DIY VHF aerial

[rogerthebodger]

I need to make a VHF aerial to test my new installed fixed VHF radios as I don't not have the mast or goal posts up yet.

I know you can strip out the centre of a coax cable but what length do I strip out.

Not interested in range as testing will be with my HH VHF radio and don't wist to damage fixed radios

 

[beneteau_305_553]

expose a core length of 931 mm and cut away the coax.

(0.97 x half wavelength )

 

[rogerdog]

make a simple dipole - attach one length of (almost any conductor) to the centre and one to the coax braid - each 'bit' to be one foot 6 inches - just make sure that the inner and outer of the coax cannot accidentally touch

 

[st599]

[ QUOTE ]
expose a core length of 931 mm and cut away the coax.

(0.97 x half wavelength )

[/ QUOTE ]

Don't you mean 1/4 wavelength for a monopole?

 

[VicS]

From a very old PBO

 

[William_H]

SimonT is right you need a portion of conductor 1/4 wavelength long connected to the inner of the coax. (or unnshielded coax inner exposed) this is about 17 inches long. You also need a ground plane connected to the outer which can be a large area of conductor (like a car roof) or as Vic describes another piece of 1/4 wavelenght long wire or even the braid of the original coax.

I use as a permanent VHF antenna 1/4 wavelength of exposed centre conductor with a ground plane 1/4 wavelength of braid from a larger coax
which extends from the end of the small coax braid down 17 inches over the original small coax. The whole is insulated in plastic tube mounted vertically on the pushpit so that the end of the additional braid is a foot or so above the rail. It has a low VSWR and I havn,t yet run out of range. olewill

 

[rogerthebodger]

That's the one I was thinking of thanks very much Vic and thanks to all who responded.