[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 <paulswedb at gmail.com> 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 _ <bpl521 at outlook.com> 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&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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