You are right about balancing (or MATCHING) the AGC pilot frequency carrier level ONLY AFTER the proper MANUAL alignment has been established. The "reference" carrier is the AGC pilot carrier that is notated on the AGC module. The "pilot" frequency is what the AGC is tracking to and the bode circuit is aligned to NOT the highest operating frequency. IF the highest operating frequency IS the AGC pilot, THEN the technician would have been correct in his statement.
When balancing the forward in MANUAL, you should balance with pad and equalizer (preferably) to the highest band edge carrier if available (after Manual Back-off from pilot frequency). THEN match the AGC pilot carrier level (after calculating the proper AGC pad). If you balance to "IN BAND" carrier(s) while in MANUAL, this could very possibly cause the AGC (when engaged) not to operate properly as the pilot frequency very often is in the response "hump" (in a non-swept system) and causes the AGC pilot to be out of the "capture range". If you balance to band edges while in AGC, a very similar issue can occur depending on how flat the system is. This can happen with ANY manufacturers equipment.
Issues of "humps", "valleys" and "roll-off" can be observed if the system is not properly swept. The flatness of the spectrum is directly proportional to how well your AGC will perform and how it was aligned.
In any event, it can be confusing if not fully explained as this has been an argument for YEARS among many system technicians.
I used to work for Scientific-Atlanta if that helps with your answer source.
Greg Tobin
(314) 422-4423 cellular
Re: manual backoff setup on SA high gain dual
Member #: 7190
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Name:
Greg Tobin
Name:
Greg Tobin
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Interactive Broadband Technical Services
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HFC Engineer/Consultant
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