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ContinuousWave: Small Boat Electrical
Splitter for AM/FM and VHF Antenna
|Author||Topic: Splitter for AM/FM and VHF Antenna|
posted 08-12-2008 01:46 PM ET (US)
I'm installing an am/fm/cd radio on my Outrage 18'. I have an 8' antenna for my vhf. Is a splitter worth the cost? Some reviews on westmarine.com indicate that they do not enhance fm reception at all.
If not a splitter, what is the consensus on amplified am/fm antennas? Are they worth the installation time and hook up to the electric panel?
Or, should I install the least expensive 16" flexible antenna and be done with it?
posted 08-12-2008 01:54 PM ET (US)
On my old Montauk, I tried both an inexpensive AM/FM antenna and then I added a splitter to my VHF. The splitter definitly worked better until I got a ways offshore than I would have trouble with reception. On my Outrage, since I have a T-top I added a 4 ft Digital AM/FM antenna whic has no trouble picking up reception anywhere. I was 25 mles out in the gulf last week and the stereo worked great.
Hope this helps
posted 08-12-2008 11:00 PM ET (US)
There are several problems in using a VHF Marine Band antenna as a receive antenna for an AM Broadcast Band and FM Broadcast Band receiver. The principal problem is when transmitting on the VHF Marine Radio.
On receive, the vessel's antenna will not be resonant on the broadcast frequencies. This will reduce its efficiency. The situation looks like this:
VHF Marine = 156-MHz
A non-resonant antenna is better than no antenna, however in the case of AM Broadcast, the antenna may not have much efficiency at all due to the very short electrical length.
On transmit you have to keep the 25-watt transmission from blowing out the other two receivers. The best way to do that is to use an active device. Typically a relay is actuated when the transmitter power is sensed, and it disconnects the other devices. If the splitter is passive, it can use high-pass, low-pass, and band-pass filters to attempt to isolate the three device ports from each other.
Personally, I would rather not add something to my VHF Marine Band radio system that might have any negative effect. The radio is very important, particularly if you go offshore any distance. I'd do with a separate AM/FM antenna for the broadcast receivers.
posted 08-13-2008 08:26 AM ET (US)
Installed a splitter on my Ventura in 2003 and been using it ever since. It has in no way affected either the receive or send side of my VHF radio. I run two ICOM 504 one uses the splitter configuration and the other is connected straight to the vhf antenna. The input/output is the same on both radios.
|Over the LINE||
posted 08-13-2008 09:42 AM ET (US)
I do not use my VHF for anything more than race management (close in work), but I have seen no ill effects from having a splitter. I do not listen to AM so I can not comment on reception quality.
I can tell you it is one less antenna on my 18' Outrage and helped to keep my electrical panel clean. My FM reception is just fine.
My splitter was not hard to install but I put it on my wiring panel before installing it. It is not an amplified splitter and did not require power.
posted 08-13-2008 09:14 PM ET (US)
I am using a Shakespeare Model 4357 splitter with satisfactory results. Two years and counting.
posted 08-14-2008 10:46 AM ET (US)
I agree with jimh. I would never add another source of failure to a critical safety component, just for the purpose of supporting an (optional) entertainment component.
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