Ed, Tuning the cavity should peak everything - it just maximizes the excitation power at the microwave frequency, so you get the most output from the Rb light wavelengths. A mechanical cavity resonator will have a very wide (compared to the modulation frequencies you're looking for) bandwidth, so unless something happened to it physically, it should be OK as originally built or adjusted. However, you may want to look at the multiplier chain and SRD bias circuit components and adjustments - those could have drifted quite a bit over forty years, limiting the microwave power due to being off-frequency, or having poor multiplication efficiency. I'm guessing that the second harmonic is indeed present, but just buried in the noise, and the loop still can "lock" because of the further signal processing, even though you don't see the evidence - remember it's a lock-in amplifier capable of digging a tiny signal out of the noise. If you go through the multiplier and check and tweak things, you may get more excitation power and signs that it's getting back to normal. Once you get enough power, if the Rb cells are still good, the second harmonic signal should show up large enough for the circuit to detect sufficient S/N ratio and provide a valid lock indication. Ed Breya Ed Palmer wrote: Could the drift be at least partially responsible for the lack of second harmonic? A message on the list ( <http://www.febo.com/pipermail/time-nuts/2006-April/020562.html>http://www.febo.com/pipermail/time-nuts/2006-April/020562.html ) said that you could peak the second harmonic by adjusting the cavity tuning. If the cell and the cavity are out of sync would that kill the second harmonic? How close to they have to be? If this thing has a cavity tuning adjustment I haven't found it.

Hi Ed, On 4/24/2012 4:13 PM, ed breya wrote: > Ed, > > Tuning the cavity should peak everything - it just maximizes the > excitation power at the microwave frequency, so you get the most > output from the Rb light wavelengths. A mechanical cavity resonator > will have a very wide (compared to the modulation frequencies you're > looking for) bandwidth, so unless something happened to it physically, > it should be OK as originally built or adjusted. However, you may want > to look at the multiplier chain and SRD bias circuit components and > adjustments - those could have drifted quite a bit over forty years, > limiting the microwave power due to being off-frequency, or having > poor multiplication efficiency. I was able to insert an attenuator into the SRD drive circuit and found that I could drop the level by 6db without affecting the maximum amplitude of the error signal so there seems to be lots of power. I will be checking the multiplier chain, but first I have to build an extender board. There was supposed to be one in the unit, but it evaporated. > I'm guessing that the second harmonic is indeed present, but just > buried in the noise, and the loop still can "lock" because of the > further signal processing, even though you don't see the evidence - > remember it's a lock-in amplifier capable of digging a tiny signal out > of the noise. If you go through the multiplier and check and tweak > things, you may get more excitation power and signs that it's getting > back to normal. Once you get enough power, if the Rb cells are still > good, the second harmonic signal should show up large enough for the > circuit to detect sufficient S/N ratio and provide a valid lock > indication. Nope. The reason it locks is that there's a switch that bypasses the 2nd harmonic and sweep circuitry and connects the error signal to the oscillator. Once I adjust the error signal to zero (i.e. resonance) and flip that switch, the 2nd harmonic is irrelevant. I just realized that I haven't mentioned that there's a partial manual for this thing online. It's missing a few schematics, but is otherwise complete. The URL is http://sundry.i2phd.com/ServiceManual_304b.pdf . Ed > Ed Breya > > > Ed Palmer wrote: > > Could the drift be at least partially responsible for the lack of second > harmonic? A message on the list ( > <http://www.febo.com/pipermail/time-nuts/2006-April/020562.html>http://www.febo.com/pipermail/time-nuts/2006-April/020562.html > ) said > that you could peak the second harmonic by adjusting the cavity tuning. > If the cell and the cavity are out of sync would that kill the second > harmonic? How close to they have to be? If this thing has a cavity > tuning adjustment I haven't found it.

When all else fails check the grounds. Especially 40 year old screws. On Tue, Apr 24, 2012 at 6:13 PM, ed breya <eb@telight.com> wrote: > Ed, > > Tuning the cavity should peak everything - it just maximizes the > excitation power at the microwave frequency, so you get the most output > from the Rb light wavelengths. A mechanical cavity resonator will have a > very wide (compared to the modulation frequencies you're looking for) > bandwidth, so unless something happened to it physically, it should be OK > as originally built or adjusted. However, you may want to look at the > multiplier chain and SRD bias circuit components and adjustments - those > could have drifted quite a bit over forty years, limiting the microwave > power due to being off-frequency, or having poor multiplication efficiency. > > I'm guessing that the second harmonic is indeed present, but just buried > in the noise, and the loop still can "lock" because of the further signal > processing, even though you don't see the evidence - remember it's a > lock-in amplifier capable of digging a tiny signal out of the noise. If you > go through the multiplier and check and tweak things, you may get more > excitation power and signs that it's getting back to normal. Once you get > enough power, if the Rb cells are still good, the second harmonic signal > should show up large enough for the circuit to detect sufficient S/N ratio > and provide a valid lock indication. > > Ed Breya > > > Ed Palmer wrote: > > Could the drift be at least partially responsible for the lack of second > harmonic? A message on the list ( > <http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html> > >http://www.**febo.com/pipermail/time-nuts/**2006-April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html>) said > that you could peak the second harmonic by adjusting the cavity tuning. > If the cell and the cavity are out of sync would that kill the second > harmonic? How close to they have to be? If this thing has a cavity > tuning adjustment I haven't found it. > > > > > > > > > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. >

Paul, On 4/24/2012 5:24 PM, paul swed wrote: > When all else fails check the grounds. Especially 40 year old screws. Been there, done that. This unit had multiple problems with bad soldered ground connections. I went through the unit and resoldered everything that looked the least bit odd. I didn't find any screws that were electrically significant. Maybe I should look again! Ed > On Tue, Apr 24, 2012 at 6:13 PM, ed breya<eb@telight.com> wrote: > >> Ed, >> >> Tuning the cavity should peak everything - it just maximizes the >> excitation power at the microwave frequency, so you get the most output >> from the Rb light wavelengths. A mechanical cavity resonator will have a >> very wide (compared to the modulation frequencies you're looking for) >> bandwidth, so unless something happened to it physically, it should be OK >> as originally built or adjusted. However, you may want to look at the >> multiplier chain and SRD bias circuit components and adjustments - those >> could have drifted quite a bit over forty years, limiting the microwave >> power due to being off-frequency, or having poor multiplication efficiency. >> >> I'm guessing that the second harmonic is indeed present, but just buried >> in the noise, and the loop still can "lock" because of the further signal >> processing, even though you don't see the evidence - remember it's a >> lock-in amplifier capable of digging a tiny signal out of the noise. If you >> go through the multiplier and check and tweak things, you may get more >> excitation power and signs that it's getting back to normal. Once you get >> enough power, if the Rb cells are still good, the second harmonic signal >> should show up large enough for the circuit to detect sufficient S/N ratio >> and provide a valid lock indication. >> >> Ed Breya >> >> >> Ed Palmer wrote: >> >> Could the drift be at least partially responsible for the lack of second >> harmonic? A message on the list ( >> <http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html> >>> http://www.**febo.com/pipermail/time-nuts/**2006-April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html>) said >> that you could peak the second harmonic by adjusting the cavity tuning. >> If the cell and the cavity are out of sync would that kill the second >> harmonic? How close to they have to be? If this thing has a cavity >> tuning adjustment I haven't found it. >> >> >> >> >> >> >> >> >> ______________________________**_________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/** >> mailman/listinfo/time-nuts<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. >

Ed look for pop rivetted ground logs. Famous for going bad. HP even used them. Drill em out and put real bolts and lock washers in On Tue, Apr 24, 2012 at 7:34 PM, Ed Palmer <ed_palmer@sasktel.net> wrote: > Paul, > > > On 4/24/2012 5:24 PM, paul swed wrote: > >> When all else fails check the grounds. Especially 40 year old screws. >> > > Been there, done that. This unit had multiple problems with bad soldered > ground connections. I went through the unit and resoldered everything that > looked the least bit odd. I didn't find any screws that were electrically > significant. Maybe I should look again! > > Ed > > On Tue, Apr 24, 2012 at 6:13 PM, ed breya<eb@telight.com> wrote: >> >> Ed, >>> >>> Tuning the cavity should peak everything - it just maximizes the >>> excitation power at the microwave frequency, so you get the most output >>> from the Rb light wavelengths. A mechanical cavity resonator will have a >>> very wide (compared to the modulation frequencies you're looking for) >>> bandwidth, so unless something happened to it physically, it should be OK >>> as originally built or adjusted. However, you may want to look at the >>> multiplier chain and SRD bias circuit components and adjustments - those >>> could have drifted quite a bit over forty years, limiting the microwave >>> power due to being off-frequency, or having poor multiplication >>> efficiency. >>> >>> I'm guessing that the second harmonic is indeed present, but just buried >>> in the noise, and the loop still can "lock" because of the further signal >>> processing, even though you don't see the evidence - remember it's a >>> lock-in amplifier capable of digging a tiny signal out of the noise. If >>> you >>> go through the multiplier and check and tweak things, you may get more >>> excitation power and signs that it's getting back to normal. Once you get >>> enough power, if the Rb cells are still good, the second harmonic signal >>> should show up large enough for the circuit to detect sufficient S/N >>> ratio >>> and provide a valid lock indication. >>> >>> Ed Breya >>> >>> >>> Ed Palmer wrote: >>> >>> Could the drift be at least partially responsible for the lack of second >>> harmonic? A message on the list ( >>> <http://www.febo.com/****pipermail/time-nuts/2006-****April/020562.html<http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html> >>> <http://www.**febo.com/pipermail/time-nuts/**2006-April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html> >>> > >>> >>>> http://www.**febo.com/**pipermail/time-nuts/**2006-**April/020562.html<http://febo.com/pipermail/time-nuts/**2006-April/020562.html> >>>> <http://www.**febo.com/pipermail/time-nuts/**2006-April/020562.html<http://www.febo.com/pipermail/time-nuts/2006-April/020562.html>>) >>>> said >>>> >>> that you could peak the second harmonic by adjusting the cavity tuning. >>> If the cell and the cavity are out of sync would that kill the second >>> harmonic? How close to they have to be? If this thing has a cavity >>> tuning adjustment I haven't found it. >>> >>> >>> >>> >>> >>> >>> >>> >>> ______________________________****_________________ >>> >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/****<https://www.febo.com/cgi-bin/**> >>> mailman/listinfo/time-nuts<htt**ps://www.febo.com/cgi-bin/** >>> mailman/listinfo/time-nuts<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<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<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. >

Paul, Good suggestion, but I don't think pop rivets had been invented when they built this thing! :-D It's built like a piece of mil-spec equipment. When I google for individual parts, I keep tripping over NSN numbers. Now that I look closely at it, I realize that the case is just the case with no electrical connection between it and the circuit other than the BNC jacks on the front panel. The concept of 'chassis ground' is an unknown concept. I don't think there's even one chassis ground lug anywhere. Even when I'm poking around inside the unit, there are no live wires that I can touch, everything is insulated. The build quality is very high. But now that you've got me thinking about it, I think there's something weird about the grounding in the physics package. I've got to take another look at that. Thanks! Ed On 4/25/2012 8:59 PM, paul swed wrote: > Ed look for pop rivetted ground logs. Famous for going bad. HP even used > them. > Drill em out and put real bolts and lock washers in > > On Tue, Apr 24, 2012 at 7:34 PM, Ed Palmer<ed_palmer@sasktel.net> wrote: > >> Paul, >> >> >> On 4/24/2012 5:24 PM, paul swed wrote: >> >>> When all else fails check the grounds. Especially 40 year old screws. >>> >> Been there, done that. This unit had multiple problems with bad soldered >> ground connections. I went through the unit and resoldered everything that >> looked the least bit odd. I didn't find any screws that were electrically >> significant. Maybe I should look again! >> >> Ed >> >> On Tue, Apr 24, 2012 at 6:13 PM, ed breya<eb@telight.com> wrote: >>> Ed, >>>> Tuning the cavity should peak everything - it just maximizes the >>>> excitation power at the microwave frequency, so you get the most output >>>> from the Rb light wavelengths. A mechanical cavity resonator will have a >>>> very wide (compared to the modulation frequencies you're looking for) >>>> bandwidth, so unless something happened to it physically, it should be OK >>>> as originally built or adjusted. However, you may want to look at the >>>> multiplier chain and SRD bias circuit components and adjustments - those >>>> could have drifted quite a bit over forty years, limiting the microwave >>>> power due to being off-frequency, or having poor multiplication >>>> efficiency. >>>> >>>> I'm guessing that the second harmonic is indeed present, but just buried >>>> in the noise, and the loop still can "lock" because of the further signal >>>> processing, even though you don't see the evidence - remember it's a >>>> lock-in amplifier capable of digging a tiny signal out of the noise. If >>>> you >>>> go through the multiplier and check and tweak things, you may get more >>>> excitation power and signs that it's getting back to normal. Once you get >>>> enough power, if the Rb cells are still good, the second harmonic signal >>>> should show up large enough for the circuit to detect sufficient S/N >>>> ratio >>>> and provide a valid lock indication. >>>> >>>> Ed Breya >>>> >>>> >>>> Ed Palmer wrote: >>>> >>>> Could the drift be at least partially responsible for the lack of second >>>> harmonic? A message on the list ( >>>> <http://www.febo.com/****pipermail/time-nuts/2006-****April/020562.html<http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html>) >>>> said that you could peak the second harmonic by adjusting the cavity tuning. >>>> If the cell and the cavity are out of sync would that kill the second >>>> harmonic? How close to they have to be? If this thing has a cavity >>>> tuning adjustment I haven't found it.

Some pix of the rg would be great On Wed, Apr 25, 2012 at 11:43 PM, Ed Palmer <ed_palmer@sasktel.net> wrote: > Paul, > > Good suggestion, but I don't think pop rivets had been invented when they > built this thing! :-D It's built like a piece of mil-spec equipment. > When I google for individual parts, I keep tripping over NSN numbers. Now > that I look closely at it, I realize that the case is just the case with no > electrical connection between it and the circuit other than the BNC jacks > on the front panel. The concept of 'chassis ground' is an unknown concept. > I don't think there's even one chassis ground lug anywhere. Even when I'm > poking around inside the unit, there are no live wires that I can touch, > everything is insulated. The build quality is very high. > > But now that you've got me thinking about it, I think there's something > weird about the grounding in the physics package. I've got to take another > look at that. > > Thanks! > > Ed > > > On 4/25/2012 8:59 PM, paul swed wrote: > >> Ed look for pop rivetted ground logs. Famous for going bad. HP even used >> them. >> Drill em out and put real bolts and lock washers in >> >> On Tue, Apr 24, 2012 at 7:34 PM, Ed Palmer<ed_palmer@sasktel.net> wrote: >> >> Paul, >>> >>> >>> On 4/24/2012 5:24 PM, paul swed wrote: >>> >>> When all else fails check the grounds. Especially 40 year old screws. >>>> >>>> Been there, done that. This unit had multiple problems with bad >>> soldered >>> ground connections. I went through the unit and resoldered everything >>> that >>> looked the least bit odd. I didn't find any screws that were >>> electrically >>> significant. Maybe I should look again! >>> >>> Ed >>> >>> On Tue, Apr 24, 2012 at 6:13 PM, ed breya<eb@telight.com> wrote: >>> >>>> Ed, >>>> >>>>> Tuning the cavity should peak everything - it just maximizes the >>>>> excitation power at the microwave frequency, so you get the most output >>>>> from the Rb light wavelengths. A mechanical cavity resonator will have >>>>> a >>>>> very wide (compared to the modulation frequencies you're looking for) >>>>> bandwidth, so unless something happened to it physically, it should be >>>>> OK >>>>> as originally built or adjusted. However, you may want to look at the >>>>> multiplier chain and SRD bias circuit components and adjustments - >>>>> those >>>>> could have drifted quite a bit over forty years, limiting the microwave >>>>> power due to being off-frequency, or having poor multiplication >>>>> efficiency. >>>>> >>>>> I'm guessing that the second harmonic is indeed present, but just >>>>> buried >>>>> in the noise, and the loop still can "lock" because of the further >>>>> signal >>>>> processing, even though you don't see the evidence - remember it's a >>>>> lock-in amplifier capable of digging a tiny signal out of the noise. If >>>>> you >>>>> go through the multiplier and check and tweak things, you may get more >>>>> excitation power and signs that it's getting back to normal. Once you >>>>> get >>>>> enough power, if the Rb cells are still good, the second harmonic >>>>> signal >>>>> should show up large enough for the circuit to detect sufficient S/N >>>>> ratio >>>>> and provide a valid lock indication. >>>>> >>>>> Ed Breya >>>>> >>>>> >>>>> Ed Palmer wrote: >>>>> >>>>> Could the drift be at least partially responsible for the lack of >>>>> second >>>>> harmonic? A message on the list ( >>>>> <http://www.febo.com/******pipermail/time-nuts/2006-****** >>>>> April/020562.html<http://www.febo.com/****pipermail/time-nuts/2006-****April/020562.html> >>>>> <http://www.**febo.com/**pipermail/time-** >>>>> nuts/2006-**April/020562.html<http://www.febo.com/**pipermail/time-nuts/2006-**April/020562.html> >>>>> >**) >>>>> said that you could peak the second harmonic by adjusting the cavity >>>>> tuning. >>>>> If the cell and the cavity are out of sync would that kill the second >>>>> harmonic? How close to they have to be? If this thing has a cavity >>>>> tuning adjustment I haven't found it. >>>>> >>>> > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. >

I wondered if anyone would ask for pictures. They'll be ready soon. Ed On 4/26/2012 6:21 AM, paul swed wrote: > Some pix of the rg would be great > > On Wed, Apr 25, 2012 at 11:43 PM, Ed Palmer<ed_palmer@sasktel.net> wrote: > >> Paul, >> >> Good suggestion, but I don't think pop rivets had been invented when they >> built this thing! :-D It's built like a piece of mil-spec equipment. >> When I google for individual parts, I keep tripping over NSN numbers. Now >> that I look closely at it, I realize that the case is just the case with no >> electrical connection between it and the circuit other than the BNC jacks >> on the front panel. The concept of 'chassis ground' is an unknown concept. >> I don't think there's even one chassis ground lug anywhere. Even when I'm >> poking around inside the unit, there are no live wires that I can touch, >> everything is insulated. The build quality is very high. >> >> But now that you've got me thinking about it, I think there's something >> weird about the grounding in the physics package. I've got to take another >> look at that. >> >> Thanks! >> >> Ed

Nothing like looking at the ole antiques On Thu, Apr 26, 2012 at 6:49 PM, Ed Palmer <ed_palmer@sasktel.net> wrote: > I wondered if anyone would ask for pictures. They'll be ready soon. > > Ed > > > > On 4/26/2012 6:21 AM, paul swed wrote: > >> Some pix of the rg would be great >> >> On Wed, Apr 25, 2012 at 11:43 PM, Ed Palmer<ed_palmer@sasktel.net> >> wrote: >> >> Paul, >>> >>> Good suggestion, but I don't think pop rivets had been invented when they >>> built this thing! :-D It's built like a piece of mil-spec equipment. >>> When I google for individual parts, I keep tripping over NSN numbers. >>> Now >>> that I look closely at it, I realize that the case is just the case with >>> no >>> electrical connection between it and the circuit other than the BNC jacks >>> on the front panel. The concept of 'chassis ground' is an unknown >>> concept. >>> I don't think there's even one chassis ground lug anywhere. Even when >>> I'm >>> poking around inside the unit, there are no live wires that I can touch, >>> everything is insulated. The build quality is very high. >>> >>> But now that you've got me thinking about it, I think there's something >>> weird about the grounding in the physics package. I've got to take >>> another >>> look at that. >>> >>> Thanks! >>> >>> Ed >>> >> > ______________________________**_________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/** > mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > and follow the instructions there. >