VHF Aerial splitters?

Medskipper

Medskipper

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Anyone tried to use one aerial for two VHF sets?
I have seen splitters that allow the user to hook up a VHF and a normal radio for music etc. I am wondering if I can use one VHF on the flybridge and one below, obviously only one VHF would be used at any one time, but would splitting the lead affect the performance of either VHF ? and if this is possible, does anyone know of a good splitter that is on the market?
All comments gratefully received,

Barry
 
I've used one - no problems and better than another bit of wire on the top of the boat!
Don't know about spltting the signal again but give it a go - you've got nothing to loose - plenty to choose fron - check out jgtech.co.uk - threy sell them
No connection other than as satisfied cust.
 
I would be very cautious about this. I'm no expert but what if there was feedback of signal between the two sets, couldn't that burn something out. I mean, surely if it was an OK thing wouldn't loads of people be doing it to save money and clutter?
Talk to someone lik Greenham Marine or send an Email to someone like ICOM. Better safe than sorry.
 
I would suggest a co-ax switch is better than a splitter.
This way you will isolate the radio not being used.
These are only about £20 from Waters and Stanton
www.wsplc.com

Splitters are the normal thing if you want to use your VHF Antenna for your broadcast radio.

Regards
 
Dead right, Byron. I made a specific enquiry a couple of years ago and it was pointed out to me that if you merely use a splitter, the first time you transmit on one set, it all goes whizz bang round a very short loop and blows the insides out of the other one. If using only one aerial is essential, then some sort of isolation device has to be installed
 
Yes

Much better idea than a splitter

I wouldn't use a splitter even for a broadcast receiver there is a power loss at best.

A neat alternative may be to use a co-ax relay powered from one of the sets so that when you turn the set on the aerial automatically switches to that set.

But a simple switch is good
 
Agree dont use a standard splitter - its the same as the AIS engine. You get 25W ploughed straight into the other set. Not good!
 
Barry, what you need is to get a Diplexer, this is a professional bit of kit, which will allow you to use two transmitters into the same antenna.
Havent seen them in marine circles, but they are available from professional Private Mobile Radio companies.. and used extensively on multiple TX sites.
There may be an amateur product available for 2 metres which would also do the job so check out Lowe Electronics, Martin Lynch, and Waters and Stanton.

It is very important to provide a high degree of attenuation on the Radio which is not actually transmitting, to prevent the Reciever front end being overloaded and the front end FET brom being fried.

A coaxial switch would be a simple and effective solution, and much cheaper than a diplexer which is going to expensive when compared to buying another antenna or a coax switch.

Steve.
 
Hi!

True Heading in Sweden has a splitter for sharing a VHF antenna between a AIS reciever and the normal VHF. Maybe that it works for you too? It works by disconnecting or muting the signal to the AIS engine when it sees transmission from the VHF unit.

/Kaj
 
Re: VHF Aerial splitters...more.

The only downside with switching is that you need to remember to switch the right radio.
If you transmit into an open circuit..ie antenna switched out, then you could Pop the output transistors of your transmitter.
Also it is not very handy in a confused distress situation.

I seem to remember that there were RF activated coaxial relays available on the amateur market at one time.
These automatically sense where the RF is coming from and switch the antenna in when transmitting.
Usual amateur radio places will have these if available.

Steve.
 
If you decide on a co-ax switch you can get one 5 mins from your location,think they are around 20 quid ish .You will o corse need another 3 PL259 plugs to complete the job,plus soldering iron.Around thirty quid in all.
 
With a normal antenna splitter you will burn the receiver on VHF 1 the moment you transmit on VHF 2.
Splitters for AIS are now available, but they are only made for setups with one transmitter and one (AIS) receiver. They actively switch off the antenna connection of the AIS receiver the moment the VHF is transmitting, but this does not work with two transmitters.

Holger
 
If you use an ordinary 3dB splitter, half the power will go to the antenna, half to the output stage of the other transceiver - expect smoke!

Diplexers work with two different input frequencies. The same problem would occur as with a 3dB coupling.

An antenna switch would work, but care would be needed as if a transmitter transmits into an open circuit, the VSWR would rocket and more smoke would be produced. Can circulators be bought fo VHF which would circulate the reflection to a dummy load?
 
Damm.Caught out again.Do wish prrps would not examine cost breakdown.Must have forgotten to mention there is a 3 beer additional charge to be factored in.
Normally slip this in under "fluids" somewhere in invoice.Normally add a bit on cos of risks involved going to that rough old marina /forums/images/graemlins/grin.gif
 
I have seen and installed same band diplexers, Pye used to do 'em..common on talkthrough systems..with 4 or 8Mhz shift, but you are right ,thinking about it, not same freq diplexers.
I suppose you could circulate/isolate into a dummy load, but at 2m they are going to be fairly chunky cavities...mounting might be a bit of an issue...
There could be an even simpler solution with an RF sensing relay that grounds the antenna input of the RX not in use.

Steve.
 
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