Just think of a square box from: 5 to 40 MHz at the input of all amplifier and NODE. on the system. The level of this square box should be + 15 to + 20 dBmV, I like + 15 dBmV which is closer to the real life. Remember this box is from 5 to 40 MHz, and is actually situated at the right of the amplifier and NODE, looking at them from the front. You must add the test point loss, which I belive to be 20 dB test point on these amp. Then the level at the output (return) should be + 35 dBmV if you selected + 15 dBmV level. If you have a 30 dB multitap at the output of the amp. or NODE, then the output of a cablemodem connected to this multitap should have for operating level. 15 + 30 (loss multitap) + 1.37 dB (loss of 100 feet of RG-6 @ 40 MHz) + eitheir (loss of 2 way splitter or 6 dB coupler), = (15+30+1.37+4.5 (splitter) = 50.87 dBmV out of the cablemodem. DOCSIS cablemodem are capable of + 58.0 dBmV in QPSK and + 55.0 dBmV in 16 QAM. With these level you should have a good wwindow in case of INGRESS or return NOISE. Hope this help.
Re: input return levels for Jerrold sx550 & jlx550
Member #: 3359
Registered: 1996-2001
Posted:
1285
Name:
Andy Lamarre
Name:
Andy Lamarre
Company:
Catv Expert
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Dir.
Location:
Montreal, Quebec, Canada
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Ancient
Experience:
~66 years
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