Technical Manual Alignment and Testing
© SPECTRA ENGINEERING 2006 Revision 4.2.3
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should be approx. 2.8V and <250mV respectively. Reduce RF drive
until PA output is 10W and disconnect PA RF output cable. Measure DC
voltage on CN4-8 and CN4-5 again. These should now both read lower
approximately 1V. Remove PTT.
5.2.4 VCO Board
Test Equipment:
Tested MX800 with Exciter VCO removed
PC with MXTOOLS software
RF Communications test set
Multimeter
Oscilloscope
+13.8VDC power supply
Preliminaries:
Program upper, middle and lower frequencies of band (refer section 5.4 for
band split details) into 3 channels in MXTOOLS channel screen. (Note that
'Continuous Update Enabled' on the MXTOOLS channel screen should be
ticked for these tests)
Remove top cover from Exciter module and fit VCO under test. As the TX
and RX VCO’s are identical the RX VCO may also be tested in an exciter.
As the receiver VCO operates at F
RX
- 90MHz the frequencies
Connect Exciter to working Micro Controller via 16-way ribbon cable.
Disconnect Exciter RF drive output CN1 from PA.
Procedure:
1. Select mid channel. Connect SKU from exciter to VCO, switch DC
power on, assert PTT and measure RF output power on VCO SKT-6.
This should be 0dBm to +3dBm. Measure RF output level on SKU-1.
This should be 0dBm to +3dBm (Note that if SKU-1 is disconnected
from the exciter the loop will lose lock). Reconnect SKT and SKU to
exciter.
1. Select lower channel. Assert PTT and check that loop is locked. Adjust
trim cap CT1 on VCO for 3VDC (2VDC for N2 band) on SKT-1. Select
upper channel. Check that the loop is locked and that the voltage on
SKT-1 is <18VDC.
1. The following test is not required for the RX VCO. Connect Exciter
output to comms test set. Inject 1kHz tone at nominal line input level
and check that Exciter RF output is modulated and that the depth of
modulation can be controlled through the MXTOOLS channel screen.
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