Split VHF Antenna to Two Radios with T-Connector?

[Nighthawk98TJ]

Hi All,

I have a VHF antenna on my vehicle and I am out of location for new antennas. I have two VHF radios (a fire/EMS radio and a 2m HAM). I would like to share the antenna for both radios. If I use a T-connector and do not have both radios on at the same time, will I be able to do this without damaging either radio?

Thanks!

 

[petnrdx]

Tee connector.

No, that won't work.
The transmitter from one radio WILL fry the RX of the other if on the same antenna whether the second radio is turned on or not.
With both radios being on the same band (VHF) you will have to get another antenna.
If you were using two different bands, then a di-plexer would work.

 

[Nighthawk98TJ]

OK, I will look into an interior mounted horizontal loop. Thanks!

 

[petnrdx]

Horizontal

You probably don't want a horizontal antenna.
Unless is it designed to have a vertical radiation pattern.
There is usually several dB of loss ( can be as much as 20 dB) when you try to operate "cross" polarized to the station you want to communicate with.
Since most FM comms are with vertically polarized antennas, you want to stick with that.
If you REALLY only use one radio at a time, you could use an antenna switch.
My vote is always for a second antenna.

 

[N0IU]

I have a VHF antenna on my vehicle and I am out of location for new antennas.

Then you're not trying very hard! Be creative!

 

[N8IAA]

OK, I will look into an interior mounted horizontal loop. Thanks!

You definitely don't want to do that! There is no where that you can put a magmount? And don't mount the two VHF antennas closer than a 1/2 wave apart. You will have a similar problem as trying to use the "T" connector.
Larry

 

[wyShack]

If you are only going to use one radio at a time, you might want to consider a coax switch to select which radio is connected to the antenna- remember this would disconnect the radio not in use. Remeber that receiving also requires an antenna. If it was me I would install two antennas as far apart as fesible.

 

[KC9AXZ]

If you have full control over your Fire/EMS rig (you own it), you could program your 2 Meter frequencies into that. If you don't own the rig maybe look into getting a used one and having it programmed. You can find used commercial VHF equipment on eBay, Batlabs, or Wiscomm.com - Motorola Radios (Used), Programming, Repair, Parts, Cables, Batteries == We Buy Motorola ==. Using a commercial grade radio beats the "amateur" stuff any day. If that isn't an option then go with 2 antennas or power down one rig and use a switch. The biggest problem with the switch is trying to remember to use it when you change rigs.

 

[SCPD]

One radio off

No, that won't work.
The transmitter from one radio WILL fry the RX of the other if on the same antenna whether the second radio is turned on or not.
With both radios being on the same band (VHF) you will have to get another antenna.
If you were using two different bands, then a di-plexer would work.

Although there is NO way I would do what he is asking about, one of the things he is saying is that the radio not in use will be turned off. hmmm. Still think it would fry something in the other radio?
But like I said, no way I would try it.

 

[SCPD]

Best suggestion

If you are only going to use one radio at a time, you might want to consider a coax switch to select which radio is connected to the antenna- remember this would disconnect the radio not in use. Remeber that receiving also requires an antenna. If it was me I would install two antennas as far apart as fesible.

You got it. I would put the fire radio antenna in the most desirable spot, in the middle of the roof. And the 2M antenna on the trunk lid.
Even with the 2M antenna in a compromise location, I'm sure he can still make the machines just fine.

 

[petnrdx]

Turned off or not...

Absolutely, the transmit energy of one radio WILL fry the receiver of the other radio.
It doesn't matter whether the RX is powered up or not...
I suppose there is a chance with very low power radios that it would not fry something.
But anything over a quarter watt or so is VERY likely to fry the first stages of the RX.
As another poster stated, even on separate antennas, if the antennas are close you can still fry the RX.