1. Troubleshooting
Scott Honaker, N7SS

2. Using a Multitester Resistance/Continuity Voltage
Insure circuit is not powered and dead
Use the continuity setting (diode)
If not available, use lowest resistance setting
Voltage
Start with higher range and work down
Watch polarity (less important on digital meters)
Don’t touch tips of both leads with fingers

3. Using a Cable Tester Connect cable ends and start sweep of conductors
Lights will show connections on both ends
Generally, lights will illuminate in order
Watch for missing lights (no connection)

4. Simple Cable Failure Modes
True for coax and any multiconductor cable
Open conductor
Broken in the cable (cable damage may be detectable)
Not properly terminated at connector
Shorted conductors
“Miswired” multiconductor cable
Null modem serial cable
468A vs. 468B (crossover) network cable
USB “charging cable” with no data lines

5. Complicated Failure Modes
Intermittent
Broken conductor/connection may still make contact
Wiggle cable and ends while testing
Wrong impedance
Requires analyzer to test
Need TDR or antenna analyzer and dummy load
Could have observable kink/crush damage
Connectors poorly installed (overheated is common)
High Resistance (Return Loss)
Also needs TDR or 2 port VNA to test
Antenna analyzer less effective
Most likely corrosion, look for water ingress route
Could be bad connector install

6. Testing Cables Disconnect from radio and antennas
Visual/tactile inspection of connectors/jacket
Look for cuts, pinches, signs of overheating, corrosion, any sign of water ingress, broken or bent connectors
Simply destroy and discard cable
Perform continuity check on each conductor
Check for shorts across conductors

7. Voltage Issues Most mobile radios rated for 13.8V ±15%
That’s 11.8V V
Fully charged lead/acid battery is 12.6V nominal
That’s 2.1V per cell x6 cells
Note that is only 0.8V above minimum rated requirement
Cars and power supplies provide 13.8V
Charging battery requires 12.6V + 10% or 13.8V
Radios may work lower but won’t have clean output
With low voltage will work on receive, not transmit
Extra current load causes large voltage drop
Display may dim or flicker

8. Lead Acid Battery Capacity

9. Testing Power Measure at the source loaded and unloaded
Measure both source and load end
Look for voltage drop
Remember ohm’s law – voltage drop increases with current draw
Consider connectors, fuse holders
Look at power inside radio
Remove lid and find power connection on board
Look for external connector with 12v available

10. Exercise - Test Power Leads
Use multitester and visual inspection of cables
Record voltage at source
Inspect and test each lead
Record voltage for each lead
Continuity test as needed
Which lead(s) are good?
Pass cables clockwise as needed
We’ll test with radios when complete

11. How is Radio Working? Does it power up and receive?
Does it transmit on low power?
What does the radio display show?
Can it be heard on another radio?
Is there power output?
What is the current draw?
Does it transmit on high power?
Kenwood TM-261 Results –
Radio will transmit normally at low power with some display dimming
Radio appears to transmit on mid and high power but no actual output on meter or other radio and display pulses/flickers
Icom IC-880 Results –
Can transmit on low power normally
On mid and high power the display shows TX and power output for ~1 second then neither. Mike has red TX light but no output on meter and no signal on other radio
Yaesu FT-8800 Results –
On mid and high power the display shows TX with normal bars but no output

12. Exercise - Test Sample Cables
Use testers and visually inspect cables
Record cable ID letter
Record test results (shorted, open center, good, etc.)
Visual inspection results
Should you use this cable (Yes/No)?
Pass cables clockwise around the room
Test at least 5 cables