[time-nuts] Distribution amplifier for 10MHz

[DM]

Yep, been there, done that! 
I used a modified Extron ADA 3-80, then replaced it with an ADA 6, both of which did have the CLC409 amps. Eventually, I replaced all with a real DA from Montronics (Fluke). Had to modify it for 10 MHz, since it maxed out at 5 MHz. Changing capacitors in tuned circuits fixed that problem, Using a Spectracom DA now, but I believe the old Montronics unit is a better DA. Might bring it back to life and see how they compare. 

Thanks for the trip down memory lane! 
Dave M 

----- Original Message -----

From: "Charles Steinmetz" <csteinmetz at yandex.com> 
To: time-nuts at lists.febo.com 
Sent: Saturday, March 16, 2019 10:57:49 PM 
Subject: Re: [time-nuts] Distribution amplifier for 10MHz 

Dave M wrote: 

> Excellent advice from Charles, especially concerning isolation criteria. 
> Should you be looking to distribute a standard 10 MHz frequency to various bench instruments, I'd recommend that you take a look at Extron video distribution amps. Several models on Ebay right now, at reasonable prices. 

One particular series of Extrons is the subject of the modification 
instructions in my second link. 

One caveat -- there are at least two "generations" of Extron video DAs. 
Some have discrete circuits, and some are built using high-speed, 
high-current opamps (the now-obsolete Comlinear CLC409). 

The discrete circuits are all unmitigated CRAP. Horrible video DAs, 
unworkable as 10MHz/+13dBm DAs without major efforts and headaches. 
Absolutely not recommended. 

So, if you intend to convert an Extron video DA for 50 ohm use, make 
sure it is one based on high-speed opamps. 

To make everything just that little bit more fun, *NOTE* that Extron 
used some model numbers for first-generation discrete products and 
*re-used* the same model numbers for later-generation opamp products. 
One product number I'm sure this is true of is "ADA 3 180." Another may 
be "ADA 3 80." 

I'm pretty sure that all of the models named on the cover page of my 
modification instructions are opamp-only. 

Best regards, 

Charles