[time-nuts] Rock, gas, and air

Mon Mar 1 02:22:39 UTC 2010

Probably hot air...

Murray

-----Original Message-----
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Sent: Monday, 1 March 2010 2:56 p.m.
To: time-nuts at febo.com
Subject: time-nuts Digest, Vol 68, Issue 3

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Today's Topics:

   1. Re: Rock, gas, and air (Bruce Griffiths)
   2. Re: Rock, gas, and air (Bill Hawkins)
   3. Re: Rock, gas, and air (Stanley Reynolds)
   4. Re: DMTD Mixer Terminations (Bob Camp)
   5. Re: Rock, gas, and air (Bob Camp)

----------------------------------------------------------------------

Message: 1
Date: Mon, 01 Mar 2010 14:41:20 +1300
From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] Rock, gas, and air
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <4B8B1B40.8030507 at xtra.co.nz>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Bill Hawkins wrote:
> Rock I take to be crystal. How about gas and air?
>
> Bill Hawkins
>
> -----Original Message-----
> From: Magnus Danielson
> Sent: Sunday, February 28, 2010 5:15 PM
> To: pg5g at b737.co.uk; Discussion of precise time and frequency
measurement
> Subject: Re: [time-nuts] My DIY frequency counter and a request for
help
>
> ------%<------
>
> I think I have a fairly good setup including bunches of rock, gas and
> air clocks alongside a fair set of counters, so I could probably do
some
> testing, but I am located over in Sweden.
>
>
>    
Gas = rubidium vapour??

Bruce

------------------------------

Message: 2
Date: Sun, 28 Feb 2010 19:47:55 -0600
From: "Bill Hawkins" <bill at iaxs.net>
Subject: Re: [time-nuts] Rock, gas, and air
To: "'Discussion of precise time and frequency measurement'"
	<time-nuts at febo.com>
Message-ID: <44F1D726CC5F42F99145FE8CB0F3FE8B at cyrus>
Content-Type: text/plain;	charset="us-ascii"

Whack! (sound of hand hitting forehead)

Gas must be Ru and Cs.

How do you run your pneumatic clocks?

Bill Hawkins

-----Original Message-----
From: Bill Hawkins [mailto:bill at iaxs.net] 
Sent: Sunday, February 28, 2010 7:34 PM
To: 'Discussion of precise time and frequency measurement';
'pg5g at b737.co.uk'
Subject: Rock, gas, and air

Rock I take to be crystal. How about gas and air?

Bill Hawkins 

-----Original Message-----
From: Magnus Danielson
Sent: Sunday, February 28, 2010 5:15 PM
To: pg5g at b737.co.uk; Discussion of precise time and frequency
measurement
Subject: Re: [time-nuts] My DIY frequency counter and a request for help

------%<------

I think I have a fairly good setup including bunches of rock, gas and 
air clocks alongside a fair set of counters, so I could probably do some

testing, but I am located over in Sweden. 

------------------------------

Message: 3
Date: Sun, 28 Feb 2010 17:50:22 -0800 (PST)
From: Stanley Reynolds <stanley_reynolds at yahoo.com>
Subject: Re: [time-nuts] Rock, gas, and air
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <380617.65743.qm at web30307.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1

A while back we had a thread about Paris and a network of air synced
clocks ?

Stanley

----- Original Message ----
From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
Sent: Sun, February 28, 2010 7:41:20 PM
Subject: Re: [time-nuts] Rock, gas, and air

Bill Hawkins wrote:
> Rock I take to be crystal. How about gas and air?
>
> Bill Hawkins
>
> -----Original Message-----
> From: Magnus Danielson
> Sent: Sunday, February 28, 2010 5:15 PM
> To: pg5g at b737.co.uk; Discussion of precise time and frequency
measurement
> Subject: Re: [time-nuts] My DIY frequency counter and a request for
help
>
> ------%<------
>
> I think I have a fairly good setup including bunches of rock, gas and
> air clocks alongside a fair set of counters, so I could probably do
some
> testing, but I am located over in Sweden.
>
>
>? ? 
Gas = rubidium vapour??

Bruce

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Message: 4
Date: Sun, 28 Feb 2010 20:54:53 -0500
From: Bob Camp <lists at rtty.us>
Subject: Re: [time-nuts] DMTD Mixer Terminations
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <43BE29B2-DCB6-43E2-A23B-7AD1DEB6BEDD at rtty.us>
Content-Type: text/plain; charset=us-ascii

Hi

The Minicircuits guys claim 800 to 1000 mv / radian. In my units that
would be 5 to 6.2 volts per cycle. I believe I'm getting ~ 3 X that
mostly from the open circuit termination at audio. It's certainly
something I could head back downstairs and check. 

The < 10% increase in slope between resistive and capacitive termination
has never really been enough with the RPD-1 to make it seem to be worth
it. It's certainly worth it with a ZAD-3.

Bob

On Feb 28, 2010, at g8:39 PM, Bruce Griffiths wrote:

> The results for the RPD-1's are about what I expected: there's little
difference in slope between either a 50 ohm +47nF termination or a 47nF
termination.
> The slopes are about 6.5x greater than the values given by
Minicircuits. (8mv/degree = 2.88V/cycle). I assume that they use 500
ohms connected directly to ground not via a capacitor.
> So there's something in NISTs claims of improved slope at least for
the RPD-1.
> I suspect that NISTs original 50 ohm terminations were actually 50
ohms direct to ground not via a capacitor.
> Using a series capacitor increases the termination impedance at the
beat frequency substantially over that when the resistor is connected
directly to ground.
> 
> Since its is also claimed by NIST and others that reactive termination
reduces the noise, one also needs to measure the output noise spectral
density for the various IF port terminations.
> 
> Bruce
> 
> Bob Camp wrote:
>> Hi
>> 
>> Here's some data:
>> 
>> The setup is very simple:
>> 
>> Two oscillators at 10 MHz driving common base / 50 ohm output
buffers. The buffers ensure that the source impedance is really 50 ohms.
One puts out 9.3 dbm the other 9.5 dbm. They can be tuned for a beat
note in the 0 to 100 Hz range.
>> 
>> The basic mixer termination filter is a pair cascaded / identical L
networks. Both have 10 uh in the series leg and 0.047 uf to ground in
the shunt leg. The "audio end" of the filter hooks straight into a
digitizing scope.
>> 
>> The termination options for the mixer are:
>> 
>> 1) inductive - just running into the 10 uh of the first L network.
>> 2) 50 ohms - drop a 57 ohm in series with 0.047 from the mixer output
to ground
>> 3) Capacitive - 0.047 uf  to ground at the mixer output.
>> 
>> The data is computed from the time to cross the center 50% of the
output waveform. If the output is 1V p-p then the data would cover the
range -.25 to +.25 volts. I've normalized it to "volts / cycle". Divide
by 2* pi if you want to get volts / radian.

>> 
>> 
>> mixer		50 ohms			inductive
capacitive
>> 
>> ZAD-3		3.51			2.96
9.98
>> RPD-1 #1	17.77			10.50			18.85
>> RPD-1 #2	17.40			10.058			18.53
>> 10514A #1	5.796			4.396			10.31
>> 10514A #2	5.826			4.406			10.33
>> 10534A		5.402			4.078
10.88
>> ZP3-MH		8.06			5.81
11.28
>> ZAD-1H		7.73			5.93
9.38
>> 
>> Since not everybody has memorized mixer catalogs:
>> 
>> ZAD-3 		typical minicircuits 7 to 10 dbm mixer
>> RPD-1		500 ohm output phase detector (50 ohms is the
"wrong" termination for it)
>> 10514, 10534 HP products from a ways back
>> ZP3-MH		a 13 dbm class mixer, 9 dbm should be under
driving it
>> ZAD-1H		a 17 dbm class mixer, should be 8 db under
driven.
>> 
>> Bottom line - Capacitive termination helps some parts more than
others. The RPD-1 does not get a real big boost, but the ZAD-1 certainly
does. There's no real way to know what it's going to do without checking
your mixer under your conditions.
>> 
>> A few other notes:
>> 
>> 1) The measurement technique slightly under states the slope for the
50 ohm case. Since the beat note is approximately a sine wave in all
cases, the true slope at zero is a bit higher than this technique
indicates.
>> 
>> 2) The Inductive termination gives the widest linear region. The
output is very nearly an ideal triangle wave. It would make the best
"wide range" phase detector.
>> 
>> 3) The terminations are not precise, but they are identical in all
cases. A more purely inductive load could be constructed. The parts are
just what I had lying around.
>> 
>> 4) No strange bumps or peaks were detected in the beat notes of any
of the mixers. Never seen one, regardless of what NIST says they have
seen.
>> 
>> 5) Eventually I'll go back and check the RPD's with 500 ohms. I stuck
with 50 simply to keep everything as "same same" as I could.
>> 
>> 6) Sweeping the beat note from 100 Hz to 1 Hz showed no change in the
output amplitude.
>> 
>> 7) Contrary to my previous post the peak-peak output voltages are
within 10% for all terminations. Slope and peak to peak are different
things.....
>> 
>> 8) All mixers are running into essentially an open circuit load at
audio. The scope input is>  1 M ohm and the capacitive reactances
are>100 K ohms.
>> 
>> 9) No attempt was made to set up directional couplers and figure out
what the "real" input to the mixers actually is.  Ditto on playing with
series resistors to improve the match.
>> 
>> So there it is. Anybody else got some data to compare to.
>> 
>> Bob
>> 
>> On Feb 28, 2010, at 3:53 PM, Bruce Griffiths wrote:
>> 
>>   
>>> My simulations indicate that terminating the Mixer IF port in an RF
short (with both RF and LO ports saturated) increases the beat frequency
zero crossing slope by more than a factor of 2 (exact value depends on
mixer component characteristics) but doesnt significantly increase the
beat frequency amplitude over that with a high value resistive
termination. To achieve this the IF port termination impedance needs to
be high at the beat frequency and its significant harmonics. The value
above which the impedance is considered high depends on mixer details
such as transformer turns ratio, RF source impedance, diode
characteristics and RF input levels, etc.
>>> 
>>> Bruce
>>> 
>>> Bob Camp wrote:
>>>     
>>>> Hi
>>>> 
>>>> Putting The C on the feedback R in a positive gain setup is only
going to take the "roll off" gain down to 1. Doing the same with an
inverting amp or using a series R / cap to ground will drop the gain a
lot more in the roll off region.
>>>> 
>>>> I would worry about any resistor that's marked as 10K and reads
20K. It's likely noisy.
>>>> 
>>>> A typical DBM has a loss of 5 to 7 db when not in compression. With
a +7  to +10 dbm  drive that should give you an output of 0 to 2 dbm .
The mixer output should be in the .6 to .8 V p-p range into 50 ohms. You
should get about twice that on the beat note running into a load>   500
ohms. A gain of  20 should be plenty. That would give you .6 x 2 x 20 =
24 V p-p out of the amp.
>>>> 
>>>> If you "rf short" the output of the mixer you may double the beat
note again (total of 4X the 50 ohm value). Net would be a 2.4 to 3.2 V
p-p beat note. Anything much over a gain of 10 would be a problem then.
This is one of the cases where 2 X 2 probably does not = 4, so
measurements are indeed in order.
>>>> 
>>>> 
>>>> Bob
>>>> 
>>>> 
>>>> 
>>>> 
>>>> On Feb 28, 2010, at 1:01 AM, Brian Kirby wrote:
>>>> 
>>>> 
>>>>       
>>>>> The values in the schematics are wrong for the op amp gain.  The
drawing was from an earlier drawing where I made a preamp to start
checks on the mixers, and I sent it to you (Bruce G).  Thats when you
determined I did not have enough gain to get near the noise floor.  The
THAT1512/1646 ICs were ordered to make a new preamp for the future
measurements on the mixers.
>>>>> 
>>>>> When I use the scope and check the outputs of the IC, I have 20
volts peak to peak, sine-wave.  I know from previous readings I see
about 500 mv p-p out of the mixer.
>>>>> 
>>>>> I went down to the bench and the resistors I used were still there
(I bought several taped reels of Dale RN55D resistors when a local
business went out).  I used 294 ohms and 14.9  kilo-ohms, for a gain of
50 (the power rails are +/- 15 volts).  Also not shown on the schematic
is a 0.47 uF cap around the 14.9 kilo-ohm resistor.  I think I was
trying to limit the bandwidth to around 15 hertz.
>>>>> 
>>>>> Also the resistor going between the op amp and the limiting diodes
was marked 10K, its 20K.  The diodes are 1N4148.  Corrected drawing
attached.
>>>>> 
>>>>> This is what happens to time nuts who can only play on the weekend
and stay up all night....and my employer just thinks I party too
hard.....for Monday mornings.
>>>>> 
>>>>> 
>>>>> 
>>>>> Brian KD4FM
>>>>> 
>>>>> 
>>>>> 
>>>>> Bruce Griffiths wrote:
>>>>> 
>>>>>         
>>>>>> The LT1037 is shown with a gain of ~1690x, if this amplifier is
used to amplify the beat frequency signal, it will saturate.
>>>>>> Opamp recovery from saturation is poorly documented and may be
very slow.
>>>>>> It would be better to use some diodes in the amplifier feedback
network to limit the large signal gain to 5x (so that the LT1037 remains
stable as it isn't unity gain stable).
>>>>>> This will ensure a somewhat faster recovery from overload as the
LT1037 then avoids saturation and the opamp input stage remains in the
linear region.
>>>>>> 
>>>>>> Bruce
>>>>>> 
>>>>>> Bob Camp wrote:
>>>>>> 
>>>>>>           
>>>>>>> Hi
>>>>>>> 
>>>>>>> Assuming that the junction of the back to back diodes goes
trough a chunk of coax to get to the counter:
>>>>>>> 
>>>>>>> You are forming a low pass filter with the 10K resistor and the
coax capacitance. The LT1037 is quite happy driving a 600 ohm load. You
could easily drop the impedance at that point below 300 ohms. That
should give you a faster edge into the counter.
>>>>>>> 
>>>>>>> You also should check the slew rate performance of the 1037. You
don't want the op amp to be slew rate limited.
>>>>>>> 
>>>>>>> Bob
>>>>>>> 
>>>>>>> 
>>>>>>> On Feb 27, 2010, at 12:41 PM, Brian Kirby wrote:
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>>             
>>>>>>>> I am in the process of designing a DMTD system.  As an
experiment to do basic measurements on the chosen mixer, I used a
capacitor (0.01 uF) in series to ground with a 47 ohm metal film
resistor.  Where the capacitor and resistor meets, another resistor is
attached (390 ohms) that goes to ground.  The idea is to provide a 50
ohm termination at 20 Mhz and a lighter termination at audio
frequencies.  I seen this is a NBS note and I can say, its a starting
point for my experiments.
>>>>>>>> 
>>>>>>>> This (my) system is designed for 10 Mhz, using a 10 hertz beat.
A schematic is attached of what I am experimenting with at the moment.
A HP5370B is the recording instrument.  The noise floor from 1 days
observations show  2x10-11 at 0.1 seconds, 2x10-12 at 1 sec, 5x10-13 at
10 sec, 6x10-14 at 100 sec, 7x10-15 at 1000 sec, and 7x10-16 at 10,000
secs.   It will be interesting when the project is completed to see how
much improvement there will be.
>>>>>>>> 
>>>>>>>> As I understand (or learning..) mixer performance is the key to
the DMTD system.   It occurs to me that maybe a capacitor designed for
50 ohms at 20 mhz may be a better termination (for the IF port) for this
mixer.  A 16 pF capacitor is 50 ohms at 20 mhz, and for comparison at 10
hertz, it would be 100 meg-ohms, which would give maximum amplitude at
10 hertz.   As I understand, a capacitor terminated mixer will give a
triangle wave output, which is very beneficial to the design - as the
end result is to get maximum slope out of the mixer.  I would say,
unqualified as I am, the capacitor termination matches the 20 mhz
signal, and helps attenuates the harmonics of the mixer, and has no , or
very little effect on the audio frequencies that we are interested in.
>>>>>>>> 
>>>>>>>> And saying/rambling on... that if maximum slope is needed, its
needed on the 10 hertz beat signal - so maybe a capacitive termination
on the 10 hertz signal only and something resistive on the 20 mhz
signal........another idea use the 16 pF direct off the mixer, then a
series resistor for isolation and then a large capacitor on the 10 hertz
beat for maximum slope.
>>>>>>>> 
>>>>>>>> At the present, I am awaiting parts to build a low noise preamp
base on the THAT1512 so I can make better measurements on the mixer.
Bruce has provided a lot of good suggestions and helpful comments on my
project and Ulrich has provided me quite a bit of user support on his
program, Plotter.  Thanks to all.
>>>>>>>> 
>>>>>>>> Comments ?     Brian KD4FM
>>>>>>>> <DMTD_Plans.pdf>_______________________________________________
>>>>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>>>>> and follow the instructions there.
>>>>>>>> 
>>>>>>>> 
>>>>>>>>               
>>>>>>> _______________________________________________
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>>>>>>> 
>>>>>>> 
>>>>>>>             
>>>>>> 
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>>>>>> 
>>>>>>           
>>>>> <DMTD_C_Plans.pdf>_______________________________________________
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>>>>>         
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>>>>       
>>> 
>>> 
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>>   
> 
> 
> 
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------------------------------

Message: 5
Date: Sun, 28 Feb 2010 20:56:04 -0500
From: Bob Camp <lists at rtty.us>
Subject: Re: [time-nuts] Rock, gas, and air
To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Message-ID: <8D388AFF-5F33-42A9-9883-85418323E1A0 at rtty.us>
Content-Type: text/plain; charset=us-ascii

Hi

The winds in Sweden change directions in a *very* predictable fashion?

Bob

On Feb 28, 2010, at 8:50 PM, Stanley Reynolds wrote:

> A while back we had a thread about Paris and a network of air synced
clocks ?
> 
> Stanley
> 
> 
> 
> ----- Original Message ----
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> To: Discussion of precise time and frequency measurement
<time-nuts at febo.com>
> Sent: Sun, February 28, 2010 7:41:20 PM
> Subject: Re: [time-nuts] Rock, gas, and air
> 
> Bill Hawkins wrote:
>> Rock I take to be crystal. How about gas and air?
>> 
>> Bill Hawkins
>> 
>> -----Original Message-----
>> From: Magnus Danielson
>> Sent: Sunday, February 28, 2010 5:15 PM
>> To: pg5g at b737.co.uk; Discussion of precise time and frequency
measurement
>> Subject: Re: [time-nuts] My DIY frequency counter and a request for
help
>> 
>> ------%<------
>> 
>> I think I have a fairly good setup including bunches of rock, gas and
>> air clocks alongside a fair set of counters, so I could probably do
some
>> testing, but I am located over in Sweden.
>> 
>> 
>>     
> Gas = rubidium vapour??
> 
> Bruce
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> 
> 
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> 

------------------------------

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