Twin VHF Antenna's

[SteveHall]

I have a few posts on here about poor VHF performance - And this got me thinking about the possibility of twin antenna's? You see some craft with more antennas - and I guess most of these would be for extra equipment (multiple vhf, duplex vhf, ais, fm, etc) but is it possible to have twin antenna for one VHF?

Would twins on opposite sides of the a frame really make any difference - only a foot or so apart?

(This is a really old photo but I thought I could remove the spots and then put one antenna in each place)

How would twin antennas be wired up, not to cause more problems with loads? I have a standard VHF with one antenna connection.

[ShinyShoe]

Twin transmit - halves the power to each...

Twin receive - receives twice the interference!

Unless the wire length is millilmeter accurate I suspect twin receive will receive the same signal twice as slightly different phases. In fact unless the signal is coming from exactly central to the twin antennas the same would happen I think.

If one has a fault it may affect the balance of that whole config.

I think when you are seeing multiple antennas they are:

VHF >> AIS >> Working Channel VHF or Spare not connected

[SteveHall]

Guessed it wouldnt be easy and would have problems - thats why I asked.

[jyasaki]

Plus you get interference that creates dead spots (transmitting; I don't think that would affect receive.)

jky

[9D280]

I have 2.... and a patch panel inside the console.

One is a spare. I may use it for ais in the future.

[Firefly]

Don't try connecting 2 antennas, you will almost certainly damage your VHF. It will create impedence mismatch, an unbalanced antenna circuit, very poor VSWR and ultimately damage to your RF stage.

[SteveHall]

Think I am going to give that idea up as a bad one...

[OSPREY RIBS]

Originally Posted by SteveHall

Think I am going to give that idea up as a bad one...

Best Option is to fit one good one. When it comes to VHF antennas height really is the most important thing !.

We fit the Shakespeare "Little Giant" Antennas they work very well.

[Last Tango]

Never had an issue with VHF performance.
My A frames have always been grounded which acts as a "ground plane reflector" creating a "bi-pole" type performance from the aerial.

Google " VHF Ground plane reflector".

With 25 watts the horizon should be your limiting issue. I also use the, much maligned, Cobra radios and have never had any problems with them.
(Two dead Icoms in the shed)

[Firefly]

Originally Posted by Last Tango

Never had an issue with VHF performance.
My A frames have always been grounded which acts as a "ground plane reflector" creating a "bi-pole" type performance from the aerial.

Google " VHF Ground plane reflector".

With 25 watts the horizon should be your limiting issue. I also use the, much maligned, Cobra radios and have never had any problems with them.
(Two dead Icoms in the shed)

Exactly right. that's all you need. A good antenna grounded to a good ground plane, creating a 1/2 wave dipole, and, of course, a decent VHF transceiver.