[BC] Comcast, PBX, and DSL filters

[jon]

One of my clients decided to ditch their POTS lines from the local telco,
and go with the Comcast telephone product. Basically, it has POTS lines
output that we connect to the PBX and Telos.

Keep in mind this is at a 10Kw AM, with the tower about 100 feet or so
from the studio building.

I knew RF was going to be a problem when one of the Comcast techs burned
himself on the *ground* of the RG-6 when he was stripping it to put a
connector on. At that point, I told him to stop, and grabbed my 'scope to
see how hot it was. This was before they installed the grounding block.

Oh, and I saw a spark when the poor tech grabbed the line.

My trusting 'scope showed 300+ volts of RF on the shield of the line.

I suggested to the techs that they want to use gloves, and ground the line
ASAP. After grounding, I measured virtually no RF on the cable.

They hook up the router and telephone doodad, tested, and all was
ok....until....

We were going to wait to hook up the comcast box until the numbers had
ported over. We were told that would take 15 days. We'll, it took 3 hours.

So, I was on the phone with the poor IT guy. Fortuntately, I had showed
him how to do punches earlier in the day. He punched it over, but only
could make the PBX *OR* the Telos work. Not both at the same time. That
had me stumped for awhile.

When both were connected, it would show off-hook (even when on).

I had a bright idea: I sent him down to the local radio shack to buy four
DSL filters (one for each line). I had him install them right at the
comcast box. Problem solved!

DSL filters are great filters from 3kHz all the way into the HF spectrum.


Jon