N6EX Receiver Performance

Prior to integrating the modified receiver with the rest of the system, the unit was aligned per the TK-931 service manual. The following items were checked/aligned:

PLL Control Voltage (Verify between 1.0 and 7.0 volts)
First Local Oscillator Frequency (Adjust TCXO A/R to within 50 Hz)
- LO Freq = Receive Frequency - 39.0375 MHz
Adjust LNA matching capacitor (TC300) for best quieting sensitivity
Adjust Discriminator coil (L304) for maximum audio output
Adjust First IF matching coils (L300, L301, L302) for minimum distortion
Measure overall receive sensitivity (quieting or SINAD)
Adjust/measure threshold squelch sensitivity
Verify PL/DPL decode performance
Measure current consumption

Notable Receiver Measurements

Current Consumption

Squelched: 403 mA (at 13.5 VDC)
Unsquelched (min. volume): 416 mA (at 13.5 VDC)

Receive Sensitivity

0.35 uV for 20 dB quieting

Threshold Squelch

0.13 uV (later readjusted due to on-site noise level)

Audio Frequency Characteristics

Measured Prior-to and Following Audio Buffer Board

click for larger image (28KB)

Audio response is flat within 1 dB over the 300 Hz to 3 kHz range. The response before and after the buffer board is virtually identical. Input to the radio for this test was a -70 dBm RF signal with a deviation of + 1.5 kHz.

Click for raw Excel spreadsheet data of measurements.

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