Steve,
I think the post you were responding to is almost 2-years old. But after reading in more depth, the SA-I or "Suitecase" housing would be the seperate bridger. The LE modules could be either SA-I or SA-II. The SA-I LE had diplex filters that were almost the 2/3 size of a cigarette pack and were typically 450/550 modules. The SA-II LE had much smaller diplexers and were typically 550/750 units. Both had a "removable" -20dB diplex testpoint due to the forward output testpoint not being common in many versions and was used for return injection reasons.
Sweeping to match a "reference" number is only accurate when injecting a common output level at ALL "like" amplifiers that simulate the same RF input to the hybrid with the SAME injection point and level. That simply is apples and apples.
If an amplifier (i.e. LE vs AMP) has 4dB less insertion loss another amplifier, this must be compensated for by sweeping to the TELEMETRY level and confirming that proper injection level has been changed (i.e. LE = 44dBmV, AMP = 48dBmV) and match the telemetry level for accurate numbers.
There have been many operators who have matched REFERENCE level and not TELEMETRY level and have not compensated for such causing inconsistant RF drive level to the return input hybrid. Depending on your theory and plant design, this may be insignificant as to noise contribution but in todays world of noise and ingress, every little bit helps!
Re: SA II Return on Dual hybrids
Member #: 7190
Registered: 1996-2001
Posted:
483
Name:
Greg Tobin
Name:
Greg Tobin
Company:
Interactive Broadband Technical Services
Occupation:
HFC Engineer/Consultant
Location:
www.interactive-broadband.com
Personal:
Experience:
~45 years
There is 1 reply to this message
