Re: [time-nuts] Basic question regarding comparing two frequencies
jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Sage advice Bill!
Heathkid, you don't need another Rb unit when you have 3 perfectly
decent ones! You really need a standard to calibrate your Rb units to,
a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob
Mokia, fluke.l, on fleeBay sells them separately or as a starter kit
with everything there to get you going. Once you have this up and
running for quite some time and see that things are looking stable in
the Lady Heather application, then you can start to think about
calibrating the FEI-5680's but only after you have run them in well. I
don't know your counter but does it have an input for an external
reference source? If so you will be able to use the T'Bolt as an
external reference for it, providing the required reference is 10MHz.
If it's not, you can divide down the T'Bolt's output to match. If your
frequency counter has no reference input (apart from throwing it in
the bin) you should be able to engineer it into the instrument,
depending on your skill set.
So, first get yourself a frequency standard to work with, IE. a T'Bolt
or the like.
My 2c worth,
Steve
On 25/07/2010, WB6BNQ wb6...@cox.net wrote:
To Bob and Stan (W1LE),
[p.s. But not just to you two alone]
Why complicate the answers to Heathkid (now Brice KA8MAV) with a bunch of
different directions that should only be decided after one gains enough
knowledge and understanding (they are not the same) to properly grasp the
subject matter ? ? ? ?
Clearly Heathkid needs some guidance. The form should be to start out with
the very basics and get his feet on the ground. He already has three (3) Rb
sources that should keep him busy for quite some time. However, his counter
is really junk from a lab point of view. Nonetheless, even it can be useful
if it is understood how to apply it after understanding its limitations.
What Heathkid needs to understand is it is not about equipment. It is all
about how to measure and account for errors and unknowns. Actually, quite a
daunting task depending upon the level of achievement.
I agree he needs some kind of external reference and I agree the Trimble
Thunderbolt (Tbolt) would be the right item for his true reference. Even
the Tbolt has its issues that need to be understood.
He will also need a method of comparison. The oscilloscope is a good start
but very tedious. Here Burt's project would help him a lot when Burt gets
it done. I guess he is close. I guess, also, the PICTIC II would fit the
bill after he understands what it is.
Still he needs to understand how to apply and use this stuff. Confusing him
with suggesting all of the different Rb sources available is only making him
think a better one { relative statement } would be the answer which is not
true. His FEI-5680's are so much better for his particular level, it is not
even funny.
What has not been asked of him is what are his goals and intentions. If it
is to just say you have an atomic frequency reference, then sit the FEI-5680
on the coffee table; job done. One cannot be properly guided if the goals
are unknown.
BillWB6BNQ
Bob Camp wrote:
Hi
The only way to be sure of what's going on is to have several (hopefully)
accurate references. With at least three you can begin to guess how good
they are.
The TBolt is different from the Rb in a couple of regards:
1) It's short term stability isn't as good when locked tightly to the GPS.
2) It's long term stability is much better than the Rb when it's locked.
3) It's easier to tell what's happening with it if you hook up a PC and
the Lady Heather (free) program.
The Rb will need a couple of things to make it play right:
1) It's got to have a pretty good heat sink on it. An 8 x 10 piece of
1/4 aluminum is a reasonable start
2) It's got to be run for a while (possibly 24 hours) before it will be
stable
3) You need to watch the lock, and lamp voltages to be sure it's not doing
something crazy.
My recommendation based on cost is the Efratom LPRO for a cheap Rb. They
are in the ~$60 range and seem to work pretty well.
Setup wise, I would get a TBolt in addition to the Rb. You need something
to calibrate the Rb (and your counter TCXO) against. Both are secondary
standards. They (unlike a Cesium) are adjusted to match a known good
reference.
Once you have the Rb and the TBolt, next step is up to you. Cesium is
always an alternative, so's a Hydrogen Maser
Bob
On Jul 24, 2010, at 3:32 PM, Heathkid wrote:
Hello Bob,
What would you recommend? I already have three FE-5680A Rb standards
(which I'm quickly learning likely aren't worth the powder to blow them
to (*insert your own word here*). Okay, that was probably my first
mistake (thoughts?).
My frequency counter is one I built from a kit from aade.com that has
the TCXO option (although I had to tweak it myself so I have NO idea how
close it is to any accuracy or precision). I have access to some really
nice HP
Re: [time-nuts] Basic question regarding comparing two frequencies
The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
You can always use the ready, fire, aim, approach. Make a tiny adjustment and see if it makes the Lissajous figure move faster, so you know your going the wrong way, or slower, and then you'll know your on the correct path. Steve On 26/07/2010, J. L. Trantham jlt...@att.net wrote: The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
No, if it's moving left to right the OCXO is low (I just had my coffee). Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. L. Trantham Sent: Sunday, July 25, 2010 7:05 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Excuse my replying to my own posting please.
This post is really about the DFD1 frequency counter.
Heathkid: You are comparing a Rb against a frequency counter with a
TCXO that you tweaked yourself to calibrate it against no known
frequency standard. Try running the three FEI-5660s for 24 hours and
then measure the output of each with your frequency counter. Pick the
mean of them and adjust your DFD1 to match that. At least you should
be in a better position than you are now.
As you built the DFD1 yourself, you should have the schematic and may
be able to engineer in a connection for an external reference. There
is plenty of people here who would be happy to advise you on a
suitable interface if you can attach the part of the circuit where the
TCXO is located. If you do get a T'Both, you would be able to use it
as a reference or, perhaps, build in one of the FEI-5660s as an
internal reference. The limiting factor though is how good is the
circuit used in the DFD1 which will limit it's stability and accuracy.
There are many factors, including input circuit, voltage regulation,
counter stage design, level detection, etc. which have a major impact
here. What I'm getting at is that to write-off a bunch of FEI-5660s
after checking them with such a device as this, is a very poor
decision.
Maybe you could look at a better counter on fleeBay before you make
further assumptions.
73,
Steve
On 26/07/2010, Steve Rooke sar10...@gmail.com wrote:
Sage advice Bill!
Heathkid, you don't need another Rb unit when you have 3 perfectly
decent ones! You really need a standard to calibrate your Rb units to,
a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob
Mokia, fluke.l, on fleeBay sells them separately or as a starter kit
with everything there to get you going. Once you have this up and
running for quite some time and see that things are looking stable in
the Lady Heather application, then you can start to think about
calibrating the FEI-5680's but only after you have run them in well. I
don't know your counter but does it have an input for an external
reference source? If so you will be able to use the T'Bolt as an
external reference for it, providing the required reference is 10MHz.
If it's not, you can divide down the T'Bolt's output to match. If your
frequency counter has no reference input (apart from throwing it in
the bin) you should be able to engineer it into the instrument,
depending on your skill set.
So, first get yourself a frequency standard to work with, IE. a T'Bolt
or the like.
My 2c worth,
Steve
On 25/07/2010, WB6BNQ wb6...@cox.net wrote:
To Bob and Stan (W1LE),
[p.s. But not just to you two alone]
Why complicate the answers to Heathkid (now Brice KA8MAV) with a bunch of
different directions that should only be decided after one gains enough
knowledge and understanding (they are not the same) to properly grasp the
subject matter ? ? ? ?
Clearly Heathkid needs some guidance. The form should be to start out
with
the very basics and get his feet on the ground. He already has three (3)
Rb
sources that should keep him busy for quite some time. However, his
counter
is really junk from a lab point of view. Nonetheless, even it can be
useful
if it is understood how to apply it after understanding its limitations.
What Heathkid needs to understand is it is not about equipment. It is
all
about how to measure and account for errors and unknowns. Actually, quite
a
daunting task depending upon the level of achievement.
I agree he needs some kind of external reference and I agree the Trimble
Thunderbolt (Tbolt) would be the right item for his true reference. Even
the Tbolt has its issues that need to be understood.
He will also need a method of comparison. The oscilloscope is a good
start
but very tedious. Here Burt's project would help him a lot when Burt
gets
it done. I guess he is close. I guess, also, the PICTIC II would fit
the
bill after he understands what it is.
Still he needs to understand how to apply and use this stuff. Confusing
him
with suggesting all of the different Rb sources available is only making
him
think a better one { relative statement } would be the answer which is
not
true. His FEI-5680's are so much better for his particular level, it is
not
even funny.
What has not been asked of him is what are his goals and intentions. If
it
is to just say you have an atomic frequency reference, then sit the
FEI-5680
on the coffee table; job done. One cannot be properly guided if the
goals
are unknown.
BillWB6BNQ
Bob Camp wrote:
Hi
The only way to be sure of what's going on is to have several
(hopefully)
accurate references. With at least three you can begin to guess how good
they are.
The TBolt is different from the Rb in a couple of regards:
1) It's short term stability isn't as good when locked tightly to the
GPS.
2) It's long term stability is much better than the
Re: [time-nuts] Basic question regarding comparing two frequencies
J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Hal Murray wrote: jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. Yes.. I was at a meeting at work last week where we discussed this. Seems it works like this: The equipment mfrs have about 6 month turnaround on patch cycles, so your instrument is almost always vulnerable. But, if you don't connect it to anything or use it as a browser, you're ok. Then, someone plugs a USB stick in (that is infected from some other PC).. and that infects the instrument. SInce the instrument isn't running anti virus (they're of limited value anyway, and usually have a performance impact that's unacceptable in embedded systems), the virus lurks there. Then, when you DO connect to the network, it leaps into action, or, it infects the USB stick of the next poor schlub to use it. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
That seems to indicate these devices are running a version of embedded Windows for them to get infected by a virus and I wonder why they need such a sledgehammer internally. Steve PS. sorry for top-posting but that's the only way I can reply at the moment (basic HTML Gmail). On 26/07/2010, jimlux jim...@earthlink.net wrote: Hal Murray wrote: jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. Yes.. I was at a meeting at work last week where we discussed this. Seems it works like this: The equipment mfrs have about 6 month turnaround on patch cycles, so your instrument is almost always vulnerable. But, if you don't connect it to anything or use it as a browser, you're ok. Then, someone plugs a USB stick in (that is infected from some other PC).. and that infects the instrument. SInce the instrument isn't running anti virus (they're of limited value anyway, and usually have a performance impact that's unacceptable in embedded systems), the virus lurks there. Then, when you DO connect to the network, it leaps into action, or, it infects the USB stick of the next poor schlub to use it. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Hi No, the LPRO is not obviously better than the FE's, depending on which version of the 5680 you have. The 5680 comes in two common varieties, one only has a 1 PPS output, the other will put out 10 MHz as well. Both can be digitally tuned to come up with oddball frequencies in the vicinity of their intended output. Bob On Jul 24, 2010, at 5:46 PM, Heathkid wrote: Bob, so you're saying the Efratom LPRO is better than the three FE-5680A's I already have? Sounds like I do need a TBolt anyway. - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 5:20 PM Subject: Re: [time-nuts] Symmetricom X72 Hi The only way to be sure of what's going on is to have several (hopefully) accurate references. With at least three you can begin to guess how good they are. The TBolt is different from the Rb in a couple of regards: 1) It's short term stability isn't as good when locked tightly to the GPS. 2) It's long term stability is much better than the Rb when it's locked. 3) It's easier to tell what's happening with it if you hook up a PC and the Lady Heather (free) program. The Rb will need a couple of things to make it play right: 1) It's got to have a pretty good heat sink on it. An 8 x 10 piece of 1/4 aluminum is a reasonable start 2) It's got to be run for a while (possibly 24 hours) before it will be stable 3) You need to watch the lock, and lamp voltages to be sure it's not doing something crazy. My recommendation based on cost is the Efratom LPRO for a cheap Rb. They are in the ~$60 range and seem to work pretty well. Setup wise, I would get a TBolt in addition to the Rb. You need something to calibrate the Rb (and your counter TCXO) against. Both are secondary standards. They (unlike a Cesium) are adjusted to match a known good reference. Once you have the Rb and the TBolt, next step is up to you. Cesium is always an alternative, so's a Hydrogen Maser Bob On Jul 24, 2010, at 3:32 PM, Heathkid wrote: Hello Bob, What would you recommend? I already have three FE-5680A Rb standards (which I'm quickly learning likely aren't worth the powder to blow them to (*insert your own word here*). Okay, that was probably my first mistake (thoughts?). My frequency counter is one I built from a kit from aade.com that has the TCXO option (although I had to tweak it myself so I have NO idea how close it is to any accuracy or precision). I have access to some really nice HP counters at work so that's my next step is to try one of those. My DFD4 measured the output of one of my 5680A's to 10.000.007 MHz after about a 10 minute warm-up. I don't know which one is off. Reading the specs on the 5680A's before I bought them looked like they were pretty decent. I'm learning... So, what reasonably priced Rb standard would you recommend? Should my next step in this process be a Trimble Thunderbolt? Am I starting over? Thanks... - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 9:31 AM Subject: Re: [time-nuts] Symmetricom X72 Hi At least looking at the spec sheet it's not really very impressive. Bob On Jul 23, 2010, at 11:06 PM, Heathkid wrote: Hello. Does anyone have any experience with the Symmetricom X72? Thanks... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Steve Rooke wrote: That seems to indicate these devices are running a version of embedded Windows for them to get infected by a virus and I wonder why they need such a sledgehammer internally. Steve PS. sorry for top-posting but that's the only way I can reply at the moment (basic HTML Gmail). Yes.. most are running some flavor of Windows Embedded (formerly known as WinCE) or WinXP. It's a cost driven thing.. small form factor motherboards are readily available, windows gives you a familiar (to most users) interface for doing things like setup of the network interface, file system, etc. I'd say it's probably cheaper (in a capital investment sense) to put a small PC into the instrument than to design your own custom controller board, write embedded software for it, etc.) Especially if you want commonality across your whole line, where the higher end instruments have fairly sophisticated add-on software (all those slick applications that analyze signals, set things up), choosing some sort of popular OS platform makes sense. MS makes it pretty easy to do the development.. The Visual Studio products are inexpensive, well integrated, etc. They've got decent documentation for generating stripped down installs suitable for instruments. They also have update management, etc. Some flavor of Linux is really the alternative, and the learning curve to get started with embedded applications is a bit steeper, especially if you want more than what can be done by a command line interface. Which GUI toolkit do you use? Where do you get it? etc. With Windows, that whole list of choices has been made for you. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
ROFLMAO! -John == jim...@earthlink.net said: But over the next few years, I suspect you'll see more and more of it coming onto the surplus market. My fond hope is that my daughter will be able to capitalize on it. A friend had a fancy scope with an Etherenet. It got infected with the virus-de-jour. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Jim, It might appear on the 2nd user market sooner, but the odds are you won't be able to either repair it or calibrate it as the manufacturer will have been the only supplier of either of these services, and no service manuals will exist. If it is still in support, the mfr will calibrate/fix it for you if your pockets are deep enough (probably as much or more than you pay for it). If (as is likely), it is out of support, then it will only be good for re-cycling or land-fill :-( H does anyone but us old fogies see anything wrong with a business model where stuff can't be fixed and has a support lifetime of 5 years or so ? Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: 25 July 2010 14:16 To: j...@quik.com Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John = The only problem with the lissajous approach is you can't tell if your OCXO is high or low relative to the reference figure. This is resolved by triggering the scope with the reference. If the trace is moving left to right, the OCXO is high, and vice versa, IIRC (I just woke up). Otherwise, it works fine for fine adjustments aligning an unknown oscillator to match a known reference. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Geoffrey Smith Sent: Sunday, July 25, 2010 2:58 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Basic question regarding comparing two frequencies Mark, I have been measuring the difference between a GPSDO and a HP 10811A TCXO. To avoid any triggering issues I put the CRO into XY mode. The resulting Lissajous curve figure flips at the rate of the frequency difference good old Wikipedia has the maths. Just sit and watch the Lissajous and you can adjust the TCXO to have the not flip and set accuracies in small fractions of a Hertz. Geoff -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Sunday, 25 July 2010 3:29 AM To: time-nuts@febo.com Subject: [time-nuts] Basic question regarding comparing two frequencies Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter. I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Yup. Newer equipment is just not fixable. I have a HP 8753D VNA with the 6 GHz option. The 3-6 GHz band is sick and I cannot get any response out of Agilent for anything more than a simplified block diagram from the manual. They want me to send the module back for a $7500 fix. I can buy a used module on eBay for about $4300. Neither are in the budget. I think the thing is fixable, but not w/o the info. FWIW, -John == Jim, It might appear on the 2nd user market sooner, but the odds are you won't be able to either repair it or calibrate it as the manufacturer will have been the only supplier of either of these services, and no service manuals will exist. If it is still in support, the mfr will calibrate/fix it for you if your pockets are deep enough (probably as much or more than you pay for it). If (as is likely), it is out of support, then it will only be good for re-cycling or land-fill :-( H does anyone but us old fogies see anything wrong with a business model where stuff can't be fixed and has a support lifetime of 5 years or so ? Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux Sent: 25 July 2010 14:16 To: j...@quik.com Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Basic question regarding comparing two frequencies J. Forster wrote: Probably yes. There are also a number of lower cost instruments (just above consumer grade)like HF-VHF VNAs that implement much of the smarts in a PC on the market. As to high end instruments w/ USB or Ethernet, I'm not so sure. The USA is doing less and less hardware development, so instruments are not being bought in anything like the quantity as in the past. A lot of the new Agilent and Tek gear (at all price points) seem to have Ethernet, especially if it has a LCD front panel. (there's that LXI interface thing, too) Even power supplies. Not much USB (at least for control.. these days, using a USB stick for data transfer seems ubiquitous.. they've replaced the floppy drive on scopes, etc.), except for RF power meters.. There's a whole raft of power meter heads that are USB, which makes sense.. the hard part is in the actual sensor, not in the meter which displays the power reading. Mind you, because they do this by using single board PCs instead of the dedicated instrument controller inside, they're subject to all the ills of PCs (e.g. expectation of patch cycles, etc.) It also seems that there's a more rapid turnover of equipment these days (probably because accounting rules allow 3 or 5 year depreciation) and so the idea of a place hanging onto a signal generator for 20 years is less common. So that newer gear will show up used sooner (I hope!) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
This is close to the project I showed at the SF Bay Area Maker Faire in May. I showed fractional ppb difference measurements using a $25 flea market scope. The photo below is by a former NIST Cs fountain researcher who stopped by: http://www.flickr.com/photos/oskay/4640673869/in/set-72157623988565617/ Leigh/WA5ZNU On 07/24/2010 10:28 AM, Mark Spencer wrote: Hello: Just for grins I decided to compare the frquency from my GPSDO to the time base in my 5328A counter. I connected the 10 mhz time base from the counter to channel A of my 100 Mhz scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T adaptor also fed this signal into the input of the counter.I scope to trigger from Channel B. The drift betwen the two signals on the scope seems to match the error in the displayed frquency on the counter. (ie. if the counter shows .9998 it takes approx 5 seconds for the the wave form on channel A to slip a full cycle realitve to channel B.) Is this a reasonable approach or is there a better way to compare two frequencies using a scope ? Best regards Mark Spencer ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Steve, Thank you for your reply. Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a option wasn't available at the time) is not going to be my primary counter. It's just something I had laying around that I use when I'm working with QRP and QRPp rigs that don't have *any* frequency readout. I've built a *lot* of tiny transceivers that are either xtal based or use a PTO (you have to learn to love the sound of the chirp but once people learn what it is I'm transmitting with they don't mind as much), or some other form of VFO. So, a digital readout is quite helpful and necessary, especially with the PTO where the tuning takes place by screwing a 6-32 brass screw in and out of a coil. That said, I did build it up as a bench counter and not a digital display. It still does what I need it to do (for the ham radios) but there were some mods that were done if you look at the site (http://www.aade.com/DFD4A/dfd4a.htm). The one I built is actually pictured there. I know it's not very accurate, precise, or even all that stable. But... once I get a known frequency reference and accurately calibrate it... it'll be better. Most likely right now it's off around 7 Hz but I usually operate on 40m so at 7.040 MHz +/- a few Hz isn't going to matter much (try adjusting a screw with a knob on the end of it to change the oscillator 1 Hz anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There are many factors, including input circuit, voltage regulation, counter stage design, level detection, etc. which have a major impact here. What I'm getting at is that to write-off a bunch of FEI-5660s after checking them with such a device as this, is a very poor decision. Maybe you could look at a better counter on fleeBay before you make further assumptions. 73, Steve On 26/07/2010, Steve Rooke sar10...@gmail.com wrote: Sage advice Bill! Heathkid, you don't need another Rb unit when you have 3 perfectly decent ones! You really need a standard to calibrate your Rb units to, a Trimble Thunderbolt is likely to be the cheapest choice for you. Bob Mokia, fluke.l, on fleeBay sells them separately or as a starter kit with everything there to get you going. Once you have this up and running for quite some time and see that things are looking stable in the Lady Heather application, then you can start to think about calibrating the FEI-5680's but only after you have run them in well. I don't know your counter but does it have an input for an external reference source? If so you will be able to use the T'Bolt as an external reference for it, providing the required reference is 10MHz. If it's not, you can divide down the T'Bolt's output to match. If your frequency counter has no reference input (apart from throwing it in the bin) you should be able to engineer it into the instrument, depending on your skill set. So, first
Re: [time-nuts] Basic question regarding comparing two frequencies
My attempt to understand your diagram, not sure about how the quadrature hybrid is connected. Stanley - Original Message From: J. Forster j...@quik.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sun, July 25, 2010 10:29:23 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John snipattachment: Jfoster.jpg___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Thanks Bob. I'm understanding a lot more now. The FE-5680A's that I have output both the 1pps as well as 10 MHz (and programmable to other frequencies). Yes, I also understand now how the Rb physics package and the DDS work together to come up with the output frequency. With the TBolt on the way now... and in the process of looking for a good/used real counter... I'll get there. :) Best regards, Brice - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 11:01 AM Subject: Re: [time-nuts] Symmetricom X72 Hi No, the LPRO is not obviously better than the FE's, depending on which version of the 5680 you have. The 5680 comes in two common varieties, one only has a 1 PPS output, the other will put out 10 MHz as well. Both can be digitally tuned to come up with oddball frequencies in the vicinity of their intended output. Bob On Jul 24, 2010, at 5:46 PM, Heathkid wrote: Bob, so you're saying the Efratom LPRO is better than the three FE-5680A's I already have? Sounds like I do need a TBolt anyway. - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 5:20 PM Subject: Re: [time-nuts] Symmetricom X72 Hi The only way to be sure of what's going on is to have several (hopefully) accurate references. With at least three you can begin to guess how good they are. The TBolt is different from the Rb in a couple of regards: 1) It's short term stability isn't as good when locked tightly to the GPS. 2) It's long term stability is much better than the Rb when it's locked. 3) It's easier to tell what's happening with it if you hook up a PC and the Lady Heather (free) program. The Rb will need a couple of things to make it play right: 1) It's got to have a pretty good heat sink on it. An 8 x 10 piece of 1/4 aluminum is a reasonable start 2) It's got to be run for a while (possibly 24 hours) before it will be stable 3) You need to watch the lock, and lamp voltages to be sure it's not doing something crazy. My recommendation based on cost is the Efratom LPRO for a cheap Rb. They are in the ~$60 range and seem to work pretty well. Setup wise, I would get a TBolt in addition to the Rb. You need something to calibrate the Rb (and your counter TCXO) against. Both are secondary standards. They (unlike a Cesium) are adjusted to match a known good reference. Once you have the Rb and the TBolt, next step is up to you. Cesium is always an alternative, so's a Hydrogen Maser Bob On Jul 24, 2010, at 3:32 PM, Heathkid wrote: Hello Bob, What would you recommend? I already have three FE-5680A Rb standards (which I'm quickly learning likely aren't worth the powder to blow them to (*insert your own word here*). Okay, that was probably my first mistake (thoughts?). My frequency counter is one I built from a kit from aade.com that has the TCXO option (although I had to tweak it myself so I have NO idea how close it is to any accuracy or precision). I have access to some really nice HP counters at work so that's my next step is to try one of those. My DFD4 measured the output of one of my 5680A's to 10.000.007 MHz after about a 10 minute warm-up. I don't know which one is off. Reading the specs on the 5680A's before I bought them looked like they were pretty decent. I'm learning... So, what reasonably priced Rb standard would you recommend? Should my next step in this process be a Trimble Thunderbolt? Am I starting over? Thanks... - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 9:31 AM Subject: Re: [time-nuts] Symmetricom X72 Hi At least looking at the spec sheet it's not really very impressive. Bob On Jul 23, 2010, at 11:06 PM, Heathkid wrote: Hello. Does anyone have any experience with the Symmetricom X72? Thanks... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts
Re: [time-nuts] Symmetricom X72
Hello Brice, I like my HP-5384A freq counter, spec'd to 225 MHz, LCD display and enough digits for my ham radio work. This counter has a small foot print on the bench at ~8.5 wide, 3.5 high and 12 deep. low Ac power consumption. Other older counters have taken up a lot more bench space and electrical power. I use the Trimble T'Bolt as an external 10 MHz reference. This counter was an upgrade from a HP-5245L/M nixie display counter. I continue to use a HP-5340A microwave counter, good to 26.5 GHz, LED display. Ebay can be your friend, but the rule of Caveat Emptor still applies, either pay the bigger bucks for a vendor's guarantee or treat it like a flea market item, you will not how it works until you get it on your test bench. Bid accordingly. A permanent search on Ebay can be helpful for specific models you are considering. I have made some scores on Ebay, especially used HP test equipment, but I have extraordinary patience. I have horror stories too. Other counters I have considered: HP-5345 HP/Agilent 53132 Stanford Research Systems model 620 Others will also have some great counter experiences and why a specific model satisfied their needs. Be cautious on the A/B/C models as well as the vendor options. Most vendors I deal with are simply junque dealers and have no clue as to the options and their function. Stan, W1LE Cape Cod FN41sr On 7/25/2010 12:19 PM, Heathkid wrote: Steve, Thank you for your reply. Last night, as suggested by several people on this list... I ordered a Trimble Thunderbolt from Bob Mokia, fluke.l so I should be in pretty good shape there to get started once it arrives. The counter I mentioned (it's a DFD4 - modified with the tcxo as the a option wasn't available at the time) is not going to be my primary counter. It's just something I had laying around that I use when I'm working with QRP and QRPp rigs that don't have *any* frequency readout. I've built a *lot* of tiny transceivers that are either xtal based or use a PTO (you have to learn to love the sound of the chirp but once people learn what it is I'm transmitting with they don't mind as much), or some other form of VFO. So, a digital readout is quite helpful and necessary, especially with the PTO where the tuning takes place by screwing a 6-32 brass screw in and out of a coil. That said, I did build it up as a bench counter and not a digital display. It still does what I need it to do (for the ham radios) but there were some mods that were done if you look at the site (http://www.aade.com/DFD4A/dfd4a.htm). The one I built is actually pictured there. I know it's not very accurate, precise, or even all that stable. But... once I get a known frequency reference and accurately calibrate it... it'll be better. Most likely right now it's off around 7 Hz but I usually operate on 40m so at 7.040 MHz +/- a few Hz isn't going to matter much (try adjusting a screw with a knob on the end of it to change the oscillator 1 Hz anyway). :) By the way, when I built it, I calibrated it by zero beating against WWV at 10 and 20 MHz. That was the best way I had at the time and if the DFD4 is now 7 Hz off after all these years... it's not doing so bad (based on it's limitations). So... that's what that counter is for and not for what I'm doing now. I'm currently looking for a nice/used HP counter. Please don't think I'm going to use the DFD4 for measuring my Rb standards. It's a wonderful counter for what it was designed for and that's it. I'm not giving up on the FEI's anytime soon. I understand now that along with the Trimble Thunderbolt (and a decent counter) I'll be on my way to getting started. 73 Brice KA8MAV - Original Message - From: Steve Rooke sar10...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 8:40 AM Subject: Re: [time-nuts] Symmetricom X72 Excuse my replying to my own posting please. This post is really about the DFD1 frequency counter. Heathkid: You are comparing a Rb against a frequency counter with a TCXO that you tweaked yourself to calibrate it against no known frequency standard. Try running the three FEI-5660s for 24 hours and then measure the output of each with your frequency counter. Pick the mean of them and adjust your DFD1 to match that. At least you should be in a better position than you are now. As you built the DFD1 yourself, you should have the schematic and may be able to engineer in a connection for an external reference. There is plenty of people here who would be happy to advise you on a suitable interface if you can attach the part of the circuit where the TCXO is located. If you do get a T'Both, you would be able to use it as a reference or, perhaps, build in one of the FEI-5660s as an internal reference. The limiting factor though is how good is the circuit used in the DFD1 which will limit it's stability and accuracy. There
Re: [time-nuts] Basic question regarding comparing two frequencies
The splitter makes two identical signals from Ref 1 The quadrature hybrid makes two signals out of Ref 2, but with a 90 degree phase shift between the signals. It's essentially a QPSK Demodulator, but set up to run in the linear region, rather than clipping. It's also sometimes called an I-Q detector. There is some closely related info here: http://www.minicircuits.com/pages/pdfs/mod11-2.pdf -John === My attempt to understand your diagram, not sure about how the quadrature hybrid is connected. Stanley - Original Message From: J. Forster j...@quik.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sun, July 25, 2010 10:29:23 AM Subject: Re: [time-nuts] Basic question regarding comparing two frequencies There is a cute way to use a scope. It requires a power splittere, a quadrature hybrid, and two mixers (all appropriate for the frequencies you are comparing), and an X-Y scope. Mini-Circuits sells appropriate parts. The stuff is hooked up like this: X Axis S | H P MIX Y REF 1--L B -- REF2 I MIX R T | I Y Axis D The 'scope display will be roughly a circle if the frequencies are a bit different and the spot will go around CW or CCW depending on which Ref is higher. -John snip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
I bought two HP 5345A's for short money on e-Pay. The second one is the organ donor !! I bought these primarily because it has a 1,000 second gate time. When using a GPSDO as the reference, I can resolve down to mHz (If I believe that !!). But, the resolution is a lot better than the HP's that have a 10 second Gate Time. 73, Dick, W1KSZ -Original Message- From: Heathkid heath...@heathkid.com Sent: Jul 25, 2010 12:55 PM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Symmetricom X72 Thanks Bob. I'm understanding a lot more now. The FE-5680A's that I have output both the 1pps as well as 10 MHz (and programmable to other frequencies). Yes, I also understand now how the Rb physics package and the DDS work together to come up with the output frequency. With the TBolt on the way now... and in the process of looking for a good/used real counter... I'll get there. :) Best regards, Brice - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 11:01 AM Subject: Re: [time-nuts] Symmetricom X72 Hi No, the LPRO is not obviously better than the FE's, depending on which version of the 5680 you have. The 5680 comes in two common varieties, one only has a 1 PPS output, the other will put out 10 MHz as well. Both can be digitally tuned to come up with oddball frequencies in the vicinity of their intended output. Bob On Jul 24, 2010, at 5:46 PM, Heathkid wrote: Bob, so you're saying the Efratom LPRO is better than the three FE-5680A's I already have? Sounds like I do need a TBolt anyway. - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 5:20 PM Subject: Re: [time-nuts] Symmetricom X72 Hi The only way to be sure of what's going on is to have several (hopefully) accurate references. With at least three you can begin to guess how good they are. The TBolt is different from the Rb in a couple of regards: 1) It's short term stability isn't as good when locked tightly to the GPS. 2) It's long term stability is much better than the Rb when it's locked. 3) It's easier to tell what's happening with it if you hook up a PC and the Lady Heather (free) program. The Rb will need a couple of things to make it play right: 1) It's got to have a pretty good heat sink on it. An 8 x 10 piece of 1/4 aluminum is a reasonable start 2) It's got to be run for a while (possibly 24 hours) before it will be stable 3) You need to watch the lock, and lamp voltages to be sure it's not doing something crazy. My recommendation based on cost is the Efratom LPRO for a cheap Rb. They are in the ~$60 range and seem to work pretty well. Setup wise, I would get a TBolt in addition to the Rb. You need something to calibrate the Rb (and your counter TCXO) against. Both are secondary standards. They (unlike a Cesium) are adjusted to match a known good reference. Once you have the Rb and the TBolt, next step is up to you. Cesium is always an alternative, so's a Hydrogen Maser Bob On Jul 24, 2010, at 3:32 PM, Heathkid wrote: Hello Bob, What would you recommend? I already have three FE-5680A Rb standards (which I'm quickly learning likely aren't worth the powder to blow them to (*insert your own word here*). Okay, that was probably my first mistake (thoughts?). My frequency counter is one I built from a kit from aade.com that has the TCXO option (although I had to tweak it myself so I have NO idea how close it is to any accuracy or precision). I have access to some really nice HP counters at work so that's my next step is to try one of those. My DFD4 measured the output of one of my 5680A's to 10.000.007 MHz after about a 10 minute warm-up. I don't know which one is off. Reading the specs on the 5680A's before I bought them looked like they were pretty decent. I'm learning... So, what reasonably priced Rb standard would you recommend? Should my next step in this process be a Trimble Thunderbolt? Am I starting over? Thanks... - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 9:31 AM Subject: Re: [time-nuts] Symmetricom X72 Hi At least looking at the spec sheet it's not really very impressive. Bob On Jul 23, 2010, at 11:06 PM, Heathkid wrote: Hello. Does anyone have any experience with the Symmetricom X72? Thanks... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list --
Re: [time-nuts] Basic question regarding comparing two frequencies
Corrected Drawing.attachment: Jfoster.jpg___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Hi, Yes Stanley, that's what I has in mind. My appologies for not noticing the drawing attached to your OP. Thanks, -John == Corrected Drawing.___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Test gear with embedded PCs Re: Basic
David C. Partridge wrote: Jim, It might appear on the 2nd user market sooner, but the odds are you won't be able to either repair it or calibrate it as the manufacturer will have been the only supplier of either of these services, and no service manuals will exist. But is this any different than existing test equipment? I agree that there will be some weird widget interface between the embedded PC and the hardware, and that might be challenging to reverse engineer and duplicate, but overall, I don't know that it's any different than doing it for 20 year old gear. Different processes, but fundamentally the same kind of problem. What would be a bigger problem is availability of device drivers and such, especially if the OS has some sort of inherent life limit built into it (e.g. a digital rights management feature like Windows Genuine Advantage.. can't connect to the server, and your scope stops working) For the intended original market, having to connect to a server every 6 months or year when it's in for cal isn't a big deal. However, in the recycled market, 10 years later, If it is still in support, the mfr will calibrate/fix it for you if your pockets are deep enough (probably as much or more than you pay for it). If (as is likely), it is out of support, then it will only be good for re-cycling or land-fill :-( Yes.. H does anyone but us old fogies see anything wrong with a business model where stuff can't be fixed and has a support lifetime of 5 years or so ? I don't know that it's can't be fixed any more than any other old test equipment. There's plenty of HP gear out there that has parts that cannot be obtained any more, and folks who are motivated find substitutes, etc. It's certainly uneconomic to fix, in the sense that for someone who's using the equipment in their business, there comes a point where it's cheaper to buy/lease new gear rather than fix the old stuff. And, an equipment mfr can make a legitimate decision to not design for infinite repair life in exchange for lower original sales price. Yes, this sort of shafts the hobby/tinkerer market, but it's the economic world we live in. And not only the hobby market gets the problem. At JPL we've got bunches of 8663 signal generators that are decades old, and for which there's no equivalent modern replacement that has all the features of the 8663. (that is, the new E8663 doesn't work anything like the old 8663 in terms of sweep behavior, phase modulation, or reference input handling) But, because those 8663s were real workhorses, and because we have enough hangar queens to scavenge parts from, we kept them going for long, long after their intended life span, and never invested in finding a suitable new replacement (or, more properly, finding a new replacement and working around its idiosyncracies, like we did with the 8663). Had we had a regular replace every N years strategy (where N is 5 or 7 or ??) we wouldn't be lulled into complacency. (note that a given space mission has a lifetime from buy equipment to end of mission on the order of 7-8 years.. for something like Cassini, it takes 7 years just to get to Saturn, after 3-4 years of development of the hardware) It's really a test setup design philosophy issue.. how much do you depend on idiosyncracies? Or can you design for a generic widget. Even if you're working in the consumption of surplus, if you can design for the generic widget, then you shouldn't care that there's a planned obsolescence thing going on. IN theory, all that obsolescence should result in more surplus gear on the market at lower prices. (assuming that the surplus market evolves...) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Test gear with embedded PCs Re: Basic
This kind of behaviour just sucks (pardon my French). I bought some antivirus SW and later discovered it stopped working after a year and they demanded a renewal fee. I refused and filed a Consumer Complaint against the company, because they failed to disclose the renewal cost nonsense on the box. A similar thing happened with an early schematic CAD program (Futurenet). They wanted something like $1000 per year for SW maintenance. I never wanted upgrades or new bells and whistles. I just wanted what I bought to work and keep working. Both of these are deceptive trade practices, IMO. Now, apparently, that concept has moved into hardware. IMO, it's just a ripoff. FWIW, -John = [snip] What would be a bigger problem is availability of device drivers and such, especially if the OS has some sort of inherent life limit built into it (e.g. a digital rights management feature like Windows Genuine Advantage.. can't connect to the server, and your scope stops working) [snip] ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom X72
Hi A couple others to put on the list: HP 5335 HP 5365 HP 5370(A and B) HP 5371 All of them come up from time to time at prices that are all over the map. The 70 and 71 are a pretty good deal if you can get them for less than $200. The 65 and 35 should be below $150. They all show up with nonsense prices ( $1,000) on a regular basis. I can think of no reason to pay over $300 for any of them. Bob On Jul 25, 2010, at 4:57 PM, Said Jackson wrote: Hi Brice, One of the best low cost counters is an hp 5334a. Get the one with internal memory (b model?) The 1.3ghz third input is also great. You can find them starting at $125. If you average for 99 seconds and do offset, it gives you 11 digits of resolution for low $$. 9 digits with 1s gate time. Most importantly: it does not have a fan. Some counters like 53132a have fans that run even if the counter is off that can drive you nuts.. Bye, Said Sent from my iPad On Jul 25, 2010, at 9:55, Heathkid heath...@heathkid.com wrote: Thanks Bob. I'm understanding a lot more now. The FE-5680A's that I have output both the 1pps as well as 10 MHz (and programmable to other frequencies). Yes, I also understand now how the Rb physics package and the DDS work together to come up with the output frequency. With the TBolt on the way now... and in the process of looking for a good/used real counter... I'll get there. :) Best regards, Brice - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 25, 2010 11:01 AM Subject: Re: [time-nuts] Symmetricom X72 Hi No, the LPRO is not obviously better than the FE's, depending on which version of the 5680 you have. The 5680 comes in two common varieties, one only has a 1 PPS output, the other will put out 10 MHz as well. Both can be digitally tuned to come up with oddball frequencies in the vicinity of their intended output. Bob On Jul 24, 2010, at 5:46 PM, Heathkid wrote: Bob, so you're saying the Efratom LPRO is better than the three FE-5680A's I already have? Sounds like I do need a TBolt anyway. - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 5:20 PM Subject: Re: [time-nuts] Symmetricom X72 Hi The only way to be sure of what's going on is to have several (hopefully) accurate references. With at least three you can begin to guess how good they are. The TBolt is different from the Rb in a couple of regards: 1) It's short term stability isn't as good when locked tightly to the GPS. 2) It's long term stability is much better than the Rb when it's locked. 3) It's easier to tell what's happening with it if you hook up a PC and the Lady Heather (free) program. The Rb will need a couple of things to make it play right: 1) It's got to have a pretty good heat sink on it. An 8 x 10 piece of 1/4 aluminum is a reasonable start 2) It's got to be run for a while (possibly 24 hours) before it will be stable 3) You need to watch the lock, and lamp voltages to be sure it's not doing something crazy. My recommendation based on cost is the Efratom LPRO for a cheap Rb. They are in the ~$60 range and seem to work pretty well. Setup wise, I would get a TBolt in addition to the Rb. You need something to calibrate the Rb (and your counter TCXO) against. Both are secondary standards. They (unlike a Cesium) are adjusted to match a known good reference. Once you have the Rb and the TBolt, next step is up to you. Cesium is always an alternative, so's a Hydrogen Maser Bob On Jul 24, 2010, at 3:32 PM, Heathkid wrote: Hello Bob, What would you recommend? I already have three FE-5680A Rb standards (which I'm quickly learning likely aren't worth the powder to blow them to (*insert your own word here*). Okay, that was probably my first mistake (thoughts?). My frequency counter is one I built from a kit from aade.com that has the TCXO option (although I had to tweak it myself so I have NO idea how close it is to any accuracy or precision). I have access to some really nice HP counters at work so that's my next step is to try one of those. My DFD4 measured the output of one of my 5680A's to 10.000.007 MHz after about a 10 minute warm-up. I don't know which one is off. Reading the specs on the 5680A's before I bought them looked like they were pretty decent. I'm learning... So, what reasonably priced Rb standard would you recommend? Should my next step in this process be a Trimble Thunderbolt? Am I starting over? Thanks... - Original Message - From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 24, 2010 9:31 AM Subject: Re: [time-nuts] Symmetricom X72 Hi
Re: [time-nuts] Basic question regarding comparing two frequencies
There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. There may be a small amount of missing data in the vicinity of the foldback, but if life threatening this could be avoided by running a second unit with the signals delayed to be near quadrature, and using the better data of the two. I use a lower frequency version of this system to monitor clocks (mechanical ones with pendulums). Cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
Hi Neville, There are plenty of ways to compare frequencies. I posted the BPSK demod scheme as a simple way to quickly tweek in the correct direction without Lissajous Figures. Best, -John There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. There may be a small amount of missing data in the vicinity of the foldback, but if life threatening this could be avoided by running a second unit with the signals delayed to be near quadrature, and using the better data of the two. I use a lower frequency version of this system to monitor clocks (mechanical ones with pendulums). Cheers, Neville Michie ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
On 26/07/2010, jimlux jim...@earthlink.net wrote: Some flavor of Linux is really the alternative, and the learning curve to get started with embedded applications is a bit steeper, especially if you want more than what can be done by a command line interface. Which GUI toolkit do you use? Where do you get it? etc. With Windows, that whole list of choices has been made for you. This is really an old excuse now as Linux has been around a long time and there are already a lot of embedded systems running it. As for a GUI toolkit, you have choices with Linux, ie. QT and GTK, to name but two, and Windows only gives you a single choice. As for development environments, the World is your oyster with Linux and it all comes without expensive licensing issues. Steve -- Steve Rooke - ZL3TUV G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Basic question regarding comparing two frequencies
There is another way to compare two frequencies, relevant when they are very close together. I divide a reference down to 100KHz and use it to clock a phase detector made of a pair of D flip flops. The unknown (divided to 100KHz) is fed into the circuit and an output that is proportional to the phase difference appears on the output as a changing mark-space ratio. I like it. Thanks. How did you pick 100 KHz? Using CMOS and a precise power supply (because under no load, CMOS output is precisely rail to rail), the averaged output (100ms RC filter) is fed to a strip chart recorder. Has anybody checked the edge cases and/or linearity of a setup like this? The recorder shows the changing phase difference and folds back each time a whole cycle passes. A 12 bit analog data logger resolves 2.5ns of phase and gives data for further analysis. Is 2.5 ns good enough? What would you gain by using a 16 bit DAC? If 2.5 ns is good enough, I'll bet you can do the whole thing in digital logic. Just get a fast FPGA/CPLD. I haven't done a serious design, but a quick check at some old data sheets shows it's not silly. You could probably bump it up by another factor of 2 with some external (p)ECL chips. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
