Joe,
All GainMaker system amps and LE's, the HGD in particular, require a return input pad for each of the forward output legs. If an internal splitter or DC is installed in a HGD, pads with the equivalent loss of the splitter or the DC legs should be installed.
Look at a schematic for the HGD. The return path does not pass through the internal DC [unlike the SAIII]. Therefore, a pad must be installed to duplicate the forward loss created by the DC.
This has nothing to do with the return amplifier operation. Like you said, the return amp is set up with the output pad and EQ to acheive unity gain. The return input pads are there to force modems and set tops to run at higher levels because of the lower tap values used on the forward path on those particular legs.
We just completed the design for 124 miles of plant for a customer. We designd the system to use return input pads and return conditioning in-line EQ's to optimize return path performance. Typically, the design software called for 0, 1, or 2 pads on all the amps. On the HGD amps, we found pad values between 10 and 14 were called for on legs with an internal DC12, 6-10 pads with a DC8, and 2-4 pads on the thru legs and splitters.
Test results back from the field indicate the cable modems are operating between 45db and 53 db regardelss of where they are placed in the system. When, for example, a 12 pad is replaced with a 0 pad, the modems respond accordingly. The 12db drop in output level puts the signal from the modem that much closer to the noise floor. Our customer reports the number of modem related problems for this area is considerably lower then other sections of the system.
Re: Gainmaker return input pads
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