Fm antenna - what do i use, where do i get one??

[Anonymous]

Hey i need some help, just found you guys on the net and hope you can help.

Me and some buddies are setting up a radio and have acquired a 500mw,12v fm transmitter but the aerial we thought we could use is not compatible.

What kind of aerial would we need to broadcast with and where can we get one????
Any help or tips would be greatly appreciated, you can reach me at
jamoxr06@aut.ac.nz

Cheers

[nomadradio]

Hi SLim Jim,
Rather than reply direct by e-mail, I tend to just post a reply here. The single largest supply of low-power FM broadcast hardware here in the states is http://www.ramseyelectronics.com

I'm just assuming that FM broadcasting in Z-land occupies the same approximate frequencies as here in North America.

The antenna hookup used by all of Ramsey's stuff is the standard (approximate) 50-ohm output used for most voice 2-way radios. Don't know what kind of antenna hookup your 500 mW transmitter is built for. If it was meant to have a piece of wire stuck to the side of it, a 50-ohm feedline and antenna may not agree with it. Could this be the reason your first antenna attempt proved unsuccessful?

A broadcasting antenna is generally meant to be omnidirectional, and for simple setups, a vertical monopole is pretty popular. Ramsey has more than one variety of those, last I looked.

Just choose a frequency that won't clobber an established (licensed) broadcaster's signal. That's the quickest way to a loud knock on the door whatever the local regulations may be. Of course, the peanut-whistle broadcaster has an incentive to choose a quiet spot, to get the best range for his signal.

73

[TrumpyNZ]

Hi there guys,
Just be sure that the set is made to have a 50 ohm antenna connected to it, some FM transmitters I've seen have a 75 ohm output impedance.
One way of being reasonably sure, is by the type of antenna connector on it.
If it has an SO-239 (threaded) connector on it, it's more than likely 50 ohm.
If it has a BNC (looks sort of like the base of a light bulb) connector, it's 75 ohm.
Sorry about the shocking descriptions!.
BTW, nomad, our FM band is 88-108MHz.

Cheers,
Trumpy.

[555]

Hey i need some help, just found you guys on the net and hope you can help.

Me and some buddies are setting up a radio and have acquired a 500mw,12v fm transmitter but the aerial we thought we could use is not compatible.

What kind of aerial would we need to broadcast with and where can we get one????
Any help or tips would be greatly appreciated, you can reach me at
jamoxr06@aut.ac.nz

Cheers

Hello Slim Jim,
First off we need to know what this radio is exactly, if it's broadcast band, ham radio, business band, emergencie bands or what. It sounds like it's possibly a ham radio or a business radio that uses repeaters hence the (500mw,12v) that you described. If it's ham you need to be licensed to use it anyways and some business radios may require a permit. you really need to give us better information about the radio, on the back of the radio it might give the frequencie(s) that it's intended. 73's Jim

[Dazz]

If you want an easy solution you could just cut a surplus, unloaded, all stainless steel whip to length for the frequency of interest.
About 73 centemetres should be good for around 100mhz.
screw this to a standard cb antenna base grounded to a tin roof or gutter.
if your house has an all tin roof thats slanted, put it right up on the apex or the highest point and it should get out reasonably well.
If u want to get out better, surf around on the net 4 the plans to make a j pole or even a 3 element yagi- smoken'!! Done the latter and i live up on a high hill (about 50 metres above average terrain, 90 metres above sea level) and got out with a flat chat signal for 10kms while only runnin' a few watts.
was great experement. good luck.

[Frequency]

Check out http://www.ramseyelectronics.com, just like what 73 said, it has the info you need.

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