Hi Usually what happens is you have a broadband oscillation at 3.5 to 4 GHz (based on your 3 GHz upper limit). The “munge” mixes with this and that creating interference at RF. Bob > On Dec 7, 2016, at 1:28 PM, Van Horn, David <david.vanhorn@backcountryaccess.com> wrote: > > Well so far at least #3 is not true. > > It may be something happening below the noise floor or outside the bandwidth, but I was looking from 0-5MHz. > I have 3Ghz+ available, but I wouldn't expect these parts to be that fast. > > It's a mystery, but I love solving mysteries. > > -----Original Message----- > From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Bob Camp > Sent: Wednesday, December 7, 2016 9:43 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Totally unrelated, but.. > > Hi > > You probably have proven one of the most basic design truths: Parts will *always* oscillate just outside the bandwidth of your test gear” :). A few other possible issues: > > 1) Something else is oscillating and it is simply interacting with the regulator in an odd way. > 2) The oscillation / noise is at a very low level and it’s below your test gear’s noise floor > 3) Testing stops the oscillation > > Bob > >> On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@backcountryaccess.com> wrote: >> >> Lots of discussion on here about low noise regulation so someone may know what to look for. >> >> I have a receiver which is getting a lot of interference from somewhere. >> Antenna disconnected, interference still high. >> After much poking around, we found that replacing a voltage regulator with a slightly different part cures the problem. >> Running that section on external battery is also fine, so it appears the original regulator causes some problem. >> We tried various batteries over a range of voltages within the chip spec, and couldn't make it have a problem. >> >> I looked at the reg input and output with scope and spectrum analyzer, and I don't see anything that indicates excessive noise or oscillation. >> The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, I couldn't lay it out any better. >> Replacing the input and output caps didn't change anything. >> Replacing the input and output caps with parts that should be "better", like Johanson Tancerams or tantalums has no effect. >> >> Just for laughs, we tried a number of different regulator chips, all new from the reel. >> The parts with the quietest and with the most noisy specs caused problems. >> One part, with a noise spec more or less in the middle of the spread is the one that works. >> >> So what is it that a monolithic regulator (linear) can do which is not observable on a scope or SA, which would cause a receiver to think it's getting a signal or significant noise in band? >> Everything else in the system is shut down, I am sure the regulator chip is the culprit, but so far I don't see how it's causing the problem. >> I could just use the quiet chip and move on, but experience tells me that I'd just have problems again down the road. That's voodoo, not science. >> >> >> Ideas? >> >> >> >> -- >> David VanHorn >> Lead Hardware Engineer >> >> Backcountry Access, Inc. >> 2820 Wilderness Pl, Unit H >> Boulder, CO 80301 USA >> phone: 303-417-1345 x110 >> email: >> david.vanhorn@backcountryaccess.com<mailto:david.vanhorn@backcountryac >> cess.com> >> >> _______________________________________________ >> 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.

You can buy opamps off the shelf with an input referred noise less than a 50 ohm resistor to build up a preamp (of course you can build up something even lower with discretes, but then it's a time commitment over a basic opamp preamp) Even if your regulator is low noise if it's running with low phase margin you can get noise peaking. On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David < david.vanhorn@backcountryaccess.com> wrote: > > > I replaced the original caps, and I added caps, I substituted good > Jonhansen RF caps, and Tanceram caps. > > No help at all. > > > > The layout and routing is as good as I could do, and the only improvement > I could see possible would be to move one cap closer to the reg. > > The difference would be less than the tolerance of part placement on the > existing pads. > > > > Fortunately this isn't a critical piece of equipment, but I want it > working RIGHT before I put it back in service. > > It's a custom receiver for 457 kHz. > > > > > > -----Original Message----- > > From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Graham / > KE9H > > Sent: Wednesday, December 7, 2016 10:41 AM > > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] Totally unrelated, but.. > > > > Remember that the internal Voltage reference in the original three > terminal regulator designs is a Zener. > > (Zeners are also useful as RF white noise sources.) The regulator is > generally an amplifier with DC feedback. > > If you look at the application notes on the early regulators, they require > capacitors to ground on both the input and outputs. > > If these capacitors are missing, or too low in value, or not good > capacitors at RF frequencies, then the Zener noise is amplified by the > regulator amplifier and pushed out the output port. > > I would experiment by putting a good ceramic 0.1uF cap to ground, right at > the regulator output port. > > > > > > --- Graham > > > > == > > > > > > On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb8tq@n1k.org> wrote: > > > > > Hi > > > > > > You probably have proven one of the most basic design truths: Parts > > > will > > > *always* oscillate just > > > outside the bandwidth of your test gear” :). A few other possible issues: > > > > > > 1) Something else is oscillating and it is simply interacting with the > > > regulator in an odd way. > > > 2) The oscillation / noise is at a very low level and it’s below your > > > test gear’s noise floor > > > 3) Testing stops the oscillation > > > > > > Bob > > > > > > > On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@ > > > backcountryaccess.com> wrote: > > > > > > > > Lots of discussion on here about low noise regulation so someone may > > > know what to look for. > > > > > > > > I have a receiver which is getting a lot of interference from > somewhere. > > > > Antenna disconnected, interference still high. > > > > After much poking around, we found that replacing a voltage > > > > regulator > > > with a slightly different part cures the problem. > > > > Running that section on external battery is also fine, so it appears > > > > the > > > original regulator causes some problem. > > > > We tried various batteries over a range of voltages within the chip > > > spec, and couldn't make it have a problem. > > > > > > > > I looked at the reg input and output with scope and spectrum > > > > analyzer, > > > and I don't see anything that indicates excessive noise or oscillation. > > > > The PCB layout is as tight as you could ask for. Fat tracks, lots of > > > ground, I couldn't lay it out any better. > > > > Replacing the input and output caps didn't change anything. > > > > Replacing the input and output caps with parts that should be > > > > "better", > > > like Johanson Tancerams or tantalums has no effect. > > > > > > > > Just for laughs, we tried a number of different regulator chips, all > > > > new > > > from the reel. > > > > The parts with the quietest and with the most noisy specs caused > > > problems. > > > > One part, with a noise spec more or less in the middle of the spread > > > > is > > > the one that works. > > > > > > > > So what is it that a monolithic regulator (linear) can do which is > > > > not > > > observable on a scope or SA, which would cause a receiver to think > > > it's getting a signal or significant noise in band? > > > > Everything else in the system is shut down, I am sure the regulator > > > > chip > > > is the culprit, but so far I don't see how it's causing the problem. > > > > I could just use the quiet chip and move on, but experience tells me > > > that I'd just have problems again down the road. That's voodoo, not > > > science. > > > > > > > > > > > > Ideas? > > > > > > > > > > > > > > > > -- > > > > David VanHorn > > > > Lead Hardware Engineer > > > > > > > > Backcountry Access, Inc. > > > > 2820 Wilderness Pl, Unit H > > > > Boulder, CO 80301 USA > > > > phone: 303-417-1345 x110 > > > > email: david.vanhorn@backcountryaccess.com<mailto:david.vanhorn@ > > > backcountryaccess.com> > > > > > > > > _______________________________________________ > > > > 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. > >

Hi Just for reference, KTB in 1 Hz at 50 ohms is roughly 0.9 nV at room temperature. The previously mentioned 2 nV is equivalent to about 250 ohms. Bob > On Dec 7, 2016, at 6:58 PM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > > You can buy opamps off the shelf with an input referred noise less than a > 50 ohm resistor to build up a preamp (of course you can build up something > even lower with discretes, but then it's a time commitment over a basic > opamp preamp) > > Even if your regulator is low noise if it's running with low phase margin > you can get noise peaking. > > On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David < > david.vanhorn@backcountryaccess.com> wrote: > >> >> >> I replaced the original caps, and I added caps, I substituted good >> Jonhansen RF caps, and Tanceram caps. >> >> No help at all. >> >> >> >> The layout and routing is as good as I could do, and the only improvement >> I could see possible would be to move one cap closer to the reg. >> >> The difference would be less than the tolerance of part placement on the >> existing pads. >> >> >> >> Fortunately this isn't a critical piece of equipment, but I want it >> working RIGHT before I put it back in service. >> >> It's a custom receiver for 457 kHz. >> >> >> >> >> >> -----Original Message----- >> >> From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Graham / >> KE9H >> >> Sent: Wednesday, December 7, 2016 10:41 AM >> >> To: Discussion of precise time and frequency measurement >> >> Subject: Re: [time-nuts] Totally unrelated, but.. >> >> >> >> Remember that the internal Voltage reference in the original three >> terminal regulator designs is a Zener. >> >> (Zeners are also useful as RF white noise sources.) The regulator is >> generally an amplifier with DC feedback. >> >> If you look at the application notes on the early regulators, they require >> capacitors to ground on both the input and outputs. >> >> If these capacitors are missing, or too low in value, or not good >> capacitors at RF frequencies, then the Zener noise is amplified by the >> regulator amplifier and pushed out the output port. >> >> I would experiment by putting a good ceramic 0.1uF cap to ground, right at >> the regulator output port. >> >> >> >> >> >> --- Graham >> >> >> >> == >> >> >> >> >> >> On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb8tq@n1k.org> wrote: >> >> >> >>> Hi >> >>> >> >>> You probably have proven one of the most basic design truths: Parts >> >>> will >> >>> *always* oscillate just >> >>> outside the bandwidth of your test gear” :). A few other possible issues: >> >>> >> >>> 1) Something else is oscillating and it is simply interacting with the >> >>> regulator in an odd way. >> >>> 2) The oscillation / noise is at a very low level and it’s below your >> >>> test gear’s noise floor >> >>> 3) Testing stops the oscillation >> >>> >> >>> Bob >> >>> >> >>>> On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@ >> >>> backcountryaccess.com> wrote: >> >>>> >> >>>> Lots of discussion on here about low noise regulation so someone may >> >>> know what to look for. >> >>>> >> >>>> I have a receiver which is getting a lot of interference from >> somewhere. >> >>>> Antenna disconnected, interference still high. >> >>>> After much poking around, we found that replacing a voltage >> >>>> regulator >> >>> with a slightly different part cures the problem. >> >>>> Running that section on external battery is also fine, so it appears >> >>>> the >> >>> original regulator causes some problem. >> >>>> We tried various batteries over a range of voltages within the chip >> >>> spec, and couldn't make it have a problem. >> >>>> >> >>>> I looked at the reg input and output with scope and spectrum >> >>>> analyzer, >> >>> and I don't see anything that indicates excessive noise or oscillation. >> >>>> The PCB layout is as tight as you could ask for. Fat tracks, lots of >> >>> ground, I couldn't lay it out any better. >> >>>> Replacing the input and output caps didn't change anything. >> >>>> Replacing the input and output caps with parts that should be >> >>>> "better", >> >>> like Johanson Tancerams or tantalums has no effect. >> >>>> >> >>>> Just for laughs, we tried a number of different regulator chips, all >> >>>> new >> >>> from the reel. >> >>>> The parts with the quietest and with the most noisy specs caused >> >>> problems. >> >>>> One part, with a noise spec more or less in the middle of the spread >> >>>> is >> >>> the one that works. >> >>>> >> >>>> So what is it that a monolithic regulator (linear) can do which is >> >>>> not >> >>> observable on a scope or SA, which would cause a receiver to think >> >>> it's getting a signal or significant noise in band? >> >>>> Everything else in the system is shut down, I am sure the regulator >> >>>> chip >> >>> is the culprit, but so far I don't see how it's causing the problem. >> >>>> I could just use the quiet chip and move on, but experience tells me >> >>> that I'd just have problems again down the road. That's voodoo, not >> >>> science. >> >>>> >> >>>> >> >>>> Ideas? >> >>>> >> >>>> >> >>>> >> >>>> -- >> >>>> David VanHorn >> >>>> Lead Hardware Engineer >> >>>> >> >>>> Backcountry Access, Inc. >> >>>> 2820 Wilderness Pl, Unit H >> >>>> Boulder, CO 80301 USA >> >>>> phone: 303-417-1345 x110 >> >>>> email: david.vanhorn@backcountryaccess.com<mailto:david.vanhorn@ >> >>> backcountryaccess.com> >> >>>> >> >>>> _______________________________________________ >> >>>> 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.

Yes, the short hand I like to use is 4 nV*sqrt(R/1000). 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta vbe gained up ~10x. On Wed, Dec 7, 2016 at 7:03 PM Bob Camp <kb8tq@n1k.org> wrote: > Hi > > > > Just for reference, KTB in 1 Hz at 50 ohms is roughly 0.9 nV at room > > temperature. The previously mentioned 2 nV is equivalent to about 250 ohms. > > > > Bob > > > > > On Dec 7, 2016, at 6:58 PM, Scott Stobbe <scott.j.stobbe@gmail.com> > wrote: > > > > > > You can buy opamps off the shelf with an input referred noise less than a > > > 50 ohm resistor to build up a preamp (of course you can build up > something > > > even lower with discretes, but then it's a time commitment over a basic > > > opamp preamp) > > > > > > Even if your regulator is low noise if it's running with low phase margin > > > you can get noise peaking. > > > > > > On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David < > > > david.vanhorn@backcountryaccess.com> wrote: > > > > > >> > > >> > > >> I replaced the original caps, and I added caps, I substituted good > > >> Jonhansen RF caps, and Tanceram caps. > > >> > > >> No help at all. > > >> > > >> > > >> > > >> The layout and routing is as good as I could do, and the only > improvement > > >> I could see possible would be to move one cap closer to the reg. > > >> > > >> The difference would be less than the tolerance of part placement on the > > >> existing pads. > > >> > > >> > > >> > > >> Fortunately this isn't a critical piece of equipment, but I want it > > >> working RIGHT before I put it back in service. > > >> > > >> It's a custom receiver for 457 kHz. > > >> > > >> > > >> > > >> > > >> > > >> -----Original Message----- > > >> > > >> From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of > Graham / > > >> KE9H > > >> > > >> Sent: Wednesday, December 7, 2016 10:41 AM > > >> > > >> To: Discussion of precise time and frequency measurement > > >> > > >> Subject: Re: [time-nuts] Totally unrelated, but.. > > >> > > >> > > >> > > >> Remember that the internal Voltage reference in the original three > > >> terminal regulator designs is a Zener. > > >> > > >> (Zeners are also useful as RF white noise sources.) The regulator is > > >> generally an amplifier with DC feedback. > > >> > > >> If you look at the application notes on the early regulators, they > require > > >> capacitors to ground on both the input and outputs. > > >> > > >> If these capacitors are missing, or too low in value, or not good > > >> capacitors at RF frequencies, then the Zener noise is amplified by the > > >> regulator amplifier and pushed out the output port. > > >> > > >> I would experiment by putting a good ceramic 0.1uF cap to ground, right > at > > >> the regulator output port. > > >> > > >> > > >> > > >> > > >> > > >> --- Graham > > >> > > >> > > >> > > >> == > > >> > > >> > > >> > > >> > > >> > > >> On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb8tq@n1k.org> wrote: > > >> > > >> > > >> > > >>> Hi > > >> > > >>> > > >> > > >>> You probably have proven one of the most basic design truths: Parts > > >> > > >>> will > > >> > > >>> *always* oscillate just > > >> > > >>> outside the bandwidth of your test gear” :). A few other possible > issues: > > >> > > >>> > > >> > > >>> 1) Something else is oscillating and it is simply interacting with the > > >> > > >>> regulator in an odd way. > > >> > > >>> 2) The oscillation / noise is at a very low level and it’s below your > > >> > > >>> test gear’s noise floor > > >> > > >>> 3) Testing stops the oscillation > > >> > > >>> > > >> > > >>> Bob > > >> > > >>> > > >> > > >>>> On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@ > > >> > > >>> backcountryaccess.com> wrote: > > >> > > >>>> > > >> > > >>>> Lots of discussion on here about low noise regulation so someone may > > >> > > >>> know what to look for. > > >> > > >>>> > > >> > > >>>> I have a receiver which is getting a lot of interference from > > >> somewhere. > > >> > > >>>> Antenna disconnected, interference still high. > > >> > > >>>> After much poking around, we found that replacing a voltage > > >> > > >>>> regulator > > >> > > >>> with a slightly different part cures the problem. > > >> > > >>>> Running that section on external battery is also fine, so it appears > > >> > > >>>> the > > >> > > >>> original regulator causes some problem. > > >> > > >>>> We tried various batteries over a range of voltages within the chip > > >> > > >>> spec, and couldn't make it have a problem. > > >> > > >>>> > > >> > > >>>> I looked at the reg input and output with scope and spectrum > > >> > > >>>> analyzer, > > >> > > >>> and I don't see anything that indicates excessive noise or oscillation. > > >> > > >>>> The PCB layout is as tight as you could ask for. Fat tracks, lots of > > >> > > >>> ground, I couldn't lay it out any better. > > >> > > >>>> Replacing the input and output caps didn't change anything. > > >> > > >>>> Replacing the input and output caps with parts that should be > > >> > > >>>> "better", > > >> > > >>> like Johanson Tancerams or tantalums has no effect. > > >> > > >>>> > > >> > > >>>> Just for laughs, we tried a number of different regulator chips, all > > >> > > >>>> new > > >> > > >>> from the reel. > > >> > > >>>> The parts with the quietest and with the most noisy specs caused > > >> > > >>> problems. > > >> > > >>>> One part, with a noise spec more or less in the middle of the spread > > >> > > >>>> is > > >> > > >>> the one that works. > > >> > > >>>> > > >> > > >>>> So what is it that a monolithic regulator (linear) can do which is > > >> > > >>>> not > > >> > > >>> observable on a scope or SA, which would cause a receiver to think > > >> > > >>> it's getting a signal or significant noise in band? > > >> > > >>>> Everything else in the system is shut down, I am sure the regulator > > >> > > >>>> chip > > >> > > >>> is the culprit, but so far I don't see how it's causing the problem. > > >> > > >>>> I could just use the quiet chip and move on, but experience tells me > > >> > > >>> that I'd just have problems again down the road. That's voodoo, not > > >> > > >>> science. > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> Ideas? > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> > > >> > > >>>> -- > > >> > > >>>> David VanHorn > > >> > > >>>> Lead Hardware Engineer > > >> > > >>>> > > >> > > >>>> Backcountry Access, Inc. > > >> > > >>>> 2820 Wilderness Pl, Unit H > > >> > > >>>> Boulder, CO 80301 USA > > >> > > >>>> phone: 303-417-1345 x110 > > >> > > >>>> email: david.vanhorn@backcountryaccess.com<mailto:david.vanhorn@ > > >> > > >>> backcountryaccess.com> > > >> > > >>>> > > >> > > >>>> _______________________________________________ > > >> > > >>>> 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. > >

Am 08.12.2016 um 01:20 schrieb Scott Stobbe: > Yes, the short hand I like to use is 4 nV*sqrt(R/1000). > > 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta > vbe gained up ~10x. > Methinks the advantage comes from converting their reference (whatever that may be) to a really high impedance current source where a few uF help tremendously in cleaning things up. regards, Gerhard

On Thursday, 8 December 2016 2:59 PM, Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Yes, the very low frequency noise of these regulators isn't anywhere near as impressive as their high frequency noise.However for some RF circuits the low frequency power supply noise may not be as significant as other effects. Bruce   On Thursday, 8 December 2016 2:59 PM, Gerhard Hoffmann <dk4xp@arcor.de> wrote: Am 08.12.2016 um 01:20 schrieb Scott Stobbe: > Yes, the short hand I like to use is 4 nV*sqrt(R/1000). > > 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta > vbe gained up ~10x. > Methinks the advantage comes from converting their reference (whatever that may be) to a really high impedance current source where a few uF help tremendously in cleaning things up. regards, Gerhard _______________________________________________ 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.

On 12/7/16 4:20 PM, Scott Stobbe wrote: > Yes, the short hand I like to use is 4 nV*sqrt(R/1000). > > 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta > vbe gained up ~10x. > > On Wed, Dec 7, 2016 at 7:03 PM Bob Camp <kb8tq@n1k.org> wrote: > >> H the cool thing about those parts is that their PSRR extends up to several MHz. A lot of LDOs have good PSRR to kHz. Someone at LT did a good job on that design.

Hi > On Dec 7, 2016, at 11:36 PM, jimlux <jimlux@earthlink.net> wrote: > > On 12/7/16 4:20 PM, Scott Stobbe wrote: >> Yes, the short hand I like to use is 4 nV*sqrt(R/1000). >> >> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta >> vbe gained up ~10x. >> >> On Wed, Dec 7, 2016 at 7:03 PM Bob Camp <kb8tq@n1k.org> wrote: >> >>> H > > the cool thing about those parts is that their PSRR extends up to several MHz. A lot of LDOs have good PSRR to kHz. Which to bring it back to noise in radios ….. could be the issue there. The device isn’t oscillating, it’s just not blocking the crud from upstream. Bob > > Someone at LT did a good job on that design. > > _______________________________________________ > 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.

It would be helpful to give some specific info about the circuit and regulators used for these experiments, such as operating voltage, load current, and regulator type. I may have missed some points in the discussion on this, but I think the following things are the case: 1. The circuit exhibits excessive internal interference only when using certain regulator ICs, but works fine with others of the same type. 2. No apparent oscillation or excessive output noise can be found with scopes and SAs to explain it. 3. Various battery voltages have been tried in place of the regulator to run the circuit and seem OK. 4. The receiver carrier is 467 kHz (not MHz?). 5. The regulators in question are LM78XX, which use a band-gap reference. 6. Changing or adding various filtering caps seem to have no effect on a "bad" regulator. Without additional info, I would suspect that the bad parts have a low-level oscillation somewhere near (or harmonically near) the carrier, the LO, or the IF, that is too small to see above the PS noise floor, but big enough to cause problems. It is likely these frequencies are in the range of where a linear regulator could oscillate. I doubt that one could oscillate in the VHF or microwave region, out of reach of your SA's span and sensitivity (presumably, depending on what you have). If the regulator could oscillate up there, it could certainly leak through or around any typical near-band filtering and decoupling in the receiver, and cause problems. Looking in the time domain with a scope, there will be less sensitivity and dynamic range, so there could be something below the floor, and maybe below the SA's bottom frequency range too. The SA's low-end can be compromised by the need to safely AC-couple the PS voltage into the 50 ohm input. A reasonably-sized coupling cap may put it too far up to see a small but important signal in the kHz range. If it's a low frequency or in-band oscillation, you may want to look at the receiver circuits for internal susceptibility and PSRR - you may have discovered an unanticipated weakness, separate from the regulator issue. Another thing to consider is that there may be a specific supply voltage that causes the problem - like a marginal circuit in the receiver front or LO going unstable. The battery test, I presume, was at certain discrete voltages. It may be worth running it on a variable PS over a continuous range. It's possible that the bad regulators just happen to land at a "bad" voltage. With a fairly wide tolerance spec, they could be all over the place. One way to eliminate this is to measure as precisely as possible the output voltage of a bad regulator, then replicate it with a variable supply. If the receiver circuit works fine throughout its supply range, then the regulator is again the prime suspect. Also consider what the load current is versus its max rating - if it's anywhere close, it could be on the verge of current-limiting, and all sorts of strange things can happen. If this is the case, adding a helper resistor from input to output should get it back into the normal range. If you haven't already, before all kinds of experiments and analysis, try the good old heat and cool methods - blast a bad regulator with freeze spray or a heat gun and see what happens. And of course, do the same to a "good" one. And maybe also the LO. This is an interesting case, and I think we all would like some more info on the particulars. Ed

Ed wrote: > It would be helpful to give some specific info about the circuit and > regulators used for these experiments, such as operating voltage, > load current, and regulator type. I concur. It would also be helpful to have more detail about the phenomenon you are observing (see below). Also, consider the possibility that what you are hearing and concluding is RF interference may be noise generated elsewhere, for example in the audio section of the rx. If the audio section is quasi-stable, it could be sensitive to the absolute power supply voltage, or to the output impedance of the regulator. The same could happen in the AGC circuit, or the local oscillator. Can you see the noise on the signal strength monitor or on the AGC line? (If the rx doesn't have a SS monitor, you may need to add one for troubleshooting.) Over what range of frequencies is the interference/noise produced? Listen for it on a wideband receiver (which has much greater sensitivity above noise than a S/A). To do this, make a test antenna by stripping a couple of feet of shield off a length of coax and forming the insulated center conductor into a solenoid with several turns. Feed this into the 50 ohm receiver input, then "sniff around" the misbehaving circuit. Tune the wideband rx up and down to gauge the extent of the noise band. Is there anything about the rx that could cause unusual behavior (for example, is it a direct-conversion rx, or is there something unusual about the LO)? Best regards, Charles