Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Charles Steinmetz]

Luciano wrote:


The CLC409 datasheet show all the test response up to +12dBm (around 1Vpp 
on 75/50Ohm load)
see: pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS012748.PDF


I'm reporting what I have observed with the CLC409 (and LMH6702) when 
operated on the "absolute max" supply rails of +/- 6v.  Of course, I 
would never design a commercial product using abs max specs without 
having a serious conversation and understanding with the manufacturer 
(if then).


Clipping commences at just over +/- 2v (a touch over +16dBm).  This is 
with a 50 ohm build-out or "back termination" resistor -- you can get an 
additional 6dBm if you do without the build-out resistor and terminate 
only the load end of the cable in 50 ohms, which actually works fine as 
long as the output loads are matched at 50 ohms.  I terminate both ends 
"just in case" they aren't.  Harmonic distortion does not rise until 
there is visible clipping.



I agree that harmonic distortion is an important factor to keep in mind 
however -45dBc is a very interesting value considering the market alternatives. 
In my document I have enclosed on page 10 a little research I did online on 
similar products and as you can see the -45 are positioned at a decidedly 
higher level than other commercial solutions
see [table]:


IMO, pretty much all commercial distribution/isolation amplifiers fail 
miserably to hold distortion down to tolerable levels -- one reason why 
I have always designed my own.  Interestingly, some older, vacuum-tube 
models did better.



An extremely important factor not to be overlooked is the maximum output 
power / level of the amplifier. Measurement systems such as the HP3048A for 
phase noise measurement use mixers that require minimum signal levels of + 
15dBm at higher PO1 and the CLC409 will never meet these requirements.


As noted above, it will if it is operated on abs max supplies, even with 
a 50 ohm build-out resistor.  Without the build-out resistor, it will 
supply +22dBm (+20dBm on +/- 5v supplies).



In your modification document: Residual phase noise of <-165dBc at 10 MHz
I suppose you mean @100kHz, The buffer I propose is -170dBc @100KHz


I normally cite 10kHz measurements, but I don't recall if I cited 100kHz 
or 10kHz measurements (my bad for the incomplete spec).  One or the other.



In the end I don't think this should be a competition among Distribution 
Amplifiers.


Nor I.  I built a few dozen of the modified Extron DAs, which I've 
passed on to other time nuts over the years.  I still have one around, 
but it is not in daily use.  I currently use two different designs, both 
scratch-built, one IC-based and one discrete.  As I've said before, I 
distinguish between distribution amplifiers (lots of outputs) and 
isolation amplifiers (where only 2 or maybe 3 outputs are needed, but 
distortion, residual PN, and transit delay must be truly 
state-of-the-art for sensitive measurements).


On re-reading my original post, I see the tone could be taken as a bit 
confrontational.  That was certainly not my intent -- I just wanted to 
defend IC designs against some "received wisdom" (*NOT* from you) that 
they are inferior.  Thank you for giving me the benefit of the doubt and 
responding as a gentleman.



For a "ready" solution at low cost like DA the Extron I think is a great 
solution.


Me, too, which is why my first efforts as a time-nuts newbie were made 
in that direction.


Best regards,

Charles



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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[tim...@timeok.it]

   Charles wrote:
   >Well, there is a distinct difference between DAs that use a single
   amplifier (discrete or integrated) to drive each output channel (as your
   design does), and DAs that drive multiple outputs from each amplifier
   using build-out resistors. In the case of the Extron integrated circuit
   DAs using CLS409 opamps, the isolation is 30dB between outputs fed from
   one amplifier, and >90dB between outputs fed from different amplifiers
   (see my document detailing recommended modifications to the Extron DAs,
   downloadable from):
   

   So, simply by using only some of the outputs of an Extron IC-based DA,
   one gets isolation roughly equal to your design.


   < The solution I proposed is a 107dB channnel to channel isolation (gain set 
+3dB).



> One advantage of the IC design is considerably lower distortion -- the
   harmonics are all below -65dBc at 10MHz, +16dBm output, compared to
   -45dBc at +13dBm for your design (per your table). Further, the
   distortion products of the IC design are essentially all odd-order
   harmonics, while your design shows predominant even-order harmonics.

   < The CLC409 datasheet show all the test response up to +12dBm (around 1Vpp 
on 75/50Ohm load)
see: pdf.datasheetcatalog.com/datasheet/nationalsemiconductor/DS012748.PDF

   I agree that harmonic distortion is an important factor to keep in mind 
however -45dBc is a very interesting value considering the market alternatives. 
In my document I have enclosed on page 10 a little research I did online on 
similar products and as you can see the -45 are positioned at a decidedly 
higher level than other commercial solutions
   see:
   
http://www.timeok.it/wp-content/uploads/2015/08/Frequency-Distribution-Design-Basic-Module-v-4.1.pdf

   An extremely important factor not to be overlooked is the maximum output 
power / level of the amplifier. Measurement systems such as the HP3048A for 
phase noise measurement use mixers that require minimum signal levels of + 
15dBm at higher PO1 and the CLC409 will never meet these requirements.


   >In your modification document: Residual phase noise of <-165dBc at 10 MHz


The Extron is a very nice solution, certainly of modest price, but we must 
consider * * * the low separation between the output channels.

   Well, there is a distinct difference between DAs that use a single
   amplifier (discrete or integrated) to drive each output channel (as your
   design does), and DAs that drive multiple outputs from each amplifier
   using build-out resistors. In the case of the Extron integrated circuit
   DAs using CLS409 opamps, the isolation is 30dB between outputs fed from
   one amplifier, and >90dB between outputs fed from different amplifiers
   (see my document detailing recommended modifications to the Extron DAs,
   downloadable from):

   


   So, simply by using only some of the outputs of an Extron IC-based DA,
   one gets isolation roughly equal to your design. Of course, one could
   easily build a one-output-per-amplifier DA using the Extron circuit
   (with LMH6702 or other suitable opamps) to have a DA with ~100 dB of
   isolation between all outputs (the exact isolation will be dependent
   upon the layout, just as it is with your design).

   One advantage of the IC design is considerably lower distortion -- the
   harmonics are all below -65dBc at 10MHz, +16dBm output, compared to
   -45dBc at +13dBm for your design (per your table). Further, the
   distortion products of the IC design are essentially all odd-order
   harmonics, while your design shows predominant even-order harmonics.

   Odd-order harmonics are symmetrical, so they do not generate additional
   amplitude-to-phase modulation when the output feeds a squarer/zero-cross
   detector. Even-order harmonics, conversely, *DO* generate additional
   amplitude-to-phase modulation when the output feeds a squarer/zero-cross
   detector. This is very important because the vast majority of
   measurement equipment likely to be fed by a DA/iso amp feeds its inputs
   directly to a ZCD. See reference in next paragraph.

   We have, in the past, disagreed about the importance of low distortion
   in DA/iso amplifiers, but I have satisfied myself that a timing DA/iso
   amp should have, at a bare minimum, -65dBc harmonic suppression. For
   just one reason, see the NIST publication, "The Effect of Harmonic
   Distortion on Phase errors in Frequency Distribution and Synthesis"
   (Walls and Ascarrunz), available at:

   


   Best regards,

   Charles



   

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Charles Steinmetz]

Luciano wrote:


The Extron is a very nice solution, certainly of modest price, but we must 
consider   *   *   *   the low separation between the output channels.


Well, there is a distinct difference between DAs that use a single 
amplifier (discrete or integrated) to drive each output channel (as your 
design does), and DAs that drive multiple outputs from each amplifier 
using build-out resistors.  In the case of the Extron integrated circuit 
DAs using CLS409 opamps, the isolation is 30dB between outputs fed from 
one amplifier, and >90dB between outputs fed from different amplifiers 
(see my document detailing recommended modifications to the Extron DAs, 
downloadable from):




So, simply by using only some of the outputs of an Extron IC-based DA, 
one gets isolation roughly equal to your design.  Of course, one could 
easily build a one-output-per-amplifier DA using the Extron circuit 
(with LMH6702 or other suitable opamps) to have a DA with ~100 dB of 
isolation between all outputs (the exact isolation will be dependent 
upon the layout, just as it is with your design).


One advantage of the IC design is considerably lower distortion -- the 
harmonics are all below -65dBc at 10MHz, +16dBm output, compared to 
-45dBc at +13dBm for your design (per your table).  Further, the 
distortion products of the IC design are essentially all odd-order 
harmonics, while your design shows predominant even-order harmonics.


Odd-order harmonics are symmetrical, so they do not generate additional 
amplitude-to-phase modulation when the output feeds a squarer/zero-cross 
detector.  Even-order harmonics, conversely, *DO* generate additional 
amplitude-to-phase modulation when the output feeds a squarer/zero-cross 
detector. This is very important because the vast majority of 
measurement equipment likely to be fed by a DA/iso amp feeds its inputs 
directly to a ZCD.  See reference in next paragraph.


We have, in the past, disagreed about the importance of low distortion 
in DA/iso amplifiers, but I have satisfied myself that a timing DA/iso 
amp should have, at a bare minimum, -65dBc harmonic suppression.  For 
just one reason, see the NIST publication, "The Effect of Harmonic 
Distortion on Phase errors in Frequency Distribution and Synthesis" 
(Walls and Ascarrunz), available at:




Best regards,

Charles



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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Bob kb8tq]

Hi

What is the objective?

If this is a setup to feed a bunch of RF test gear on a lab bench, that’s a 
petty typical 
thing for roughly 99% of the “need” out there. The gear sits there forever and 
ever 
connected to the end of the same piece of cable. It has a PLL of some sort 
inside
the box to “clean up” the incoming signal. The device is likely happy with a 
wide range
of levels and may or may not provide a 50 ohm termination. 

An amp feeding a Mini Circuits splitter is overkill for this sort of 
application. Indeed you
can probably switch most of the gear to “don’t terminate” and run it with a 
bunch of tee
connectors. The gear will be happy and it will be just as functional as if you 
drove it with
something super duper. 

For not much more than the splitter on eBay (and possibly a bit less) a bunch 
of CMOS
gates driving simple filters will give you isolated outputs. It’s overkill, but 
easy to do and
essentially bulletproof. 

Indeed if you are trying to drive a reference into a -170 dbc / Hz phase noise 
test set you 
will need something better. None of the solutions above will really do the 
trick in that case. 
Best to have one setup to drive all the bench stuff and do a separate system 
for that kind
of thing. 

Bob

> On Oct 19, 2019, at 12:04 PM, paul swed  wrote:
> 
> extrons are dead simple. But to modify the unit say a 6 output amp RBG+S
> then you have some 20-30 BNC nuts to take off. Fun.
> So while you are hacking it you can also add more outputs. Most have the
> holes. Add BNC and a chip R. Most of the Rs are on the back and no need to
> take off the nuts. Just depends on how much work you want to put in.
> Regards
> Paul
> WB8TSL
> 
> On Sat, Oct 19, 2019 at 6:03 AM Bryan _  wrote:
> 
>> There is a schematic here on the Extron uploaded by a TN member. The
>> schematic for the Extron looks looks dead simple that one could really just
>> make a simple 3 channel with the included mods in the writeup, only problem
>> is I don't see a source for a CLC409 any longer, and I don't have the
>> experience or knowledge to use a substitute ADA800x ??
>> 
>> <
>> http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf
>>> 
>> 
>> -=Bryan=-
>> 
>> 
>> From: time-nuts  on behalf of ed breya <
>> e...@telight.com>
>> Sent: October 18, 2019 1:39 PM
>> To: time-nuts@lists.febo.com 
>> Subject: Re: [time-nuts] Using commercial video amplifier for 10MHz clock
>> distribution.
>> 
>> I have a Hitachi VD-1000 video distribution unit that's been sitting
>> unused for years, waiting until I finally get around to making it into a
>> reference unit. I just dug it out and looked inside. It is full of RCA
>> jack cables for jumping the signals around in different ways. I
>> apparently had changed things around already, to make one section into a
>> 15-output distributor. I have forgotten all about it long ago, so now
>> it's just a dizzying array of cabling. I must have made notes somewhere,
>> that I'll have to find for when I eventually (probably fairly soon) do
>> the proper conversion.
>> 
>> It uses CLC404 amplifiers, which appear to be older and a little noisier
>> than the CLC409, but should be OK for this. Unfortunately, it uses a
>> small switching supply, which I dislike for things like this, so
>> ultimately will make a linear one for it.
>> 
>> This thing has 40 BNC connectors on the back, which would allow for lots
>> of I/O and branching combinations. This is likely way more than I'll
>> ever need, so the "new" plan is to incorporate some improvements,
>> considering what I recently learned during my work on the frequency
>> multiplier project. I'll be reducing the total fanout, and changing some
>> of the outputs to have fully-floating transformer coupling, to reduce
>> ground loop effects in high sensitivity applications, and also
>> independent volume controls for some. I may do the same on the source
>> inputs too. I don't know how many of each thing yet, but definitely
>> some. In any of the BNC spots, I can easily put an isolating type BNC,
>> or a volume control pot. The front panel is mostly blank, so there's
>> lots of room for even more stuff there. I just have to be careful to not
>> get carried away and make it too wonderful and complicated and never
>> finished.
>> 
>> I also have an Efratom something-something distribution rack with five
>> "MBF" modules that have four outputs each. They should pretty good too,
>> but unfortunately it's all for 5 MHz only - there's low- or band-pass

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Taka Kamiya via time-nuts]

I've done some quick test.
Specimen is one of my Extron MDV3.Instruments used were 

TruePosition based GPSDO producing 10MHz at 11.9dBmHP8644A producing 15MHz at 
10dBmHP8591EM spectrum analyzer
HP437B power meter + 482A sensor

I connected 10MHz to OUTPUT port of Extron MDV3.  Nothing was detected on input 
or other output ports.  Non detectable either by power meter or SpecAn.I 
connected 10MHz to OUTPUT port and looked at other OUTPUT port.  Nothing 
detected as well.
I connected 10MHz to INPUT port and took a power measurement at output port of 
Extron.  11.2dBmI connected 10MHz to INPUT port and looked at output port by 
SpecAn.  Keeping eyes on CRT
Then I connected 15MHz to OUTPUT port, zero change on CRT
As far as Saturation, up to 12.3dBm input, it was clean.  Above this, 2nd 
harmonic started to show up.  At 14dBm, all harmonics were -40dB below the 
primary signal.  This is probably the limit I'd go.
With this, I can conclude this particular device has a "pretty good" isolation 
between output port and output to input port, as well as sufficient protection 
for reverse leakage.  Obviously, my result is specific to my device.  Some 
future/past design revision, other models, other makes, etc has to be 
re-measured.  

I left test setup as-is.  If anyone want me to test something else, I'd be 
happy to.
--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Saturday, October 19, 2019, 2:02:32 PM EDT, tim...@timeok.it 
 wrote:  
 
 
  Hi,

  A premise must be made to define the performance of these DAs as EXTRON can 
be compared to those built for the distribution of reference frequencies.
  The Extron is a very nice solution, certainly of modest price, but we must 
consider that its performances are limited. This especially if we talk about 
saturation levels but much more important is the low separation between the 
output channels. These two factors can be negligible if the required 
level/stability is good but not excellent, in fact by disconnecting a load or 
simply changing the length of a coax connection on a channel almost certainly a 
change in level / phase will occur in the adjacent output.

  If anyone is interested, you will find my solution here:

  
http://www.timeok.it/wp-content/uploads/2015/08/Frequency-Distribution-Design-Basic-Module-v-4.1.pdf

  Using it as a buffer for the low phase noise HP 10811-60109 and BVA 8600 
there is no deterioration of the phase / noise floor.

  I ordered some new PCBs related to the buffer only. If anyone is interested 
let me know off list.

  Luciano

  tim...@timeok.it


  Da "time-nuts" time-nuts-boun...@lists.febo.com
  A "Discussion of precise time and frequency measurement" 
time-nuts@lists.febo.com
  Cc
  Data Sat, 19 Oct 2019 08:30:02 +0000
  Oggetto Re: [time-nuts] Using commercial video amplifier for 10MHz clock 
distribution.
  There is a schematic here on the Extron uploaded by a TN member. The 
schematic for the Extron looks looks dead simple that one could really just 
make a simple 3 channel with the included mods in the writeup, only problem is 
I don't see a source for a CLC409 any longer, and I don't have the experience 
or knowledge to use a substitute ADA800x ??

  
<http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf>

  -=Bryan=-

  
  From: time-nuts  on behalf of ed breya 

  Sent: October 18, 2019 1:39 PM
  To: time-nuts@lists.febo.com 
  Subject: Re: [time-nuts] Using commercial video amplifier for 10MHz clock 
distribution.

  I have a Hitachi VD-1000 video distribution unit that's been sitting
  unused for years, waiting until I finally get around to making it into a
  reference unit. I just dug it out and looked inside. It is full of RCA
  jack cables for jumping the signals around in different ways. I
  apparently had changed things around already, to make one section into a
  15-output distributor. I have forgotten all about it long ago, so now
  it's just a dizzying array of cabling. I must have made notes somewhere,
  that I'll have to find for when I eventually (probably fairly soon) do
  the proper conversion.

  It uses CLC404 amplifiers, which appear to be older and a little noisier
  than the CLC409, but should be OK for this. Unfortunately, it uses a
  small switching supply, which I dislike for things like this, so
  ultimately will make a linear one for it.

  This thing has 40 BNC connectors on the back, which would allow for lots
  of I/O and branching combinations. This is likely way more than I'll
  ever need, so the "new" plan is to incorporate some improvements,
  considering what I recently learned during my work on the frequency
  multiplier project. I'll be reducing the total fanout, and changing some
  of the outputs to have fully-floating transformer coupling, to reduce
  ground loop effe

Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[tim...@timeok.it]

   Hi,

   A premise must be made to define the performance of these DAs as EXTRON can 
be compared to those built for the distribution of reference frequencies.
   The Extron is a very nice solution, certainly of modest price, but we must 
consider that its performances are limited. This especially if we talk about 
saturation levels but much more important is the low separation between the 
output channels. These two factors can be negligible if the required 
level/stability is good but not excellent, in fact by disconnecting a load or 
simply changing the length of a coax connection on a channel almost certainly a 
change in level / phase will occur in the adjacent output.

   If anyone is interested, you will find my solution here:

   
http://www.timeok.it/wp-content/uploads/2015/08/Frequency-Distribution-Design-Basic-Module-v-4.1.pdf

   Using it as a buffer for the low phase noise HP 10811-60109 and BVA 8600 
there is no deterioration of the phase / noise floor.

   I ordered some new PCBs related to the buffer only. If anyone is interested 
let me know off list.

   Luciano

   tim...@timeok.it


   Da "time-nuts" time-nuts-boun...@lists.febo.com
   A "Discussion of precise time and frequency measurement" 
time-nuts@lists.febo.com
   Cc
   Data Sat, 19 Oct 2019 08:30:02 +0000
   Oggetto Re: [time-nuts] Using commercial video amplifier for 10MHz clock 
distribution.
   There is a schematic here on the Extron uploaded by a TN member. The 
schematic for the Extron looks looks dead simple that one could really just 
make a simple 3 channel with the included mods in the writeup, only problem is 
I don't see a source for a CLC409 any longer, and I don't have the experience 
or knowledge to use a substitute ADA800x ??

   
<http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf>

   -=Bryan=-

   
   From: time-nuts  on behalf of ed breya 

   Sent: October 18, 2019 1:39 PM
   To: time-nuts@lists.febo.com 
   Subject: Re: [time-nuts] Using commercial video amplifier for 10MHz clock 
distribution.

   I have a Hitachi VD-1000 video distribution unit that's been sitting
   unused for years, waiting until I finally get around to making it into a
   reference unit. I just dug it out and looked inside. It is full of RCA
   jack cables for jumping the signals around in different ways. I
   apparently had changed things around already, to make one section into a
   15-output distributor. I have forgotten all about it long ago, so now
   it's just a dizzying array of cabling. I must have made notes somewhere,
   that I'll have to find for when I eventually (probably fairly soon) do
   the proper conversion.

   It uses CLC404 amplifiers, which appear to be older and a little noisier
   than the CLC409, but should be OK for this. Unfortunately, it uses a
   small switching supply, which I dislike for things like this, so
   ultimately will make a linear one for it.

   This thing has 40 BNC connectors on the back, which would allow for lots
   of I/O and branching combinations. This is likely way more than I'll
   ever need, so the "new" plan is to incorporate some improvements,
   considering what I recently learned during my work on the frequency
   multiplier project. I'll be reducing the total fanout, and changing some
   of the outputs to have fully-floating transformer coupling, to reduce
   ground loop effects in high sensitivity applications, and also
   independent volume controls for some. I may do the same on the source
   inputs too. I don't know how many of each thing yet, but definitely
   some. In any of the BNC spots, I can easily put an isolating type BNC,
   or a volume control pot. The front panel is mostly blank, so there's
   lots of room for even more stuff there. I just have to be careful to not
   get carried away and make it too wonderful and complicated and never
   finished.

   I also have an Efratom something-something distribution rack with five
   "MBF" modules that have four outputs each. They should pretty good too,
   but unfortunately it's all for 5 MHz only - there's low- or band-pass
   filtering built into each channel, so needs reverse engineering and mods
   for 10 MHz. I vaguely recall looking for info on this about a year ago,
   and stumbled upon an old time nuts thread. Someone (maybe Chuck Harris?)
   had reported successful mods for 10 MHz on these, but there were no
   links to any info about it. So Chuck, if you see this, and it was you,
   or anyone else, I'd sure appreciate this info. If it was just my
   imagination, then never mind.

   Ed

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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[ed breya]

I think there may be some confusion due to similarity of names.

Extron apparently makes or made video gear.

Efratom made Rb sources and precision frequency distribution stuff.

I'd like to find info on the Efratom distribution system, and 
specifically the "MBF" modules.


Ed

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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[paul swed]

extrons are dead simple. But to modify the unit say a 6 output amp RBG+S
then you have some 20-30 BNC nuts to take off. Fun.
So while you are hacking it you can also add more outputs. Most have the
holes. Add BNC and a chip R. Most of the Rs are on the back and no need to
take off the nuts. Just depends on how much work you want to put in.
Regards
Paul
WB8TSL

On Sat, Oct 19, 2019 at 6:03 AM Bryan _  wrote:

> There is a schematic here on the Extron uploaded by a TN member. The
> schematic for the Extron looks looks dead simple that one could really just
> make a simple 3 channel with the included mods in the writeup, only problem
> is I don't see a source for a CLC409 any longer, and I don't have the
> experience or knowledge to use a substitute ADA800x ??
>
> <
> http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf
> >
>
> -=Bryan=-
>
> 
> From: time-nuts  on behalf of ed breya <
> e...@telight.com>
> Sent: October 18, 2019 1:39 PM
> To: time-nuts@lists.febo.com 
> Subject: Re: [time-nuts] Using commercial video amplifier for 10MHz clock
> distribution.
>
> I have a Hitachi VD-1000 video distribution unit that's been sitting
> unused for years, waiting until I finally get around to making it into a
> reference unit. I just dug it out and looked inside. It is full of RCA
> jack cables for jumping the signals around in different ways. I
> apparently had changed things around already, to make one section into a
> 15-output distributor. I have forgotten all about it long ago, so now
> it's just a dizzying array of cabling. I must have made notes somewhere,
> that I'll have to find for when I eventually (probably fairly soon) do
> the proper conversion.
>
> It uses CLC404 amplifiers, which appear to be older and a little noisier
> than the CLC409, but should be OK for this. Unfortunately, it uses a
> small switching supply, which I dislike for things like this, so
> ultimately will make a linear one for it.
>
> This thing has 40 BNC connectors on the back, which would allow for lots
> of I/O and branching combinations. This is likely way more than I'll
> ever need, so the "new" plan is to incorporate some improvements,
> considering what I recently learned during my work on the frequency
> multiplier project. I'll be reducing the total fanout, and changing some
> of the outputs to have fully-floating transformer coupling, to reduce
> ground loop effects in high sensitivity applications, and also
> independent volume controls for some. I may do the same on the source
> inputs too. I don't know how many of each thing yet, but definitely
> some. In any of the BNC spots, I can easily put an isolating type BNC,
> or a volume control pot. The front panel is mostly blank, so there's
> lots of room for even more stuff there. I just have to be careful to not
> get carried away and make it too wonderful and complicated and never
> finished.
>
> I also have an Efratom something-something distribution rack with five
> "MBF" modules that have four outputs each. They should pretty good too,
> but unfortunately it's all for 5 MHz only - there's low- or band-pass
> filtering built into each channel, so needs reverse engineering and mods
> for 10 MHz. I vaguely recall looking for info on this about a year ago,
> and stumbled upon an old time nuts thread. Someone (maybe Chuck Harris?)
> had reported successful mods for 10 MHz on these, but there were no
> links to any info about it. So Chuck, if you see this, and it was you,
> or anyone else, I'd sure appreciate this info. If it was just my
> imagination, then never mind.
>
> Ed
>
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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Gerhard Hoffmann]

Am 19.10.19 um 10:30 schrieb Bryan _:

There is a schematic here on the Extron uploaded by a TN member. The schematic 
for the Extron looks looks dead simple that one could really just make a simple 
3 channel with the included mods in the writeup, only problem is I don't see a 
source for a CLC409 any longer, and I don't have the experience or knowledge to 
use a substitute ADA800x ??




It seems that LMH6702 should fit, at least electrically.
Check for the right package b4 buying. Current feedback op amps have a
preferred value for the feedback resistor. The existing 240 Ohms fit
for the LMH6702. No wonder, it's intended as the replacement.

regards, Gerhard

< https://www.digikey.de/products/de?keywords=lmh6702 >



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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Bryan _]

There is a schematic here on the Extron uploaded by a TN member. The schematic 
for the Extron looks looks dead simple that one could really just make a simple 
3 channel with the included mods in the writeup, only problem is I don't see a 
source for a CLC409 any longer, and I don't have the experience or knowledge to 
use a substitute ADA800x ??

<http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf>

-=Bryan=-


From: time-nuts  on behalf of ed breya 

Sent: October 18, 2019 1:39 PM
To: time-nuts@lists.febo.com 
Subject: Re: [time-nuts] Using commercial video amplifier for 10MHz clock 
distribution.

I have a Hitachi VD-1000 video distribution unit that's been sitting
unused for years, waiting until I finally get around to making it into a
reference unit. I just dug it out and looked inside. It is full of RCA
jack cables for jumping the signals around in different ways. I
apparently had changed things around already, to make one section into a
15-output distributor. I have forgotten all about it long ago, so now
it's just a dizzying array of cabling. I must have made notes somewhere,
that I'll have to find for when I eventually (probably fairly soon) do
the proper conversion.

It uses CLC404 amplifiers, which appear to be older and a little noisier
than the CLC409, but should be OK for this. Unfortunately, it uses a
small switching supply, which I dislike for things like this, so
ultimately will make a linear one for it.

This thing has 40 BNC connectors on the back, which would allow for lots
of I/O and branching combinations. This is likely way more than I'll
ever need, so the "new" plan is to incorporate some improvements,
considering what I recently learned during my work on the frequency
multiplier project. I'll be reducing the total fanout, and changing some
of the outputs to have fully-floating transformer coupling, to reduce
ground loop effects in high sensitivity applications, and also
independent volume controls for some. I may do the same on the source
inputs too. I don't know how many of each thing yet, but definitely
some. In any of the BNC spots, I can easily put an isolating type BNC,
or a volume control pot. The front panel is mostly blank, so there's
lots of room for even more stuff there. I just have to be careful to not
get carried away and make it too wonderful and complicated and never
finished.

I also have an Efratom something-something distribution rack with five
"MBF" modules that have four outputs each. They should pretty good too,
but unfortunately it's all for 5 MHz only - there's low- or band-pass
filtering built into each channel, so needs reverse engineering and mods
for 10 MHz. I vaguely recall looking for info on this about a year ago,
and stumbled upon an old time nuts thread. Someone (maybe Chuck Harris?)
had reported successful mods for 10 MHz on these, but there were no
links to any info about it. So Chuck, if you see this, and it was you,
or anyone else, I'd sure appreciate this info. If it was just my
imagination, then never mind.

Ed

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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[paul swed]

I have used the amplifiers for years. Good grade GVGs and extrons. They
just work.
Though like everyone I considered shifting to 50 ohms it never seemed worth
the effort.
In fact most of my distribution is 75 ohms.
Cable and connectors are cheap well shielded and easy to install.
They make very fine 75 ohm crimp bnc connectors also. Not so cheap.
Also many of the amps will pass square wave signals just fine. Think of the
60 Hz sync pulse.
They would not be good for 1 PPS.
I did do something recently that turned out well. Convert the reference to
a 110 ohm balanced signal using AD8131 amplifiers and drive cat6 cable. Far
end mini ckt 110-75 ohm xformer.
Works very well and allows 4 signals on one cable. No emissions I can
easily detect. 100 watt transceivers do not upset things. My cable run is
150'. Loss is expected and the far end amp makes up for it. Now the
basement equipment is locked to the upstairs equipment without additional
divider chains.
Crazy silly I know.
Regards
Paul
WB8TSL

On Fri, Oct 18, 2019 at 3:09 PM Bob Bownes  wrote:

> I have a few of the 2 in 5 out video distribution amps. I took one apart
> and converted it to 50Ω from 75Ω, and to be honest, I can't really see a
> difference.
>
> Bob
>
>
> On Fri, Oct 18, 2019 at 8:08 AM Charles Steinmetz 
> wrote:
>
> > Taka Kamiya wrote:
> >
> > > I am using Extron MDA 3V for distributing 10MHz at several places in my
> > lab.  MDA3V is a one port in - 3 port out device made for VIDEO market
> and
> > rather low end at that.  Input and output is 75 ohm and bandwidth extend
> to
> > 150MHz or so.  Looking at 10MHz sine wave through it, it looks good.  No
> > visible distortions.  Gain is unity between input and one of the ports.
> > >
> > > Couple of questions though.  This device is 75ohm.  It's easy to add
> > 150ohm in parallel to a matching resister and make it 50ohm.  However,
> I'm
> > guessing 50 ohm / 75 ohm mismatch is not really a big deal that I'm not
> > doing anything about it.  Input and output cables are RG58 (50 ohm)  VSWR
> > is 1.5, For external sync port, many equipment is not exactly spec'd for
> 50
> > ohm, but often only spec'd for voltage or at db level without any
> specific
> > impedance mentioned.  Recommended cable is 50 ohm though.  I typically
> shy
> > away from consumer grade gear but looking inside, it's just an op-amp and
> > registers.  If I use square wave which contains higher frequency
> > components, would this be inadequate?
> > > There are many web pages by people doing exactly what I'm doing with
> > usually bigger Extron devices.  I'd like to consult the Time-Nut
> community
> > of sanity in what I am doing.
> >
> > I published a doc with recommended mods to the opamp-based Extron video
> > DAs for use as 1-10MHz clock/timing DAs:
> >
> > <
> >
> http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf
> > >
> >
> > Whether you make the changes or not, you may find some helpful
> > information there.
> >
> > Best regards,
> >
> > Charles
> >
> >
> >
> > ___
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> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[ed breya]

I have a Hitachi VD-1000 video distribution unit that's been sitting 
unused for years, waiting until I finally get around to making it into a 
reference unit. I just dug it out and looked inside. It is full of RCA 
jack cables for jumping the signals around in different ways. I 
apparently had changed things around already, to make one section into a 
15-output distributor. I have forgotten all about it long ago, so now 
it's just a dizzying array of cabling. I must have made notes somewhere, 
that I'll have to find for when I eventually (probably fairly soon) do 
the proper conversion.


It uses CLC404 amplifiers, which appear to be older and a little noisier 
than the CLC409, but should be OK for this. Unfortunately, it uses a 
small switching supply, which I dislike for things like this, so 
ultimately will make a linear one for it.


This thing has 40 BNC connectors on the back, which would allow for lots 
of I/O and branching combinations. This is likely way more than I'll 
ever need, so the "new" plan is to incorporate some improvements, 
considering what I recently learned during my work on the frequency 
multiplier project. I'll be reducing the total fanout, and changing some 
of the outputs to have fully-floating transformer coupling, to reduce 
ground loop effects in high sensitivity applications, and also 
independent volume controls for some. I may do the same on the source 
inputs too. I don't know how many of each thing yet, but definitely 
some. In any of the BNC spots, I can easily put an isolating type BNC, 
or a volume control pot. The front panel is mostly blank, so there's 
lots of room for even more stuff there. I just have to be careful to not 
get carried away and make it too wonderful and complicated and never 
finished.


I also have an Efratom something-something distribution rack with five 
"MBF" modules that have four outputs each. They should pretty good too, 
but unfortunately it's all for 5 MHz only - there's low- or band-pass 
filtering built into each channel, so needs reverse engineering and mods 
for 10 MHz. I vaguely recall looking for info on this about a year ago, 
and stumbled upon an old time nuts thread. Someone (maybe Chuck Harris?) 
had reported successful mods for 10 MHz on these, but there were no 
links to any info about it. So Chuck, if you see this, and it was you, 
or anyone else, I'd sure appreciate this info. If it was just my 
imagination, then never mind.


Ed

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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Bob Bownes]

I have a few of the 2 in 5 out video distribution amps. I took one apart
and converted it to 50Ω from 75Ω, and to be honest, I can't really see a
difference.

Bob


On Fri, Oct 18, 2019 at 8:08 AM Charles Steinmetz 
wrote:

> Taka Kamiya wrote:
>
> > I am using Extron MDA 3V for distributing 10MHz at several places in my
> lab.  MDA3V is a one port in - 3 port out device made for VIDEO market and
> rather low end at that.  Input and output is 75 ohm and bandwidth extend to
> 150MHz or so.  Looking at 10MHz sine wave through it, it looks good.  No
> visible distortions.  Gain is unity between input and one of the ports.
> >
> > Couple of questions though.  This device is 75ohm.  It's easy to add
> 150ohm in parallel to a matching resister and make it 50ohm.  However, I'm
> guessing 50 ohm / 75 ohm mismatch is not really a big deal that I'm not
> doing anything about it.  Input and output cables are RG58 (50 ohm)  VSWR
> is 1.5, For external sync port, many equipment is not exactly spec'd for 50
> ohm, but often only spec'd for voltage or at db level without any specific
> impedance mentioned.  Recommended cable is 50 ohm though.  I typically shy
> away from consumer grade gear but looking inside, it's just an op-amp and
> registers.  If I use square wave which contains higher frequency
> components, would this be inadequate?
> > There are many web pages by people doing exactly what I'm doing with
> usually bigger Extron devices.  I'd like to consult the Time-Nut community
> of sanity in what I am doing.
>
> I published a doc with recommended mods to the opamp-based Extron video
> DAs for use as 1-10MHz clock/timing DAs:
>
> <
> http://www.ko4bb.com/getsimple/index.php?id=download=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf
> >
>
> Whether you make the changes or not, you may find some helpful
> information there.
>
> Best regards,
>
> Charles
>
>
>
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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Dana Whitlow]

Hello Taka,

As long as you stick to CW sinewaves *and* the distribution amp specs are
honest when they say "buffered out puts", the problem is fairly simple.  If
you're not seeing distortion under your operating load and signal
amplitudes,
it's OK and I'd not bother to change anything.

By "honest ..." I  mean that each output has its own independent output
amplifier.  However, this device looks to be fairly inexpensive and it's
possible that the mfr uses a single amplifier with a low output impedance
and distributes that through three 75-ohm resistors.  In this event there is
a possibility that with lower than 75-ohm loads, the amplifier's drive
current
capability might be exceeded, leading to distortion.

So, I'd suggest that you keep an eye on distortion levels on each output,
especially after making any system changes.  And, I'd take care to load
any unused outputs with a termination whose resistance equals the
impedance of the cable you're using for distribution.  If you fail to do
this,
and the *electrical* length of any *unterminated* cable is anywhere near
1/4 wavelength at 10 MHz, the impedance seen by the afflicted distro
amp output could be much lower than the intended 75 ohms, again
leading to risk of significant distortion.

I'd try to avoid distributing non-sinusoidal signals unless you're
careful to make sure that the cable impedance matches the output
impedance of the distro amp *and* the input impedance of whatever
your load is.  Otherwise the situation can get more complicated in
a hurry, with the prospect of both nonlinear distortion and edge
distortion due to reflections bouncing around in the cable.  But if
you must, the key is again to check the waveforms at the far ends
of the cables with the intended loads attached.  If the waveforms
look just like what you're expecting (with clean transitions at the
leading and falling edges), you should be OK.

One other issue with a poorly-buffered distro amp is that something
about a given output (like it's phase and/or amplitude) might change
depending on what loads are connected to the other outputs (and the
cable lengths involved).  If this is a concern to you, then you should
check for this effect to establish the viability of your system.

I hope this helps.  Sorry to say, nothing is ever really simple.

Dana



On Fri, Oct 18, 2019 at 3:17 AM Taka Kamiya via time-nuts <
time-nuts@lists.febo.com> wrote:

> I am using Extron MDA 3V for distributing 10MHz at several places in my
> lab.  MDA3V is a one port in - 3 port out device made for VIDEO market and
> rather low end at that.  Input and output is 75 ohm and bandwidth extend to
> 150MHz or so.  Looking at 10MHz sine wave through it, it looks good.  No
> visible distortions.  Gain is unity between input and one of the ports.
>
> I also have distribution Amps from Spectracom.  These, of course, are made
> for clock distribution purpose and I don't question usage for the purpose.
> The level of "accuracy" of distribution is that I need frequency stability,
> but time delay in coax, slight phase shift in coax, and other small nuances
> are not my concern.  (should they be?)  I'm not running a competitive
> service to NIST and this is not for commercial purpose.  I'm just a junior
> time nuts.
> Couple of questions though.  This device is 75ohm.  It's easy to add
> 150ohm in parallel to a matching resister and make it 50ohm.  However, I'm
> guessing 50 ohm / 75 ohm mismatch is not really a big deal that I'm not
> doing anything about it.  Input and output cables are RG58 (50 ohm)  VSWR
> is 1.5, For external sync port, many equipment is not exactly spec'd for 50
> ohm, but often only spec'd for voltage or at db level without any specific
> impedance mentioned.  Recommended cable is 50 ohm though.  I typically shy
> away from consumer grade gear but looking inside, it's just an op-amp and
> registers.  If I use square wave which contains higher frequency
> components, would this be inadequate?
> There are many web pages by people doing exactly what I'm doing with
> usually bigger Extron devices.  I'd like to consult the Time-Nut community
> of sanity in what I am doing.  Is this really not an issue, or "it's not
> simple as THAT" type situation?
> Thank you very much
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Clint Jay]

FWIW, I've been using an Extron video distribution amp for almost three
years now, bought with the intention of modifying it to 50R but never got
round  to it.

I've never been able to identify a practical reason  to change it because
it works perfectly for my needs though I'm sure others will tell me why I'm
wrong.

On Fri, 18 Oct 2019, 09:17 Taka Kamiya via time-nuts, <
time-nuts@lists.febo.com> wrote:

> I am using Extron MDA 3V for distributing 10MHz at several places in my
> lab.  MDA3V is a one port in - 3 port out device made for VIDEO market and
> rather low end at that.  Input and output is 75 ohm and bandwidth extend to
> 150MHz or so.  Looking at 10MHz sine wave through it, it looks good.  No
> visible distortions.  Gain is unity between input and one of the ports.
>
> I also have distribution Amps from Spectracom.  These, of course, are made
> for clock distribution purpose and I don't question usage for the purpose.
> The level of "accuracy" of distribution is that I need frequency stability,
> but time delay in coax, slight phase shift in coax, and other small nuances
> are not my concern.  (should they be?)  I'm not running a competitive
> service to NIST and this is not for commercial purpose.  I'm just a junior
> time nuts.
> Couple of questions though.  This device is 75ohm.  It's easy to add
> 150ohm in parallel to a matching resister and make it 50ohm.  However, I'm
> guessing 50 ohm / 75 ohm mismatch is not really a big deal that I'm not
> doing anything about it.  Input and output cables are RG58 (50 ohm)  VSWR
> is 1.5, For external sync port, many equipment is not exactly spec'd for 50
> ohm, but often only spec'd for voltage or at db level without any specific
> impedance mentioned.  Recommended cable is 50 ohm though.  I typically shy
> away from consumer grade gear but looking inside, it's just an op-amp and
> registers.  If I use square wave which contains higher frequency
> components, would this be inadequate?
> There are many web pages by people doing exactly what I'm doing with
> usually bigger Extron devices.  I'd like to consult the Time-Nut community
> of sanity in what I am doing.  Is this really not an issue, or "it's not
> simple as THAT" type situation?
> Thank you very much
> ---
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
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Re: [time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Charles Steinmetz]

Taka Kamiya wrote:


I am using Extron MDA 3V for distributing 10MHz at several places in my lab.  
MDA3V is a one port in - 3 port out device made for VIDEO market and rather low 
end at that.  Input and output is 75 ohm and bandwidth extend to 150MHz or so.  
Looking at 10MHz sine wave through it, it looks good.  No visible distortions.  
Gain is unity between input and one of the ports.

Couple of questions though.  This device is 75ohm.  It's easy to add 150ohm in 
parallel to a matching resister and make it 50ohm.  However, I'm guessing 50 
ohm / 75 ohm mismatch is not really a big deal that I'm not doing anything 
about it.  Input and output cables are RG58 (50 ohm)  VSWR is 1.5, For external 
sync port, many equipment is not exactly spec'd for 50 ohm, but often only 
spec'd for voltage or at db level without any specific impedance mentioned.  
Recommended cable is 50 ohm though.  I typically shy away from consumer grade 
gear but looking inside, it's just an op-amp and registers.  If I use square 
wave which contains higher frequency components, would this be inadequate?
There are many web pages by people doing exactly what I'm doing with usually 
bigger Extron devices.  I'd like to consult the Time-Nut community of sanity in 
what I am doing.


I published a doc with recommended mods to the opamp-based Extron video 
DAs for use as 1-10MHz clock/timing DAs:




Whether you make the changes or not, you may find some helpful 
information there.


Best regards,

Charles



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[time-nuts] Using commercial video amplifier for 10MHz clock distribution.

[Taka Kamiya via time-nuts]

I am using Extron MDA 3V for distributing 10MHz at several places in my lab.  
MDA3V is a one port in - 3 port out device made for VIDEO market and rather low 
end at that.  Input and output is 75 ohm and bandwidth extend to 150MHz or so.  
Looking at 10MHz sine wave through it, it looks good.  No visible distortions.  
Gain is unity between input and one of the ports.

I also have distribution Amps from Spectracom.  These, of course, are made for 
clock distribution purpose and I don't question usage for the purpose.  The 
level of "accuracy" of distribution is that I need frequency stability, but 
time delay in coax, slight phase shift in coax, and other small nuances are not 
my concern.  (should they be?)  I'm not running a competitive service to NIST 
and this is not for commercial purpose.  I'm just a junior time nuts.
Couple of questions though.  This device is 75ohm.  It's easy to add 150ohm in 
parallel to a matching resister and make it 50ohm.  However, I'm guessing 50 
ohm / 75 ohm mismatch is not really a big deal that I'm not doing anything 
about it.  Input and output cables are RG58 (50 ohm)  VSWR is 1.5, For external 
sync port, many equipment is not exactly spec'd for 50 ohm, but often only 
spec'd for voltage or at db level without any specific impedance mentioned.  
Recommended cable is 50 ohm though.  I typically shy away from consumer grade 
gear but looking inside, it's just an op-amp and registers.  If I use square 
wave which contains higher frequency components, would this be inadequate?
There are many web pages by people doing exactly what I'm doing with usually 
bigger Extron devices.  I'd like to consult the Time-Nut community of sanity in 
what I am doing.  Is this really not an issue, or "it's not simple as THAT" 
type situation?
Thank you very much
--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
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