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Vhf radio problem

Old 06-05-2016, 09:41 AM
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Default Vhf radio problem

I have a Icom M45 marine radio. When I try to transmit (PTT) the power drops down to 1 watt. I checked the voltage at the battery, 12.55v and at the back of the radio, also 12.55v. The low battery icon flashes in the lower right screen on the radio. I can receive the weather channels loud and clear. I can transmit at only 1 watt, which does not get me anywhere. Any idea of whats happening?
Old 06-05-2016, 10:33 AM
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Is this on all channels? Some channels (bridges, ports, etc) are limited to 1 watt, and the radio automatically makes the switch for you. If it does it on Chan.16, there appears to be a problem with the radio.

Also, make sure the radio is configured for the US channel set.
Old 06-05-2016, 03:28 PM
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You are most likely in the low power mode, 1 watt. Hit the H/L button on the VHF or mike to get into the high power mode, some channels are low power only such as US channel 17. Check your manual.


If the low voltage indicator b is flashing in the lower right of the display you have a power/wiring issue.


Jim
Old 06-05-2016, 08:16 PM
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US channels 13 and I believe 67 are low TX power only.
What channel were you attempting to Tx on when the set was defaulting to 1 watt?

I wonder if you have an internal memory battery which may be failing & prompting the screen alert?
Old 06-07-2016, 06:08 PM
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Is there an internal battery in the Icom M45 radio? I was calling SeaTow automated radio check on channel 27. Have tried channel 67,68, 16 and others with no luck. What is the best way to check to see if the antenna is working properly?
Old 06-08-2016, 01:07 PM
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From the manual:

"D Low voltage indicator When “b” appears and flashes as shown at right, there is a DC power source problem. In this case, check your vessel’s battery and DC power cable."

So it's not an internal battery problem.

As for the antenna, you can either hook up another VHF to compare , or use a VSWR tester like Shakespeare's ART-3 to test according to instructions after quickly calibrating each time.
Looking for standing wave ratio of less than 2:1. 1.5 is typically good and 1.2 is quite good to see as I recall.
And the ART-3 can give you and idea of the TX power of your set.
The experts which I am not prefer more accurate more expensive testers but IMO this tester is more than adequate for a quick occasional check by boaters like us.

But track down & remedy the low supply voltage issue 1st, including looking at the connectors and wiring itself and holder contacts for any inline fuses, etc., all the way back to battery + if necessary . Don't neglect to confirm excellent path to known good neg. ground.
Old 06-08-2016, 03:03 PM
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My Lowrance did the same thing....the owners manual suggested a faulty antenna could cause this which I am currently addressing

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