View Full Version : Need Marine Radio Help
Doc
I installed a Ratheon 45 marine radio in my brothers '95 Lund last summer. I put it under his dash, with a 3' plastic ratcheting mount antenna and did all per mfg. instructions. Wired it to a terminal block, pos. to a fuse block, with the radio on its own fuse. Worked fine until the rest of the boat gets turned on 50HP Honda, Eagle Optima locator, etc. The reception is fine but when things are on his transmissions are just noise. Wires
(antenna and power) are close but not touching each other or any other wires. Extra antenna wire is coiled and secured. Is there a "filter" for such an application? If so where do I put it and where do I get one? Would I be better off running seperate wires both + & - to the radio with an in line fuse and not use the terminal block/fuse block? STUMPED!! Wired my boat the same way as his is with no trouble. Please help. Thanks in advance.
Doc
Go to Radio Shack and get a filter. They have a sealed unit, don't know the model number, meant for use in automobiles with Ham Radio transmitters. Get the 20A model -- cost's about $25.00 if I remember. It's a small black rectangular box with three wires. Mount it in an enclosed place under the dash. Wire it in SERIES with the "hot" lead to your radio - RED wire toward your battery, BLUE wire toward your radio, and the BLACK wire to your battery negative (ground) side.
Hans
I'd try going directly to the battery with the Positive wire first. That alone may solve the prob. Make sure all connections are soldered.
I would also suggest you shorten the coax to have no coil in it. If there is a coil in it, that will act as a balun. This can create a high "Standing Wave Ratio" and reduce the sensitivity of the reciver, and allow noise into the front end. It will also reduce the output as there is a self limiting circuit to protect the output transistors. Find a Ham operator with a VHF SWR bridge to check out the match between the radio and the antenna. Good luck FISHING...Kaz
Doc
Kaz, if the problem is the coiled coax wouldn't it affect the transmissions without the rest running? Or does it act as an antenna for the other noise? It only bothers the radios that are trying to receive him. His receives fine with all on. We had 2 boats with radios trying to receive his tranemissions and both had trouble. I have a 3' stainless antenna and could only hear noise. The other guy had an 8' antenna and could just make out the transmission over the noise. Thanks for the help.
Doc
Doc
JKJ, if I understand correctly, I should run a separate hot wire directly from the battery to an in line fuse directly to the radio. Then I could run the neg. to the terminal block. Would there be any benifit to run a separate neg. wire to the battery? Thanks for the help.
Doc
Doc
Hans, thanks for the post. Is this filter fix a common thing? Would it be O.K. to use it in conjunction with the separate wire of JKJ's post? The running of a separate wire is not a real big deal. Maybe I should do one at a time to see what works. Another post from Kaz tells me to shorten the coax. I think I will run a wire first with out routing it for good and test it then try the filter then the shorten deal. Will post the results. May take a while the boat is still in storage. Thanks again for the help.
Doc
Slip_Bobber
04-10-2001, 03:34 PM
I'd suggest a seperate ground wire to the battery before anything. This has cured many VHF problems. The ground wires from a terminal block to the battery are most of the time to small. Even on some new boats.
If he is transmitting noise, then he may have trouble with his grounding. The coiled up coax can also cause all kinds of troubles. Try a portable or differant antenna, or with the coax streached out and see what happens. The filter Hans suggested is a way to filter out noise that gets into the power line, and is a good idea. But if the SWR is very high, then power is automatically reduced, and the noise gennerated by the motor is stronger than the modulation from the mic. As I understand it all works good without the motor running. Hash is heard when the motor is running. The filter should get rid of the hash, but with the coil in the coax, the range will be reduced. The coiled coax is still not a good thing. Strange things happen in the radio world. Nothing is for sure. Two meters (ham freqencys) are very close to the marine bands and a direct heavy gauge wire to the battery is a given. Next make sure all connections are tight or sodered. Keep antennas feed clear of any other electrical connections and not coiled, unless you are purposely using it as a matching device, mostly on the lower frequencies. Check out the SWR and watts out to the antenna with a power reflective watt meter. The shorter the antenna lead the less loss you will have, caused by length of the coax. 25 watts, what marine radios are rated for should carry a good 10 to 15 miles over water and does a good job around islands. On Lake of the Woods, I can relieably talk from the Rainy River gap to Garden Island, about 25 miles. My friend uses only a 18" whip on his 17' Sylvan, and we communicate a good 7 to 10 miles without any problems, I have an 8' 6db gain antenna on my boat. In the winter I use a 36" base loaded whip on the top of my King Crow fish house, and I talk to the trucks and the resorts from, 5 miles to the trucks, to 15 miles out to the resorts..If you are in the Twin Cities or close, let me know, as I have the test equiptment, and would be willing to help. Good luck.....Kaz
Kaz & Slip Bobber, it sounds as though the first thing to do is to run direct + & - wires to the radio from the battery. What is the recomended guage for this? (Bat. in the back to dash in the middle of 16' boat.) The wires off the radio, as you know, are small and in this situation have to be routed with all other wires from the back. Would this create additional problems? I will also shorten the antenna coax to the recomended length, if for no other reason, to get more distance. I will do the same for my boat. I don't normally need a lot of distance but for saftey sake it is a good idea. Thanks again for all the help.
Doc
Bucko
04-10-2001, 06:19 PM
Kaz,
I just installed a Ray 45 on my boat. The instructions that came with the radio said to make the antenna lead as short as possible. The instructions that came with the Raytheon 8' antenna said not to cut the lead. Not sure what to do I coiled the lead. You seem to know what you're talking about, so I'm headed to the garage to shorten the lead. Thanks for all the information.
Bucko
rngrfshm
04-10-2001, 07:21 PM
Hi Doc,
I run my radios directly to the battery and in some cases a seperate battery that isnt the starter, but seperate altogether. Small 12v Gel Cell 7ah or 20ah battery. I have done it directly to the starter with no problems on boats but never had much success going the route you did without an inline filter. Try going direct to the battery for + and - first either the starter or all together a seperate small 12v like a gel or something similiar. I have some small 7ah Gells sitting in my one locker beside the console that all of my electronics are in and have them wired up to the onboard charger. Works great and have installed several boats this same way with no drainage on the starter motor. I have seen that some motors do not have a big enough amperage charge to recharge your starter battery after it has been shut of all day long running your electronics on the same battery draining it. That has happened to me and several friends so that is one of the reasons to go to a separate battery and less interferance.
Kaz,
If he shortens the coax, doesn't that absolutely neccesitate putting an SWR meter on it to tune the antenna? I always assumed the factory length of the coax supplied with the antenna was of the proper length to at least get you in the ballpark of an "ideal" SWR.
DOC,
Here is something extremely simple and fast you may want to try: If the rear of the radio is metal (some radios even include a lug), attach a piece of wire to it and run it to ground. Worked wonders for me with a reception problem, perhaps it will work for your transmission problem as well.
ET: The coax that comes with the antenna is not necessarly the best length for the antenna match. In most cases they give you 20' so it will reach the radio in most boats. You would loose more output to the antenna if you had to put connectors and couplers inline to reach the radio if the antenna was supplied with a stub coax. As ham radio operator, I always, on VHF, which marine radio is, use the direct, shortest, antenna lead as possible. Any SWR under 1.5 to 1, will be well within the acceptable limits for a tuned antenna. The loss you get from a longer coax, both recive and transmit, with a coil in it, out weighs the benifits of the feed line resonance. I would cut the antenna lead and ground the transciver directly to the boat and battery. I would also use 12 gauge wire for the +12 volts and the ground. Good luck....Kaz
Bucko: See my responce to ET. I have helped several of my friends with their radios, and always had good results. In electronic installations, "Shorter is better". In a fiber glass boats I have even placed ground radials under the antenna mount, 18" long, to give the "Ground plane effect", which improves the reciver sensitivity and transmit range. Good luck FISHING...KAZ
Yes#1, the filter should be available at any neighborhood Radio Shack store.
Yes#2, running a direct DC cable to your battery (including the filter) is a good idea.
Yes#3, a short coax (within reason) is a good idea in most cases, but I don't think that's your problem. BUT, some antenna designs use the coax braid as a counterpoise of sorts and the length in those cases *IS* important, so don't cut it if the mfgr says not to.
Yes#4, dress out excess coax in long "back and forth" runs, not in a neat coil.
Another point -- make all your power ground connections to the BATTERY, not to the HULL! They are not always the same, and you could cause some interesting damage if you violate this rule!
ATTENTION: Go back and read the last paragraph again! :-)
Hans