H.C.,
I have not worked with that exact model but the response looks familiar. These are some things that I would check:
1. IF you have confirmed that the problem is IS NOT the node output(s) and you suspect the amplifier try this. NORMALIZE to the INPUT of the HGD. Look at the amplifier output with TILT COMP and see if the problem is there. If you do not have enough level at the input testpoint to trigger the sweep try a tap prior or remove module and REFERENCE from input with a barrel for a reflection-free trace. This will confirm if the amplifier module is causing this.
2. CONFIRM that you have S-A equalizers (if using SA) or C-COR EQ's (if using C-COR)....NOT a cheaper re-manufactured replacement equalizer. There are so many clones for so many amplifiers there are differences from version to version and amp to amp. What your trace looks like is an EQ that was PEAKED at 55MHz to make up for a DIPLEXER roll-off from a different amplifier version...THIS IS JUST AN EDUCATED GUESS NOT A VALID STATEMENT. I have worked with many amplifiers that need SPECIFIC EQ's both INPUT and INTERSTAGE and through testing you can determine if your EQ's are the issue. To confirm also use a "strip-line jumper" with NO EQ and this should also provide good data.
3. In the SA-II HGD's SA had a sheet with CORRECT AGC module numbers to be used with a specific HGD or UBT units. If the wrong AGC was used, a response problem was seen and also grounding issues were noted. Metal covers and plastic covers all needed specific units, but without a sweep, you would not know a problem existed in many instances.
4. Confirm that you have a GOOD 75-ohm termination and GOOD sweep references as well. Reflections could also cause this.
I am not clear on what the exact amplifier module you have and am not familiar with the internal components...but the SA 750MHz HGD had the same possibilities mentioned above and it was not consistent with so many versions that were made. There are so many possibilities and I hope that I have gave you a few ideas.
Good luck!
Greg Tobin
314-422-4423 cellular
Interactive Broadband Technical Services, LLC
Re: Sweep Responce 870 HGD
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
