which way does my aerial face?

[WiLL]

Hi chaps,

I am not a sound engineer and google has failed me so I turn to you.

My trantec radio mics (mmm feel the quality) have aerial extensions which terminate in large white rods out of which projects a metal 'bracket'. My question is does the bracket face the stage or sit at the rear of the rod. I attach a picture to clarify.

piccie

[BigYinUK]

I may be completely wrong in this case but my experience of aerials would suggest to me that your example is an omni-directional aerial, in which case it won't matter which way it faces.

 

Regards

 

Jon

[cedd]

It's a reflector. It's used to give you a little gain in the direction on the opposite side to the reflector. So in your drawing the aerial is the wrong way round.

 

Here's what Canford have to say about them (read the bit about the HBD);

 

 

 

Wide-band Dipole Antennae

Built inside grey plastic tubes, with attached 1.5 metre cable and BNC type connectors (other terminations available to special order - contact Sales), these 50 ohm devices are suitable for reception and transmission up to 50W. They are supplied complete with versatile spring clamps for attachment to fences, trees and many other convenient fixtures, very handy when on location. MBD and HBD types are not true dipoles in that they are fitted with reflectors to give up to 3dB gain, but are available as true dipoles without reflectors to special order (contact Sales). This will lead to a 3dB drop in gain and to compensate, clip on reflectors can be used to re-acquire this 3dB of gain. Customers must specify which model of dipole the clip-on reflector is to be used with, when ordering.

 

 

I actually quite like them - you get the wide pickup pattern of the dipole (though it's not a true Omni - you don't get gain for nothing) with a little gain.

 

And the Trantec gear is great once you get up in to the S5 range, I actually prefer it to Sennheiser. The cheaper Trantec's can be a bit plasticky though I admit.

 

 

 

[sam.spoons]

It looks like #1 is correct from what cedd's Canford quote says. You could just try one and see what effect turning it around has on the signal meter on the receiver?

[paulears]

Def a reflector. You start with a vertical dipole, then the next element is the reflector, if you add further elements to become directors, increasing gain again, then they all go in front. Viewed from the top, what you have looks just like a cardioid microphone pattern. In effect, these aerials have a null where the reflector is, but no very obvious extra gain when pointing the right way, which is why they're quite useful.

[bruce]

Sounds like a Lintec dipole with reflector http://www.lintec-antennas.co.uk/pages/catalogue/dipole.html

 

Most of the ones I've seen are grey, but they also come in white.

 

As paul & cedd say, the reflector sits "behind" the antenna, and gives about an extra 3db.

[sam.spoons]

But which is the reflector, is it the exposed element or concealed in the plastic tube, the lintel document doesn't specify, the pics show a wall mount which implies it's the exposed wire bit in which case #3 would be correct.....?

[bruce]

The exposed bit is the reflector. Pic 3 is correct.

 

On some variants, the reflector clips on and off, to give you a choice of polar patterns.

[cedd]

Sorry, I've only just looked at your picture properly. I glanced and saw the aerial drawing top left as being the wrong way round compared to the 3 mics, not noticing the 3 numbered aerials below. Number 3 is indeed correct. Think of it without the wire loop and you've suddenly just got a regular dipole aerial. The loop is simply reflecting energy back towards the aerial. It means there's a null in that side. Also remember that dipoles have nulls sticking out as cones from their ends too.

Good aerials to have close to your mics. The pickup pattern is quite wide (cardioid as someone else said) so there are no dead spots once you're out of the aerial's pickup pattern, and the transmitters are close so gain doesn't have to be too high. With the null positioned towards the audience (so on the front of the stage) it also handily adds a little more rejection of interference sources from them.

[mackerr]

I may be completely wrong in this case but my experience of aerials would suggest to me that your example is an omni-directional aerial, in which case it won't matter which way it faces.

 

Regards

 

Jon

 

As others have pointed out, picture 3 is correct. As far as it not mattering which way an omni antenna faces, it is not truly "omni", it is toroidal. Along the long axis of the antenna is a null. The pole should be vertical, and it will cover 360º with the caveat that there will be some amount of forward gain due to the reflector.

 

Mac

[WiLL]

cheers guys, (I may write 'front' on the aerial rod to make sure I don't forget again)