[time-nuts] Thunderbolt Distribution Amplifier Needed

Brucekareen at aol.com Brucekareen at aol.com
Tue Aug 21 12:52:11 EDT 2012


Chris,
 
I was able to mount my David Partridge divider board inside an Extron ADA 6 
 300MX television distribution amplifier along with a 1 MHz sine wave 
filter and  a 10 MHz to 100 MHz multiplier.
 
On the front panel is a selector switch for selecting the division  ratio, 
BNC jacks for this and the other board outputs, plus 1 MHz, 10 MHz,  and 100 
MHz sine wave output connectors.  These distribution  amplifiers have a 
very nice case with a blank front panel and are mostly empty  inside.
 
Everything inside is powered from the internal Extron power supply,  
although I had to add a 12/5-V switching convertor and Murata filter to obtain  
the 320 ma 5-V current needed for the divider board.  The internal power  
supply generates 12 VDC at about 25 VA.  a 7508 5V regulator provides +5  VDC to 
the DA board.  An LT1054CT switching convertor develops -12 V that  is 
passed through a 7905 regulator to provide -5 V to the DA.  The power  supply 
has vacant 12 V connection points that can be used for powering other  
devices. 
 
This Extron product is intended to provide six 75-ohm outputs each of RGB  
and sync.  I used the sync DA for 1 MHz square wave and the RGB DAs for 1,  
10, and 100 MHz sine wave outputs.  As I recall, the internal DAs frequency  
response extends to about 300 MHz.  I converted the 75-ohm outputs to  
50-ohms by changing the buildout resistors from 75 to 50 ohms.  These  
distribution amplifiers are available rather inexpensively on eBay as a result  of 
the demise of NTSC.  I think I paid about US$20. 
 
Bruce, KG6OJI


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