Do I need a balun for a dipole antenna (70cm) UHF?

Question

Hi. I'm building a dipole antenna for 446MHz PMR frequency and my wisdom on antennas isn't the greatest.

I've been looking around on ebay for a dipole antenna but found very little, I found an 88MHz to 108MHz VHF dipole which I'm going to cut down to size to match the UHF 446 frequency, however I'm kinda doubtful on how good this antenna will preform. 

I was thinking alls a dipole is, is its a piece of metal. What is so special about it? and how different would a standard piece of wire work from a dipole?

I'm thinking I'm missing something here? there must be more to a dipole other then two pieces of metal, a dipole thats actually going to have some kinda performance. 

Will a balun make the difference and if so, what would one look like for this particular frequency? 

I'm going to be using 50 ohm low loss coax and a modified dipole, is it necessary to add a balun to my list?

Does anybody  have any recommendations for a better idea and something thats not to scrappy.

Thanks.

Anonymous · Accepted Answer

Whether you you require a balun or not is down to the Rx. Cutting the VHF antenna to suite is a bad idea, as it has many facets that are designed to exclude 446 Ms/c. You are better off just splitting a lenght of Co-ax to frequency

The original Peter G · Answer

A balun will improve signal transfer from the dipole into the coax by quite a few dB. However it's not an essential, most TV aerials don't bother with one. Unless you know exactly what to do a home build might have a negative effect. The simplest one would be a centre tapped coil, perhaps 5 turns with the dipole connected across the full col, and the coax to one end, screen to centre tap. Be prepared to experiment, or see if there's a local amateur radio group who could be more helpful.
Just for once the "Maplin" Catalogue wasn't any help

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Do I need a balun for a dipole antenna (70cm) UHF?

2 Answers