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Old 01-05-2017, 08:59 PM   #1
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Default VHF/AM/FM Signal Splitter

Disclaimer........I know they are horrible in terms of safety. Just for use on fresh water where VHF is virtually useless for emergency calls. I will disconnect anytime I am at the cost (1-2 times per year max). No speaches please.

Looking for a recommendation for one that is good quality and holds up. The short FM antennas don't have enough height to pick up anything on the lake where we frequently are. Need the height from the 8' antenna to get sufficient radio reception where I typically am on the boat. Cell phone signal is fine for calls, but not steaming. Primary use is picking up sporting events, so playing from memory on the phone won't work.
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Old 01-05-2017, 10:34 PM   #2
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Splitters only use the braid of the VHF antenna cable.
For AM/ FM broadcast frequencies, height is irrelevant.
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Old 01-06-2017, 04:24 AM   #3
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Splitters only use the braid of the VHF antenna cable.
For AM/ FM broadcast frequencies, height is irrelevant.
That very well might be the case in theory. I know on my brothers boat where he has a dedicated FM antenna, reception is significantly better when the antenna is raised versus lowered against the T-top. Perhaps that is due to it getting away from other interference, but it is a very notable difference (The only electronics in the electronics box is the stereo). I have noticed the same amongst the other boats that we raft up with. Those that have a standard antenna close get garbage reception, but those that have a taller antenna tend to do fine.

I would love to do a tall dedicated FM antenna, there simply isn't room on the starboard side of the boat where the helm is. It definitely needs to be at the helm station so that I can access it to fold when going under lower bridges.
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Old 01-06-2017, 04:37 AM   #4
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Digital makes a good 8' VHF/AM-FM antenna. Not sure if there's a splitter or if its two independent elements running up the fiberglass tube. I opened up an old Digital combined Cell/AM-FM antenna and it appeared to have independent elements that extended about halfway up.
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Old 01-06-2017, 04:39 AM   #5
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Originally Posted by Auburn1 View Post
Digital makes a good 8' VHF/AM-FM antenna. Not sure if there's a splitter or if its two independent elements running up the fiberglass tube. I opened up an old Digital combined Cell/AM-FM antenna and it appeared to have independent elements that extended about halfway up.
Are the elements of the tip of the incident or towards the base. If the latter, I'm confused as to the reason.
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Old 01-06-2017, 04:46 AM   #6
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Originally Posted by autobaun70 View Post
That very well might be the case in theory. I know on my brothers boat where he has a dedicated FM antenna, reception is significantly better when the antenna is raised versus lowered against the T-top. Perhaps that is due to it getting away from other interference, but it is a very notable difference (The only electronics in the electronics box is the stereo). I have noticed the same amongst the other boats that we raft up with. Those that have a standard antenna close get garbage reception, but those that have a taller antenna tend to do fine.

I would love to do a tall dedicated FM antenna, there simply isn't room on the starboard side of the boat where the helm is. It definitely needs to be at the helm station so that I can access it to fold when going under lower bridges.
There are 2 functions. My car antennas when extended receives well but retracted hardly anything. Thats what you are describing. The actual height of my car makes no difference.
Attached close up of a splitter shows the centre core of the AM/FM antenna on the right being crimped to the braid of the VHF antenna. As most people coil up this VHF wire they actually do the same as my car antenna and get poor performance from the spiltter.
The VHF cable when used with a splitter should be extended as best as possible.
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Old 01-06-2017, 05:19 AM   #7
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Raising and lowering the FM antenna changes the polarization from horizontal to vertical. This can make a difference depending on the FM station. Also if your top has metal tubing the antenna is influenced by this metal and becomes a directional antenna or de-tuned.


Height does make a difference just like on your VHF radio, it is still line of site to the horizon, so height can make a difference.


When I am out 15 plus miles I have to raise my FM antenna to continue to receive stations. It makes a huge difference for me past 20 miles or so. My top is all fiberglass.


Jim
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Old 01-06-2017, 05:37 AM   #8
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Raising and lowering the FM antenna changes the polarization from horizontal to vertical. This can make a difference depending on the FM station. Also if your top has metal tubing the antenna is influenced by this metal and becomes a directional antenna or de-tuned.


Height does make a difference just like on your VHF radio, it is still line of site to the horizon, so height can make a difference.


When I am out 15 plus miles I have to raise my FM antenna to continue to receive stations. It makes a huge difference for me past 20 miles or so. My top is all fiberglass.


Jim
Thanks for your input. This sounds like my situation. We are usually about 1/2 way between two major radio markets, on the outskirts of each. Between competing signals, and distance, reception can be very tough. Height seems to be the only thing that helps.

Any experience with using a stainless whip type antenna for this application? I currently have an 8' Shakespeare, but would consider dropping down to stainless whip if they are compatible with a splitter.
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Old 01-06-2017, 06:33 AM   #9
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Shakespeare makes an AM/FM/VHF band separator that I've heard few complaints about other than somewhat decreased VHF performance, which you don't seem concerned about. Part #4357-S

I do second the mention to not coil up your antenna cable. I use a $2 string antenna and have in extended in my console full of electronics and I get perfect reception.
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Old 01-06-2017, 07:03 AM   #10
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Shakespeare makes an AM/FM/VHF band separator that I've heard few complaints about other than somewhat decreased VHF performance, which you don't seem concerned about. Part #4357-S

I do second the mention to not coil up your antenna cable. I use a $2 string antenna and have in extended in my console full of electronics and I get perfect reception.
This is probably what I'll do. My coastal boating is rarely during football/baseball season. We we are on the saltwater, I can just bypass it and plug the antenna directly into the VHF, and use a string type for the stereo. Takes all of 30 seconds to get to on my boat.
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Old 01-06-2017, 07:37 AM   #11
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Originally Posted by autobaun70 View Post
Thanks for your input. This sounds like my situation. We are usually about 1/2 way between two major radio markets, on the outskirts of each. Between competing signals, and distance, reception can be very tough. Height seems to be the only thing that helps.

Any experience with using a stainless whip type antenna for this application? I currently have an 8' Shakespeare, but would consider dropping down to stainless whip if they are compatible with a splitter.


I have used a stainless whip just for FM, but I never use the VHF/FM splitters, dedicated FM/AM antenna and dedicated VHF antenna.


I want nothing to possibly interfere with my VHF out on the water some 30 miles plus.


Jim
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Old 01-06-2017, 08:56 AM   #12
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FM radio sucks anyway. Too many commercials and DJ chatter. Better off looking into a cell signal booster and antenna and streaming Pandora.
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Old 01-06-2017, 09:18 AM   #13
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Originally Posted by Auburn1 View Post
FM radio sucks anyway. Too many commercials and DJ chatter. Better off looking into a cell signal booster and antenna and streaming Pandora.




Cell service does not work that far out regardless of a booster.


I listen to NFL football games on FM on Sundays via FM.


I do stream from our phones and other devices as well. But I still use FM many times as it is so much easier especially when it gets rough, or it rains or going out and back in.


Jim
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Old 01-06-2017, 09:45 AM   #14
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FM radio sucks anyway. Too many commercials and DJ chatter. Better off looking into a cell signal booster and antenna and streaming Pandora.
For music, I agree, and only use my itunes/amazon music downloads (no signal required). If you want to pick up LIVE college sports, especially baseball, there is often no streaming option. Also, not sufficient cell service to stream them if there is one.Without FM coverage......some members of the group will forego getting out on the water....which isn't good.
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Old 01-06-2017, 10:17 AM   #15
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Originally Posted by isitstuffed View Post
... The VHF cable when used with a splitter should be extended as best as possible.
I never had a problem with mine but on previous threads luck varied widely among users. This is definitely a good place to look when trouble shooting. Thanks, I will keep it in mind if I use a splitter again.
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Old 01-06-2017, 10:49 AM   #16
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Raising and lowering the FM antenna changes the polarization from horizontal to vertical. This can make a difference depending on the FM station...
In the USA, stations in the FM Broadcast band traditionally used vertical polarization for their transmitting antenna, so a vertical orientation of the receiving antennas is best. But in the past few decades many USA FM Broadcast stations have changed to transmitting circular polarization, and for those stations the orientation of the receiving antenna is less important.

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Height does make a difference just like on your VHF radio, it is still line of site to the horizon, so height can make a difference.
Yes--this is a good point. The behavior of radio wave propagation doesn't change because the licensed service is Broadcasting instead of Maritime.

AM Broadcasting in the USA is always vertically polarized. All receiving antennas are very short compared to a half-wavelength. Effective AM Broadcast band antennas on vehicles are often very carefully tuned and designed to give good performance. It is unlikely that on a boat with some randomly tuned, randomly coupled antenna created from the transmission line of your VHF radio you will get the same performance as a good vehicle AM antenna and radio. But there is no harm in trying it.

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I listen to NFL football games on FM on Sundays via FM.
Coverage of live sporting events, particularly football, is probably about the only good reason to listen to Broadcast radio these days for entertainment.
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Old 01-06-2017, 01:16 PM   #17
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Have you considered Sirius XM radio, you'll get your sports with that no problem, I just use a standard car kit with the magnetic antenna mounted on the top.
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Old 01-06-2017, 01:35 PM   #18
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Originally Posted by jhebert View Post
In the USA, stations in the FM Broadcast band traditionally used vertical polarization for their transmitting antenna, so a vertical orientation of the receiving antennas is best. But in the past few decades many USA FM Broadcast stations have changed to transmitting circular polarization, and for those stations the orientation of the receiving antenna is less important.



Yes--this is a good point. The behavior of radio wave propagation doesn't change because the licensed service is Broadcasting instead of Maritime.

AM Broadcasting in the USA is always vertically polarized. All receiving antennas are very short compared to a half-wavelength. Effective AM Broadcast band antennas on vehicles are often very carefully tuned and designed to give good performance. It is unlikely that on a boat with some randomly tuned, randomly coupled antenna created from the transmission line of your VHF radio you will get the same performance as a good vehicle AM antenna and radio. But there is no harm in trying it.



Coverage of live sporting events, particularly football, is probably about the only good reason to listen to Broadcast radio these days for entertainment.
The antenna height on a boat receiving 108 MHz FM specifically, is really still at Sea Level plus minus 20 feet or so. When you consider the land based transmitter antenna is hundreds of feet, if not meters above sea level a few feet on a boat seems superfluous. AM radio can skip around the world at night. My FM alarm clock receives from 30 miles without an external antenna. Doesn't matter if its downstairs at 3 ft or upstairs at 20. I suppose it all applies to those operating at the extreme range limitations of the transmitter including its transmitter power.
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Old 01-06-2017, 01:42 PM   #19
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Disclaimer........I know they are horrible in terms of safety. Just for use on fresh water where VHF is virtually useless for emergency calls. I will disconnect anytime I am at the cost (1-2 times per year max). No speaches please.
How so?

I used a Shakespeare splitter on my VHF radio antenna for years and years while boating in the briney blue. Nary a problem. Could transmit/receive on VHF and listen to tunes on the FM radio. Never felt that my safety was compromised in any manner.

Now the problem was that traffic on the VHF was so frequent and inane that I would frequently just turn the damn thing off. But I had that problem long before I installed the splitter.
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Old 01-06-2017, 01:49 PM   #20
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Have you considered Sirius XM radio, you'll get your sports with that no problem, I just use a standard car kit with the magnetic antenna mounted on the top.
I have, but they don't cover Clemson baseball, which is the biggest need.
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