Type: MKS PRO-RX8 single conversion 35MHz PPM
Receiver system: single converting 4116 with LM393 and counter 74ACH164
IF =455kHz, FM decoder: ceramic resonator
IF filter, 455kHz ceramic
RX frequency was +300Hz using: Yellow label HImodel crystal
RX frequency was -200Hz using: White label Type 35-12 crystal
So both crystals works fine with this receiver.
Antenna wire desoldered (101cm long) and 50 Ohm RF test generator attached.
modulation: 1kHz sine and 2.5kHz deviation.
The demodulated audio signal was found on a test point.
Sensitivity -102.7dBm (1.6uV) at 10dB SINAD, not good
with -70dBm input level, the IF frequency width is measured to = 18kHz
with -50dBm input level, the IF frequency width is measured to = 22kHz
Sensitivity to injected noise on the power line
I inject a sine wave signal 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 or servo wires
35MHz RF input signal level at -90dBm this gives us 19dB SINAD
Noise frequency with worst interference = 455KHz due to the IF frequency.
Input noise voltage level when the wanted signal is 9dB SINAD (Demodulated signal drops 10dB SINAD)
Measured to : 900mVpp
so I dont expect you will see any problems from electric planes
Mirror frequency and other issues:
Since this is a single conversion receiver we will expect to see no mirror rejection
so at 34.1MHz we have -93dBm sensitivity this is compleetly normal.
Jan 6 2008, Thomas Scherrer