1. Trunking Radio Compatibility Issues
by
John Raymond Steffes
Manager, Voice Systems
January 2004
Kennedy Space Center
Florida, 32899

2. Trunking Radio Compatibility Issues
1
Introduction
The need for equipment using radio communications ranges from megawatt
power radars used to track objects the size of a golf ball at a distance of a hundred miles
or more to milliwatt power wireless computerized equipment that provides copper path
elimination enabling greater system efficiency. The effects of non-ionizing radio
frequency (R.F.) waves that makes these devices possible are a concern to all, since the
R.F. spectrum is a finite resource and certain levels of radiation intensity may cause
unintentional interference to other equipment and affect human anatomy.
This paper reflects those R.F. concerns regarding compatibility issues with respect
to the new Motorola Trunking Radio system currently being implemented at Kennedy
Space Center (KSC). This system also supports the central computer trunking radio
operations for nearby government facilities and United States Air Force installations.
The scope of this effort includes:
 The rationale and purpose for use of trunking radio
 Electric field and antenna gain discussion that acquaints the reader to technical
aspects of radio wave propagation and the peculiarities of radio transmission
measurement
 Consideration of standards and specifications and their comparisons that affect
compatibility issues
 Power conservation features of the new trunking radio portable radios that
substantially reduce radiated emission

3.  Conclusions and recommendations regarding trunking radio compatibility issues.
2
Rationale for Trunking Radio
In an effort to promote efficient and effective R.F. communications, the National
Telecommunications and Information Administration (NTIA) has planned mandates
requiring a more restricted R.F spectrum that will apply to KSC, Cape Canaveral Air
Force Station (CCAFS), Patrick Air Force Base (PAFB), and the Malabar Test Site
(Malabar) radio communication operations. In addition, the NTIA will require a
reduction of communication transmission bandwidth also known as narrowbanding. The
NTIA mandates will result in a substantial change in the radio communication
methodology and operation currently in use at KSC, CCAFS, PAFB and Malabar.
In terms of R.F. spectrum restrictions, the new spectrum band plan for
government use will result in the redistribution of all discrete communica tion frequency
use within the Very High Frequency (VHF) portion spectrum by the year 2005.
Additional frequency budgeting will affect the currently used discrete Ultra High
Frequency (UHF) operations by 2008. Implementation of this plan will allow re-distribution
of those discrete frequencies currently used by KSC, CCAFS, PAFB, and
Malabar.
Narrowbanding restrictions are described in chapter 5, section 5.3.5.2 of the
NTIA Manual of Regulations & Procedures for Federal Radio Frequency Management.
The standards outlined in that section apply to narrowband systems at KSC and its
environs designed to operate in the 138-150.8, 162-174 and 406.1-420 MHz bands.
Mandated transmission bandwidth characteristics indicate that the levels of emission to

4. be 70 dB down from the carrier peak at 12.5 kHz from the carrier center frequency. It
should be noted that a substantial portion of the current land/mobile radio VHF
communication equipment used by KSC does not meet this 12.5 kHz requirement.
Consequences of nonconformance with the provisions of this chapter will result in
the responsibility for eliminating the harmful interference. These consequences normally
shall rest with the agency operating in nonconformance.
The problem presented by the NTIA mandate regarding KSC radio operation is
how compliance will be achieved through implementation of the proposed band plan in a
timely manner with respect to VHF and UHF frequency redistribution, and conformance
with equipment specifications that will ensure 12.5 kHz maximum bandwidth
3
characteristics.
A potential solution regarding the NTIA band plan and bandwidth limit restriction
for KSC, CCAFS, PAFB, and Malabar has been procured, installed, and is in the process
of final implementation. It is called trunking radio; however, there are technical,
managerial, and operational related issues that require resolution prior to full trunking
radio implementation. As planned, the proposed trunking radio system at KSC will be
fully compliant to all planned NTIA mandates for the VHF portion of the radio spectrum
by 2005 and the UHF portion by 2008; thus, the planned frequency redistribution can be
achieved and nonconformance of standards will not be jeopardized near or long term.
Electric Field and Antenna Gain Discussion
The following discussion introduces the reader to some of the technical aspects of
the trunking radio R.F. performance with respect to antenna gain, power output attributes,

5. and the use of field measurements regarding antenna gain characteristics. Please note that
the power levels indicated in this discussion are absolute worst case or highest power
examples; thus, may not reflect actual operational conditions. This section is based on
actual field measurements taken in August 2003 as provided by the Boeing-KSC-N120-
53410-03 report as performed by Electromagnetic Laboratory (EML) personnel at KSC.
Calculation of the equivalent isotropic radiated power (EIRP), in dBm, emanating
from the transmitting antenna is shown below. The calculation, based on the point-to-point
received signal strength measured at a 25’ over an undisclosed height above the
ground at a distance and 416.82 MHz, is as follows:
Distance (RM ) = 25’  .3048 m/ft = 7.62 meters.
Received signal power (S R ) developed at the receiver input = 1.17 dBm.
Free space path attenuation (N ) = 20 log10 {(4 M R   )  M }
where  M = c  f, or 300  416.82 = .72 m
4
N = 20  log10 {(4 62 . 7   ) 72.  }
= 42.47 dB
Published receiver antenna gain over an isotropic source at 416.82 MHz (GdBi ) = 4.9 dB
Measured receiver cable loss at 416.82 MHz (LC ) = 0.5 dB
The EIRP or P T from the transmitting antenna source is calculated as:
P T = S R + N - GdBi + LC

6. = 1.17 dBm + 42.47 dB - 4.9 dB + 0.5 dB
5
= 39.24 dBm
Thus, EIRP emanating from the transmitting antenna over an isotropic source is
calculated to be 39.24 dBm. The EIRP emanating from the transmitting antenna in watts
(W) is given by:
P T = {log 1
 (38.89 dBm  10)}  10 3
10
= 8,413 milliwatts  10 3
= 8.413 W
To determine the volts per meter (V/m) at a distance of 25’ from the emanating
transmit antenna, two methods of calculation will be employed. The first method requires
that the antenna factor of the receiving antenna is known. The antenna factor equation is
given as:
AF (dB) = (20  log10Frequency in MHz.) – published receiving antenna gain (GdBi ) –
29.8 dB
= (20  log10 416.82) – 4.9 dB – 29.8 dB
= 17.70 dB
Now the E field intensity in microvolts per meter, or E (V/m), at 25’ may be
expressed as:

7.  ((S R + 107dBV + LC + AF)  20)
 ((1.17 dBm + 107dBV + .5 dB + 17.70 dB)  20)
6
E (V/m) = log 1
10
= log 1
10
= 2,082,092 V/m or 2.08 V/m
The second method requires that the gain of the transmitting antenna is
determined. The gain (GT ) of the transmitting antenna is calculated as P T  P A where P
A is the maximum output power in watts of the transmitter final amplifier (4 Watts)
delivered to the transmitting antenna expressed as:
GT = P T  P A
= 8.413 W  4 W
= 2.10
The equation for the E field intensity at a distance is given as:
E (V/m) = (30  P A  GT ) 2 / 1  RM
= (30  4 W  2.10) 1/ 2  7.62m
= 2.08 V/m

8. The two E field intensity results agree. If we carry out this exercise for the remaining
samples from the Boeing report using the tabulated EIRP data at 25’ distance converted to V/m,
the transmitting antenna gains may be calculated using the following:
7
(GT ) 2 / 1 = (E V/m  RM )  (30  P A ) 2 / 1
Sample 1
(GT ) 2 / 1 = (2.09 V/m  7.62m)  (30 4 W) 2 / 1
= 1.45
GT = 2.11
Sample 2
(GT ) 2 / 1 = (1.83 V/m  7.62m)  (30 4 W) 2 / 1
= 1.27
GT = 1.62
Sample 3
(GT ) 2 / 1 = (1.53 V/m  7.62m)  (30 4 W) 2 / 1
= 1.06
GT = 1.13
Sample 4
(GT ) 1/ 2 = (1.97 V/m  7.62m)  (30 4 W) 1/ 2
= 1.37

9. E Field vs PA @ 25'
Figure 1
8
GT = 1.87
Calculating the statistical average of the antenna gains reveals that x = 1.68; however,
the , or standard deviation, is .415. This high value of  suggests that the true antenna gain is
uncertain within the band of frequencies of 411.35 through 418.02 MHz, as the coefficient of
variation as measured by   x is almost 25%. In fact, for E field intensity projections,
published antenna gains produced by the manufacturer are highly desirable, if not mandatory, for
use with standardized commercial E field calculations. Thus, proper E field measurements can
only be approximated by actual measurement as electromagnetic field perturbations resulting
from ground irregularities and soil conditions, signal reflections, atmospheric conditions, and
other phenomena cause signal distortion at a distant point of interest.
Figure 1 indicates the V/m versus transmitter power output (P A ) as a function on antenna
gain at a distance of 25’. It is assumed that the antenna gain of the trunking radio portable units is
2 1   , or, 0dB to 3 dB gain over an isotropic source.
3.5
3
2.5
2
1.5
1
0.5
0
Ant. Gain = 2
Ant. Gain = 1
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
Volts per meter
Transmitted Power to Antenna (W)

10. Consideration of Standards and Specifications
There are various KSC and other industry documents that specify and outline overall
requirements regarding Electromagnetic Compatibility. SL-E-0002 – Specification
Electromagnetic Interference Characteristics Books 1, 2, and 3 are examples of such documents
used by the Space Shuttle Program and KSC. These books apply to specified and unspecified
airborne and ground equipment; thus they become a conflicting source of standards information
when juxtaposed with other existing KSC and other documents such as MSFC-SPEC-521B -
Electromagnetic Compatibility Requirements on Payload Equipment and Subsystems, SSP
30237 - Space Station Electromagnetic Emission and Susceptibility Requirements, NASA-STD-
8719.12, Safety Standards for Explosives, Propellants, and Pyrotechnics, and MIL-STD-1576 -
Electroexplosive Subsystem Safety Requirements and Test Methods for Space Systems.
The SL-E-0002 books 1, 2, and 3 are divided as a function of equipment
procurement date. Book 1 refers to affected equipment procured prior to February 11,
1993, while Book 2 is assigned to equipment procured between February 11, 1993 and
prior to May 7, 2001, and Book 3 includes equipment procured since May 7, 2001.
The specified radiated susceptibility limits for Book 1, revision E, released in July 2001,
are derived from MIL-STD-461A, as released in 1968. That released document indicated a
radiated susceptibility (RS03) specification of 1 V/m from 14 kHz to 10 GHz. There have been 4
major revisions of MIL-STD-461A since 1968 directly affecting specifications used in
determining susceptibility limits by radio frequency emission; however, subsequent revisions of
MIL-STD-461A have not impacted SL-E-0002 Books 1 and 2. In essence, SL-E-0002 Books 1
and 2 continue to use the 1 V/m RS03 standard while MIL-STD-461E currently uses 10 or 20
9

11. V/m RS03 standard depending upon ground or space operation. Industry professionals
considered the 1 V/m susceptibility limit a severe requirement; thus, it was relaxed by following
revisions of MIL-STD-461 starting in 1980, prior to STS-1. It is interesting to note that the 1
V/m standard with respect to the RS03 specification is used today in SL-E-0002 Books 1 & 2 as
an upper boundary guideline for the Radiated Emissions (RE102) specification for the purposes
of issuing many deviations and waivers with respect to the RE102 specification. Variances of +
40 dB over the RE102 limits are typical and have been granted using the RS03 as an upper
10
boundary limit.
There is one indicated waiver with respect to the RS03 specification in the Space Shuttle
Specification Electromagnetic Compatibility Requirements for Equipment, SL-E-0001 Book 1
regarding the super lightweight headsets that were found susceptible to R.F. interfere nce below 1
V/m at 200 MHz. Other than the super lightweight headset example, specific equipment
susceptible to R.F. emissions above 1 V/m between 400 MHz and 420 MHz is not known.
The specified limits for RS03 in SL-E-0002 Book 3, revision basic released July 2001,
indicates an equipment susceptibility limit of 20 V/m between 30 MHz and 1 GHz. The point of
this discussion is that there exist varying degrees of susceptibility tolerances depending on date
of equipment procurement and the origin of the standard. The next section will explore the
variance of susceptibility specifications and standards.
A Relative Comparison of Specifications
This section will give the reader some insight as to various susceptibility limits
and specifications regarding R.F. emissions by other agencies and standards. These

12. susceptibility limits apply to the maximum allowable human exposure, sensitive
equipment thresholds, and electroexplosive threshold levels.
The first example is referenced from the FCC OET Bulletin 65, Evaluating Compliance
with FCC Guidelines for Human Exposure to Radio Frequency Electromagnetic Fields. Using
412 MHz to calculate the maximum permissible exposure E field strength, a value is 71.72 V/m
or 1.373 mW/cm2 as calculated from the table below from that bulletin. This frequency was
selected since the trunking radio samples used in the previous section are fairly represented.
Shown below is the table as it appears in the FCC OET Bulletin 65 document.
LIMITS FOR MAXIMUM PERMISSIBLE EXPOSURE (MPE)
Limits for Occupational/Controlled Exposure
________________________________________________________________________
Frequency Electric Field Magnetic Field Power Density Averaging Time
Range Strength (E) Strength (H) (S) |E|2, |H|2 or S
(MHz) (V/m) (A/m) (mW/cm2 ) (Minutes)
________________________________________________________________________
0.3-3.0 614 1.63 (100)* 6
3.0-30 1842/f 4.89/f (900/f2)* 6
30-300 61.4 0.163 1.0 6
300-1500 -- -- f/300 6
1500-100,000 -- -- 5 6
________________________________________________________________________
f = frequency in MHz
*Plane-wave equivalent power density
The second example is referenced from the SSP 30237- Space Station Electromagnetic
Emission and Susceptibility Requirements, Revision C. As shown below, the susceptibility
requirement for Space Station components with respect to the trunking radio frequency spectrum
11
is 60 V/m.

13. 60 V/m is 59 V/m above the 1 V/m requirement of SL-E-0002 Books 1 and 2 and 40 V/m above
the 20 V/m requirement of SL-E-0002 Book 3.
The third example refers to MSFC-SPEC-521B - Electromagnetic Compatibility
Requirements on Payload Equipment and Subsystems. In Change Notice 1 of that specification,
12
the chapter and verse appears as below.
3.3.2.2.1 Electric Field (RS03)
Payload equipment shall not be susceptible to an electric field strength of 2.0 volt
per meter from 14 kHz to 10 GHz, in addition equipment mounted in the payload
bay shall not be susceptible to the field strength levels specified in Figure 3-9 for
the frequencies show in Table 4-1. The levels in Figure 3-9 may be reduced by
20 dB for equipment installed in the space lab module or any enclosure known to
have equal or greater shielding capability. Equipment that protrudes above the
payload bay or that is ejected from the payload bay may be subjected to higher
KU-band and S-band fields. These will be defined depending on the orientation
and whether there are approved operational restrictions on the transmitters for the
specific project.
Figure 3.9 and Table 4-1 from the MSFC-SPEC-521B specification refer to
specific equipments and their operating frequencies. No equipment is identified operating
at or around the trunking radio frequency spectrum in those figures or tables. It is
interesting to note the 20 dB requirement reduction once the payload is installed into an
enclosed space. A 20 dB reduction to 2 V/m is equivalent to 19.95 V/m.
The fourth example references NASA-STD-8719.12, Safety Standards for
Explosives, Propellants, and Pyrotechnics. Table IV, Recommended EED Safe

14. Separation Distances and Power Densities in that document indicates (by calculation) the
exposed EED maximum radiation limit to be .68096 W/m2 or 15.9 V/m at 400MHz. The
maximum radiation limits for the EED in storage or transport is calculated to be 6.81
W/m2 or 50.3 V/m at 400 MHz. Both examples are well above the 1 V/m standard and
are considered conservative as compared to guidelines indicated in MIL-STD-1576,
Electroexplosive Subsystem Safety Requirements and Test Methods for Space Systems.
Motorola XTS 3000 Portable Trunking Radio Power Conservation Features
The Motorola XTS 3000 series radios have a programmable power conservation feature
that automatically adjusts the output power (P A ) level of the transmitter to less than full rated
output (4 watts) when conditions permit. This feature extends battery life between charges since
the nominal P A output can be significantly reduced as the transmission confidence margin
dictates. To illustrate how this feature works, consider a trunking radio transmission from
Launch Complex 39-A. The Motorola XTS 3000 series radios are required to communicate to
one of two repeater towers for proper trunking sequence of operation. Assume the distance
between Pad-A and one of the towers is conservatively 5 miles. We will incorporate the
previously used Boeing report power data at 416.82 MHz and introduce trunking radio receiver
characteristics at the 500’ Weather Tower for purposes of this discussion.
Distance (RM ) = 5mi  5,280 ft/mi  .3048 m/ft = 8,046.72 meters.
Free space path attenuation (N ) = 20 log10 {(4 M R   )   M }
where  M = c  f, or 300  416.82 = .72 m
13

15. N = 20  log10 {(4 8,046.72).72 }
14
= 82.46 dB
Now the signal applied to the receiver input terminals is expressed as:
S R = P T - N + GdBi - LC
Where
S R = Signal received at the receiver input terminals in dBm
P T = EIRP of the transmitting antenna
N = Free Space Path Loss
GdBi = Published numerical gain (dB) of the 500’ Weather Tower antenna over an
isotropic source
LC = Calculated cable loss from antenna to receiver at the 500’ Weather Tower
S R = 39.24 dBm – 82.46 dB + 6 dB – 3 dB
= - 40.22 dBm
Expressed as Watts:
= {log 1
 (-40.22 dBm  10)}  10 3
10
= .00009506 milliwatts  10 3
= .00000009506 W or 9.5 8 10  W

16. For a 50  system the Voltage E, applied across the receiver input terminals is
15
expressed as:
E = (S R  50) 2 / 1
= (9.5 8 10   50) 2 / 1
= .00218 V = 2.18 mV = 2,180  V
Now the trunking radio receiver sensitivity at the 500’ Weather Tower is
published to be .25 V for a maximum bit error rate of 5%. We will use this figure as a
minimum threshold for receiving and processing useful voice and data for purposes of
acceptable trunking operation. Taking the applied or detected voltage across the receiver
input and comparing it to the minimum threshold receiver input sensitivity establishes a
margin of confidence that the receiver will properly detect and decode the intended
information. This margin of confidence may be expressed in dB and used in overall
system path loss budgets. For our example we may express the margin in dB as:
20  log (2,180 V  .25 V) or 78.81 dB.
This is an extremely high margin of confidence. To put this in perspective,
assume that the EIRP or P T of an XTS 3000 portable is 8.413 W or 39.25 dBm and the P
A from the transmitter to the antenna is 4 watts as in the previous sample 1. If we reduced
the input power P A to 2 watts or 3dB, the resulting EIRP would be 36.25 dBm or 4.206
W. That would leave a confidence margin of 78.81 dB – 3 dB or 75.81 dB. This remains

17. an extremely high margin. By reducing the P A another 50% the result would be 33.25
dBm or 2.103 W leaving a confidence margin of 75.81 dB – 3 dB or 72.81 dB. Please
note that these margins apply to ideal conditions. In a real world, a transmission
path/system loss budget based on probabilistic information theory would be required to
reflect an environment in which reliable margins could be established. Using data from
known good engineering practices the theoretical transmission path/system loss error
budget may include up to a 15 to 20 dB loss from atmospheric and ground conditions,
and 20 dB additional losses resulting from building structure attenuation. If we added
(worst case) 40 dB as an error budget to the signal strength of our minimum required
power, the result would be 1.1 milliwatt (mW) EIRP required output from the
transmitting antenna to reach the 500’ Tower for 100% effective communications. At a
distance of 25’ the resulting E field magnitude from the 1.1 mW EIRP would be .024
V/m. The point of emphasis of this discussion is the unlikely probability that the portable
trunking radio units would ever be transmitting at full power, or near full power, since
only a fraction of that full reserve is required for proper operation throughout the entire
16
Kennedy Space Center.
Conclusions and Recommendations
The Motorola Trunking Radio system is an efficient and reliable means of radio
communications that will meet all NTIA mandated requirements both near and long term.
Failure to meet these requirements will jeopardize both near and long term performance
standards set by the NTIA.

18. True radio transmitting characteristics should be established using only published
or certified antenna data. Field data has been shown to result in a sizeable data scatter of
the portable radio antenna gain characteristics.
The radiated susceptibility specification per SL-E-0002 Books 1 and 2 is severe.
The current specification of 1 V/m indicated in SL-E-0002 Books 1 and 2 is based on a
1968 revision of a Department of Defense standard that has since been updated 4 times to
reflect a 10 to 20 V/m susceptibility limit. Other susceptibility specifications and
standards that apply to human exposure, sensitive electronic equipment, and
electroexplosive devices indicate a limit that would permit the use of trunking radio
portable units at the full power compliment to operate safely at a reasonable distance.
Equipment that is potentially susceptible to trunking radio R.F. emission has not been
17
identified.
It is highly improbable that the trunking radio portable units will transmit at full
rated power since they are designed to allow for path loss energy budgeting enhancing
battery conservation. Theoretically, the new trunking radios can communicate from the
LC-39A to the 500’ Weather Tower using about 100 microwatts of power with a 0dB
margin of confidence. The probability of exceeding 1 V/m at 25’ during operation of the
new trunking radio portables is extremely low since power conserving programming
feature is in effect.
Based on no known evidence of susceptibility to equipment by the R.F. emissions
of the new portable trunking radios within reasonable transmission distances, it is
recommended that the Motorola Trunking Radio Program for use at KSC and its environs
continue with full planned implementation.

19. References Cited
The Boeing Company Kennedy Space Center. (2003). Test Report KSC UHF Trunking
Transceiver 1 Volt/Meter versus Distance Measurement NAS 10-02007
NTIA Manual of Regulations & Procedures for Federal Radio Frequency Management
(May 2003 Edition, September 2003 Revisions)
Federal Communications Commission. (1997). Evaluating Compliance with FCC
Guidelines for Human Exposure to Radio frequency Electromagnetic Fields.
OET Bulletin 65, Edition 97-01
Department of the Air Force Military Standard. (1984). Electroexplosive Subsystem
Safety Requirements and Test Methods for Space Systems. MIL-STD-1576
National Aeronautics and Space Administration. (2001). Specification Electromagnetic
Interference Characteristics Book 1- Hardware Prior to February 11, 1993. SL-E-0002
Book 1, Revision F
National Aeronautics and Space Administration. (2001). Specification Electromagnetic
Interference Characteristics Book 2 - Hardware After February 11, 1993 and Prior to
May 7, 2001. SL-E-0002 Book 2, Revision F
National Aeronautics and Space Administration. (2001). Specification Electromagnetic
Interference Characteristics Book 3 - New or Modified Equipment. SL-E-0002 Book 3
Volume 1
Department of Defense Military Standard. (1968). Electromagnetic Interference
Characteristic Requirements for Equipment. MIL-STD-461A
National Aeronautics and Space Administration. (1990). Electromagnetic Compatibility
Requirements on Payload Equipment and Subsystems. MFSC-SPEC-521B
National Aeronautics and Space Administration, et all. (1996). Space Station
Electromagnetic Emission and Susceptibility Requirements. SSP 30237, Revision C
NASA Technical Standard, Safety Standards for Explosives, Propellants, and Pyrotechnics.
(2003). NASA-STD-8719.12 (Draft)
18