[c-nsp] Line Code Violations on DS3 - Follow up

[Nick Voth]

> Nick Voth wrote:
>>>> Hello folks,
>>>> 
>>>> I need another set of eyes on this. We have a new channelized DS3
>>>> plugged in > to a Cisco 7206-VXR with a PA-MC-T3 card. We can't seem to
>>> get rid of
>>>> the Line Code Violations and P-bit Coding Violations. See what we've done
>>>> below this output...
>>> Try putting a 12 db attenuator on the transmit portion, then re-try your
>>> loopback. We've found that the PA-MC-T3 cards tend to overdrive the DS3 a
>>> bit, and the only way that we've been able to get rid of the errors is
>>> attenuating the transmit load.
>>> 
>>> Cisco makes a kit for this, but the part number escapes me now.. Try
>>> searching for DS3 Attenuator on google..
>>> 
>> 
>> Interesting, you're saying to put an attenuator on the transmit portion of
>> the card. Some of the Cisco documentation is saying to put it on the receive
>> portion. Is there any way using the "show controller" output to tell which
>> one has the "hot" signal?
> 
> The "cablelength" command can be used to reduce the transmit signal
> (shorter length reduces signal).  Too hot of a transmit level will
> result in far end errors, not near end errors.
> 
> In our experience, when attenuators are needed, it has been on the
> receive side of the card.
> 
> There are 75 ohm variable/stepped attenuators made for the cable
> television industry that can be useful to dial in the right value, then
> replace with a fixed pad of that value.  One example here:
> 
> http://www.kayattenuators.com/manual_step_attenuators.htm
> 
> These can occasionally be found at ham radio swapmeets and the like
> pretty cheap.  Make sure you get the 75-ohm version.
> 
> --
> Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
> Impulse Internet Service  -  http://www.impulse.net/
> Your local telephone and internet company - 805 884-6323 - WB6RDV

I just wanted to post a follow-up to the Line Code Violations we were
having. It was definitely the inbound signal from the DS3. We put a 10 db
attenuator in line and she's running clean!

If anyone needs a good source for them, we found the 75 ohm versions here:

   http://www.smelectronics.us/bnc,fattenuators.htm

They are a little pricey, but they have a lot of them in stock and got them
to me over night.

Thanks for everyone's help.

-Nick Voth