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Old 24-08-2022, 04:45   #1
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ICOM M802 TX issues

Good afternoon all

I am after some advice, as I know there is a huge wealth of knowledge on this site, and it could potentially save me a lot of time, hassle and money.

I am currently delivering on a good friends Grand Soleil 45 currently in A Courna, Spain, and the boat is making its way over to Grenada for January.
We have a ICOM M802 and AT140 fitted and then connected through to the insulated backstay, and a KISS grounding wire system.

When crossing Biscay over the last few days I have managed to receive weather fax to a good standard, however the unit does not appear to be transmitting at all.
I have had a good read of quite a few of the previous blog posts and tried to follow the diagnostic that have been suggested to others as much as possible, I shall try and list what I have tried and if you have any more suggestions I would be really grateful.
I feel the next step may be to take it out and get a ICOM dealer to have a look at it, but I hope its a simple fix.

- Voltage at the transceiver and at the ATU on the control cable is 13.4V.
- Using a clamp on amp meter on the input when the unit is on it draws around 2.4 amps. When the PTT button is pushed in low, med or high mode on FKS mode this goes up to only 5.8 Amps.
- When the PTT button is pushed there is 1 click on the main unit and the ATU.
- Upon pushing the PTT button on the screen TX comes on, no bars appear at all.
- Upon pressing Tune, TX briefly flashes and then THRU is displayed.
- I have checked the Coxial cable between the main unit and the ATU, both core and screen show around 3-4 Ohms. High resistance when cross connected at one end.
- Connection from output of tuner to backstay is still ok.

- I do not know the last time a good voice transmission was made (or if one ever has been made on this yacht) I know that really doesnt help!

If there are any other checks I should do before I look at trying to find someone in Spain to have a look and no doubt fork out a load of money hunting a read herring, any advice would be really appreciated.

The ultimate goal is to get the Pactor IIe working to RX GRIB for Atlantic crossing in Jan, but just some Voice TX for now would be good!

Kind Regards
Edward

S/Y Magic Dragon
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Old 24-08-2022, 05:01   #2
ejs
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Re: ICOM M802 TX issues

SSB is carrier suppressed, so there is no output unless you are talking . Repeat the test and talk into the microphone .
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Old 24-08-2022, 05:09   #3
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Re: ICOM M802 TX issues

Quote:
Originally Posted by ejs View Post
SSB is carrier suppressed, so there is no output unless you are talking . Repeat the test and talk into the microphone .
EJS,
Thanks for the response.
All the above were done while whistling into the mic.
I have repeated with talking at a normal volume and results are exactly the same.
Mic cable/unit is relatively new, replaced 2021 and basically unused.
Ed
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Old 24-08-2022, 05:45   #4
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Re: ICOM M802 TX issues

Ok whistling would have been fine. The fact that it doesn't show "tune" after you tune it says there is an issue with the antenna. The tuner should click a bunch when you hit tune and it should say tune when it finishes. Try different bands, and see if you can get it to tube, and if not, start checking the antenna, could be a short or open. Receive is much less sensitive to a mismatched antenna than transmit
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Old 24-08-2022, 20:29   #5
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Re: ICOM M802 TX issues

Whistling is fine but that is old school. We now have the technology in our hands to produce a fine tone for testing. It is your phone. It can produce single tone or dual tone without having to wet your lips and try to get some kind of sound out of your lips. So... use your phone, even pressing one digit on the phone app will give you a good tone in the speaker or earpiece.

OK... if you haven't done so, start at the radio and work your way aft, or start at the tuner and work your way forward. What ever is easiest for you.

You are going to disconnect all the wires and cables one at a time. You will clean each connection and put the cable back where it belongs. Inspect the connects, both the wire and the connector it was connect to. When one is done, move to the next. You are looking for corrosion or broken wires.

On the coax, you will test to see if the connector is spinning on the cable. It should not. If it does then your ground (screen) is broken. You will need to repair the cable.

If you have any contact cleaner you can use that. NO WD-40!

One other possibility I can think of is incorrect configuration of the tuner/radio interface. Meaning, either the radio's tuner program is not correctly selected or the tuner is not configured for that particular radio. Reaching here, but it is still possible.

When troubleshooting I follow the 3 P theory; Power (electrical/RF) / Parameters (radio to tuner interface / data device to radio interface); Parts (replace parts that have failed). The method keeps me focused, and I never chase more that one problem at a time. It is like chasing rabbits; catch one rabbit at a time else one will be running around chasing and never catch any.

Good luck, and as always, JMHO
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Old 30-11-2022, 02:56   #6
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Re: ICOM M802 TX issues

Exactly same problem here. It appears like the radio is not sending out any power. I worked thru all the steps above and can not find any discrepancy.
I brought the radio and tuner used. Maybe this guy spoiled me.
The over thing is the „excess“ cable from the radio to the tuner. I coiled it up to look nice and tiny. Maybe this „coil“ prevents the power from going to the antenna. I have to dry next time.
Any experience with that?

Cheers

Dominic
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Old 30-11-2022, 03:52   #7
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Re: ICOM M802 TX issues

After checking the obvious things listed above, the next step is to connect the transmitter to a dummy load, and see if it transmits into that.

https://mfjenterprises.com/collectio...oducts/mfj-261


If it can't make power into the dummy load, the transmitter needs repair.


If it works fine into the dummy load, the problem is in the feedline, tuner, antenna, or ground.
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