Correspondence Reference Number 9870

FCC ID: DD4UC2B

Test Report

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FCCID_61949

MICROPHONES AND ELECTRONIC COMPONENTS

Shure Brothers
Incorporated

222 Hartrey Avenue
Evanston, IL 60202-3696 • U.S.A.

October 4, 1999

Mr. George Tannahill
FCC Application Processing Branch

Re: FCC ID DD4UC2B
Correspondence Reference Number: 9870
731 Confirmation Number: EA94794
Date of Original E-mail: 09/29/1999

Dear Mr. Tannahill,

With respect to the questions you raised in your E-mail message of the above date:

1. The occupied bandwidth plots were obtained by following the procedure detailed below,
which was previously recommended by your office:

First, the modulation frequency of maximum response was established by supplying an
audio signal to the transmitter input, at a level well below the onset of limiting, and varying
its frequency over the entire audio range until the point was found where maximum
deviation occurs. Then, the audio signal was adjusted so as to produce 50% modulation
(22.5 kHz deviation, in the case of the UC2B) on a Boonton Model 8200 modulation
analyzer, and the audio input level was recorded. Next the audio frequency was changed
to 2500 Hz, and the input level was increased by 16 dB over that which was recorded at
the frequency of maximum response. A plot was then made of the resulting emission. In
addition, several other plots were made at other representative modulation frequencies,
using the same input level, so as to demonstrate the transmitter’s modulation
characteristics. A reference plot was also made with no audio modulation applied.

Note that this transmitter incorporates a 32.768 kHz continuous pilot (control) signal
(referred to by Shure as “Tone Key”). Note also, that the Boonton modulation analyzer
employs a broadband demodulator. Thus, the deviation of the pilot signal affects the
setting of the 50% modulation point. This is probably why the modulation plots appear to
be undermodulated. A percentage of the deviation is due to the pilot signal.

It is possible to perform the procedure in such a way that the modulation due to the pilot
signal is ignored in determining the audio input level for 22.5 kHz deviation. To
demonstrate this, the above procedure was repeated with the pilot signal temporarily
disabled while the audio input level for 22.5 kHz deviation was being determined. A
second series of plots showing the resulting emissions have been provided with this
attachment. All occupied bandwidth plots were made with the pilot signal re-enabled, with
the exception of one reference plot which was made with the pilot signal disabled and no
audio input. You will observe that although larger than in the previous set of plots which
were included in the original submission, in no case does the occupied bandwidth of the

UC2B Modulation vs Frequency for
10mV RMS Input
75
70
65
60
Deviation kHz

55
50
45
40
35
30
25
20
15
10
5
0
50Hz 100Hz 250Hz 500Hz 1kHz 2kHz 4kHz 6kHz 8kHz 10kHz 15kHz 20kHz

Frequency

UC2B Input Level Vs Deviation
80
+/-kHz Deviation

75
70
65 80Hz
60
55
50 500Hz
45
40
35 2.5kHz
30
25
20 10kHz
15
10
5
15kHz
0

-80 -70 -60 -50 -40
Input Level dBV

Mr. George Tannahill
FCC Application Processing Branch

FCC ID DD4UC1B
Correspondence Reference Number: 9790
731 Confirmation Number: EA94793
Date of Original E-mail: 9/23/99

Dear Mr. Tannahill,

With respect to the questions you raised in your E-mail message of the above date:

Please provide an ERP relative to a dipole power output measurement and show all measured
values and calculations.

Page 31 (field strength) is updated and included with this letter.

The emission designator requested is F3B. Based on the rest of the report it appears F3E is more
appropriate. Please justify the requested designator.

The correct emission designator is F3E. This was an error made when doing the data entry.

Arnom (Arine) Rowe
Test Engineer
EMC-001375-NE

11.0 FIELD STRENGTH OF SPURIOUS EMISSION MEASUREMENTS (CON'T)
PART 2.1053

As stated in Part 74, Section 74.861 (e-1 iii) the limit is 250 mW in the frequency range 614 to
806 MHz.

To determine the LIMIT for Spurious Emissions, the following method was used:

Mean output power in watts:

Manufacturer’s rated wattage 20 mW (See Paragraph 6.0, page 8)

Free Space Formula

Convert to 3 meter test distance using the Free Space Formula

49.2 * rated wattage = 49.2 * .02 w = .330655913 volts/meter
Distance 3

.330655913 v/m = 330655.914 uV/m

20*Log(330655.914) = 110.39 dBuV/m

So, the Fundamental at three meters equals 110.39 dBuV,

The emissions must be reduced by:

43 + 10*LOG10(0.02 watts) = 26.01 dB

Therefore, the LIMIT at three meters equals:

110.39 dBuV/m extrapolated level for 0.02 watts
-26.01 dB required reduction below the unmodulated fundamental
84.38 dBuV/M maximum spurious emissions allowed

Page 31

Document Created: 1999-10-05 10:08:30
Document Modified: 1999-10-05 10:08:30

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