AM/FM antenna different from vhf antenna?

[yjmechanic]

When i bought my horizon, it had a white fiberglass 8' vhf antenna and doesnt match the boat at all. i wanted a shorter black antenna so i went out to the store and looked. The only one they had was a shakespeare 5420xt AM/FM antenna in the height and color i wanted. I asked the sales guy and he said the only differance is the plug that comes with it. Well i bought it and cut the plug off and looked at the wiring, it looks the same as the vhf and the antenna is the same thick fiberglass construction, so i installed it. havent been able to try it out but im curious if I did the right thing. The guy told me the antenna doesnt matter whether its one or the other in the heavy type of antenna. Is he right? did I just install something that wont work? I have searched all over and cant find an answer, please help if anyone knows. another guy i talked to said if i transmitted through it, it would screw up my vhf radio. i really dont want to kill a good radio over an idiot sales person's advice, please help me out if you know and give me a brief explanation so i can learn from my mistakes. thanks

 

[Overnighter20]

Re: AM/FM antenna different from vhf antenna?

I can't give all the technicals, but I don't think it will work. The 8 ft antenna is generally 6db, and the height is needed for range, which generally is only as far as line of sight from the tip of the antenna to the horizon. FM radio waves are completely different frequencies than vhf radios.

 

[Boatist]

Re: AM/FM antenna different from vhf antenna?

Do you know the antenna brand and model?
Only way to be sure is to find out what you bought.
AM/FM is usually for the radio band your car has in it and that is likely what you got.
If that is what you got it will not work at all.
Most VHF Radios will go into a transmiter protect mode and not transmit today if the Standing Wave Ratio is over 3 to 1.
If antenna is a standard AM/FM antenna then the SWR would be over 3 to 1.

What type connector did it have on the cable??
Was it a coax with a center pin sticking out and the outer connector made to push in a hole?? If so then it will not work on your VHF and would cause the transmiter to shutdown.

If you have the model and type I am sure you could google it and find out information about what it is for.

 

[JoLin]

Re: AM/FM antenna different from vhf antenna?

Guess I'll be the PITA here, and my apologies to the OP if I offend...

Your VHF radio is a safety device, like your fire extinguisher and horn. It's also a line of sight transmitter/receiver, which means (among other things) that the height of your antenna directly effects the range of your radio.

An 8' antenna generally gives you an effective transmission range of 4-5 miles. A shorter antenna decreases that range accordingly. 4' will give you about 2 miles.

Do you really want to do that just so your antenna will "match your boat" ?

 

[Gary H NC]

Re: AM/FM antenna different from vhf antenna?

The guys are dead on about this one.The windings in the short fiberglass antenna are totally different than the copper windings in the 8 ft VHF antenna.
The SWR (standing wave ratio) will be way off.If the radio does transmit it could damage the final outputs in the radio.
It may receive from close range but thats about it.

For my FM i installed a regular stereo antenna.It his hidden in the gunnel and picks up fine.

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

thanks for the replies guys, i did list what the antenna model and brand were in the original post, shakespeare galaxy 5420xt. this is not a little fm car antenna. this is made to be a long range heavy duty antenna. it is constructed the exact same as a vhf antenna, but sounds like the frequency is differant and there for will not work. i understand what you guys are saying about the antenna size but yes i will sacrifice it for matching the boat. this boat is a freshwater boat that stays in a smile stretch of river, not an ocean boat. this is a 40k$ sport boat, i will not have a 8ft antenna hanging off of it. i looked up the vhf specs for a 4 ft vhf antenna and it says about 5 miles. at the fiver i will never be farther than that and in the ocean i would not go out further than that with a sport boat

 

[JoLin]

Re: AM/FM antenna different from vhf antenna?

thanks for the replies guys, i did list what the antenna model and brand were in the original post, shakespeare galaxy 5420xt. this is not a little fm car antenna. this is made to be a long range heavy duty antenna. it is constructed the exact same as a vhf antenna, but sounds like the frequency is differant and there for will not work. i understand what you guys are saying about the antenna size but yes i will sacrifice it for matching the boat. this boat is a freshwater boat that stays in a smile stretch of river, not an ocean boat. this is a 40k$ sport boat, i will not have a 8ft antenna hanging off of it. i looked up the vhf specs for a 4 ft vhf antenna and it says about 5 miles. at the fiver i will never be farther than that and in the ocean i would not go out further than that with a sport boat

That 5 mile range assumes that the receiving antenna is at least the same height as yours. As you noted, however, it's a non-issue for the type of boating you do. Good luck. Have fun.

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

yeah i am never far away from land or other boats, i dont need the range and most the other boats around me have much larger antennas, i really just have the radio for emergency situations and general communication, i wasnt trying to be cheap or anything with this antenna, i thought they were differant and was going to order one, but the guy at the store insisted that they were the same and id be fine. guess they will b hearing from me about there customer service advisors

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

Well bass pro is where i got the antenna and the bad advice, i talked to their manager and he contacted shakespeare antenna and verified they were wrong. they dont carry the one i need but he is trying to special order it and even offered to have his techs install it when it comes in. i wont let someone else touch my boat (prob drill holes in bulkhead to route it) but the offer is nice. they are handling it really well actually, so far. he also said if my radio was damaged that he would work something out for me there, just thought everyone would like an update

 

[turbinedoctor]

Re: AM/FM antenna different from vhf antenna?

I find a good percentage of salemen don't know as much about what they are selling as you would think they should.

Try this for fun. Pick a product, research it very well even at the manufactureres web site, then go into a store that sales it and start asking questions as if you don't know anything. It may suprise you as to some of the answers you get.

Moral of the story: Do your own research and then go into the store. A buyer well knowledged is a buyer well protected!!

Durwood

 

[jhebert]

Re: AM/FM antenna different from vhf antenna?

An antenna which is designed as a transmitting antenna for a VHF Marine Band transmitter should be quite different in its electrical properties from an antenna designed as a receiving antenna for an AM Broadcast Band receiver. However, it could very well be that in the field of recreational marine electronics a manufacturer could sell the same antenna for both applications and just change the connector. It is unlikely an antenna that was really optimized for VHF Marine Band transmitting would work really well as an AM Broadcast Band receive antenna, but it is nearly impossible that an antenna designed as an AM Broadcast Band receive antenna would be able to work at all as a transmitting antenna for a VHF Marine Band transmitter.

It could also very well be that the antenna for VHF Marine Band transmitting is completely different in its electrical characteristics from an antenna designed for AM Broadcast Band receivers, and the "sales guy" who told you they were the same is an idiot and not to be trusted.

 

[Outsider]

Re: AM/FM antenna different from vhf antenna?

Sounds to me as if you should ditch the radio altogether and use your cell phone for emergencies. If an 8' destroys the ambiance of the boat, a 4'er won't do much for it, either.

the windings in the short fiberglass antenna are totally different than the copper windings in the 8 ft VHF antenna.

Most, if not all 8'ers don't have copper windings, only a standing element that goes to the tip. Good ones will be solid copper, cheap ones may be a coax extension ...

 

[Boatist]

Re: AM/FM antenna different from vhf antenna?

Yjmechanic

I apologia I did not see the antenna type in your first post.
5420-XT is for a Am/Fm Fm Stereo radio like in your car.

That antenna is not for a VHF Marine Radio and could blow the finals on your radio if you try to transmit. Most likely your Radio will go into transmitter protect mode and prevent the transmitter from transmitting at all.
Your VHF radio needs a 50 ohms impedence and a much difference frequency.

The antenna is 93 ohms and notice it does not have a power output rating that all transmiting antenna would have. This is a antenna to recieve standard AM/FM Stereo.


http://shakespeare-marine.com/antennas.asp?antenna=5420-xt

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

Sounds to me as if you should ditch the radio altogether and use your cell phone for emergencies. If an 8' destroys the ambiance of the boat, a 4'er won't do much for it, either.


nah the four foot looks fine and the black makes it blend it better, its just the vinyl wrap around the whole boat is black and the antenna at 8' ran most of the length of the boat folded down and just looked out of place, as well as people would hit it on the way out of the boat and one person actually cracked it, i figure the holes are already there might as well keep it and just make the antenna shorter and matching color to the boat. the 4' black thats on there now (the wrong one) is ok with me, i am a function over form guy for the most part but when i dont need something and can help out the form a little, why not

 

[Boatist]

Re: AM/FM antenna different from vhf antenna?

yjmechanic
So do you mean your going to install a AM/FM radio and not have a working VHf Radio for the saftey of your boat and Crew?
Good luck
A cell phone on the water most of the time is totally worthless to get fast help.
Good Luck.

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

yjmechanic
So do you mean your going to install a AM/FM radio and not have a working VHf Radio for the saftey of your boat and Crew?
Good luck
A cell phone on the water most of the time is totally worthless to get fast help.
Good Luck.

no-no what im saying is, i needed a better fitting antenna for my vhf radio(as it had a giant antenna and looked out of place on the boat, and i dont need the range) the salesman sold me a am/fm antenna saying it would work. i am now getting the correct antenna for the vhf. my fm radio is satellite and never had anything to do with this, i just needed a different vhf antenna that matched the boat better and got screwed with bad advise from a salesman. no when this is done my vhf and fm will both work independently of eachother. safety first but if it can look good too why not?

 

[Boatist]

Re: AM/FM antenna different from vhf antenna?

That great. You had me worried for a while.
I do not know if I have seen any black 4 foot VHF but I know they do make a great quality Shakespeer 8 foot.
Hope you find your Black 4 footer.

I think I would go back to the place that gave you the bad information and see if they would at least correct the error by selling you the antenna you want at cost.
If they want to keep your business they should. Know the normal cost of antenna you want before going in.
EnJoy your boat.

 

[NYBo]

Re: AM/FM antenna different from vhf antenna?

Marine VHF antennas are available in several different lengths. Mine is 5'. It's white, but that's nothing a can of spray paint couldn't change. Regular spray paint (i.e. nonmetallic) is transparent to radio waves. While the points about line-of-site and longer=better are technically correct, remember that the Coast Guard base station antennas are situated up to hundreds of feet above water level. So a shorter antenna on the boat is not really a major factor for us inland boaters.

 

[yjmechanic]

Re: AM/FM antenna different from vhf antenna?

yeah well the last news i got from bass pro was that they were special ordering my antenna and for the confusion he agreed to sell me the correct antenna at a severely lowered price, about 70% off. and they are taking back the wrong one they sold me even thought i chopped off the connector and it has sealant all over it. i am disappointed with the salesman but i am very impressed with the length the manager is going to in order to make me happy. the antenna i want is not even one they carry so they have to order if from shakespeare and then have a skew number created in there database for it just so they can sell it to me at a price that is below cost.

 

[NYBo]

Re: AM/FM antenna different from vhf antenna?

It's good to hear how these situations pan out. Thanks for letting us know, and congratulations on the good outcome!