Vhf/fm Radio Splitters

[twodzusfittings]

I am doing an upgrade on my boat and want to use the mast antenna for both the VHF and the FM radios. I fear some interference while both are in use simultaneously. I have looked on line and have found a wide range of options, from simple TV cable splitters to expensive amplified units. Would a simple co axle cable splitter like this do the trick?

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[Jackdaw]

I am doing an upgrade on my boat and want to use the mast antenna for both the VHF and the FM radios. I fear some interference while both are in use simultaneously. I have looked on line and have found a wide range of options, from simple TV cable splitters to expensive amplified units. Would a simple co axle cable splitter like this do the trick?

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Your VHF performance will suffer if you do. Best to use a cheap AM-FM whip/wire, of if you need more FM performance, look into one of these.

http://www.amazon.com/Shakespeare-4357S-Vhf-Band-Separator/dp/B005AI6KVA

 

[Rich Stidger]

The picture of the spliter you show is for TV only. The only "combiner" that I have ever seen has a switch to connect the antenna to either the VHF or the FM radio. For a variety of reasons I believe that these are a bad idea. You are better off with Jackdaw's solution.

Another option if you also need a TV antenna is that the round UFO type antennas have a connection for a FM radio as well as a TV output. I use that and it works great.

 

[joker460]

You may want to look at this http://radioworld.ca/marine-am-fm-tv-antennas-ra201-p-567.html

 

[redhead78]

I bring the same sirius reciever back and forth from both cars to the boat. I got i install kit with the reciever, and bought 2 extras, and installed in the boat. Has a remote and I simply lift out reciever and insert in the boat, no interference at all, cost me $9.95 a month for ala carte deal. I wish I did it years ago..crystal clear....Red

 

[Bill Roosa]

The TV rated splitter is a 75 ohm device and will work for your stereo. Your VHF is a 50 ohm device and will suffer a major loss of radiated power and received signal strength if you put this in the antenna circuit. There are devices that will interface 75 and 50 ohm systems. Google VHF FM antenna splitters or check the WM site.
Also make sure the coax from your stereo to the splitter is 75 ohm and the coax for antenna and VHF radio to the splitter is 50 ohm.

 

[Crazy Dave Condon]

Shakespear has for years made a specfic marine VHF antenna splitter for specifc use for receiving both VHF and Am/Fm signals. Never had an issue nor any interfernce with the VHF either in clarity, strength, signal, etc.. All my customers were grateful for that little handy item. It does not cost much and is easy to install. West Marine sells them.

Crazy Dave Condon

 

[jcrumpley]

depends on fm signal strength

If you have good fm signal strength in the area you sail, I'd just go with a separate 10 dollar rubber whip antenne mounted inside the cabin. If you need more reception than that, go with the Shakespeare 4357S Am/Fm/Vhf Band Separator. I have that on my boat with an amplified glomex on the mast and get great fm reception. The shakespeare piece was well worth the price to me.

 

[med2463]

We installed a Shakespeare antenna splitter for VHF and FM. Works great since antenna is at top of mast. Not a big deal to install. Got it at West Marine who sold it for lower Defender price. http://www.westmarine.com/webapp/wc...toreNum=50157&subdeptNum=50187&classNum=50192

 

[twodzusfittings]

Finally finished my electronics wall. I purchased a simple VHF/FM splitter off Ebay for $22, as a trial unit. Works really well. Need to set up a signal strength meter to test strength. So far so good. Will report back when the season gets underway to let all know about signal strength.

 

[Forrest15112]

A simple splitter is not what you want. The device many here are referring to you will prevent the high power from your VHF transmit from damaging the sensitive receiver in the stereo. Hopefully, that's what you got off eBay. There will be no interference when both are receiving, however the stereo receiver will be desensitized some when you transmit on VHF. The important thing is to not destroy the stereo receiver.

 

[twodzusfittings]

The set up is identical in values as the Shakespeare unit everyone has eluded to. In the "box" from which the connecting wires come from are the diodes and resistors neccersary to avoid backfeed, wow and flutter in addition to avoiding one unit damaging the other.

 

[KD3PC]

The set up is identical in values as the Shakespeare unit everyone has eluded to. In the "box" from which the connecting wires come from are the diodes and resistors neccersary to avoid backfeed, wow and flutter in addition to avoiding one unit damaging the other.

likely not true....but it is your gear at risk...a splitter does nothing to prevent the transmitter from damaging gear on the same antenna or coax...

wow and flutter are terms used to describe issues with analog recordings (ie tape and such)

what are you trying to say this box does?

 

[Bill Roosa]

I agree with kd3pc, a diodes and resistors are of little use in "protecting" an alternating current circuit like an antenna feed line. There is just as much current and voltage going in one direction as the other.
The VHF radio/FM radio antenna duplexer (the technical term) uses the fact that VHF is at 165ish MHz and FM is 88-105is MHz and is actually a band pass filter. It will not allow the wattage of the transmitting (or receiving for that matter) VHF into the FM stereo side of the circuit but will pass the 88-105 MHz just fine. It also acts as an impedance matcher to turn the 50 ohm antenna and coax for the VHF to 75 ohms for the FM radio.
This is accomplished with capacitors and inductors (coils of wire) BTW not diodes and resistors.

 

[cephius (Dave)]

Fm ? ? ?

I can't stand the advertising on broadcast radio. My last stereo upgrade included a port for my iPod. Who needs FM

Its actually a drawer that swings out to hold the iPod snug and dry inside the unit.

 

[Bill Roosa]

Hey Dave
If you listen to country music you don't get those type of advertising. The liberals have long since given up trying to convince us of their idology
Uncle Sam, King James, trucks, chicks, and beer. Now that is music!
You also get local news and weather. Not sure if an Ipod can do that or not. does it have an app for that?

 

[cephius (Dave)]

Not my iPod. I get the weather from my VHF, and there is a morning cruisers broadcast on the VHF as well for local news. I never thought I see that in the upper midwest, inland lakes.

 

[twodzusfittings]

I agree with kd3pc, a diodes and resistors are of little use in "protecting" an alternating current circuit like an antenna feed line. There is just as much current and voltage going in one direction as the other.
The VHF radio/FM radio antenna duplexer (the technical term) uses the fact that VHF is at 165ish MHz and FM is 88-105is MHz and is actually a band pass filter. It will not allow the wattage of the transmitting (or receiving for that matter) VHF into the FM stereo side of the circuit but will pass the 88-105 MHz just fine. It also acts as an impedance matcher to turn the 50 ohm antenna and coax for the VHF to 75 ohms for the FM radio.
This is accomplished with capacitors and inductors (coils of wire) BTW not diodes and resistors.

Wow, good stuff. I stand corrected. I have learnt a lot from those that have responded with their knowledge. Much appreciated. The new radio has a USB and a aux jack for my Ipod which will be the more preferred "channel".

 

[Kivalo]

When you folks say there is a loss of FM performance, how much of a loss is it? This summer my sailing will be strictly limited to Owasco Lake, its 11miles long by a mile wide. Almost no need for the VHF. Hell, my handheld receives NOAA really well where I am.

 

[timothy_c]

I have been workin on my antenna and radio system this spring. I have the shakespear splitter. At the dock I get more stations on my truck radio in the parking lot than the boat. I contacted shakespear and found that the splitter utilizes the shield of the coax for FM reception not the antenna on top of the mast. Considering the coax is run through the boat, then inside an aluminium mast. This has to obscure FM reception to some extent; yes / no ????