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My 2 year old M402 seems to broadcast very well, but I am unable to pick up boats which should be in range (10-15 miles), some of which are also broadcasting on identical radios. My antenna is a new, good quality 8' Shakespeare mounted on my T-Top. How do I check this out? How do I improve reception? Thanks for the help.
By the way, I also have a Humminbird 3000 Deep fishfinder. I read a thread on this board where someone thought this fishfinder interfered with VHF reception. I have not tried my VHF with the fishfinder turned off. Just thought I'd provide that information as well. Thanks.
There are a few things to check. First, did you leave the excess cable when you installed the antenna? A coil of cable will act as a loading coil which will reduce your reciever's sensitivity. Is the PL 259 connector clean and, tightly installed on the radio?
You can check your depth sounder's influence by opening the squelch all the way, then turn your depth sounder on and, off, while listening to static. If you detect a difference in the sound or, quality of the static while toggling the Hummingbird on and, off, this means you're having that issue.
More advanced checks, would be checking the SWR of your antenna. You'll need a meter for this that was designed to work in VHF. A CB meter isn't going to help. I suggest finding a ham radio operator and, bum his/her meter. 1.5 SWR is about the worst I would allow. If your SWR is high, then your problem is in the antenna.
If your antenna checks out, have the radio bench tested. On a signal generator, -110 dBm is about what I would expect and, -120dBm would be outstanding. Anything less than -100 dBm is malfunctioning. You ham friend might have a sig gen (signal generator) or, a local two way radio shop can easily check this for you. Go by on Friday afternoon with a six pack and, they might do it for free.
Thanks much. I did leave a couple of ft of cable when I installed the new antenna. I'll trim it off and install a new connector. I'll also do the fishfinder checks too. If no improvement, I'll do the other checks. Thanks again.
I checked the radio squelch vs fishfinder on/off as you suggested. Definitely there was a change in the interference noise. I've emailed Humminbird. Hopefully, they will have a solution. Thanks again.
I had the same problem with my hummingbird wide scan interferring with my standard horizon radio. I tried everything -- had radio checked -tested the antenna -- wrapped the antenna in foil and the tranducer cable. Never did find the problem. I did buy a NEW antenna made by Digital, an ICOM 402S and a new Furuno 1850wfd --- NO MORE radio interference
Humminbird advised me to mount the radio lower than the fishfinder (a last resort for me as the radio and fishfinder are already installed in my overhead electronics box), make sure the antenna cable does not run near the transducer cable, and to run the radio and fishfinder from separate power supplies.
Based on your comments and Humminbird's, I'm planning the following steps, each time using Radioshop's suggested procedure to check for interference:
1) Trim excess antenna cable presently coiled in the electronics box. I'll probably use the new solderless connectors to remake the connections.
2) Separate the antenna and transducer cables as best I can. The antenna cable comes from above my T-Top (obviously) and the transducer cable from below, but they come into the box through the same hole and I am sure lie together for a foot or so.
3) Power the fishfinder from a different source than the radio. My electronics box has a power strip from which both devices are now powered. It should not be too much trouble to power the fishfinder from the power strip in my console.
Thanks again to all for their suggestions. I love this Board.
Well, let's see here. If your T-Top is 8 feet above the water and your buddy's boat is set up the same way you both have 16' antenna heights. If you do the math on a pair of them at that height you come up with a range of 12 miles as the maximum, and that assumes that neigher of you are in the trough of a wave. So I'm not too suprised that you can't hear your buddy when he is 10~15 miles away.
I understand your point completely. What's interesting is that my buddy has the identical radio that I do. He can hear me but I cannot hear him...and we're usually no more than 10 miles apart. Most of the things to be done don't appear to be a huge amount of trouble anyway so I'm going to do them. Thanks.
Bill,
I'm sitting here turning this over in my head and, some thoughts occur to me. First, your if your VHF antenna is on the T-Top, and, the depth sounder transducer is under water on or, near the transom. Far be it from me to dispute Hummingbird, because maybe they know something I don't, but, something doesn't add up.
Your depth sounder's transducer is an antenna. You're going to put the depth sounder transmitter overhead and, it's antenna has to be sumberged. Then, you're going to move your VHF transmitter lower, while it's antenna is mounted overhead. It seems to me you'd be better served moving the depth sounder down and, leaving the VHF overhead. This way the wires don't need to cross paths. The way Hummingbird has you moving things, cables are guaranteed to cross paths. Your VHF would have a shorted antenna cable, which is even better. You can leave what's called a service loop on the VHF antenna, which is just enough cable to pull the radio out of the box. Also, you could shorten the depth sounder power cord, if you moved it down.
I separated the VHF antenna cables from the fishfinder cables which were wrapped together by the boat builder behind both instruments in my electronics box. I just pulled the VHF cables away from the other cables to maximize the distance between them and let them lay in the box. As soon as I did so, the radio interference that Radioshop mentioned went away. I'm going to shorten and rerun the antenna cable to maximize its distance from other cables. Then, I'll test it on a trip or two before I go to the trouble of repowering anything. Thanks again to all.
I had some transmit and reception problems with my m402 also.It was about 2 yrs. old last year.Heard on the "net" that there was a problems with some of them.Called Icom,they said send it back it has a 3 year warrenty.Sent it back,said they did a Factory update.Has worked great since then.You still need to check the obvious things first.Hope this helps![Mike]
DO NOT USE LOCKTITE ON IT!!!!!!! Loctite is diaelectric (sp?), it's in essence a plastic, which is an insulator. The outer ring on your PL-259 is the ground and, it's important to make sure it's making good electrical contact. Take a pair of pliers and, snug the connector down. Count on checking that item twice a year.
I just realized that my transducer cable runs up to my FF tied to my antenna wire coming down to the radio. Is there something I could sleave it in? I'd like to avoid moving the electronics around.
Tom
I'm not moving my electronics (receivers) around, but I am re-routing and shortening the antenna cable for the vhf so it does not run near the FF transducer or power cables. I think this will fix me up fine.
ICOM M402 Reception 
* There will be other thoughts.* 
Loctite is diaelectric (sp?), it's in essence a plastic, which is an insulator. The outer ring on your PL-259 is the ground and, it's important to make sure it's making good electrical contact. Take a pair of pliers and, snug the connector down. Count on checking that item twice a year. 
