Company: Art Tech
Art Tech ATRXD01 DUAL conversion 35MHz PPM
Receiver system: DUAL converting 31136G with LM393 and counter 74ACH164
IF1 =10.7MHz, ceramic filter (first osc the xtal is -10.7 from the rx frequency)
IF2 =455kHz, ceramic filter
FM decoder: ceramic resonator
RX frequency was accurate within 700Hz using: Original Art Tech yellow label crystal
Antenna wire desoldered (94cm 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 -93.7dBm (4.5uV) at 10dB SINAD, this is 4dB better than their specifications (only 7uV) with -70dBm input level, the IF frequency width is measured to = 15.7kHz
with -50dBm input level, the IF frequency width is measured to = 20.1kHz
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 15dB SINAD
Noise frequency with worst interference = 455KHz due to the IF frequency.
Input noise voltage level when the wanted signal is 5dB SINAD (Demodulated signal drops 10dB SINAD)
Measured to : 2.2Vpp, so that is really good!
you will newer see any problems from electric planes
Mirror frequency and other issues:
Since this is a DOUBLE conversion receiver we will expect to see mirror rejection
so at 13.7MHz rx frequency-(2x10.7MHz) we have -23dBm sensitivity this is 71dB rejection, quite impressive
GROUND black wire on power and servos is UP
Need more channels ?? the 7th and 8th signal is available inside it:
carefully solder a wire to pin 12 and pin 13 of the ACH164 chip !
Feb 6 2008, Thomas Scherrer
both boards opened