PM1000
II
Operation/Installation Manual
Page 4
Revision 8, April 2020
feedback is a high-pitched squeal that varies with the
volume controls.
Due to the variety of the radio equipment found in
today's general aviation aircraft, there is the potential
of both radiated and conducted noise interference. The
PM1000
II
has a specially designed power supply to
reduce conducted electrical noise on the power bus of
the aircraft by at least 50dB. Although this is a very
large amount of attenuation, it does not eliminate all
noise when the amount is excessive. There must be at
least 12 Volts DC present at the
PM1000
II
for the
power supply to work within its designed regulation.
Otherwise, it will not be able to attenuate noise proper-
ly.
Shielding can protect the system from radiated noise
(rotating beacon, electric gyros, switching power sup-
plies, etc.). However, installation combinations can
occur where minor interference is possible. The
PM1000
II
was designed in an interference -protected
chassis and has internal filter capacitors on all input
lines.
Ground loop noise occurs when there are two different
return paths for the same signal, such as airframe and
ground return wire. Large cyclic loads such as strobes,
inverters, etc., can inject audible signals onto the air-
frame return path. Follow the wiring diagram very
carefully to help insure a minimum of ground loop
potential. Radiated signals can be a factor when low
level mic signals are bundled with current carrying
power wires. Keep these cables separated.
Insulating washers are required on all mic and head-
phone jacks to isolate them from aircraft ground. The
use of a conductor instead of a shield for ground return
eliminates these ground loop paths.
2.4.2 Power Requirements
The
PM1000
II
was designed to work with either
12/28 volt DC negative ground systems. The
PM1000
II
must be externally protected with a one
ampere (1A) circuit breaker or fuse.
2.4.3 Entertainment Input
Entertainment devices can be connected to the
PM1000
II
. Install 1/8" jacks convenient the pilot to
connect the entertainment device into the system. A
"Soft Mute" system is installed in the
PM1000
II
that
will mute the music during intercom or radio activity.
The 11920 has two entertainment inputs.
In the ALL or ISO modes, Music #1 is heard by every-
one (except by the pilot in ISO mode). In the CREW
mode, pilot and copilot will hear Music #1 while the
passengers will hear entertainment #2.
WARNING
: Local oscillators and other internal sig-
nals from CD or radio equipment can cause undesired
interference with VHF navigation and communication
equipment. Before takeoff, operate the entertainment
device to determine if there is any adverse effect on
aircraft systems. If any unusual operation is noted in
flight, immediately switch the entertainment device
off.
2.4.4 External PTT hook-up
Part of the installation includes the installation of PTT
(Push To Talk) switches that allow radio transmissions
from pilot and copilot positions.
There are three configurations that can be used. You
must select the case that best fits your installation.
NOTE: Only the person who presses their PTT switch
will be heard over the radio.
CASE I
The PTT is built into the pilot and copilot yokes
Simply install the plugs from the headset into the air-
craft headphone jacks. Then use the yoke mounted
PTT to transmit. No other action is required.
CASE II
Built in PTT only on the pilot side only
This configuration requires a modified external PTT
switch plugged into the copilot's mic jack. (See Ap-
pendix A) When the copilot's PTT is depressed, this
activates an internal relay that switches the mic audio
to the aircraft radio from the pilot to the copilot.
Case III
No built in PTT switch at all.
Two built-in PTT must be installed or two external,
modified PTT switches will be required for both the
pilot and copilot. Modifications to the PTT may be
required. (See Appendix A)
2.5
Post installation checkout
After wiring is complete, verify power is ONLY on
pin 14 of the connector, and airframe ground on pin 1.
Failure to do so will cause internal damage and void
PS Engineering's warranty.
1.Apply power to the aircraft and avionics.
2.Plug headsets into the pilot, copilot and passen-
ger positions.
3.Verify that the pilot position can transmit and
receive with the
PM1000
II
in the OFF posi-
tion (left hand volume knob fully counter-
clockwise).
4.Rotate the pilot volume clockwise, about half
way. Verify that the Pwr/Xmt light comes on,
and shows green. If the LED is red, stop test-
ing and trouble-shoot the microphone PTT
installation.
Note
: Use the low level (or line) output from any music device to
connect to the PM1000II. Maximum input level is 2 V peak-to-peak.
DO NOT USE SPEAKER OUTPUT.
These levels will cause internal damage.