[time-nuts] HP10514B Mixer Terminations

EWKehren at aol.com EWKehren at aol.com
Tue Mar 30 10:14:51 UTC 2010


Good morning Brian.
What do you use as an OFF SET oscillator? 
Thank you
Bert Kehren  Miami
 
 
In a message dated 3/29/2010 11:31:15 P.M. Eastern Daylight Time,  
kilodelta4foxmike at gmail.com writes:

Your  correct - your also keeping me up past my bedtime !- I got to be 90 
miles  from home tomorrow morning by 7:30 AM....

It looks like I got the  squarest wave at 150 pF.   Lesser capacitance, 
give a peaked  sinewave, like maybe a second harmonic.  Past 200 pF, it 
starts  rounding.  150pf= XC of 53 ohms....

This DMTD system, will only go  to 100 hertz maximum beat for my design...

The scope is set to 100 mV  per div, 1ms per division, I intentionally 
mis-triggered it to show rise  and fall times.  100 hz beat signal.  ANd 
Bruce told me how to  calculate slew rate, but it has to be beated in my 
thick tough  head.....

And Bruce, I'll try some coax tomorrow, if I get back home  early enough 
- my work project may keep me late.  And I plan to only  use this system 
to 100 hertz beat, I was just playing around at 1K.....I  like learning.

Good night.....Brian....KD4FM

Bob Camp  wrote:
> Hi
>
> You can get a *much* more squared output  from the mixer than the photos 
you show on the scope. The waveform looks a lit  like a triangle wave with 
the tips chopped off. Normally the fastest edge  happens into a capacitive 
load at RF that's below about  0.5 J ohms for a  "50 ohm" mixer.
>
> Bob
>
> On Mar 29, 2010, at 10:06  PM, Brian Kirby wrote:
>
>   
>> I have been  working on a Dual-Mixer Time Difference system.  In the 
first "design  type/experiment", I was using HP10514B mixers and a LT1037 
preamp and a OP27  zero crossing amplifier/limiter - all a very basic setup.  I 
obtained  some fair measurements;
>>
>> Using 10 MHz sources, a 9.9999  MHz offset for a 100 hertz beat, the 
"floor" of the system looked like  this:
>> 0.01 second = 1x10-10
>> 0.1 second =  1x10-11
>> 1 second = 1x10-12
>> 10 second =  1x10-13
>> 100 second = 1x10-14
>> 1000 second =  1x10-15
>> 10,000 second = 1x10-16
>> this was three days of  data
>>
>> Running it again, with a 10 hertz beat; it looked  like this;
>> 0.1 second = 4x10-12
>> 1 second =  4x10-13
>> 10 second = 4x10-14
>> 100 second =  4x10-15
>> 1000 second = 4x10-16
>>
>> I also had a  lot of good suggestions From Ulrich Bangert, Bob Camp and 
Bruce Griffins, who  I will call my mentors and thank for all the help.
>>
>> I  went back and did some basic experiments this evening.  Looking at 
mixer  terminations.  I have attached two photos - low  res.
>>
>> The first photo named mixer_10db, is the mixer  driven with +10 dbm on 
both ports.  The o'scope is looking thru a basic  RC filter of 1 kilo-ohm 
resistor in series with the mixer output, and on the  output of the resistor is 
a 0.1 uF capacitor to ground.  This is a mixer  that is intentionally over 
driven to use as a phase detector.  The mixer  is rated +13 dbm maximum, and 
about everybody I have talked with (NIST and  BIPM) about these mixers ran 
them at +10 dbm on both LO and RF ports.  As  these mixers are hard to find, 
and they are not made anymore, I would not  over-drive them any further.  
These mixers also have some of the lowest  phase noise measurements on record.
>>
>> The second photo  named mixer_330 pF, is the same setup, except I have 
put a 330 pF capacitor  across the mixer output.  By capacitive terminating 
the mixer, it squares  up the output of the mixer - which makes it easier to 
be converted to a high  slew rate signal.
>>
>> What I found, is you want to run the  minimum capacitance value for the 
highest beat frequency you plan to  run.  That way the signal stays "squared 
up" from the highest to the  lowest beat frequency.
>>
>> I got this value by playing  around by looking at the mixer filtered 
(RC) output at 1 hz, 10 hz, and 100  hz.  When I was using 0.1 and 1 uF 
terminations, The 1 and 10 hertz beat  was OK, but the 100 hertz beat was still a 
sine wave.  That may be why  the results above shows a difference.
>>
>> For a test, at  330 pF, I did try it at 1 KHz, it was back to a sine 
wave.  So 330 pF  looks good for trying to get a "squared" wave out of the 
mixer for 1, 10 and  100 hertz beats.....I tried 36 pF for 1 KHz, it did not 
present enough  capacitance to give the "squared" wave at 1, 10 and 100 hertz  
beat.
>>
>> We have been running email outside of Time-Nuts  group as I am not sure 
if any of you wanted to see the project I am working  on.  I did not want to 
clutter up the forum......but if there is an  interest, I can bring it 
back.  My next plans are to start over building  a new system using a much lower 
noise op amp, the LT1028.  If the mixer  terminations are OK with my 
mentors, I will use a LT1028 preamp set for about  x15 gain and it will dump into 
the first set of limiter diodes.  And I  believe that will call for 1.6 KHz 
low pass filtering on the first limiter  diodes.
>>
>> Comments ?
>>
>> Brian -  KD4FM
>>
>>  
<mixer_330pf.jpg><mixer_10dbm.jpg>_______________________________________________
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>> and follow  the instructions there.
>>      
>
>
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-------------- next part --------------
   Good morning Brian.

   What do you use as an OFF SET oscillator?

   Thank you

   Bert Kehren  Miami



   In a message dated 3/29/2010 11:31:15 P.M. Eastern Daylight Time,
   kilodelta4foxmike at gmail.com writes:

     Your correct - your also keeping me up past my bedtime !- I got to
     be 90
     miles from home tomorrow morning by 7:30 AM....
     It looks like I got the squarest wave at 150 pF.   Lesser
     capacitance,
     give a peaked sinewave, like maybe a second harmonic.  Past 200 pF,
     it
     starts rounding.  150pf= XC of 53 ohms....
     This DMTD system, will only go to 100 hertz maximum beat for my
     design...
     The scope is set to 100 mV per div, 1ms per division, I
     intentionally
     mis-triggered it to show rise and fall times.  100 hz beat signal.
     ANd
     Bruce told me how to calculate slew rate, but it has to be beated in
     my
     thick tough head.....
     And Bruce, I'll try some coax tomorrow, if I get back home early
     enough
     - my work project may keep me late.  And I plan to only use this
     system
     to 100 hertz beat, I was just playing around at 1K.....I like
     learning.
     Good night.....Brian....KD4FM
     Bob Camp wrote:
     > Hi
     >
     > You can get a *much* more squared output from the mixer than the
     photos you show on the scope. The waveform looks a lit like a
     triangle wave with the tips chopped off. Normally the fastest edge
     happens into a capacitive load at RF that's below about  0.5 J ohms
     for a "50 ohm" mixer.
     >
     > Bob
     >
     > On Mar 29, 2010, at 10:06 PM, Brian Kirby wrote:
     >
     >
     >> I have been working on a Dual-Mixer Time Difference system.  In
     the first "design type/experiment", I was using HP10514B mixers and
     a LT1037 preamp and a OP27 zero crossing amplifier/limiter - all a
     very basic setup.  I obtained some fair measurements;
     >>
     >> Using 10 MHz sources, a 9.9999 MHz offset for a 100 hertz beat,
     the "floor" of the system looked like this:
     >> 0.01 second = 1x10-10
     >> 0.1 second = 1x10-11
     >> 1 second = 1x10-12
     >> 10 second = 1x10-13
     >> 100 second = 1x10-14
     >> 1000 second = 1x10-15
     >> 10,000 second = 1x10-16
     >> this was three days of data
     >>
     >> Running it again, with a 10 hertz beat; it looked like this;
     >> 0.1 second = 4x10-12
     >> 1 second = 4x10-13
     >> 10 second = 4x10-14
     >> 100 second = 4x10-15
     >> 1000 second = 4x10-16
     >>
     >> I also had a lot of good suggestions From Ulrich Bangert, Bob
     Camp and Bruce Griffins, who I will call my mentors and thank for
     all the help.
     >>
     >> I went back and did some basic experiments this evening.  Looking
     at mixer terminations.  I have attached two photos - low res.
     >>
     >> The first photo named mixer_10db, is the mixer driven with +10
     dbm on both ports.  The o'scope is looking thru a basic RC filter of
     1 kilo-ohm resistor in series with the mixer output, and on the
     output of the resistor is a 0.1 uF capacitor to ground.  This is a
     mixer that is intentionally over driven to use as a phase detector.
     The mixer is rated +13 dbm maximum, and about everybody I have
     talked with (NIST and BIPM) about these mixers ran them at +10 dbm
     on both LO and RF ports.  As these mixers are hard to find, and they
     are not made anymore, I would not over-drive them any further.
     These mixers also have some of the lowest phase noise measurements
     on record.
     >>
     >> The second photo named mixer_330 pF, is the same setup, except I
     have put a 330 pF capacitor across the mixer output.  By capacitive
     terminating the mixer, it squares up the output of the mixer - which
     makes it easier to be converted to a high slew rate signal.
     >>
     >> What I found, is you want to run the minimum capacitance value
     for the highest beat frequency you plan to run.  That way the signal
     stays "squared up" from the highest to the lowest beat frequency.
     >>
     >> I got this value by playing around by looking at the mixer
     filtered (RC) output at 1 hz, 10 hz, and 100 hz.  When I was using
     0.1 and 1 uF terminations, The 1 and 10 hertz beat was OK, but the
     100 hertz beat was still a sine wave.  That may be why the results
     above shows a difference.
     >>
     >> For a test, at 330 pF, I did try it at 1 KHz, it was back to a
     sine wave.  So 330 pF looks good for trying to get a "squared" wave
     out of the mixer for 1, 10 and 100 hertz beats.....I tried 36 pF for
     1 KHz, it did not present enough capacitance to give the "squared"
     wave at 1, 10 and 100 hertz beat.
     >>
     >> We have been running email outside of Time-Nuts group as I am not
     sure if any of you wanted to see the project I am working on.  I did
     not want to clutter up the forum......but if there is an interest, I
     can bring it back.  My next plans are to start over building a new
     system using a much lower noise op amp, the LT1028.  If the mixer
     terminations are OK with my mentors, I will use a LT1028 preamp set
     for about x15 gain and it will dump into the first set of limiter
     diodes.  And I believe that will call for 1.6 KHz low pass filtering
     on the first limiter diodes.
     >>
     >> Comments ?
     >>
     >> Brian - KD4FM
     >>
     >>
     <mixer_330pf.jpg><mixer_10dbm.jpg>__________________________________
     _____________
     >> 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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     > and follow the instructions there.
     >
     >
     [cid:X.MA1.1269944085 at aol.com]
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