VHF 'splitters'

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VHF \'splitters\'

I am about to fit a permanent, spare VHF aerial in case the mast ever falls down, (hopefully going sideways to avoid smashing the spare aerial on the way down!) and wondered if the UHF/VHF splitters work, so we can also have an external aerial for the car-type radio/CD player.

Question: do they work/are they worth the £30?
 
Re: VHF \'splitters\'

Just to clarify, you want to run a single VHF transceiver into two antenna using a passive (3dB) splitter.

It will only work if both antennas are present and the combined radiation pattern will no longer be omni-directional. If you lose one antenna you'll see a VSWR spike and could blow the PA stage of your transceiver.
 
Re: VHF \'splitters\'

On the subject of VHF and aerials, my Shipmate VHF only receives and doesnt transmit so I'm going to get a new aerial to see if that fixes it. Glomex have 2 types of 2.4m VHF aerials (both 6db) one £40 other is £80. Should I go for cheapo or is it better to pay double ??
 
Re: VHF \'splitters\'

I don't think thats what he is suggesting. He has a spare VHF areial which he also wants to drive a domestic radio/cd player. I use a splitter from Shakespear. It works for the radio/cd player fine but I am advised to expect possibly 3dB loss of VHF signal. This is a factor of 2 in gain.
 
Re: VHF \'splitters\'

I've got a spare aerial rigged up with the coax run to the back of the VHF but not plugged in. If I loose the main aerial it's a simple case of unplugging the duff coax and plugging in the spare. Cheap, non-technical and reliable, which is just what you want if you've lost your mast!
 
Re: VHF \'splitters\'

Previous post should have concluded with: why not just connect the spare aerial directly to your FM radio/cd player and swap it over to the VHF if you loose your main aerial? Again a simple solution?
 
Re: VHF \'splitters\'

Chris to save a few quid, why dont you try your set on a friends boat and plug into their antenna. That way you will know if it is your set or something to do with your antenna.
The problem may be in the coax, as a coat hanger will transmit to a certain distance.

In answer to the original,my spare antenna is mounted on the radar pole on the stern. I have kept the spare coiled up (with about 1m spare) and taped near the back of the VHF set.In case of emergency, I merely swap out the plug on the back of the set.
 
Re: VHF \'splitters\'

Dont do it is my advice.
If you want your radio systems to work properly then keep to one antenna for one radio.
Any passive splitter will reduce the gain of the received signal.

Steve.
 
Re: VHF \'splitters\'

Thank you folks.

As you say, why add a splitter? I could leave it plugged into the radio and only move it if we ever need the VHF bit. But the ends are different. So presumably I could make up a simple adapter? And save money too!
 
Re: VHF \'splitters\'

I have a number of problems with these splitters:

They violate the KISS principle and introduce two extra connections and an additional point of failure into your VHF.

They reduce power output.

They cost money.

The alternative (a bit of wire or a connection to the rigging for your car radio) works as well, costs approximately nothing and has none of the above drawbacks.

Also, I would not permanently mount a spare antenna because, as you point out, the falling mast could take it out! If you have ever been in a dismasted boat in a rolling sea you will know it is mayhem with bits of wire and string thrashing about everywhere. Why not just keep a spare safe and dry and packed-up below in your ‘panic area’.
 
Re: VHF \'splitters\'

The VHF antenna will almost certainly come already terminated with a PL259 "UHF" series plug, whereas your car radio (or similar) will nearly always require a "banana" plug...which is smaller and has a long protruding pin.
You should be able to make a flylead up using another PL259 plug with a PL259 female to female adaptor and the other end terminated in said "banana" plug.
You should find all the bits you need in the Maplin or CPC catalogues, or at your local Maplin store.
Alternatively why dont you just fit a proper VHF Band II antenna for your FM radio reception, wire that up to your car radio or whatever, and as Benbow says leave the emergency antenna for just that..tucked away for a rainy day.
Fibreglass car radio antennae are dirt cheap, providing you dont buy one from a chandler. Once again maplin will have something suitable.
Please dont use a splitter, they are bad news and prone to failure at higher power,
which could destroy both your domestic radio and the Transmitter Output stage of your VHF Marine unit.
If you must use only a single antenna get a decent Coaxial RF Switch instead.

Steve.
 
Re: VHF \'splitters\'

He's asking a perfectly sensible question. He is wanting to fit an aerial for his FM/CD player, and wants to find a way to use it as a spare aerial for his VHF in case of an emergency. Seems fair enough to me.

The reference to KISS has nothing to do with KISS.FM!

...as Full Circle has now explained!
 
Re: VHF \'splitters\'

Masts alway fall to leeward and aft or so far in my experience, many unfortuately. However the stay wires do lay across the aft deck in a way that can rip off antenna. So there is a good case for having a removable whip antenna for VHF com that is kept stowed until youb need it. Or make up an emergency antenna as I described yesterday. good luck olewill
 
Re: VHF \'splitters\'

I agree with others regarding the splitter. If you want to have your emergency VHF antenna ready to deploy, mount it on a rail mount bracket. When not required it can be turned so it points down and is, therefore, less vulnerable. You can also remove it if you prefer, confident that you have a means of rapidly attaching it to a rail without having to improvise at a time when you will be occupied with other things. The radio end PL259 connector can be secured near the back of the radio ready to be connected when the need arises.
 
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