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Dorado

question about radio antenna

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Got a question for the great hive mind that is the Wire.  For car stereo antenna, can the signal be run down a standard wire? I'm asking because of my boat. I've recently purchased a small sailboat. I'm looking at adding a stereo to it for music and weather updates. I'd like to attach the antenna as high as I can which means running it up the mast. Would it be possible for me to hook it up to a standard wire and then back to a coax?

I'm asking because of this:

https://smile.amazon.com/Quality-Waterproof-Terminal-Connector-Marine/dp/B07G6HCYML/ref=pd_ybh_a_14?_encoding=UTF8&psc=1&refRID=191SG4QSP7KWAQ2D8QSQ

If I can use this plug then I could wire my two lights and the antenna that are up on top of the mast as well as the radio antenna. Or is 20-25' a bit much for an antenna? I don't have many other options other than just hooking it to the side of the cabin and using it there.

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Antennas are "tuned" for the frequency the're designed for. At the middle of the FM band, 98 Mhz a full wave antenna would be ten feet. Your vehicle antenna isn't that because it's probably a 1/2 or 1`/4 wave antenna OR, has coils that 'tune' it to the proper frequency. The coax run to the antenna isn't included in that measurement.

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20 minutes ago, Dubious Don #56333 said:

Antennas are "tuned" for the frequency the're designed for. At the middle of the FM band, 98 Mhz a full wave antenna would be ten feet. Your vehicle antenna isn't that because it's probably a 1/2 or 1`/4 wave antenna OR, has coils that 'tune' it to the proper frequency. The coax run to the antenna isn't included in that measurement.

:huh: uh.....

 

 

.........what?

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Do not use std wire-You will pick-up RFI(AKA 'white' noise).

Only use the correct shielded cable for ant.

That connector should not be used.

OLG

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SiriusXM makes a marine grade unit.  You might have better luck with that.  IIRC, antennas on top of a mast make great lightening rods.  :o:o

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13 minutes ago, The Original Lumpy Gritz said:

Do not use std wire-You will pick-up RFI(AKA 'white' noise).

Only use the correct shielded cable for ant.

That connector should not be used.

OLG

I figured I could run a shielded coax down the mast and connect it to that connector then come off the other side with more coax to the head unit itself. If I run the antenna on the top of the mast then I need a way to disconnect the wire through the deck hence that connector. Really couldn't find a better way.  My only other thought is to mount the antenna to the side of the cockpit but then I'd be getting the various lines caught up in it. I may be able to run it off the transom, but it'd be right down near the water.

10 minutes ago, Calamity Kris said:

SiriusXM makes a marine grade unit.  You might have better luck with that.  IIRC, antennas on top of a mast make great lightening rods.  :o:o

I really don't want to pay for a radio that only gets used on the weekends. If I had it in my truck then I'd be okay with it but I'm not going to pay for a service that I can get "free" when I only need it for a weekend at a time. Masts make great lightening rods.

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1 hour ago, Dubious Don #56333 said:

Antennas are "tuned" for the frequency the're designed for. At the middle of the FM band, 98 Mhz a full wave antenna would be ten feet. Your vehicle antenna isn't that because it's probably a 1/2 or 1`/4 wave antenna OR, has coils that 'tune' it to the proper frequency. The coax run to the antenna isn't included in that measurement.

 

1 hour ago, Dorado said:

:huh: uh.....

 

 

.........what?

 

In theory you could run coax, that's a wire made for antenna to radio connections,  to an antenna mounted....somewhere.  An antenna for FM radio would be ten feet, five feet, 2.5 feet or 1.25 feet. About. A random length of wire shoved into the back of a radio, may or may not work well. That connector you posted? Not gonna work for radio. I would purchase an antenna "system" designed for sailboats if it was me. 

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First you are receiving a signal not transmitting one. So resonance and impedance really don't matter.

And you can use that connector no problem for what you are trying to do. I do have a couple of questions though.

 

1. Do you have to disconnect the cables or is the cable run permanent?

2. How far will the radio be from this connector?

3. If close is all the cabling between the radio and connector easily accessible.

Is your mast conductive (Steel or Aluminum) or non-conductive ( Wood  or Fiberglass )

 

With the above data I can give you the best solution.

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1 hour ago, The Original Lumpy Gritz said:

There are marine grade connectors for this.

Would a solder-less PL-259 connector work?

https://www.hodgesmarine.com/SHAKESPEARE-PL-259-G-STANDARD-MARINE-RADIO-ANTEN-p/shapl-259-g.htm

 

OLG

 

Pl-259s by design are not water resistant and as such cannot be used to route a cable through a bulkhead that is exposed to the weather.

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2 hours ago, The Original Lumpy Gritz said:

Do not use std wire-You will pick-up RFI(AKA 'white' noise).

Only use the correct shielded cable for ant.

That connector should not be used.

OLG

But... but... MacGyver once took the strands of wire from steel belts on his captor's car tires, strung 'em together, tied 'em to an array of Zip-loc bags filled with farts to send 'em aloft, and was able to send a message to 007 in London using the RFID tag in his underwear as a transmitter, and his Zippo as a Morse Code key.

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23 hours ago, Sedalia Dave said:

First you are receiving a signal not transmitting one. So resonance and impedance really don't matter.

And you can use that connector no problem for what you are trying to do. I do have a couple of questions though.

 

1. Do you have to disconnect the cables or is the cable run permanent?

2. How far will the radio be from this connector?

3. If close is all the cabling between the radio and connector easily accessible.

Is your mast conductive (Steel or Aluminum) or non-conductive ( Wood  or Fiberglass )

 

With the above data I can give you the best solution.

I would have to disconnect the cables. The aluminium mast comes off for trailering. I would be mounting the radio within 3 feet of the connector. Wherever I can find a good location. Everything is fairly easy to get to.

Thinking about it I could probably mount the antenna inside the boat. I was just thinking that higher is better. The mast is about 24' up.

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1 hour ago, Dorado said:

I would have to disconnect the cables. The aluminium mast comes off for trailering. I would be mounting the radio within 3 feet of the connector. Wherever I can find a good location. Everything is fairly easy to get to.

Thinking about it I could probably mount the antenna inside the boat. I was just thinking that higher is better. The mast is about 24' up.

 

Good to know. 

You have a few options.

One is to run the coax cable to the top of the mast and install the antenna there. You will want to make sure the mount for the antenna is connected to the mast with a good electrical bond. You need to use an anti-oxidant like NOALOX on any connection to the aluminum mast.  If there are any coax connectors as part of the run be sure they are sealed against moisture intrusion and that they are protected from direct exposure to the sun's UV rays.

 

Is your mast connected in any way to a connection that makes contact with the water? If not then what I would do is connect the center conductor of the coax cable directly to the base of the mast and use the mast as the antenna. You can use a short piece of copper wire to make the connection. Make sure it fits into the center socket of the radios antenna plug and is not making contact with the outer part of the connector. Attach the other end of the wire to the mast using an existing fastener.   This is easy to test out without making any permanent connections. With an antenna connected to the radio and placed on the deck tune in a weak FM station. Now connect the center pin of the radio to the mast and see if the signal gets stronger. If it does then I would use this method. The fewer wires you have running to the top of the mast the better. If you go with coax cable, I would probably install one of these through deck waterproof fittings Sometimes

called marine glands. They are available as straight or 90 degree and allow cables to pass through decks and bulkheads with the connector attached.

 

They are available from many manufacturers but the advantage is that these is no break in the coax cable to allow water intrusion. 

 

In my current job 90% of all unscheduled maintenance on cabling is due to water intrusion into connectors. Seems that no matter how good of a job I do sealing connectors the sun eventually degrades the sealant and lets water in.

 

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Dave,

The only problem I see with what you're suggesting is that I won't be able to disconnect the wire. That's a big thing for me. The mast itself will unhook from the deck and attach at the bow pulpit and lay across the boat into a crutch at the stern of the boat for storage and transport. It's going to spend more time like this than up. I must have the antenna cable where I can disconnect it. Although I may have come across a better solution. It's not as great as having the antenna at the top of the mast but it'll work just fine for most of what I'm wanting.  No thru-hull fittings either. Although I did like the idea of using the mast as an antenna. I may use that if nothing else as I know I can make that work.

I really appreciate the help and ideas. Spent this weekend working on the boat and took it for my first sail yesterday. Perfect day for it. No hiccups except for someone in a new fancy boat crowding the docks making it difficult to maneuver.

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Cut the coax at the bottom of the mast in a convenient place and install a barrel connector.

https://www.showmecables.com/114?gclid=EAIaIQobChMIts-Nn8Li4QIVdBh9Ch2ASQ-sEAQYASABEgIcIPD_BwE

 

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On 4/14/2019 at 7:52 PM, The Original Lumpy Gritz said:

Do not use std wire-You will pick-up RFI(AKA 'white' noise).

Only use the correct shielded cable for ant.

That connector should not be used.

OLG

Never tried it myself, but in this part of the world it's not that uncommon to see a pickup with a busted off antenna patched up with a coat hanger. Lots of rednecks herebouts.

JHC :P

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Is it necessary to put an antenna at the top of the mast? FM is a line of sight signal that’s limited to the curvature is the earth, or geographical obstructions  

 

If you’re that far away from the signal, the height of your mast won’t make that much difference. 

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Mounting the antenna a few inches away from the metal mast will minimize the the signal because the mast is a large ground plane.  It needs to be at least a 1/4 wavelength away.  Even then it will have a null in the pattern in the direction of the mast.

P.S. car a marine grade car radios signal input circuits are designed for the standard automobile antennas & coax.  There are extension cables that have a capacitor in series with center conductor.  If you fabricate a long cable the signal strength sucks.  How do I know?  Been there done that.  I have a cabin in the woods of Northern PRK that is 14 miles off the grid.  I installed a car radio indoors & antenna 10 feet outside on the roof.  I fabricated a extension cable & after connecting it the AM reception was worse than when the antenna was leaning against an inside wall.  I bought a car radio extension cable which eliminated to issue.  This may not be an issue if FM band is all you care about.

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