[HCDX] WLS off

[Phil Bytheway <phil-bytheway@xxxxxxxxxxxxxx>]

Via NRC e-group

From: David Gleason [mailto:david@xxxxxxxxxxxxxxxx]
Sent: Saturday, April 28, 2001 2:11 PM

>From the short-wave newsgroup.....

WLS 890KHz will be working on their transmitter and tower from midnight
tonight
'til 5 A.M. Sunday, April 28.

MORE:

WLS-AM will be off the air from Midnight to 5 a.m. Sunday for required
transmitter and tower maintainance*. We're sorry for any inconvenience this
may cause anyone.

* For the techies among you, we are servicing the 480-volt transfer switch
that selects diesel or ComEd power source. One of the two switches is
mission-critical and impossible to service while the station is on the air.
During a recent routine infrared scan maintenance check we found one of the
contacts was heating. We need to examine the switch to preserve these
components and prevent an unexpected failure from occurring.

We will use this down time to perform several other one of a kind
inspections that can't be done when the station is in operation. We will be
inspecting and tightening all 480 v distribution switch gear that is never
de-energized.

Antenna Checks

Concurrent with the power distribution work we will be conducting main tower
impedance measurements to verify the base impedance of the main antenna.
This is an occasional compliance measurement to verify the antenna impedance
is as filed with the FCC. We will measure this by two methods; 1) Cold (no
power) impedance bridge using a low level signal. 2) in-line bridge using 5
kW signal level. 3) finally, we will use a nominal 2-watt level sweep signal
to check the antenna matching network to verify it is still as it was when
we last checked.

This data will be of value when we re-guy the main tower this fall. We
expect the tower impedance will change and we need to get a handle on the
before and after guy wire change. We will need to have data ready for filing
with the FCC to reestablish direct power measurement.

With some favorable weather (i.e. no lightning in the area) we can complete
all this in one shutdown period.
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