Belar FMHD-1, Operator'S Manual

Page: 16 / 58

FMHD-1 Operator’s Manual
Page 8 FMHD-1
10.
With the digital transmitter on and transmitting data, connect the digital RF sample feed to the FMHD-1 “IN
2” BNC jack. If the RF bargraph indicates red, immediately remove the RF feed and reduce the level of the
digital RF sample at its source.
11.
Using the rotary encoder, activate the FMHD-1 “RF Spectrum Screen”. (See Section 4 beginning on page 11
for instructions.) Activate the “Spectrum” popup menu and set “Measurements:” to “ON”.
12.
While observing the “Ratio” indication in the spectrum display, carefully adjust the “IN 2” potentiometer to
obtain the same IBOC carrier-to-sideband power ratio reading as was previously obtained using the NRSC-
G201 mask compliance procedure.
13.
Connect any desired FMHD-1 outputs and continue with the FMHD-1 setup.
Transmitter Installation Procedure—Common-Line Facilities:
1.
Mount the FMHD-1 in a rack with the required AC power and sufficient cooling.
2. Obtain a 50Ω RF sample of less than 10Vrms from the analog antenna transmission line. Install, but do not
connect, a 50Ω coaxial line to carry the IBOC RF sample to the rear panel of the FMHD-1.
3.
Apply power to the FMHD-1.
4.
After the Main Tuning Screen appears, tune the FMHD-1 to the carrier frequency using the encoder knob.
(Control of the FMHD-1 and use of the encoder knob are described under “Front Panel Operation”, on page
11.)
5.
Bring up the RF Popup Menu on the display by depressing the encoder knob. Enter the “Input Select”
sub-menu and set the input to “High Level”.
6.
Set the potentiometer adjacent to jack “IN 1” on the rear panel to roughly three-quarters fully clockwise.
7.
With the analog transmitter on, connect the IBOC RF sample feed to the FMHD-1 “IN 1” BNC jack. If the RF
Level bargraph indicates red, immediately remove the RF feed and reduce the level of the RF sample at its
source.
8.
Adjust the FMHD-1 “IN 1” potentiometer setting to obtain approximately 100% RF Level.
9.
Using the rotary encoder, activate the FMHD-1 “RF Spectrum Screen”. (See Section 4 beginning on page 11
for instructions.) Activate the “Spectrum” popup menu and set “Measurements:” to “ON”.
10.
If the RF sample is properly obtained, the “Ratio” indication in the spectrum display should be the same as the
IBOC carrier-to-sideband power ratio previously determined using the NRSC-G201 mask compliance
procedure.
11.
Connect any desired FMHD-1 outputs and continue with the FMHD-1 setup.
3.4 FMHD-1 Installation at the Studio
A good off-air (remote) installation of the FMHD-1 will provide high performance for all but
proof-of-performance measurements and critical testing. For studio installation of the unit, proceed as
follows.
The Main Tuning Screen indicates the FMHD-1 RF input level just below the tuning frequency numerals
at the top-center of the display. Both a bargraph and numerical readout indicate the RF Level, with a
green indication of “–60.0dB” or above being in the optimum range. The bargraph for off-air inputs is
demarcated in 20-dB increments. The bar lights yellow for readings below –60.0dB. Red indicates an
input overload—immediately reduce the input level.
Off-Air Antenna Requirements:
1.
Antenna is oriented directly at the transmitter and has a clear path free of any obstructions or adjacent
reflecting surfaces, prominent ground formations, and heavy vegetation. The receiving location should fall in
the main lobe of the transmitting antenna, in both the horizontal and vertical planes;
2.
Avoids strong local sources of radio-frequency interference;
3.
Provides at least 2 millivolts of
the desired signal into 75Ω. For optimum performance, 300 microvolts or
more is desirable;
4.
Uses a high-quality, low-loss 75
Ω coaxial cable, such as RG-59, to connect the receiving antenna to the
Antenna Input of the
FMHD-1
with an F connector.