[time-nuts] Distribution Amp project

[Robert Atkinson]

Hi Dave,
What Ethernet transformers are you looking for, UTP or Coax? I'd guess coax for the distribution amp. These are best scavenged from old Thin Ethernet cards. Look for cards with a BNC connector. Best place is either a electronics surplus place, computer repair shop or shop that sells used computers. Just ask for old network cards. Computer/radio flea markets are another possible source. Thin Ethernet cards also have an isolated DC-DC converter on them (either module or discrete components) with 9V out for 5 or 12V in. Lots of uses, RS232 or op-amp supplies, isolating digital panel meters in PSUs, boosting 12V supplies prior to a constant current regulator to charge 12V batteries from 12V supplies.

Robert G8RPI. 

--- On Thu, 30/7/09, Dave M <masondg44 at comcast.net> wrote:

> From: Dave M <masondg44 at comcast.net>
> Subject: [time-nuts] Distribution Amp project
> To: "TimeNuts" <time-nuts at febo.com>
> Date: Thursday, 30 July, 2009, 5:16 AM
> While investigating recent threads on
> Distribution Amps, I ran across a DA 
> project on Didier's web site at 
> http://www.ko4bb.com/Timing/Distribution_Amp/ and 
> http://www.ko4bb.com/ham_radio/Extron_3_80/. 
> Those pages describe using an 
> Extron ADA 3 80 analog video distribution amp to distribute
> a 10 MHz 
> frequency reference to lab instruments.  It seems to
> be a cheap, easy way to 
> get a set of reference frequencies throughout a small
> lab.  I would be 
> interested to hear about any further testing and
> characterization was done 
> with that setup, such as noise, distortion, etc.
> 
> I have a couple of the Extron DAs to play with, and would
> like to use them 
> if they will do the job.  I'm only looking for
> frequency distribution; not 
> timing.   Frequencies of interest are:
> 10MHz, 5MHz and 1MHz.
> I haven't been able to find schematics for the Extron DA,
> but according to 
> the author's discussion, it seems to be very similar to the
> DA circuit 
> schematics at http://www.ko4bb.com/~bruce/IsolationAmplifiers.html. 
> I 
> haven't had time to reverse engineer the circuit in my
> Extron DA, but it 
> surely would be nice to avoid it if possible.  Anyone
> have a schematic, or a 
> source for it?
> 
> Also, looking for a source of low cost 1:1 and 2:1 Ethernet
> transformers. 
> I've tried the local computer shops, but they don't seem to
> be interested in 
> helping.
> 
> Dave M
> 
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