For a basic "rule of thumb", the NOISE FIGURE is the MINIMUM of RF at the input to the hybrid at specified frequencies. This is a MINIMUM input to achieve MINIMUM carrier-to-noise for that specific amplifier under those input conditions. To IMPROVE your carrier-to-noise characteristics at that (or any amplifier) by 1dB, you will need to increase the input drive level by 1db and so on.
Carrier-to-noise is effected by INPUT level, composite-second-order, composite-triple-beat and cross-modulation is effected by OUTPUT levels. One may ask: "If I increase my input, my output will increase also. So how do I increase my input carrier-to-noise without increasing my output and distortions?" Answer: "Utilize the INTERSTAGE pad to decrease the output gain of the unit, thus reducing the output level that control output distortions.
If a driver amplifier does not have a location for a interstage pad (most do though) there should be a wide range of inputs acceptable for a "balance" of distortions between input (C/N) and output (CSO/CTB/XM).
Re: Need help with Headend Amp Input drive level
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
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