[SBE] Video DA Help

[Glenn Little WB4UIV]

Not a trick question.

Prior to me, when an STM-85N card failed, the sync for that equipment was 
picked from something close via a loop through.

We now have marginal sync in Master Control. I have bought another eight 
Video DAs and a frame (EBay is good). I have ordered 1000 feet of cable. 
When the cable arrives, All the equipment in Master Control will have a 
sync line run directly to a DA port.

I guess the STM-85N cards are a hold over from earlier equipment. They 
appear to be a mini frame sync.

When I asked this question of GVG, they would not answer directly. They 
acknowledged that loop through equipment was fine, with the end of line 
terminated. But they could not tell me what the maximum recommended 
equipments was.

To be safe, I have invested in the DAs and cable. Now to find the time to 
run the cable and document the cable runs!

At least we do have a set of drawings. They have been partially updated 
with additions and deletions. Another project that I do not have time for, 
verifying the drawings!

We have 16 STN-85N cards that only the CB outputs are being used from. I 
hope to get all of these out of the rack and replace them with 8500 series 
DA cards. We have had two of these fail recently and I find others that 
have problems. Most of the ones with problems have the far end of the cable 
disconnected from the equipment and the cable terminated.

The fun of working in an older plant.

Thanks
73
Glenn



At 10:21 PM 11/27/07, you wrote:

>is this a trick question?

>

>the "proper" the answer is one - with a 75 ohm termination

>

>- there is no real limitation (within a facility) to how many devices you 

>can daisy chain as long as each is a non terminating loop through as long 

>as the final device has the 75 ohm termination

>

>prudent engineering design dictates that you limit the number of devices 

>in such a daisy chain as removal of any device in the chain will affect 

>all of the devices until properly terminated again (think service 

>interrupting and how the GM feels about make goods)

>

>At 21:48 27-11-07 -0500, you wrote:

>>We are using GVG 8500 series Video DAs to distribute sync. How many 

>>devices can I safely deliver sync to from one port of a video DA?

>>

>>Thank You

>>

>>Glenn Little

>>Assistant Chief Engineer

>>WCIV TV/DT

>>WB4UIV

>>

>>

>>

>>

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