[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 at 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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