TM1215 Iss. 6.0 RPR750
4.7.2 Test Equipment
RF signal generator, with external FM modulation I/P
SINAD Meter
Digital Multimeter
Ceramic/insulated Bladed Trimming Tool & Probe suitable for audio frequencies
Non-invasive coupling device for RF signal e.g. small telescopic aerial connected to RF
signal generator.
4.7.3 Tuning & Test Points
Tuning Points Description
CV401 Aerial Tuning
CV402 RF Stage Amplifier Tuning
Test Points
Test Point Signal Description
TP1 Audio 30mV Audio O/P
TP2 -
TP3 455kHz IF Signal
TP4 1.0V rail (-0.05/+0.1V) 1V regulated supply
TP5 0V Ground
TP6 Pull-up Rx enable RXEN Receiver Enable
TP7 1.1 - 1.6V dc Battery Positive
4.7.4 Procedure
Set the signal generator to the RF channel frequency and modulate the carrier with the
audio output from the SINAD meter. Set the FM deviation to the appropriate level for the
channel spacing of the PCB under test. Set the RF output to high e.g. +20dBm.
Connect the audio probe from the SINAD meter between TP1 and Gnd./0V TP5.
Temporarily fit R416 (0R), or connect TP6 to TP7, to enable the receiver. Check the
battery voltage is correct (TP7) and also the 1V rail (TP4).
Adjust CV401 and CV402 for the best SINAD signal. Reduce the RF output from the
signal generator to a lower level e.g. -60dBm and further adjust CV401/2 for the best
SINAD, whilst further reducing the RF level as necessary.
Remove R416, TP6/TP7 link and any other connections made during this procedure.
Radio alignment is now complete.
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