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

Sat Oct 19 21:52:02 UTC 2019

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, timeok at timeok.it <timeok at 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

  timeok at timeok.it

  Da "time-nuts" time-nuts-bounces at lists.febo.com
  A "Discussion of precise time and frequency measurement" time-nuts at 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&file=02_GPS_Timing/Extron_ADA_6_modifications_for_use_as_10MHz_distribution_amp_STEINMETZ.pdf>

  -=Bryan=-

  ________________________________
  From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of ed breya <eb at telight.com>
  Sent: October 18, 2019 1:39 PM
  To: time-nuts at lists.febo.com <time-nuts at 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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