You should use a Quasi-Square wave for the BEST regulation of the DC power supplies that were manufactured into your CATV stations as this is what the industry designers have based their calculations on.
However, if you use BOTH SINE and/or SQUARE wave but be aware that the overall DC regulation will not be consistent with the manufacturers specifications and the possibility of current consumption and rapid failure of the DC power supply is a concern. HUM is a distortion that will be added over cascades and may not be properly be filtered out of a circuit designed to work with a rectification of a Quasi-Square design.
If you have a short (AC) on the main line your AC Sine Wave transformer will not react as a Quasi-Square or Ferro-resonant transformer would. The Ferro is designed to "open up" and not "burn up" in a short circumstance. A Sine wave or "non-ferro" would burn up and cause many related problems.
I worked in a cable system in Santiago, CHILE back in 1995 and the manager (at the time) built the entire system using standard 220VAC to 60VAC sine-wave "non-ferro" transformers using the old 550MHz Lindsay Feed-Forward amplifiers cascaded 29-deep!!!!! He had HUM problems deep in the cascade and other issues. The only reason he did not have a severe "beat" problem was because he was only using like 11-channels...even though it had nothing to do with powering.
The main reason we use a QUASI-SQUARE in CATV is for the following reasons:
1. You can not short the ferro-resonant transformer (normally)
2. Better/Best DC regulation for our power supplier that work hand-in-hand with AGC/ASC/BODE circuits.
3. Even though a 100% loaded ferro power supply is ONLY 60% efficient, it has a longer life span than a standard transformer.
FYI - If you want to get the MAXIMUM life from your CATV FERRO SUPPLY and pay MINIMUM costs to the power company monthly, you should have them 100% (or close to) full power. Example is if you have a 12A supply, load it to 12 or 11.5A. If you have a 12A supply and only draw 5A it is under-rated and less efficient, probebly 35% overall...this will cause the 12A supply to cost MORE monthly in electricity costs and over time burn-up the ferro-resonant transformer. I would replace the 12A with a 6A supply for above stated reasons.
I hope that this has helped!
Greg Tobin
Interactive Broadband Technical Services, LLC
314-422-4423 cellular
Re: Power supplies and outputs
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 are 2 replies to this message
