Heya Psyko,
Typically, the transmit level for a modem is determined by several factors.
The first thing to know is what level is needed at the node's ouptut ports to acheive the 0 dBmV at the CMTS, typically about 14-18 dBmV. This can go higher or lower depending on how the return is "optimized".
In an aligned return plant, the levels expected at all actives' output ports will be close to the same (14-18dBmV).
Now, add the losses of the tap(s), mainline cable,splits/couplers, drop cable. filters, splitters, and anything else between the amp and the modem's location.
So, say your conneted to a 23 value tap at the amp's output.
If you need 18 dBmV there, add 23 dB for the tap (41dBmV), 1 dB for 100' of drop cable (42dBmV), 3.5dB for a 2-way split (45.5dBmV). So a modem running thru this scenario would run at about 46dBmV.
A lower tap value like a 11/4way, 600' from the amp, would ask a modem to transmit lower, due to less losses from the tap to the amp port.
Hope this helps a little, our modems transmit 35-55dBmV, averaging at 42-45dBmV.
Re: Modem Output
Member #: 19319
Registered: 1996-2001
Posted:
143
Name:
Lorne
Company:
major MSO (3rd namechange in 5 years)
Occupation:
Lead System Tech
Location:
Virginia
Personal:
early 60s
Experience:
~32 years
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