The Second International Hearing Loop Conference started out as a troubled convention as far back as last June, culminating when the HLAA convention planning staff the conference site booking by not anticipating demand (after HLAA vigorously marketed the conference for six months), with many people being turned away; and many more not even coming, because it was “sold out” two weeks beforehand — This is the first time in history a convention has actually sold out! I spoke to AAA President Pat Kricos — Whom I actually felt sorry for — on Saturday about the sellout, as, having entrusted the booking to HLAA, AAA Members who depend on these classes for CEU’s were also left out in the cold.
Then, having strongly cautioned
HLAAs’ senior staff last year in Milwaukee to perform a site survey for electromagnetic interference (EMI, noise) at the venue, and to make sure every room that had loops was working properly, we walk into the HLAA Awards breakfast, switch on our T-coil receivers… Only to clearly hear the of the loop conference next door. As it turns out, loop equipment vendor Ampetronic
installed the loops but didn’t bother to check it for spillover into the main ballroom (and vice versa). Worse, this rained on the Hall of Fame Award being given to my friend Joseph Gordon, for his many decades of his effective advocacy.
Now, as an Electrical Engineer and long time hearing aid dispensing engineer, I have written extensively about my opposition to baseband induction “hearing” loop use on purely technical grounds, as it is a very troublesome “hack” that should have never been, especially for large rooms: And what happened this morning only proves the point: Even loop provider Ampetronic botched the job. Worse however, someone in authority ordered that the wonderful infra-red system donated by Williams Sound be shut down, because this “is now a Loop Conference” — Nice going.
Next, the workshop on “Understanding and Addressing Causes of Environmental Interference with Telecoils” was misleading at best, because presenter Richard McKinley of Contacta
— who himself is (fortunately) not hearing impaired — played down, and even skipped over the very real causes of EMI in the United States; and why there is less EMI in the UK & Europe than in the US. Please see section 2 of Poynting the Wrong Way: Why “hearing loops” are almost useless
for the reasons why, including that electric utilities run their distribution transformers at 110% of Φ(sat), which causes harmonics to be generated from the 60 Hz sinusoid being convolved with the B-H hysterisis curve (transfer function).,
However, McKinley made a significant error on his analysis of high voltage (115kV & up) power distribution & transmission line interference, when he stated that it is only a problem within 3-5 times the phase conductor spacing: This is demonstrably false, both from my own experiences, and also that he failed to take into account that in fact when there is negative sequence
current from a phase current unbalance on a wye power system, zero sequence currents will flow through the ground conduction path. For the tower system used for 115kV & up, the ground wires you see above the phase conductors are much thinner than the phase conductor bundles themselves, as they are there only for voltage balance and shielding against lightning: 90% of the zero sequence current is actually carried through the earth, through a buried conductor, and through the shielding of the buried relay wiring.
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