vhf splitter?

[QuickMick]

i got a new vhf radio. the old one still works just fine so i was thinking of keeping it for redundancy (though i do have a handheld) i was wondering if i can just use a splitter to connect both of them simultaneously to the antenna. then if unit 'a' failed i could just click on unit 'b'? i suppose i could just swap the plug in case of a failure...

[FishSticks]

The splitter will lower the signal strength. Stick the old one under a bunk if you think you need a backup.

[celenoglu]

It will be better to buy a second antenna, and mount it somewhere.

[chrism33]

There are down sides to combining VHF signals:
1. You add complexity and a single point of failure;
2. You reduce sensitivity (reception range is reduced by about 40%);
3. One radio will transmit singificant power into the other radio unless there is good isolation built into the splitter/combiner.

I agree that a second antenna is the way to go. It gives you complete redundancy. My boat has a backup whip antenna on the transom.

[fairbank56]

Shakespeare makes an automatic coaxial switch. When you key one of your radio's, it automatically switches to that radio. It does require a dc power feed and the insertion loss is less than 1.2db. That's about 13% and is negligible as far as the user is concerned. The model number is AS-2 and runs about $90. Or, you could go with a manual switch. Much cheaper and virtually no loss. However, I agree with the others about using a completely separate system.

Eric

[btrayfors]

I also agree about a completely separate system, i.e., the 2nd radio attached to a 2nd antenna.

However, if you must use just one antenna, a manual coax switch (such as the not inexpensive Alpha Delta) is a good way to go. It must be placed in a highly visible place, though, and clearly marked so that you don't try to transmit when the switch isn't in the correct position.

I don't like or trust the automatic relays or splitters. Aside from the insertion loss and need to connect to an external 12V source, there's always the possibility of a malfunction. To my mind, this is intolerable in what is arguably the most important safety device on your boat.

Bill

[rikhall]

It takes about ten seconds to un-screw the old antenna cable from the non-working radio and to screw it onto the new one. Save your money for something you really need.

(Just my opinion)

Rik

[GeorgeB]

You need what is known as an “active antenna switch”. If you use a splitter only, the transmitting radio’s signal will be directly pumped into the other radio’s receiver at full strength, and ruining it. The active switch will open automatically, protecting the other radio when the first one is transmitting. You will need this switch if you want your AIS receiver to share the same antenna. You can also buy a manual switch, but you can only operate one radio at a time. However, dual radios do come in handy as it allows you to monitor multiple channels at the same time.

[hellosailor]

Mick, it will probably cost you $15 to buy an 'emergency" antenna, which is basically a piece of coat hanger that screws right into the coax fitting on the radio. Totally separate and redundant, can't really fail and damage any equipment. Or you can easily make one that is the equal of any storebought one from a couple of yards of coax cable. They're essentially identical to "two meter" ham radio antennas and if you look for DIY on the web for those...many simple cheap effective ways to do it. (Two meter ham is about 146MHz, marine VHF channel 16 around 156MHz, easy to accomodate the difference.)

I wouldn't tie two radios to the same antenna, since there's always some risk when two transmitters are tied into each other--and they ain't supposed to be.