[time-nuts] Re: Best frequency to start for GHz synth ?

[Lux, Jim]

On 4/1/21 4:49 PM, Bob kb8tq wrote:

Hi

At least back when I did it for a living …. the SAW you used
for an oscillator was a bit different than the one you used for
an oscillator. The “normal” problem was coming up with
enough tune range cover the (massive) TC plus the aging.

Bob




Yeah, for filters, SAW devices are awesome. You've got a lot of control 
over the passband and stopband shape.  And they are cheap to make (at 
least for ordinary aluminum transducers on the substrate, with no ion 
milling).


for resonators - the big TC is an issue. And I don't know how high the Q 
can be. I worked for a place that used SAW resonators (on quartz) as 
sensors for all kinds of things (a multitude of SBIRs) - pressure, 
chemical presence, etc.  you name it. Bend the quartz or change the mass 
loading, and the frequency changes, in a fairly repeatable way.  They 
make a nice detector for the output of a Gas Chromatograph for instance 
- they're basically sensing mass, so they don't have poisoning problems 
like some others.






On Apr 1, 2021, at 7:40 PM, Gerhard Hoffmann  
wrote:

OOps, the 400 MHz filter is

< 
https://www.digikey.de/product-detail/de/qualcomm-rf360-a-qualcomm-tdk-joint-venture/B39401B3742H110/495-3923-1-ND/1858979
 >

Gerhard
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Bob kb8tq]

Hi

At least back when I did it for a living …. the SAW you used
for an oscillator was a bit different than the one you used for
an oscillator. The “normal” problem was coming up with 
enough tune range cover the (massive) TC plus the aging.

Bob

> On Apr 1, 2021, at 7:40 PM, Gerhard Hoffmann  
> wrote:
> 
> OOps, the 400 MHz filter is
> 
> < 
> https://www.digikey.de/product-detail/de/qualcomm-rf360-a-qualcomm-tdk-joint-venture/B39401B3742H110/495-3923-1-ND/1858979
>  >
> 
> Gerhard
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Gerhard Hoffmann]

OOps, the 400 MHz filter is

< 
https://www.digikey.de/product-detail/de/qualcomm-rf360-a-qualcomm-tdk-joint-venture/B39401B3742H110/495-3923-1-ND/1858979 
>


Gerhard
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Bruce Griffiths]

Poseidon Scientific Instruments (acquired by Raytheon) make a room temperature 
10.24GHz Sapphire loaded cavity oscillator with a low PN floor:
https://www.rdi.uwa.edu.au/__data/assets/pdf_file/0012/3447669/Raytheon-TechnologyToday-20141-Extract.pdf

Bruce 
> On 02 April 2021 at 05:06 Chris Caudle <6807.ch...@pop.powweb.com> wrote:
> 
> 
> On 2021-03-31 14:27, Richard (Rick) Karlquist wrote:
> > When I left Keysight in 2014, they were still trying to solve the
> > microphonic problem in their sapphire resonator oscillator.  Also,
> > it is still necessary to lock the oscillator to a 5 or 10 MHz
> > OCXO.  The oscillator is tuned by varying its oven temperature
> > set ppoint.
> 
> What kind of oven temperature range?  I thought sapphire oscillator was 
> pretty much synonymous with "cryogenic sapphire oscillator."  I found a 
> paper which described sapphire as a "low loss material with loss tangent 
> of 5×10^−6 at room temperature, 2×10^−8 at 77 K and 7×10^−10 at 4 K 
> giving Q-values of more than >10^7 at low temperatures."
> 
> That paper seemed to be describing some kind of temperature compensation 
> they  had developed to reduce the temperature sensitivity of 10ppm/K and 
> also move the turnover point from 77K to 92K.  92K isn't exactly what I 
> think of when I hear "oven" so presumably there is some mode that works 
> at around 300K that I didn't find discussed yet.
> 
> -- 
> Chris Caudle
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Bob kb8tq]

Hi

> On Apr 1, 2021, at 2:16 PM, Richard (Rick) Karlquist  
> wrote:
> 
> 
> 
> On 4/1/2021 10:32 AM, Lux, Jim wrote:
> 
>> And for what it's worth DROs have their microphonic problems too. We had a 
>> breadboard deep space transponder and you could demodulate your voice 
>> (poorly) using the spectrum analyzer's FM demod feature. Very cool. 
>> Unimpressive to the folks who wanted to push the technology.  We were 
> 
> Back around 1970, as LM radio switched from AM to FM,

https://ieeexplore.ieee.org/document/4066864 


The switch was pretty much a done deal by the mid 1950’s. At least
that was the way Motorola told the story to us ….. 

Bob

> the HP 608
> signal generator was losing market share because it couldn't
> do FM.  Believe it or not, there was actually an Ap Note describing
> how to obtain FM by bolting a 4" loud speaker to the 608 cabinet
> and driving it with an audio signal generator.  Those were the days ...
> 
> Rick N6RK
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Wes]

A bit more contemporaneous... it's too long a story to relate here, but I 
discovered that the internal speaker, as well as my voice, tapping on the case, 
etc would FM the VCO in the synthesizer in my Elecraft K3 transceiver.  This was 
a birth defect that affected every one of them. They used my radio (never 
figured out why they didn't use one of their own) to come up with a fix that 
entailed bonding a 1/8" thick aluminum stiffener to the circuit card.  This 
found it's way into production and a retrofit kit was offered for others.


Wes  N7WS


On 4/1/2021 11:16 AM, Richard (Rick) Karlquist wrote:



On 4/1/2021 10:32 AM, Lux, Jim wrote:

And for what it's worth DROs have their microphonic problems too. We had a 
breadboard deep space transponder and you could demodulate your voice 
(poorly) using the spectrum analyzer's FM demod feature. Very cool. 
Unimpressive to the folks who wanted to push the technology.  We were


Back around 1970, as LM radio switched from AM to FM, the HP 608
signal generator was losing market share because it couldn't
do FM.  Believe it or not, there was actually an Ap Note describing
how to obtain FM by bolting a 4" loud speaker to the 608 cabinet
and driving it with an audio signal generator.  Those were the days ...

Rick N6RK 

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[time-nuts] Re: Best frequency to start for GHz synth ?

[Lux, Jim]

On 4/1/21 11:16 AM, Richard (Rick) Karlquist wrote:



On 4/1/2021 10:32 AM, Lux, Jim wrote:

And for what it's worth DROs have their microphonic problems too. We 
had a breadboard deep space transponder and you could demodulate your 
voice (poorly) using the spectrum analyzer's FM demod feature. Very 
cool. Unimpressive to the folks who wanted to push the technology.  
We were


Back around 1970, as LM radio switched from AM to FM, the HP 608
signal generator was losing market share because it couldn't
do FM.  Believe it or not, there was actually an Ap Note describing
how to obtain FM by bolting a 4" loud speaker to the 608 cabinet
and driving it with an audio signal generator.  Those were the days ...

Rick N6RK



and people wonder why they have a speaker in the spectrum analyzer - 
it's just for this sort of debugging.



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[time-nuts] Re: Best frequency to start for GHz synth ?

[Richard (Rick) Karlquist]

On 4/1/2021 10:32 AM, Lux, Jim wrote:

And for what it's worth DROs have their microphonic problems too. We had 
a breadboard deep space transponder and you could demodulate your voice 
(poorly) using the spectrum analyzer's FM demod feature. Very cool. 
Unimpressive to the folks who wanted to push the technology.  We were 



Back around 1970, as LM radio switched from AM to FM, the HP 608
signal generator was losing market share because it couldn't
do FM.  Believe it or not, there was actually an Ap Note describing
how to obtain FM by bolting a 4" loud speaker to the 608 cabinet
and driving it with an audio signal generator.  Those were the days ...

Rick N6RK
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Poul-Henning Kamp]

Lux, Jim writes:

>SAW devices were all the rage in the 80s for signal processing. 

Also certain CPUs:  Some of the DEC Alpha's had a SAW oscillator
next to the CPU chip to get a sufficiently pure clock-signal.

They had a tempco from hell and were nearly impossible to wrangle with NTP.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Re: Best frequency to start for GHz synth ?

[Lux, Jim]

On 4/1/21 9:41 AM, Richard (Rick) Karlquist wrote:

1. Whatever the advantage of cryogenic operation, Keysight
could not consider that due to marketing reasons.  They
were happy to leave the lunatic fringe to our friends in
Western Australia.

2.  They were already limited by microphonics even at
room temperature, so cryo would be wasted.

3.  My understanding of the oven was that it was simply
a substitute for a Q reducing varactor diode tuning mechanism.
There was never an expectation that temperature compensation would
allow standalone operation of the sapphire.  Again, for marketing
reasons, it was always going to be locked to an OCXO at exactly
10 MHz.  That OCXO's EFC could be used to lock the OCXO to an
external reference with a very slow loop that would prevent
phase noise contamination.

Also of interest to time nuts:

Back when Keysight was part of Agilent, and before the sapphire
resonator, they had architectures using DRO's at about 8 GHz.
So any Sapphire replacement had to be in some sense a drop in
replacement.  Before that, there was a boondoggle project using
a 1 GHZ DRO with a resonator about the size of a hockey puck.
It kind of reminds me of the giant 1 MHz quartz resonators.
There was also a 1 GHZ Surface Transverse Wave Resonator
(STW) oscillator for a while, until the fab shut down.
It evolved from the 640 MHz SAW resonator used in early 5071's.
Again, the fab shut down and I designed it out.


SAW devices were all the rage in the 80s for signal processing. 
Dispersive delay lines (SACs and RACs) were a standard thing in pulse 
compression systems and in "real time spectrum analyzers" - Enormous 
temperature coefficients, so there were all sorts of schemes to have 
multiple devices that would cancel changes out. When ADCs and DACs got 
high enough performance, doing signal processing in the analog domain 
became passe.


Same with electro-optical systems (like real time spectrum analyzers 
using a Bragg cell and a laser) - When DSP got to ~40 dB SNR, all of a 
sudden, optical processing wasn't as interesting.







They also wasted (IMHO) a lot of resources on a "opto-electronic"
(I think that was the term) oscillator around 15 or 20 years ago.
It depended on some spool of fiber optic cable.  I never thought
that was going to work, both because of basic principles and
because of the cable spool microphonics.


Oohh, I worked on systems using this kind of thing for delay lines and 
coherent analog processing. You can build an oven, sure, but...



And for what it's worth DROs have their microphonic problems too. We had 
a breadboard deep space transponder and you could demodulate your voice 
(poorly) using the spectrum analyzer's FM demod feature. Very cool. 
Unimpressive to the folks who wanted to push the technology.  We were 
trying to build a DRO oscillator that would tune 100 MHz BW (8400-8500 
MHz) while also being able to be locked to a very narrow band source.  
We just couldn't get there because of fundamental physics - couple the 
varactor tightly enough to get tuning range, and Q goes down.
Never did think of changing the temperature to move the "rest 
frequency".. Interesting idea.







Rick N6RK

On 4/1/2021 9:06 AM, Chris Caudle wrote:

On 2021-03-31 14:27, Richard (Rick) Karlquist wrote:

When I left Keysight in 2014, they were still trying to solve the
microphonic problem in their sapphire resonator oscillator. Also,
it is still necessary to lock the oscillator to a 5 or 10 MHz
OCXO.  The oscillator is tuned by varying its oven temperature
set ppoint.


What kind of oven temperature range?  I thought sapphire oscillator 
was pretty much synonymous with "cryogenic sapphire oscillator."  I 
found a paper which described sapphire as a "low loss material with 
loss tangent of 5×10^−6 at room temperature, 2×10^−8 at 77 K and 
7×10^−10 at 4 K giving Q-values of more than >10^7 at low temperatures."


That paper seemed to be describing some kind of temperature 
compensation they  had developed to reduce the temperature 
sensitivity of 10ppm/K and also move the turnover point from 77K to 
92K.  92K isn't exactly what I think of when I hear "oven" so 
presumably there is some mode that works at around 300K that I didn't 
find discussed yet.



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[time-nuts] Re: Best frequency to start for GHz synth ?

[Richard (Rick) Karlquist]

1.  Whatever the advantage of cryogenic operation, Keysight
could not consider that due to marketing reasons.  They
were happy to leave the lunatic fringe to our friends in
Western Australia.

2.  They were already limited by microphonics even at
room temperature, so cryo would be wasted.

3.  My understanding of the oven was that it was simply
a substitute for a Q reducing varactor diode tuning mechanism.
There was never an expectation that temperature compensation would
allow standalone operation of the sapphire.  Again, for marketing
reasons, it was always going to be locked to an OCXO at exactly
10 MHz.  That OCXO's EFC could be used to lock the OCXO to an
external reference with a very slow loop that would prevent
phase noise contamination.

Also of interest to time nuts:

Back when Keysight was part of Agilent, and before the sapphire
resonator, they had architectures using DRO's at about 8 GHz.
So any Sapphire replacement had to be in some sense a drop in
replacement.  Before that, there was a boondoggle project using
a 1 GHZ DRO with a resonator about the size of a hockey puck.
It kind of reminds me of the giant 1 MHz quartz resonators.
There was also a 1 GHZ Surface Transverse Wave Resonator
(STW) oscillator for a while, until the fab shut down.
It evolved from the 640 MHz SAW resonator used in early 5071's.
Again, the fab shut down and I designed it out.

They also wasted (IMHO) a lot of resources on a "opto-electronic"
(I think that was the term) oscillator around 15 or 20 years ago.
It depended on some spool of fiber optic cable.  I never thought
that was going to work, both because of basic principles and
because of the cable spool microphonics.

Rick N6RK

On 4/1/2021 9:06 AM, Chris Caudle wrote:

On 2021-03-31 14:27, Richard (Rick) Karlquist wrote:

When I left Keysight in 2014, they were still trying to solve the
microphonic problem in their sapphire resonator oscillator.  Also,
it is still necessary to lock the oscillator to a 5 or 10 MHz
OCXO.  The oscillator is tuned by varying its oven temperature
set ppoint.


What kind of oven temperature range?  I thought sapphire oscillator was 
pretty much synonymous with "cryogenic sapphire oscillator."  I found a 
paper which described sapphire as a "low loss material with loss tangent 
of 5×10^−6 at room temperature, 2×10^−8 at 77 K and 7×10^−10 at 4 K 
giving Q-values of more than >10^7 at low temperatures."


That paper seemed to be describing some kind of temperature compensation 
they  had developed to reduce the temperature sensitivity of 10ppm/K and 
also move the turnover point from 77K to 92K.  92K isn't exactly what I 
think of when I hear "oven" so presumably there is some mode that works 
at around 300K that I didn't find discussed yet.



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[time-nuts] Re: time-nuts Digest, Vol 200, Issue 49

[William Schrempp]

Hey guys--

From a non-engineer civilian, let me express my gratitude at being able to 
listening in, as a slack-jawed rube, to your high-end ruminations about "aero 
dynamic windows" and "whispering gallery devices," which send me scurrying to 
Google. You give this mere mortal much voyeuristic pleasure.

Bill K7RY

-Original Message-
From: time-nuts-requ...@lists.febo.com  
Sent: Thursday, April 01, 2021 00:30
To: time-nuts@lists.febo.com
Subject: time-nuts Digest, Vol 200, Issue 49

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Contents of time-nuts digest..."

Today's Topics:

   1. Re: The Collapse of Puerto Rico’s Iconic Telescope [April 5th, 2021 New 
Yorker]
  (Dana Whitlow)
   2. Re: Best frequency to start for GHz synth ? (Bob kb8tq)
   3. Re: Best frequency to start for GHz synth ? (Dave ZL3FJ)
   4. Re: Best frequency to start for GHz synth ? (Bruce Griffiths)


--

Message: 1
Date: Wed, 31 Mar 2021 15:45:39 -0500
From: Dana Whitlow 
Subject: [time-nuts] Re: The Collapse of Puerto Rico’s Iconic
Telescope [April 5th, 2021 New Yorker]
To: ew ,  Discussion of precise time and
frequency measurement 
Message-ID:

Content-Type: text/plain; charset="UTF-8"

I have not yet heard what GB wants to do, but if it's long range work (return 
time of 10's of sec or longer), the problems related to T/R switching, Tn 
degradation of the receiver, etc, get a lot more tractable than one might 
suppose.

At Arecibo, the S-band radar was intended solely for long range work.  A big 
part ot T/R switching was to use separate (optimized) feeds for transmitting 
and receiving, and swap feeds during turnaround.  The receive feed was covered 
by a
carefully-
fitted sliding cover during transmit times, which provided excellent isolation. 
 There was a microswitch to sense cover position and which would block 
transmission if it was not satisfied.

Feed horn turnaround time was about 7 seconds as I recall.

The transmitter was basically operated CW, and the "imaging" technique was
"range-
Doppler".  So, the transmitter was run for slightly under the round-trip travel 
time, then feed turnaround was initiated, timed to finish shortly before the 
leading edge of the return was expected.  The receiver would do its thing for 
the duration of the return.
Note that it was also necessary to completely shut down the beam current of the 
transmit Klystrons during receive so that shot noise on the beam did not spoil 
the receiver's noise temperature.  After the receive interval was finished, the 
feeds were again swapped and a new cycle was started.  During each transmit 
period the crew of scientists would have time for a preliminary look at the 
just-recorded data to see if anything was going wrong.

OTOH, Arecibo's 430 MHz ISR for ionospheric studies clearly had to have almost 
instantaneous turnaround time, and arrangements were rather more complicated 
(more so than I can take time to describe at the moment).  But they worked 
well, and loss in the receive state of some big PIN switches in the path was 
tolerably low.
The first 35-40 dB of TX-RX isolation came from use of a "turnstile junction", 
with the remainder coming from the PIN switches.

For both radars, the non-participating receivers would also be covered, but 
with a simpler flap arrangement, some powered by small DC motors and some by 
small pneumatic cylinders.

Dana
(retired from Arecibo Dec 2016)


On Wed, Mar 31, 2021 at 2:30 PM ew via time-nuts 
wrote:

> During my days at UTC I was among other things responsible for our 
> Industrial Laser Group. We sold some 50 KW CW CO2 lasers! We had the 
> only aero dynamic window that allowed  a vacuum on one side. When not 
> in use you put a pencil through it. Patented.
>  Bert Kehren In a message dated 3/31/2021 3:17:21 PM 
> Eastern Standard Time, rich...@karlquist.com writes:
>
>
> On 3/31/2021 11:57 AM, Lux, Jim wrote:
>
> >
> > In some ways it's like high power laser labs. It's not the direct 
> > beam you worry about - nobody is going to put their hand in the beam path.
> > It's the stray reflection when something gets bumped and falls 
> > across the optical bench and reflects a stray beam at 0.01% power 
> > into your
> eyes.
>
> I did consulting at Coherent Laser Group working on CO2 lasers.
> In that lab, actually, many people had the misfortune of accidentally 
> putting their hand or arm in the invisible beam.  You could see the 
> scars on their arms.  There were also accidents where the laser burned 
> the ceiling, etc.  Very scary place to work; fortunately, I 

[time-nuts] Re: Best frequency to start for GHz synth ?

[Chris Caudle]

On 2021-03-31 14:27, Richard (Rick) Karlquist wrote:

When I left Keysight in 2014, they were still trying to solve the
microphonic problem in their sapphire resonator oscillator.  Also,
it is still necessary to lock the oscillator to a 5 or 10 MHz
OCXO.  The oscillator is tuned by varying its oven temperature
set ppoint.


What kind of oven temperature range?  I thought sapphire oscillator was 
pretty much synonymous with "cryogenic sapphire oscillator."  I found a 
paper which described sapphire as a "low loss material with loss tangent 
of 5×10^−6 at room temperature, 2×10^−8 at 77 K and 7×10^−10 at 4 K 
giving Q-values of more than >10^7 at low temperatures."


That paper seemed to be describing some kind of temperature compensation 
they  had developed to reduce the temperature sensitivity of 10ppm/K and 
also move the turnover point from 77K to 92K.  92K isn't exactly what I 
think of when I hear "oven" so presumably there is some mode that works 
at around 300K that I didn't find discussed yet.


--
Chris Caudle
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