[time-nuts] Thunderbolt Distribution Amplifier Needed
Brucekareen at aol.com
Brucekareen at aol.com
Tue Aug 21 16:52:11 UTC 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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