FMHD-1 Operator’s Manual
Page 10
FMHD-1
3.5.3
AES/EBU BNC Connections (digital output channels 1–6)
These are three 75
Ω coaxial outputs conforming to the AES-3ID serial transmission standard for
distribution via 75
Ω coaxial cables. The output swing is 0.5Vpk-pk into a properly terminated cable. The
sources designated as odd-numbered are transmitted first; those designated as even-numbered follow in
the three output channel pairings of channels 1 & 2, 3 & 4, and 5 & 6.
3.5.4
Composite Signal Outputs
The
FMHD-1
provides precision versions of the demodulation composite signals of analog FM broadcast
stations in their un-altered baseband form. These may be used to drive FM exciters in re-broadcast
applications, for performing proof-of-performance testing of FM Stereo broadcasts, for observation on an
oscilloscope, or for other test purposes. There are two analog composite outputs and two digital
composite outputs. The analog outputs appear on rear-panel BNC jacks and have a source impedance of
75Ω. Full modulation, or 75.0 kHz peak deviation, provides about 2.1 volts peak, or about 1.5Vrms
,
un-terminated. (For a terminated 75
Ω cable, divide these voltages by two.) The two digital composite
outputs appear on separate RJ-45 jacks and carry 24-bit serial data on an LVDS physical interface.
(I and Q outputs of the down-converted FM signal are also available in digital form. Consult the factory
concerning their use.)
To obtain the most the most accurate measurements, with the lowest noise and distortion residuals, set up
the
FMHD-1
at the transmitter and use a high-level input signal taken from the transmission line feeding
the antenna. With this arrangement, the analog receiver front-end is bypassed. When the LVDS digital-
format Composite Output is used, the entire demodulation chain in the
FMHD-1
is DSP-based.
3.5.5
Relay Connections
Four Form-C relays provide electrically isolated normally open (NO) and normally closed (NC) contacts
to control external circuits. The relays are activated by alarm conditions set by the user in the
Alarms/Relay Screen. Maximum ratings of the relay contacts are 10 watts, 0.5 amps, and 200 VDC.
Connections to the contacts are made via a chassis-mounted female two-row, 15-pin, sub-miniature D
connector with locking nuts mounted on the rear panel of the
FMHD-1
.
The relay D-connector pin numbers are:
Relay
Common
Normally
Open (NO)
Normally
Closed (NC)
#1
1
3
2
#2
4
6
5
#3
7
9
8
#4
10
12
11
Pins 13–15 are not used.
3.5.6
Ethernet Connection
A standard RJ-45 jack is provided to establish a connection between the
FMHD-1
and a local area
network. Addressing for the
FMHD-1
network connection is set in the Network Configuration Popup
Menu.
3.5.7
RS-232 Connection
The
FMHD-1
may be operated remotely via the rear-panel RS-232 serial interface using the PC-based
WizWin©
software. The
FMHD-1
rear-panel RS-232 connector is a male, two-row, 9-pin, D
sub-miniature connector with locking nuts.
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