Company: Multiplex (BACK)


Type: RX9 SYNTH DS IPD

Microcontroller decoder IPD (MSP430F1232 with 6.4MHz crystal)
Receiver system: double converting (61131 and SA676)
1. OSC=24.3MHz, 2. OSC=10.245 MHz
1. IF =10.7MHz, 2.IF=455kHz
FM decoder: ceramic resonator
IF filter, 10.7MHz real crystal filter and 455kHz 5pole ceramic.
RX frequency was accurate within 10Hz.

Antenna wire de-soldered (89cm length), and 50 Ohm RF test generator attached.
1kHz sine and 2.5kHz deviation.

On the RX board there is a test pad with demodulated audio signal,
so it is easy to see with a scope how the receiver perform, when wanted signal is equal to noise,
the RF input signal level is recorded.

Center frequency with best sensitivity -108dBm (0.8uV)

with -70dBm input level, the frequency width is measured to = 16.9kHz
with -50dBm input level, the frequency width is measured to = 18.9kHz

Super good sensitivity (long range), channel selectivity also impressive.

Sensitivity to injected noise on the power line
I inject sine wave signals via a 400uH coil and transfer capacitor 100nF,
directly into the power supply connector of the receiver board.
This simulates a bad motor regulator BEC or Servo current pulse, or noise picked up on long power and servo wires
35MHz RF input signal level at -90dBm
Demodulated signal observes as with the sensitivity test.
Noise frequency with best interference = none,
Input Voltage level when the wanted signal is jammed to 50% signal to noise.
Measured to : Not possible to see any kind of jamming with full power from my generator !!
When looking at the hardware, the way they have seperated all main functions, at their own pcb boards,
and even powersupply regulators on each board and filters on board to board connections, I am impressed !! a clear performance winner.
Risk of problem in electric planes = none !
I have not tested this RX in real life planes, so I have no idea about the IDP functions or performance of the IPD.
But the Radio part measures SUPER !

Mirror frequency and other issues:
This Receiver uses 10.7MHz first IF, so the mirror must be either +21.4 or -21.4
A few mirrors found, sensitivity at: 40.02MHz -40dBm, 31.004MHz -80dBm, 37.939MHz -60dBm, 28.084MHz -20dB,
so mirror attenuation is only 28dB worst case, this is really bad, but still 1000 times better compared to single conversion types,
that has compleetly open RX part in the 34-35MHz band.
the 28-32 MHz band can be used by amateurs and military instalations at hi power.


8th May 2006, Thomas Scherrer