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Need antenna for marine radio please help

munks

munks
in This Old Boat

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munks

munks

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The radio is brand new(cobra with gps )brand new antenna cable with new ends made at a marina and a brand new Shakespeare 42 inch stain less antenna I can hear great but can't transmit to no one

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Firechief48

Firechief48

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Is the antenna correct for the frequencies? It could be the mic/cord also, if you can slip another mic on that you know works try that.

munks

munks

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I'm real green when it comes to this stuff I asked the guy at the boat yard if this antenna will work for this radio and actually handed him the radio out the box he said it will work fine and you mean splice a new transmit mic on it

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Firechief48

Firechief48

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No don't cut anything just replace with a mic/cable combo if you can get one, it should unscrew from the radio. I agree with skipper though it might be transmitting although weakly. If it is then go from there, could be bad ground. Radios don't use any power receiving really just transmitting.

Edited by Firechief48
mudflat

mudflat

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what gauge wire is the power supply and how long is it?  Radios draw a lot of power to transmit and if the wire is too small you will see a significant voltage drop at the radio when you key the mic.   

jimski2

jimski2

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Check your voltage going to the radio. It will receive but not transmit if the voltage falls below 8 volts. 10 gauge wire is recommended for runs from a transom area battery. Dirty corroded connections can cause low voltage along with light gauge wire that not carry a couple amps for 25 watt transmission.

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jimski2

jimski2

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Now it works. New fuse and different fuse holder plus a different terminal for the connector. The old connections were over ten years old and they looked good but my meter pointed out the problem. A new radio and fuses were over Two hundred dollars but the new radio has gps and an emergency call button that also gives your gps location. Also it has call numbers that reach out like a telephone. I now have a pile of three old radios in my hoard in the cellar.

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Wassup8687

Wassup8687

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No still not transmitting I was told that my antenna is to weak mabey and I need to get a 8 foot at 6db instead of the 42 inch and at 3db make sense to anyone

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I'd check out the antenna connector at the radio. Use an ohm meter and put one wire on the center lead and the other wire on the outside of the connector where it screws onto the radio. You should be showing 0 ohms. If it's anything above that you have a short and it won't transmit but would receive.

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Xxx

Xxx

Posted
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42" isn't very high depending on where it's mounted, most guys run 6-8 footers and get the one which has the highest quality materials and spun to the top, Shakespeare makes a good whip with gold components and is spun with wire to the top. These radio's transmit in a strait line so the higher your antenna is the more you will receive and of course transmit. Also if you have a lot of extra Don't coil it up and use a chicken band to hang it out of the way keep the wire from touching each other. Hope this helps

skipper19

skipper19

Posted
Posted

Still the easy way to check the transmission is to get a portable, or have a buddy with a radio on the channel that is in a boat next to you. Se if anything is coming in. Nothing coming in means the radio is malfunctioning on transmission but can receive.

3 things will keep it from transmitting. The microphone.

The antenna connections, regardless of antenna size or DB gain or even power supply, but it does make sense to use large guage 10, and be sure you have full 12.4 to 12.8 volts coming to the radio.

Last, and not uncommon lately (cheap grade solder in Mexico), the radio has a problem in the finals circuit, ie, bad diodes or cracked circuit board.

Simple checks like mentioned with a meter can find troubles. Check the coaxial cable on both ends and the radio connection to rule out cable and radio grounding. Use an ohm meter.

Have someone hold the meter probes to the antenna pin hookup on the radio and then on the antenna pin end of the cable as you key the mic. Set meter on amps with the antenna hooked to the other end, and you should get about 2 amps when the radio is keyed on 25 watt max output.

Word of caution though, do not hold the mic keyed for more than a few seconds to get your readings, it can damage the circuit without proper resistance from an antenna hooked up.

As for the gain, it won't make any difference 3 or 6 or 8 other than higher gain is just more focused energy. Same power, different focus. Instances in a boat with high gain antennas, where you might get longer transmission by line of sight are in calm seas and a perpendicular antenna position, giving max range. Rough seas rocking the boat, and changing the perpendicular position to the horizon is where you would get better transmission with lower gain, but a little less distance. Rocking a high gain antenna will have the focus miss the receiving radio antenna of the same height at the horizon. In regards to reaching a base like the coast guard, the higher gain is more powerful to the tall antennas that the coast guard would use say 50 miles away due to the more focused transmission of a high gain. Neither would effect the normal power of the radio if it is functioning properly in a few miles. In eithercase, Gain is not a reason for no transmission.

The meter, ohm, and volts, and amps, is your best tool along with a buddies radio to receive on.

Ohms = 0 is good at the back of the radio, center pin to outer threaded connector.

O ohms or no buzzer center pin to cable threaded outter. Any reading and the cable is no good and shorted.

Ohms should have some continuity one end center pin to other. There is some resistance set into a cable depending on its RG number. Usually 75 or 50 ohm per 100 feet. You just want to hear a buzzer on a meter if the cable is Ok on that test.

Volts should be battery charged voltage 12.4 to 12.6 on any power lead to the radio.

Amps should be about 2 coming from the radio antenna hookup on a 25 watt setting.

Even better is to check all the amp and watt values with an SWR meter designed to hook between the radio and antenna to read all those values on one guage. See if you can borrow one from someone or have the radio tested in a shop that does that work.

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Firechief48

Firechief48

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Posted

Antennas should be matched to the radio however even a mismatched one should transmit if even only a short distance. I agree with Skipper and get a radio next to yours and see what happens first then go from there.

munks

munks

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I will try the oms test when I get back to my camp I appreciate all your help on this I tried hailing boats that were next to me at the launch and still nothing I have this feeling my ptt on my mike is not working at all

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