[BC] Re: TIS facilities

[Patrick Griffith, N0NNK / WPE9HVW]

I have visited close to two hundred TIS transmitter sites. About 95% of
them use a center loaded "whip" style antenna very similar to the old 2
MHz marine antennas. The maximum allowed height is 15 meters (49.2 feet)
unless they have a waiver. The majority of them are mounted on a
telephone pole and use only a single ground rod for the ground system.
At least one TIS manufacturer that I am familiar with produces a radial
kit consisting of about 20 short wire radials. However this kit is
generally only used for non-metallic rooftop installations. Very few TIS
installations incorporate a real ground radial system. These guys aren't
really interested in range. Most of these stations are designed to
provide line-of-site coverage.

I visited the D/FW Airport site when 1640 and 1680 were both active.
Each of the two frequencies had its own 60 foot Valcom antenna. The
license called for 60 watts but I was never able to determine if that
was transmitter power or ERP. One of the operators of these stations
told me that they received hundreds of reception reports from every
corner of the planet. They even went so far as to print up a batch of
QSL cards for these stations.

The FCC database for TIS stations does provide seperate fields for power
ouput and ERP. Here in Denver, for example, WPLX284 on 530 kHz is listed
as 10 watts power output and 40 watts ERP. It uses a top loaded 60 foot
Valcom antenna to achieve the ERP. WPDI548 on 540 kHz at Denver
International Airport uses an identical system. But their FCC info only
says 10 watts power output. The ERP field is blank.

BTW the FCC database for WPMP254 at the Nashville airport says it is 10
watts power and 10 watts ERP with a basic antenna. 

Patrick Griffith, N0NNK
CBT CBNT CRO
Westminster CO
http://community.webtv.net/N0NNK/
http://community.webtv.net/AM-DXer/