On a sunny day (Sun, 09 Jan 2022 12:58:49 +0100) it happened Jeroen Belleman
<jeroen@nospam.please> wrote in <sreilq$mnp$1@gioia.aioe.org>:
>On 2022-01-09 11:56, Jan Panteltje wrote:
>> On a sunny day (Sun, 09 Jan 2022 10:25:32 +0100) it happened Jeroen Belleman
>> <jeroen@nospam.please> wrote in <sre9mc$prb$1@gioia.aioe.org>:
>>
>>> On 2022-01-09 00:51, Clifford Heath wrote:
>>>> On 8/1/22 9:43 pm, Jeroen Belleman wrote:
>>>>> On 2022-01-08 10:53, Jan Panteltje wrote:
>>>>>> PS see https://github.com/jdesbonnet/RCWL-0516
>>>>>>
>>>>>>> Now I just received some about 3 GHz? (still have to measure
>>>>>>> it) doppler motion detectors that work through glass etc. from
>>>>>>> a local shop, also for about 2 Euro a piece, on ebay those are
>>>>>>> even cheaper: https://www.ebay.com/itm/311911747154 Is using
>>>>>>> that frequency even legal here? Plenty of stuff play with!
>>>>>>
>>>>>
>>>>>
>>>>> Interesting gadget. I suppose Q1 does double duty as oscillator and
>>>>> mixer. The schematics are of no help to figure out how it really
>>>>> works. Anyone care to comment? The secret is all in the PCB layout
>>>>> around Q1, clearly.
>>>>
>>>> I believe it's the same approach that used to be used by the 10GHz
>>>> automatic door detectors that used to trigger automotive radar
>>>> detectors. Oscillator and mixer in one device, pick out the audio
>>>> Doppler signal.
>>>>
>>>> CH
>>>
>>> I gathered that much, yes. I was more interested in a discussion
>>> of the PCB traces and how they work together to make an oscillator
>>> and antenna.
>>>
>>> I'm trying to guess the signs of the reactances between the
>>> terminals of Q1 at 3GHz. The trouble is that everything is
>>> coupled to everything else and I'm at a loss to tell what
>>> is dominant. Every damn bit of trace around Q1 looks like
>>> a resonator that could be either capacitive or inductive at
>>> 3GHz!
>>>
>>> At least I'm convinced that none of the actual /components/
>>> on the schematic are involved in determining this oscillator.
>>> (Except for Q1, of course.) It's all in the PCB traces.
>>>
>>> Jeroen Belleman
>>
>> Yes
>> it is all not so different from the twisted wire oscillator, but mine is simpler:
>> http://panteltje.com/pub/2.4GHz_twisted_oscillator_IMG_3629.GIF
>> circuit:
>> http://www.panteltje.com/pub/twisted_wire_oscillator_IMG_6629.JPG
>> probably can make my own GHz Doppler RF with that...
>>
>
>When analyzing an oscillator, I always start by identifying
>the reactances between BE, EC and CB. (Or whatever the equivalent
>nodes are on the actual gain element.)The first pair should
>have the opposite sign from the last, i.e., if the BE and EC
>reactances are capacitive, the CB reactance should be inductive
>and we have a Colpitts. In the reverse case, we have a Hartley.
>
>Any of the reactances could be a resonator of some sort, so
>what counts are the reactances at the intended oscillation
>frequency. I often see oscillators that use parasitic elements
>for one or more of these reactances. That seems to be the case
>in your example too. I usually try to avoid dependence on such
>elements when designing an oscillator.
>
>The next step is to get the magnitudes of those reactances and
>calculate the loop gain. Of course, they aren't pure reactances,
>but I usually neglect that at first. Nine times out of ten, that
>turns out well enough.
>
>Jeroen Belleman
Sure, I am but a neural net and just blob these things down without much maaz.
In the twisted wire oscillator case I started with a longer twisted pair
resulting in a much lower frequency and then cut pieces of until I had the 2.4 GHz.
Basically a wavelength related thing, twisted just to hold it together.
On the PCB of that other thing you also see a feedback path.
But I just think in [ parts of ] a wavelength.
S parameters last time I used those was in school for the exams...
One experiment is worth a thousand hours of theory, no spice in use here for this either.
In the 'twisted' LOL case maybe a low-pass from the collector will also show Doppler difference frequency
if that twisted pair picks up any reflections.
On their PCB it looks like they somehow couple it to some bigger circular area on the other side of the PCB
to get more radiation.
Reply by Jeroen Belleman●January 9, 20222022-01-09
On 2022-01-09 11:56, Jan Panteltje wrote:
> On a sunny day (Sun, 09 Jan 2022 10:25:32 +0100) it happened Jeroen Belleman
> <jeroen@nospam.please> wrote in <sre9mc$prb$1@gioia.aioe.org>:
>
>> On 2022-01-09 00:51, Clifford Heath wrote:
>>> On 8/1/22 9:43 pm, Jeroen Belleman wrote:
>>>> On 2022-01-08 10:53, Jan Panteltje wrote:
>>>>> PS see https://github.com/jdesbonnet/RCWL-0516
>>>>>
>>>>>> Now I just received some about 3 GHz? (still have to measure
>>>>>> it) doppler motion detectors that work through glass etc. from
>>>>>> a local shop, also for about 2 Euro a piece, on ebay those are
>>>>>> even cheaper: https://www.ebay.com/itm/311911747154 Is using
>>>>>> that frequency even legal here? Plenty of stuff play with!
>>>>>
>>>>
>>>>
>>>> Interesting gadget. I suppose Q1 does double duty as oscillator and
>>>> mixer. The schematics are of no help to figure out how it really
>>>> works. Anyone care to comment? The secret is all in the PCB layout
>>>> around Q1, clearly.
>>>
>>> I believe it's the same approach that used to be used by the 10GHz
>>> automatic door detectors that used to trigger automotive radar
>>> detectors. Oscillator and mixer in one device, pick out the audio
>>> Doppler signal.
>>>
>>> CH
>>
>> I gathered that much, yes. I was more interested in a discussion
>> of the PCB traces and how they work together to make an oscillator
>> and antenna.
>>
>> I'm trying to guess the signs of the reactances between the
>> terminals of Q1 at 3GHz. The trouble is that everything is
>> coupled to everything else and I'm at a loss to tell what
>> is dominant. Every damn bit of trace around Q1 looks like
>> a resonator that could be either capacitive or inductive at
>> 3GHz!
>>
>> At least I'm convinced that none of the actual /components/
>> on the schematic are involved in determining this oscillator.
>> (Except for Q1, of course.) It's all in the PCB traces.
>>
>> Jeroen Belleman
>
> Yes
> it is all not so different from the twisted wire oscillator, but mine is simpler:
> http://panteltje.com/pub/2.4GHz_twisted_oscillator_IMG_3629.GIF
> circuit:
> http://www.panteltje.com/pub/twisted_wire_oscillator_IMG_6629.JPG
> probably can make my own GHz Doppler RF with that...
>
When analyzing an oscillator, I always start by identifying
the reactances between BE, EC and CB. (Or whatever the equivalent
nodes are on the actual gain element.)The first pair should
have the opposite sign from the last, i.e., if the BE and EC
reactances are capacitive, the CB reactance should be inductive
and we have a Colpitts. In the reverse case, we have a Hartley.
Any of the reactances could be a resonator of some sort, so
what counts are the reactances at the intended oscillation
frequency. I often see oscillators that use parasitic elements
for one or more of these reactances. That seems to be the case
in your example too. I usually try to avoid dependence on such
elements when designing an oscillator.
The next step is to get the magnitudes of those reactances and
calculate the loop gain. Of course, they aren't pure reactances,
but I usually neglect that at first. Nine times out of ten, that
turns out well enough.
Jeroen Belleman
Reply by Jan Panteltje●January 9, 20222022-01-09
On a sunny day (Sun, 09 Jan 2022 10:25:32 +0100) it happened Jeroen Belleman
<jeroen@nospam.please> wrote in <sre9mc$prb$1@gioia.aioe.org>:
>On 2022-01-09 00:51, Clifford Heath wrote:
>> On 8/1/22 9:43 pm, Jeroen Belleman wrote:
>>> On 2022-01-08 10:53, Jan Panteltje wrote:
>>>> PS see https://github.com/jdesbonnet/RCWL-0516
>>>>
>>>>> Now I just received some about 3 GHz? (still have to measure
>>>>> it) doppler motion detectors that work through glass etc. from
>>>>> a local shop, also for about 2 Euro a piece, on ebay those are
>>>>> even cheaper: https://www.ebay.com/itm/311911747154 Is using
>>>>> that frequency even legal here? Plenty of stuff play with!
>>>>
>>>
>>>
>>> Interesting gadget. I suppose Q1 does double duty as oscillator and
>>> mixer. The schematics are of no help to figure out how it really
>>> works. Anyone care to comment? The secret is all in the PCB layout
>>> around Q1, clearly.
>>
>> I believe it's the same approach that used to be used by the 10GHz
>> automatic door detectors that used to trigger automotive radar
>> detectors. Oscillator and mixer in one device, pick out the audio
>> Doppler signal.
>>
>> CH
>
>I gathered that much, yes. I was more interested in a discussion
>of the PCB traces and how they work together to make an oscillator
>and antenna.
>
>I'm trying to guess the signs of the reactances between the
>terminals of Q1 at 3GHz. The trouble is that everything is
>coupled to everything else and I'm at a loss to tell what
>is dominant. Every damn bit of trace around Q1 looks like
>a resonator that could be either capacitive or inductive at
>3GHz!
>
>At least I'm convinced that none of the actual /components/
>on the schematic are involved in determining this oscillator.
>(Except for Q1, of course.) It's all in the PCB traces.
>
>Jeroen Belleman
On Mon, 3 Jan 2022 06:59:17 -0800 (PST), Rich S
<richsulinengineer@gmail.com> wrote:
>On Sunday, January 2, 2022 at 11:01:29 PM UTC, Phil Hobbs wrote:
>> Tom Del Rosso wrote:
>> > jla...@highlandsniptechnology.com wrote:
>> >>
>> >> I built my own fA parts tester before I got the Keithley, using an
>> >> LMC6001 cmos opamp. It has less wiring and no switches so tends to be
>> >> faster.
>> >>
>> >> https://www.dropbox.com/sh/aj85edzmmrx7ret/AAA6HYPHyVeBrCeKShvq82ega?dl=0
>> >
>> > The components are separated by some kind of stand-off that mustn't leak
>> > a femptoamp. What material is that?
>> >
>> >
>> Looks like a surplus Tektronix ceramic terminal strip.
>> Cheers
>>
>> Phil Hobbs
>>
>> --
>> Dr Philip C D Hobbs
>> Principal Consultant
>> ElectroOptical Innovations LLC / Hobbs ElectroOptics
>> Optics, Electro-optics, Photonics, Analog Electronics
>> Briarcliff Manor NY 10510
>>
>> http://electrooptical.net
>> http://hobbs-eo.com
>
>Ah, yes. Thanks Phil, for naming those.
>We have a drawer full of those
>back in the lab. Their purpose is obvious
>but I didn't know their origin.
>(We have a lot of old Tek repair parts
>tucked away, unless they were victims
>of another "5s+2 event".)
>
>John, thanks for sharing. Your
>"integrator" is pretty leaky (Rf=510 R) :-)
>Is that Cf a 'virtual capacitor'? It seems
>to be hidden in the wiring photo.
The opamp is a unity-gain follower. The 510r could be zero ohms, but I
thought I might add an offset pot some day, which I didn't.
>
>The output caps, Are they special film
>that you chose to minimize Dielectric Absorption*?
No, ordinary ceramics. We have a lot of RF in our place from Sutro
Tower, and I wanted to keep that out. Opamps like to rectify RF.
The measurements are DC, slow, so DA is not a concern.
It worked terribly until I figured out that the RatShack nylon binding
posts were super leaky, and added the lexan plate. That was messy.
I have a set of Pomona banana plugs with various resistors from 1K to
1T ohms. One of those plugs in as Z1 or Z2, and the DUT becomes the
other. Then measure the two voltage drops.
Another aluminum chassis is used as a shield, upside down, and can be
bolted down. That avoids errors from local e-fields, like people
walking and breathing in the room, or 60 Hz fields.
--
I yam what I yam - Popeye
Reply by Rich S●January 3, 20222022-01-03
> I haven't got a lot of use for a digital electrometer. Down in the
> picoamps and lower, seeing trends is much more important than high
> precision, not least because leakages are very unlikely to be stable to
> 3 sig figures.
>
Phil, this is an excellent point, that I want to
amplify. Even if accuracy is lacking, the
precision and stability of a piece of equipment
(no matter how old it is) is still valuable.
Thanks! = RS
Reply by Rich S●January 3, 20222022-01-03
On Sunday, January 2, 2022 at 11:01:29 PM UTC, Phil Hobbs wrote:
> Tom Del Rosso wrote:
> > jla...@highlandsniptechnology.com wrote:
> >>
> >> I built my own fA parts tester before I got the Keithley, using an
> >> LMC6001 cmos opamp. It has less wiring and no switches so tends to be
> >> faster.
> >>
> >> https://www.dropbox.com/sh/aj85edzmmrx7ret/AAA6HYPHyVeBrCeKShvq82ega?dl=0
> >
> > The components are separated by some kind of stand-off that mustn't leak
> > a femptoamp. What material is that?
> >
> >
> Looks like a surplus Tektronix ceramic terminal strip.
> Cheers
>
> Phil Hobbs
>
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC / Hobbs ElectroOptics
> Optics, Electro-optics, Photonics, Analog Electronics
> Briarcliff Manor NY 10510
>
> http://electrooptical.net
> http://hobbs-eo.com
Ah, yes. Thanks Phil, for naming those.
We have a drawer full of those
back in the lab. Their purpose is obvious
but I didn't know their origin.
(We have a lot of old Tek repair parts
tucked away, unless they were victims
of another "5s+2 event".)
John, thanks for sharing. Your
"integrator" is pretty leaky (Rf=510 R) :-)
Is that Cf a 'virtual capacitor'? It seems
to be hidden in the wiring photo.
The output caps, Are they special film
that you chose to minimize Dielectric Absorption*?
Or given that the node impedances are so low
(220 R) any plastic is OK?
(*Ref: https://www.sciencedirect.com/topics/engineering/dielectric-absorption)
= RS
Reply by ●January 2, 20222022-01-02
On Sun, 2 Jan 2022 18:01:21 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>Tom Del Rosso wrote:
>> jlarkin@highlandsniptechnology.com wrote:
>>>
>>> I built my own fA parts tester before I got the Keithley, using an
>>> LMC6001 cmos opamp. It has less wiring and no switches so tends to be
>>> faster.
>>>
>>> https://www.dropbox.com/sh/aj85edzmmrx7ret/AAA6HYPHyVeBrCeKShvq82ega?dl=0
>>
>> The components are separated by some kind of stand-off that mustn't leak
>> a femptoamp. What material is that?
>>
>>
>Looks like a surplus Tektronix ceramic terminal strip.
>
>Cheers
>
>Phil Hobbs
Yes. I got a box of unused ones at the Foothill Flea Market.
--
I yam what I yam - Popeye
Reply by Phil Hobbs●January 2, 20222022-01-02
Tom Del Rosso wrote:
> jlarkin@highlandsniptechnology.com wrote:
>>
>> I built my own fA parts tester before I got the Keithley, using an
>> LMC6001 cmos opamp. It has less wiring and no switches so tends to be
>> faster.
>>
>> https://www.dropbox.com/sh/aj85edzmmrx7ret/AAA6HYPHyVeBrCeKShvq82ega?dl=0
>
> The components are separated by some kind of stand-off that mustn't leak
> a femptoamp. What material is that?
>
>
Looks like a surplus Tektronix ceramic terminal strip.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by ●January 2, 20222022-01-02
On Sun, 2 Jan 2022 17:23:07 -0500, "Tom Del Rosso"
<fizzbintuesday@that-google-mail-domain.com> wrote:
>jlarkin@highlandsniptechnology.com wrote:
>>
>> I built my own fA parts tester before I got the Keithley, using an
>> LMC6001 cmos opamp. It has less wiring and no switches so tends to be
>> faster.
>>
>> https://www.dropbox.com/sh/aj85edzmmrx7ret/AAA6HYPHyVeBrCeKShvq82ega?dl=0
>
>The components are separated by some kind of stand-off that mustn't leak
>a femptoamp. What material is that?
The Rat Shack binding posts were super leaky so I hacked a hole in the
box and added a lexan sheet.
The terminal strip inside is a ceramic strip as used in old Tek
scopes, but the critical node is a mid-air junction.
--
I yam what I yam - Popeye
The components are separated by some kind of stand-off that mustn't leak
a femptoamp. What material is that?
--
Defund the Thought Police
Andiamo Brandon!