passive splitters. Are all the widgets the same? How much isolation is needed? How "good" does it have to be? How far away is everything? Are there ground loop/EMC

Re: [time-nuts] SMPS or conventional?

Regarding linear versus SMPS, I always prefer linear where possible. As others have said, for assessing a SMPS, try it and see. If it does the job sufficiently without too much noise, then go with it. Regarding Rb cooling, I don't know about the newer, smaller ones - I only have three big old

Re: [time-nuts] Looking for information on Brightline oscillator

One thing I've noticed in old mystery oscillators and other RF modules, is that they often use 3-terminal or other regulators inside. If you gradually increase the supply voltage, the current goes up rapidly, then levels off as sufficient overhead is reached. That gives some idea of where they

Re: [time-nuts] Oscillatek 2352

Pete wrote: "I'm planning to hook it up as an external reference for an HP59309A clock. Now my thought is to put a Schottky diode in the ground leg of the oscillator (to raise the ground reference slightly), then use a trim-pot on the CV input to fine-tune it." I'd recommend against

Re: [time-nuts] ! PPS Source

I have often wondered about all this sawtooth correction stuff, and I think I've asked here too, but never got a definitive answer. Every time this comes up, there are all sorts of explanations of the characteristic, and inevitably someone mentions the T-bolt having its internal GPS clock

Re: [time-nuts] low power divide by 5

Looks like the AC161 and AC163 are readily available, so they may be rigged for divide 5. It seems that of the counters surviving into AC, only binary ones are included, and the oddballs like decade are considered unnecessary - apparently nobody divides by 10 anymore, except inside of a

Re: [time-nuts] low power divide by 5

Well, data sheets are out there, but I don't know about the actual parts. Unfortunately, the 74AC family has far fewer members than the 74HC and others. I think each step in the evolution loses some types that aren't expected to be high enough in volume for the most modern applications. For

Re: [time-nuts] low power divide by 5

I just looked around for some AC390s - it appears they may have been made only by Toshiba and Hitachi, and have gone obsolete. Looks like you can't just call Mouser to order some up. But, looking at this site, it appears that a lot exist - at least a million pieces floating around out there,

Re: [time-nuts] low power divide by 5

. You can see it's just a matter of changing the jumpers on the preset pins. /On 6/29/2020 3:32 PM, ed breya wrote:Looks like the AC161 and AC163 are readily available, so they may be />/rigged for divide 5. It seems that of the counters surviving into AC, />/only binary ones a

Re: [time-nuts] low power divide by 5

It's been fun reminiscing about all these dividers and techniques, but getting back to the OP, the original search was for a divide by 5 with "low power" and operation from 5 to possibly 3.3V, and clocking properly at 50 MHz. One would assume also minimal size and complexity, and low cost.

Re: [time-nuts] low power divide by 5

Jim, At the risk of knocking over another bucket of worms, if your definition of "low power" can be extended to just beating the needs of the current part (circa 1W?), then you can look at ECL and its more modern derivatives, which are quite extensive. The classic bi-quinary ECL counter is

Re: [time-nuts] FW: HP-5372A operation with no CRT display.

Looking back at the OP, it appears the display is at least partially working, since there is some HV to light a dim spot on screen. I don't know what this display looks like inside, but imagine it's one or two small boards mounted open-frame on the CRT mechanical assembly, and connected to the

Re: [time-nuts] FW: HP-5732A operation with no CRT display.

I have a 5372A, and way back when I got it, I of course looked for the manual and think I got the pdf. As I recall, this was from the era where HP still provided full "real" manuals with all the schematics etc. The exception sometimes is if the entire display is an OEM unit, treated as a

Re: [time-nuts] Vibration isolation of quartz oscillators

The nicest optical bench I've ever seen in person, was in one of our labs many years ago. It was a huge, precisely flat polished granite slab about 6-8" thick, about 4x8' or maybe 5x10', mounted on active-leveling pneumatic bladders. It was loaded with thousands of threaded inserts, uniformly

Re: [time-nuts] Vibration isolation of quartz oscillators

I have mounted OCXOs, Rbs, and PLOs on small rubber motor mounts - the kind like for fan vibration reduction and such. The problem is that it's more of a guessing/empirical task, with no idea of the actual susceptibility of the device, or the mounting attenuation specs or degree of

Re: [time-nuts] low power divide by 5

74AC logic would do it just fine, but needs 5V nominal for full-speed specs. Lower supply voltage should work, but probably not all the way down to 3.3V with 50 MHz clocking. The spec sheets should indicate the possible range. The 74AC390 can provide divide by 5 directly, with another divide

Re: [time-nuts] low power divide by 5

I just looked at the 74AC390 sheet - it does say it will run to 60 MHz clocking with 3.3V supply, but that's at 25 deg C Tj. So, it looks doable, but depends on your desired operating temperature range. Ed ___ time-nuts mailing list --

Re: [time-nuts] Frequency division by 81

For a 10 MHz clock, 74HC would be fine. For small numbers like 81, a couple of 74HC163s would do it, and be good to go since they're synchronous anyway. For large numbers, my go-to divider is the 74HC4040 12-bit ripple counter. It can be rigged for any fixed integer divide ratio from 3 to

Re: [time-nuts] PDIP package 100 MHz decade dividers

One thing to be wary of, especially with 74AC running at full voltage, is that if you analog-bias an input midway, the internal supply current can go up. If the AC coupled input drive signal is big enough, then the input will spend little time near the middle threshold, so it's OK. If the

Re: [time-nuts] Double balanced mixer question

Is the 1 Hz difference signal the one you want, or do you want the sum? The sum will include 10.01 MHz but also 9.99 MHz, and 10.02 and 9.98 and 10.00, and so forth, and a whole lot of other products - basically the sums and differences of every fundamental and harmonic of

Re: [time-nuts] HP 5065 Rb update

If the only problem is that you're at the resolution limit of the pot, you may be able to slightly modify the circuit, reducing the pot's effect, but also reducing the total adjustment range. I don't recall what the circuit looks like, but from the discussion I'm guessing it's like a 10 kilohm

Re: [time-nuts] HP 5065 Rb update

Paul, if the pot is 1 k, set up as a DC divider from a low-Z reference voltage, and only lightly loaded by an amplifier circuit, you could try upping it to a 2 k or 5 k, possibly 10 k, and get an immediate resolution/set-ability boost, with little effect on the rest, and no other part changes

Re: [time-nuts] HP 5065 Rb update

OK, I see now what the circuit looks like, in the manual. The pot is used in rheostat mode, so the specific value is needed, and it would take some more modification of the circuit to increase the setting resolution. I would recommend making a simple change to the existing pot hookup though,

Re: [time-nuts] HP 5065 Rb update

I found a datasheet for the Bourns "Knobpot" type pots I have. Specs are not all that great. No info about the innards. https://www.bourns.com/pdfs/3600_obsolete.pdf Ed ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to

Re: [time-nuts] HP 5065 Rb update

Paul S. wrote "The pots on the digital counter and its actually quite small. The 3 leads all fit into an area about the size of a pencil eraser." Yeah, I know what you mean. I had assumed the pot in question was one of the more modern, fairly compact ten-turn helipots, that are about an

Re: [time-nuts] EOL Motorola Oncore Remote Antenna

Yes, without true hermetic enclosure, eventually enough moisture and other stuff will leak around or diffuse through the seals and materials. Depending on climate conditions and maintenance schedules, you could try try an old-school remedy, which is to stuff as much desiccant (like silica gel)

[time-nuts] TECs in cooling below ambient

This recent TEC talk reminded of some of my long term planned projects, and related issues. I have at least four "someday" projects involving TECs, to regulate device temperatures near or below "normal" room temperature, including a high precision DC voltage standard, a sub-fA electrometer

Re: [time-nuts] TECs in cooling below ambient

Many years ago, I got some junker DP sensors - the chilled mirror type. I never did find any specific info on the model, or get around to figuring out the guts to run them. I can't recall if the support electronics were missing, or maybe potted, or if I just didn't want to reverse engineer

Re: [time-nuts] SMPS or conventional?

Yes, the physical/thermal stress wear and tear depends on the device response relative to the ripple frequency. TECs aren't the only things with these issues - even modern high power LEDs used for illumination are known to last longest when run from "pure" DC, for a given average power level.

Re: [time-nuts] Flicker Noise Reduction

That's pretty slick. I think I see what's going on in there. It reminds me somewhat of optical chopping, but in this case, it looks like it's not about the 1/f LF/DC offsets adding to the amplitude, rather their effect on gain that's important. It seems to me that if the the gains are

Re: [time-nuts] power supply for Z3801

Look at PoE or whatever it's called type supplies - I think the standard is 48 VDC for power over ethernet. I don't know if any of the ones for this purpose are big enough to run the Z3801 though. 48 V is a very common supply, so it should be easy to find an open frame OEM supply. If size and

Re: [time-nuts] SMPS or conventional?

Regarding TEC life, in my experience, what wrecks them the most is cooling applications where the cold side is below the dew point, and water condenses out onto and into the TEC Peltier array. This eventually rots the elements from corrosion and electrolysis, until something craps out. If the

Re: [time-nuts] 5065A Rb Cavity RX - Varactor repair?

I doubt that the SRD is the problem. It's just the last thing in the chain, and a number of things ahead of it all have to work right first. I'd look first at any connections and wiring between various sections, and jiggle things around to see if the symptoms can return. Next, if ICs and

[time-nuts] Speaking of varicap diodes

The recent discussion of tweaking up the tune range of an OCXO has reminded me of another of my ongoing projects, and I thought I'd mention some of it here. The varicap diode is near and dear to hearts - whether you know it or not - for tuning RF oscillators and other functions. One of my

Re: [time-nuts] GPSDO won't lock: OCXO aged out?

One thing I forgot to mention, is that the EFC sensitivity isn't necessarily the same in this new range as it was before. In other words, having more gain may not be a big deal, or even beneficial. You're way past the steeper dC/dV slope anyway, so the actual effect of the varicap on the net

Re: [time-nuts] GPSDO won't lock: OCXO aged out?

Scott, it looks like you have already proven the tune voltage can go much higher than specified, and sufficient to get in-range for 10 MHz ideal. The currents noted show there's probably a pull-down resistor on the tune line - maybe 75-100 k. The reverse leakage of the varicap diode should be

Re: [time-nuts] "Q for dummies"

If you have a mechanical tuning fork handy, just ding it and note the gradual decay. Then wrap a small wad of paper towel on one or both arms, with some tape outside (not touching the arms - don't want adhesive residue left on there) to keep in place, and repeat. For using a wine glass or

Re: [time-nuts] "Q for dummies"

But Dana, a high Q can also be a bad thing - depends on the situation. 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.

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