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Old 12-02-2009, 14:21   #1
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SSB antenna questions

I have a Icom M710 SSb which doesn't seem to be recieving any signals other than a weak morse code. I've never had an SSB before, so I'm no expert, but I have had an SSB expert on the boat and he said that the radio was defective. I sent it to the local certified tech, who then sent it to Icom, who then sent it back. All have said that it passes all tests on all bands. The person who thought it was the SSB though said that it was the radio as you could for instance hear the same weak morse code signal on several different bands, but really nothing else. Sooo. I'd like to double check the antenna. Can I do something simple like hook up a wire to the antenna jack on the back of the unit to test it to ensure that the radio actually can recieve signals? Would that work or just create more issues. I do know not to try to transmit!
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Old 12-02-2009, 14:30   #2
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Any random length wire inserted into the center pin of the antenna connector should yield some signals.
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Old 12-02-2009, 14:35   #3
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Try this. listen on 5, 10 and 15 MHZ for time announcements. they should have a beep countdown and give GMT at the top of every minute. If you can't hear these, then you probably have an antenna issue. Try connecting a long wire from antenna tuner and run up mast. Still, nothing? delete the antenna tuner and you should still be able to pick up the time@ 5,10&15MHZ. Ground plane is not important for just the receive side, make sure your ground plane is appropriate for transmit.
The morse code you hear could be interference from the fridge/freezer units. Try turning those and other items off while listening to see if the "morse code" disappears.
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Old 12-02-2009, 16:08   #4
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ssb

Is the installation new to the boat? Has it ever worked?
What is the antenna you have?
what tuner unit do you have?
It sounds like a "fault" after the antenna connection on the back of the set.The weak cw may be interference from refreg compressor or inverter etc on board & not external signal.

The earth point at the tuner is critical & should be as short as pos.

Regards Bill
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Old 12-02-2009, 16:35   #5
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An "SSB expert" and a "certified tech" could not tell you if your radio has a receive problem? That's pitiful. I'd like to know who the tech in Annapolis is. You should be able to pick up 1430Khz Annapolis with nothing but a screwdriver touching the center pin of the antenna jack.

Eric
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Old 13-02-2009, 03:34   #6
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It is possible that your coax connectors have a short. disconnect both ends of the coax and check with an ohm meter from the center pin to the shield. Make sure you are not touching either with your hand. There should be an open circuit. I would post the names of those "experts" that could not figure out your problem. There certainly was no need to send the radio to Icom for a checkout. Make sure their is a connection from the tuner to the antenna also and that it doesn't have any shorts.

You can replace the antenna with a piece of wire attached to the center pin of the coax at the antenna connection (or tuner input) to check the antenna operation. Six feet should be enough for a test. If you get signals, the antenna is then the next suspect item. My gut would be to suspect the coax connectors with the shield braid shorting to the center pin inside the connector.

I doubt your on board refridgerator knows how to send cw. Just in case, keep it stocked with good food and beer. It may know how to do other things and you want to keep it happy.
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Old 13-02-2009, 07:26   #7
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A quick way of making a receive antenna - take a known good length of rg8x. If it has two connectors on either end, remove one, strip back the shield, and leave a 4-5 inches of the center conductor exposed. make sure the shield does not short on the center conductor

Get a length of wire, old lifeline, etc. Attach one end of the wire to the exposed center conductor of the cable. Attach a halyard to the other, and hoist it up as far as your wire length allows.

I have done this with an old lifeline with very good results.

Chris
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Old 13-02-2009, 07:43   #8
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Just trying to be comprehensive in the fault tree....I am sure you know this, but...do you have the MODE set to USB (upper side band) for the marine SSB frequencies? "USB" should appear on the screen.

Just trying to help

Best

John
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Old 13-02-2009, 08:31   #9
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Once I get it back I'll try all of the suggestions, just waiting for the local service guy to ship it. Prior to that I'll check the coax for a short. If there's no short I'll do what Chris (Witzgall) suggests. Actually, I think I'll start this now. These are great suggestions.

The SSB did work for the original owner, but I've never seen it work. We did try the time, and couldn't recieve it. We'll see, probably an update in a week or so after I get the unit back, hook it up and then try it with another antenna.

Thanks guys!
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