[c-nsp] Signal too "hot" for PA-A3-T3

[Jay Hennigan]

Rick Kunkel wrote:

> In the interface config, there's the IOS command "atm lbo short" that is
> the default, AFAIK.  Yup... just tried it...  That's for anything under
> 225 feet.

The LBO and cable-length commands affect the level of signal leaving 
your transmitter.  The range of level tolerable by your receiver is a 
factor of the circuit design and not configurable.

Of note, we just went through a similar issue with PA-MC-T3 cards fed on 
a short loop from a mux with Westell NIUs.  We found that there were 
consistent errors of around 100 LCV and PCV per 15 minutes.  A step 
attenuator on the receive side of the Cisco showed a narrow range of 
from 5dB to 9 dB where the errors diminished to near-zero but never 
completely disappeared.  We connected to the Westell NIU with a serial 
cable and turned off regeneration NET -> CPE.  That solved the problem, 
and I can now go from no attenuation to over 20 dB with zero errors.  I 
think that the Westell NIU is distorting the signal on the short loop 
that it has from the mux (in the same rack).

Note that the wording on LBO in the Westell config is counter-intuitive. 
  If you "enable LBO" this makes the signal hotter (more powerful). 
Disabling LBO reduces the signal level.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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