[Asterisk-Users] Woodpeckers

[Rich Adamson]

> I live at 8000' in the Rockies.  We have lots of woodpeckers--they 
> especially love to drill 4" holes in the north side of my house.
> 
> They also like to drill on the arial telephone cables.  Water then gets 
> into the cable and causes a partial grounding on the circuits.  This 
> causes 60Hz hum to be heard on the line as well as a loss of amplitude. 
>   Qwest says tough s--t.

Fairly common problem, but you can put some pressure on them by escalating
to the public service commission.

> All three of my POTS lines have hum.  They are connected to an Adtran 
> 750 and my asterisk system (a testbench for commercial endeavors.)

The public service commission can suggest/force various work arounds at no
cost to you (regardless of what it might cost Qwest). Example, might 
suggest iax2 connection to a colocated * server within the qwest CO to
bypass the local plant problem.
 
> The hum has always been bad on my end.  Since I installed *, several of 
> my callers have remarked about the hum.

Having worked as an engineer for a different telco for many years and 
worked with various customers on the same type of problem, there are things
the telco can do to correct the problem and/or minimize it. However, one
individual complaining generally does not cause the telco to react unless
some other pressure is applied (eg, multiple customers, public service
commission).

The hum is actually caused by imbalance between the tip/ring and ground.
The tip/ring could truly have 50 volts of AC induced into it, and if the
tip/ring pair were balanced you would never hear it, period. Some tricks
to reduce the problem have involved installing devices that essentially
adds the equivalent resistive imbalance to one side or the other of the
tip/ring pair causing the exact imbalance on both tip & ring. When the
correct values are found (and years ago it was simply a twist of knobs
on the passive devices), the problem is essentially equalized and the hum 
disappears (even though there could still be 50 volts of AC induced on 
the pair).

Other work arounds have included the use of subscriber carrier systems, 
etc.
 
> So here's the question:  Could a notch filter of sorts be installed in 
> the codecs I use?  Filter-out everything between, say, 55 and 65Hz?

Nope, will never work. There are more harmonics and other non-60hz signals
on the wire that almost makes it impossible to filter.
 
> Alternatively, is there a feature on the Adtran FXO card that deals with 
> this?

No, what you're suggesting is finding a problem-bypass and not solving the
root-cause. Wouldn't even attempt to go there as you'll be constantly
having to dick around with the bypass.

It is amazing what happens when pressure is applied at certain points. Write
the public service commission and copy senior customer service mgmt and
see what happens. Be accurate and detailed, leaving out all adjectives and
adverbs.

Rich