VHF/FM splitter

[mcanderson]

I have a T shaped ribbon FM aerial for my boat's Sony car radio. The reception has never been great and interference from the electric switch board will affect the signal. So I have been thinking about installing a VHF/FM splitter so that my FM signal is sourced from the VHF antennae at the top of the mast.

Has anyone got experience of using a splitter?

My radio is 3 years old and the boat 9.

 

[nigelmercier]

... I have been thinking about installing a VHF/FM splitter ...

That's fine, so long as you just think about it.

Search this forum for the many reasons why splitters are a terrible idea.

 

[Gypsyjoss]

I've been using a splitter for the last 10 years without any problems (that I know of!). Radio and VHF reception are very good and on the infrequent occasions that I transmitted, I had no problems - admittedly the distances were generally no more than a couple of miles. I used the Pacific unit that F4 and others sell. Perhaps I am living in blissful ignorance of some future wireless catastrophy that will befall me next year!

 

[William_H]

The simple test you can do is to remove the connector for the VFH com antenna at the radio and try this on the VHF FM car radio receiver. This will show if you get significant improvement in reception. If you don't get much better then obviously forget the idea. If get a satisfactory improvemnt then try mounting the ribbon antenna up at a similar height.
My guess si that that will also improve FM reception.
As has been said many times a splitter is not a good idea as it makes your vital VHF com more susceptible to failure in connectors etc and the car radio susceptible to damage from the transmitter if there is a fault. ie keep VHF com antnenna just for the 2 way radio.
Try various outside higher locations for the FM antenna but not near the VHF comn antenna. good lcuk olewill

 

[nigelmercier]

An analogy may help: would you cut into a seat belt in a car so you could slip over a padded cover?

 

[mcanderson]

Nigel,

You appear to have strong views. I will try to move the FM aerial before anything else. Do you have any other tips?

 

[chrisbitz]

An analogy may help: would you cut into a seat belt in a car so you could slip over a padded cover?

I think ideally, an analogy should be in some way relevant to the point they're trying to make.

Would you detonate a nuclear bomb next to an orphanage to..... No wait, that's equally irrelevant. I think we're going a little over board.

I think the point is, using a splitter *might,* in the case of *special but fairly unlikely circumstances* be a bad idea. But others can prove that they've been using them for many years without any problem.

It's like people who say "Never skimp on the price of safety stuff"? at which point I wonder why they don't hire a lifeboat to follow them everywhere, because that's *perfect* safety.

It's all about risk assessment and weighing up likelyhoods in my opinion...

 

[Gypsyjoss]

I think ideally, an analogy should be in some way relevant to the point they're trying to make.

Would you detonate a nuclear bomb next to an orphanage to..... No wait, that's equally irrelevant. I think we're going a little over board.

I think the point is, using a splitter *might,* in the case of *special but fairly unlikely circumstances* be a bad idea. But others can prove that they've been using them for many years without any problem.

It's like people who say "Never skimp on the price of safety stuff"? at which point I wonder why they don't hire a lifeboat to follow them everywhere, because that's *perfect* safety.

It's all about risk assessment and weighing up likelyhoods in my opinion...

Thank you. My thoughts entirely! Incidentally, are there any verified reports of failures in transmission/reception or exploding radios due to the use of such devices?

Pete

 

[nigelmercier]

I think ideally, an analogy should be in some way relevant to the point they're trying to make.

My point is that you are weakening a vital component to install something trivial.

 

[chrisbitz]

My point is that you are weakening a vital component to install something trivial.

I'm sure people understand what you mean, but I can't help feeling you're unreasonably exaggerating the danger. There are cases of people here using the set-up for 10 years without any apparent problem, and it's only in the instance of one of the components failing in an unlikely way that any problem would occur.

We're still awaiting any actual reports of a problem, to counteract the reports of "no problem"

 

[TSB240]

it's only in the instance of one of the components failing in an unlikely way that any problem would occur.

We're still awaiting any actual reports of a problem, to counteract the reports of "no problem"

Has anyone actually pulled an FM/VHF splitter apart.

The only components are coaxial cable, solder and ferrite rings!

Oh and a plastic case to hide the simplicity and make you pay ridiculous money for plug n play that anyone with basic skills could do for pence.

There really is no rocket science involved in a basic splitter.

 

[jerrytug]

Has anyone actually pulled an FM/VHF splitter apart.

The only components are coaxial cable, solder and ferrite rings!

Oh and a plastic case to hide the simplicity and make you pay ridiculous money for plug n play that anyone with basic skills could do for pence.

There really is no rocket science involved in a basic splitter.

That's right, and I'm another happy splitter user, my VHF can transmit from Gravelines to Dover, and my car stereo can get plenty of foreign stations which are great.
The risk of splitters exploding or whatever is similar to that of being crushed by a meteorite!

 

[RichardS]

Has anyone actually pulled an FM/VHF splitter apart.

The only components are coaxial cable, solder and ferrite rings!

Oh and a plastic case to hide the simplicity and make you pay ridiculous money for plug n play that anyone with basic skills could do for pence.

There really is no rocket science involved in a basic splitter.

However, there is a big difference between active and passive splitters apart from the obvious fact that active splitters need a power feed.

I have just bought a Vespermarine active splitter which has connections for AIS, VHF and FM so all can use the mast-head antenna. All the reports I have read suggest that the effect of additional antenna height outweighs any signal attenuation, although with a well-designed active splitter the attentuation should be compensated for by the internal amplifier anyway.

Richard

 

[rob2]

I use a VHF/FM splitter, particularly useful in the Hamble where the veritable forest of masts can make broadcast reception near impossible. Like most UK workmen, I like to have some music or a voice to keep me company whilst working on the boat. Strangely, once on the move, I prefer not to have the radio on. Actually with the advent of frequent DSC message alarms, I wish I were not obliged to have the VHF on but there are local warnings and weather that I want. Within the Solent I don't notice the attenuation losses on my VHF, but if travelling further afield I would remove the splitter and this is the main point to consider when installing it. Although it has a reasonable length of lead to allow positioning in a convenient hidey hole, mine is right next to the VHF, so I can unplug the antenna feeder and reconnect direct to the VHF in a matter of seconds. For a cross channel trip it would make sense to do this before setting off.

Rob.

 

[MartynJS]

Hi. My mate bought a splitter marked Pacific. I was worried because my own experience of these cheaper, passive splitters is poor manufacture so I offered to do some testing for him. The domestic radio connector showed a short circuit which came and went if the cable was wiggled so out came the craft knife and I opened the box. I have to say that I was horrified. The screen on the domestic radio coax had been badly cut back so that the strands could touch the screen on the marine VHF cable. This in turn was connected to the core of the domestic radio cable; thus the short. I would not want to be relying on one of these when I make my first Mayday call, although the short probably only appeared on the domestic side! This is what you get for your £25! The only filtering in there is the three ferrite rings on the marine VHF output cable. It seems to use the screen of the coax running to the marine antenna as the domestic radio antenna and relies on the fact that the two are not connected to prevent any cross talk when transmitting. In the photo, the larger (upper) cable is for the domestic radio and the smaller (lower) one is for the marine VHF.

I hope some of you find this helpful and BEWARE.

 

[chrisbitz]

Who sells these? It looks terrible.

Although it is purely a problem with Pacific, and nothing to do with the actual concept of splitting...

 

[William_H]

Well I have had a lifetime of radio techo and I would instictively no fit a splitter. Especially as the cost and inconvenience can't be so much for a dedicated VHF FM antenna.
The VHF com antenna will be about 2/3 the desired length for VHF FM 160 mhz versus 100 megahertz. If you have a 5/8 wavelenght high gain VHF com antenna ie longer than 17 inches or a stubby then tuning is even more critical.
The only attraction for the VHF comm antenna in use for VHF FM is that it is usually on top of the mast.
I would suggest OP try the ribbon antenna he currently has as high as he can get it. Try it horizontal and compare that with vertical orientation. Matching to the transmitter polarisation is pretty important for best reception.
If vertical is best and it is inconvenient to mount an antenna outside and higher up then OP might wisely consider a standby VHF com antenna fitted to the stern rail. Very useful if you lose a mast and also good for AIS.
A vertical antenna for VHF FM can be about 1 metre of rod mounted and insulated at the base where the centre of coax cabloe is connected. (75 ohm) the outer of the cable being connected to the metal that you mount the insulation and rod on to. Of course if you want MW AM reception as well then this antenna may be OK for MW but there are all sorts of compromises involved in trying to make one antenna do 2 different jobs. (AM and FM) good luck olewill

 

[yoda]

I find the self adhesive ribbon antenna for my FM radio very good. It is stuck to the saloon window. The only extra thing I seem to remember doing when fitting was connecting the screen of the aerial to the case of the radio because it was obviously designed for a car where the bodywork does this for you. Save putting in a splitter and was cheaper.

Yoda

 

[seanfoster]

Hi. My mate bought a splitter marked Pacific. I was worried because my own experience of these cheaper, passive splitters is poor manufacture so I offered to do some testing for him. The domestic radio connector showed a short circuit which came and went if the cable was wiggled so out came the craft knife and I opened the box. I have to say that I was horrified. The screen on the domestic radio coax had been badly cut back so that the strands could touch the screen on the marine VHF cable. This in turn was connected to the core of the domestic radio cable; thus the short. I would not want to be relying on one of these when I make my first Mayday call, although the short probably only appeared on the domestic side! This is what you get for your £25! The only filtering in there is the three ferrite rings on the marine VHF output cable. It seems to use the screen of the coax running to the marine antenna as the domestic radio antenna and relies on the fact that the two are not connected to prevent any cross talk when transmitting. In the photo, the larger (upper) cable is for the domestic radio and the smaller (lower) one is for the marine VHF.

I hope some of you find this helpful and BEWARE. View attachment 48493

Well I'm glad I read this thread, I bought that exact splitter from Marine Megastore a while back and was about to fit it over the coming months as part of my refit.
I'm glad I haven't now, I've bought a cheap internal aerial, I'll see how well this works: http://www.ebay.co.uk/itm/Stereo-Ra...arts_Vehicles_CarParts_SM&hash=item3a95d10a56
Not expecting miracles but less then £2.50 so worth a try!

 

[Plevier]

I opened up a passive splitter that was badged Shakespeare. The design was different but the quality about the same as the one shown above. I would definitely not use it for fear of affecting my VHF comms.
On the other hand, I now use an EasySplit active unit that deals with the VHF, the AIS and the stereo. That's a different kettle of fish altogether and I don't believe it is any more of a weakness than the Raymarine VHF.