[time-nuts] Distribution Amp for Thunderbolt and David Partridge's Divider Box

Brucekareen at aol.com Brucekareen at aol.com
Wed May 22 11:54:17 EDT 2013

A year or so ago I modified an Extron  ADA 6 300MX TV  distribution 
amplifier to house one of David Partridge's divider boards  along with a 1 MHz 
sine-wave filter and a 10 MHz to 100 MHz multiplier after  Luciano 
Paramithiotti's design.  I use the rear BNC connectors to  distribute 1, 10, & 100 MHz 
sine-waves.  The synch channel was modified  to distribute 1 MHz square-waves.
On the front panel are BNC connectors for 1, 10, & 100 MHz sine-waves;  1 
MHz & 5 MHz square-waves; and an output with rotary-switch-selected  1, 10, 
100, 1 kHz, 10 kHz, or 100 kHz square-wave from the Partridge divider  board. 
My ADA 6 300MX unit had conventional resistors on the board so it was  
relatively easy to change them to 50-ohms.  I eliminated the 0.7/1.0 V  switch.  
I found it possible to power the Partridge divider board and 10 to  100 MHz 
multiplier module as well as the distribution amplifier from the  internal 
Extron power supply by adding a 12 V to 5 V inverter module  (bought on 
eBay) and a Murata RFI filter. 
As modified, there is a single 10 MHz input to the assembly, and 5@ 1 MHz,  
3@ 10 MHz, and 5@ 100 MHz outputs on the rear panel.  There are also 5@ 1  
MHz square-wave outputs from the former sync section.  Connectors  
corresponding to the DA outputs used internally were removed and the holes  fitted 
with plastic plugs of the correct size.  
To get everything to fit, I had to shift the power supply on the lid.   
While the Extron cases are of very fine mechanical construction, the front and  
rear panels are not well bonded electrically.  I added bonding braids to  
improve the shielding and RF performance.  A nice feature of these units is  
that the front and rear panels can be easily removed for engraving.
I briefly considered trying to add miniature isolation transformers behind  
the connectors, but dropped the idea in view of the relatively marginal  
isolation between outputs, and because the amplifiers seemed to work well for 
my  workbench application.
My apology for this late comment, but I was out of town during the earlier  
Bruce, KG6OJI

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