Download Active Antenna Interface

CR602
R604
3.6K
CR601
C601
0.1
Q604
C604
2.2
R607
10
L602 C605 R609
10uH .0033
75
J601
OUTPUT
TO ACTIVE
ANTENNA
TO RADIO
OR MOD-MONITOR
100
(OPTIONAL)
COIL OF
MYSTERY
R601
10K
R603
150
TO 9VDC
"WALL WART"
100uF
'LYTIC
0.1
CERAMIC
R606
5.1K
Q601
0.1
CERAMIC
100, 1/2W
(SEE TEXT)
47uH MOLDED
CHOKE COIL
R608
10
Q603
Q602
C602
0.1
OPTIONAL
100mA FUSE
L601
47uH
+
R605
620
+
ACTIVE ANTENNA ASSEMBLY
C603
0.1
R602
10
INTERFACING THE INOVONICS ACTIVE AM ANTENNA WITH
EQUIPMENT OTHER THAN THE MODEL 520 AM MOD-MONITOR
Circuitry shown within the dashed box is located inside the active antenna
assembly. It requires a phantom-power source of about +9 volts DC to supply
the amplifier stages. Phantom power is applied through a choke coil and 'picked
off' with a coupling capacitor. This will maintain the low characteristic impedance
of the circuit, which can drive either a 50-ohm or 75-ohm antenna input with
relative impunity. If the antenna input of the radio or monitor has a
high-impedance "bridging" characteristic, the optional 100-ohm terminating
resistor should be connected.
The additional circuitry may be enclosed in a small metal box, such as a
Digi-Key HM150-ND or Mouser 546-1590A. Alternatively, components may be
added inside the radio/monitor and power taken from the existing supply. The
fuse is optional to protect the power supply and series resistor against a short
across the antenna connector.
The choke is not critical; Digi-Key part M8651-ND, Mouser 434-22-470, or
similar.
The radio/monitor power supply, or even a 9-volt "wall wart," may deliver a
good deal more than 9 volts with the small load that the antenna represents. The
100-ohm resistor in series with the DC feed should be increased in value to
maintain the phantom power somewhere between 8 and 10 volts with the antenna
connected.
.
Rev
ACTIVE ANTENNA INTERFACE
ID
Date: . 12 AUGUST 2005
Page: 1 of 1