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Old 10-08-2008, 06:34   #1
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Automatic tuner not tuninig

We bought a boat in April in the BVI. Its a Voyage 440 catamaran, owner's version, never chartered. It was commissioned in December 2004. It has an ICOM 802 with an AT140 tuner and a 23' fiberglass whip. Grounding is with a Dynaplate, though only the tuner is grounded (there is no ground connection from the back of the transciever box). I can listen fine, but I am unable to be heard on transmit. When I try to transmit, the 802 flashes "tune" for less than a second and then says "thru". From reading the manual, it seems that that means the autotuner isn't working. I do not hear any relays clicking in the tuner. I've tried switching the "thru" function on and off but it makes no difference. Any suggestions?
Derek Gale
s/v Idyll Island

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Old 10-08-2008, 07:31   #2
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It may be working OK. Just trouble-shot an 802 on Friday and found a couple of things which may be of help.

1. Be sure your power level is set to high. The one I worked on was set to low power.

2. Older 802s have a "clipping" problem, for which Icom has issued a service bulletin. This tends to cut down/off the transmit power whenever an SWR condition is sensed that the transmitter doesn't like. The factory can fix this, but you've gotta send the radio to Bellevue, WA for service.

3. The best way to tell if your radio is transmitting is to connect a good power/SWR meter to it's output, i.e., between the radio and the tuner. Better, if you have one available, connect a dummy load to the wattmeter which bypasses the tuner/antenna altogether. This will tell you how well the radio is transmitting on any chosen band.

4. The tuner may not click if it's already tuned. Have someone listen carefully at the tuner, change bands, and push the tune button. See if any clicks are heard.

5. Be sure to check all connections -- antenna and ground and power -- very carefully.

6. Ground plates IMHO are pretty worthless, especially after a few months in the Caribbean. Better to build an RF ground system which isn't dependent on them. The simplest way is via a wide copper strip from the tuner ground lug to the nearest bronze thru hull.

7. You don't need to connect the RF ground to the 802 itself. Often, doing so just creates problems (ground loops).

Good luck,


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Old 10-08-2008, 07:47   #3
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There's a switch inside the AT140 that could be in the wrong position.

I troubleshot a radio on an Oyster that the owner was confident was working correctly because he could do sailmail fine. No one could hear him in voice mode though. After looking, it was clear the tuner wasn't doing anything. I opend the tuner case and found the S1 mode switch in the OFF position. Changing the switch to NORMAL fixed the problem.

Check the switch, maybe the same guy installed your radio as the one on the Oyster...

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Old 11-08-2008, 04:58   #4
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It doesn't matter if the S1 switch in the tuner is in the OFF or NORMAL position when using the 802. All this does is protect the keying transistor from damage if the key voltage from the transceiver is over 8 volts. If you happen to be using a rig other than an Icom and it's keyline voltage is over 8 volts you should set the switch to OFF. It doesn't matter what power level you have set in the 802 either as it only transmits around 10 watts when in tune mode, regardless of the set power level. The symptoms you give is exactly what happens when there is no power out of the radio. The TUNE indicator will flash briefly and then switch to THRU. The tuner must sense forward power in order to initiate tuning, and since you say you are "unable to be heard on transmit", I would say that the 802 has no RF output...assuming it is actually going into transmit when you key/tune? You need to check for power output with a wattmeter, although there are other ways to confirm output. If there is good output and your coax, connectors and control cable check out OK, then your tuner has a problem.

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Old 12-08-2008, 07:45   #5
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When my Icom tuner goes to 'thru', it is telling me that it can't impedance match the antenna, and its time to check the ground and antenna connections to the tuner.
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Old 12-08-2008, 09:31   #6
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Yes, but it will try to tune for up to 15 seconds before going to THRU. If it goes to THRU immediately, there's a problem with the tuner, rig, or cabling other than just an antenna mismatch.

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Old 27-08-2008, 03:31   #7
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Hi Have a IC78 and a AT120 Tuner I noticed the ground on the Tuner is Bolted straight to the steel bulkhead next to the Tuner, Is this a good Idea ( boat is Steel) or should I change it to a large bolt in the Bilge ??
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Old 27-08-2008, 04:01   #8
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I would think a steel boat would make a fantastic ground plane and there would be no need to run a connection down to the bilge.

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Put my credit to shame
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Old 24-11-2008, 18:34   #9
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Came across the exact same problem today (tuner won't attempt to tune). I see good current draw on the panel load meter when hitting the tune button and get over 25 amps with a quick whistle into the mike. Must have power out right? Hook a wattmeter in line, no power out. Turns out the 802 has a bit of a quirk. There's a transmit/receive relay on the filter board just before the RF out connector but it's also just before the swr detection circuitry. This relay was not working. The PA was putting out full power but since the swr detector was after the non-working relay, the radio would not cut back the power to protect itself. The relay wasn't working because one of the pcb thru-holes on the filter board had gotten wet and corroded the thru-hole plating completely away, removing 12v from the relay coil. This was not found with visual inspection but by troubleshooting the relay control circuitry with multimeter. Once the fault was found, I could see a tiny bit of corrosion with a strong magnifying lense. A simple fix, but very lucky the PA wasn't damaged from the mismatch!

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Old 17-01-2009, 08:08   #10
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If your tuner is trying to tune for 15 seconds and then goes to the thru position, you probably have a probelm with your antenna or the connections from the tuner to the antenna. Your antenna can work ok on receive but be bad for transmitting. You could make up a simple dipole or long wire and see if that will tune.

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