Re: [telecom] ANI vs. Caller ID [Telecom]

Not only software. Hardware has to be extensively tested in the real world. I worked for Bell Labs developing transmission systems (microwave radio, coaxial carrier, etc.) from 1959 to 1990. Every time a new system went into initial factory production, a route was built somewhere in the country, and Bell labs had several months to thouroughly test it and monitor it. Things happen in the real world that you never can duplicate in the lab.

Since you've had a lot of experience testing microwave equipment in the field, I'd appreciate your help to debunk some _very_ tall tales. I have heard hundreds of apocryplal stories about microwave failures due to utterly unbelievable causes. The list includes:

1. Melted coax due to concentrated solar energy, one one particular day of the year.
2. Route switch looping, which turned out to be caused by cockroaches running up and down inside waveguide, searching for the warmest spot.
3. Repeated failures at a hosptial STL link used for remote broadcasts, supposedly tracedto frequency detuning caused by the MRI affecting the magnetron in the STL.

Please tell us why these are nonsense, and supply a list of the most exceptional failures you saw during field testing, and the root cause(s) of each. TIA.

Bill Horne Temporary Moderator

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I can tell you one that isn't "nonsense". Back in the 1980's a lot of Telstra microwave links were continually interfered with by flocks of cockatoos (large birds common in rural areas around Australia). This issue was highlighted in internal and industry technical publications at the time.

IIRC they took a liking to the particular plastic covers over the dishes, and took delight in attacking them with their beaks at every opportunity. I think the eventual solution was to change the type of plastic to something less attractive to them.

In article ,

This is unlikely, but _plausible_. I've seen stranger things in other fields of engineering.

This sounds *entirely* believable.

The energy-density off of a big transmitter' directional antenna, is

And, of course, the energy density immediately off the end of the feed horn, towards the antenna, makes the density reflected off the parabolic [antenna] look **positively** anemic. :)

Well, I guess it's _technically_ possible to have a Gooney bird killed by a long-range radar transmitter, but it always sounded like the kind of story that NCO's tell new recruits: I mean, why _would_ a Gooney bird alight on a feed arm which is spinning, you know?

Bill Horne Temporary Moderator

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Ah, that would help explain why a friend gets very good wireless access from somewhere in his village during winter and not in summer. I knew that leaves and such were a problem in summer. But I always wondered how much the branches and twigs in winter would attenuate the signal. Especially if you had a dense hedge.

Tony

I could see this happening. Every kid has taken a magnifying glass and burned holes through leaves, twigs, or paper by concentrating the sun's rays onto a spot. This is very easy to do. Sometimes the paper or leaf will burst into the flame.

It's certainly possible that an minor abberation in a window glass or piece of plastic (which are very common) served as a magnifier and when the sun hit at a certain angle it was enough to burn. Now, it probably would not be strong enough to cut entirely through a cable, but strong enough to sear the insulation so as to interfere with transmission qualities.

The 'classical' answer to that kind of question is "it seemed like a good idea at the time.

More seriously, i suspect that 'casualties' were found on the ground, or the support structure -- with an -assumption- made that they' tried to land on the feed arm, when, in fact, they'd just flown through the path of the beam and been cooked 'in flight'.

Not outside the realm of possibility is that the bird flew through the path of the beam, and became somewhat disoriented, looked for an _immediate_ place to perch, and grabbed the first reasonable possibility that rotated into view.

Which, BTW, is why "defrost" in a microwave oven is so slow. The ice absorbs zip; so the oven cooks a second, warming the food surface, pausing to let the adjacent water melt.

Then another second of power, heating that water so it melts more water, and so forth...