A TECHNICAL OVERVIEW OF
JOINT TRANSMITTING FACILITIES
FOR DIRECTIONAL AND NON-DIRECTIONAL OPERATIONS
FOR AM STATIONS

MARCH 2002

The following documents were graciously provided to NPR and its member stations by consulting broadcast engineer Donald G. Everist P.E. to illustrate some "real-world" examples of diplexed AM antenna systems. They may not be reproduced or redistributed without their author's written permission. Mr. Everist can be contacted at:

Cohen, Dippel and Everist, P.C.
Suite 1100 1300 L Street N.W. Washington, DC 20005
202.898.0111 (voice)
202.898.0895 (fax)
cde@attglobal.net

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The following information is to provide insight about a joint operation by technical
facilities of two different AM broadcast stations. There are many considerations that govern the
feasibility of a station being considered to operate from an existing transmitting site of an AM
broadcast station. Shown below are some of the initial planning factors.

1. First and foremost is compliance with the coverage and interference criteria for
daytime and nighttime set forth in Part 73 of the FCC Rules. Obviously any move
by a proposed facility to a site of an existing broadcast station requires FCC
approval in the form of a construction permit.

2. Other considerations include whether or not the site's ground system and tower
height are adequate for operation of the proposed facility.

3. Of further consideration, does the ground conductivity from the existing site
possess the necessary characteristics to achieve the coverage that is desired?

4. Is the facility in an area where reliable power is available?

5. Are the tower and guy insulators sufficient to handle the additional considerations
imposed by the new facility?

Attached hereto are two facilities that have been combined and used the site of an existing
operation. The first is a facility in Boise, Idaho. This is a directional facility for daytime and
nighttime operations.

The second represents an operation from an existing daytime non-directional operation by
a full-time non-directional facility.

DIRECTIONAL DAYTIME AND NIGHTTIME
The following examples are provided:

The first is the KBSU, Boise, Idaho, day and night directional operation to change site to
the KIDO site. This required specifying the current KIDO three-tower antenna placement and
tower heights for the proposed KBSU directional operations. It was determined that the site was
located to achieve the desired coverage and interference conditions. An application was prepared
and submitted to the FCC.

Abstracted from the report entitled, "Engineering Report Re Application to Change Site
and Increase Day Power, KBSU, Boise, Idaho, 730 KHz, 0.5/15 kW, DA-2 U, October 1992",
are the following:

! Coverage contours of the proposed KBSU daytime facility specifying the KIDO
transmitter site.

! Coverage contours of the proposed KBSU nighttime facility specifying the KIDO
transmitter site.

! Specifications for the proposed KBSU daytime facility from the KIDO transmitter
site.

! Specifications for the proposed KBSU nighttime facility from the KIDO
transmitter site.

! Property plat of the existing KIDO facility from which KBSU proposed to operate.

After receiving a FCC construction permit, phasor, matching antenna networks, and
pass-reject filters for the RF feed system were designed. After the installation of all equipment,
the antenna systems were adjusted so that minimum disruption to the KIDO operation would
result. A proof-of-performance on the KBSU facilities was performed in accordance with the old
FCC rules¹. A diagram of the R-F system is included. Also a partial proof-of-performance was
performed (in accordance with the old rules²) on the KIDO facility to demonstrate that it was
operating within its instrument of authorization.

From the engineering statement entitled, "Engineering Statement Re Directional Antenna
Proof-of-Performance, Radio Station KBSU, Boise, Idaho, Construction Permit BMP-
921112AA, 730 KHz, 0.5/15 kW, DA-2 U, January 1995", the following exhibits have been
abstracted:

! Specifications for the KBSU directional antenna system.

! The non-directional proof radiation pattern.

! The daytime directional proof radiation pattern.

! The nighttime directional proof radiation pattern.

! The common point impedance of the daytime directional facility.

! The common point impedance of the nighttime directional facility.

! The diagram of the KBSU RF feed system with pass-reject filters.

From the engineering statement entitled, "Engineering Report Re Directional Antenna
Partial Proof-of-Performance, Radio Station KIDO, Boise, Idaho, 630 KHz, 5 kW, DA-2 U,
August 1985", the following exhibits have been abstracted:

! Tabulation of the partial proof-of-performance data performed along the KIDO
proof-of-performance measurement radials.

! Tabulation of the partial proof-of-performance data performed along the KIDO
proof-of-performance measurement radials.

NON-DIRECTIONAL
For KQDS(AM), Duluth, Minnesota, a transmitter site change was desired. Application
for a construction permit was prepared to specify the KXTP(AM) non-directional transmitter site.
From the engineering statement entitled, "Engineering Report Re Application for
Construction Permit to Change Antenna Site, KQDS, Duluth, Minnesota, 1490 KHz, 1 kW,
ND-U, December 2000", the present and proposed daytime and nighttime contours are provided.
Attached are various exhibits for the proposed KQDS facility operating from KXTP(AM)
site.
For the license application exhibits for each station are provided referencing the RF system
which isolate each transmitter operating into a common tower and ground system.
From the engineering statement entitled, "Engineering Statement Re Application for
Direct Measurement of Power, KXTP(AM), Superior, Wisconsin, 970 KHz, 1 kW (day),
0.026 kW (night), ND1, January 2002", the following information has been abstracted:

! Phasor diagram with pass-reject filters and occupied band width measurements.

! Also, a lease agreement with specific details will need to be filed.

SUMMARY
Collocation of facilities directional and non-directional can be cost effective in
establishing, upgrading, or maintaining an AM facility.

¹ The new rules requires fewer radials and measurements.
² Ibid.

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