Uhf Antenna Position

[Skurfer]

Hi Guys

Just after a bit of advice. I need to mount a UHF antenna to the Leggy, i just cant decide where to put it. Really should just bite the bullet and put a short one on the bonnet, which is what i think i will do, but does anyone have any other advice, or has put one somewhere before?

 

[Buckas]

send a pm to Fisher. he doesnt own a vr4 so isnt on here too much. he has a jackaroo and has a very small antenna, used to have one of those ridiculous ones on the bull bar but the new one is tiny in comparison and is also much better. i think you could do a pretty stealth install with it somewhere (maybe on the rear wing?).
he'll be able to show you a pic and what type it is.

in the mean time here is a crappy pic:

http://harryfisherphotos.smugmug.com/gallery/9137497_7NJ2j#609267242_GyQqC

if you look at the roof you can barely see a black lump on it towards the front in the centre (ignore the mud)

 

[Peter_D]

Hi Guys

Just after a bit of advice. I need to mount a UHF antenna to the Leggy, i just cant decide where to put it. Really should just bite the bullet and put a short one on the bonnet, which is what i think i will do, but does anyone have any other advice, or has put one somewhere before?

Your best bet is to place it as far back as possible in the middle. You'll get a far better radiation pattern (circular therefore non directional) and your SWR will be better back there. That's what I found whilst doing some testing. Be sure to give your self a good ground and be careful when transmitting if you've got your head unit on as you may over load the front end receiver. Although if your using legal power on UHF that shouldn't be a problem.

I'd also suggest getting a remote mountable radio as there just isn't a good spot to mount a standard one at the front.

Oh just another idea. You could always use a magnetic base for the antenna. Just pull it out of the back and slap it on. They do give a great earth. And once your done, remove it and put it away.

 

[snickells]

You could always use a magnetic base for the antenna. Just pull it out of the back and slap it on. They do give a great earth. And once your done, remove it and put it away.

That's what I'd do. Mounting on the wing like someone suggested will result in no ground plain and will be useless.

 

[Skurfer]

Its actually more for a scanner that i use on my way to fire calls so that i can hear any further information on the incident before i get there. Most cfa members use them for this reason.

Will having no ground plane still affect RX, or does it only really matter for TX. Also antenna selection is quite small as i have to get one that covers the 160-170MHZ range, where UHF are around the 470MHZ i think. I will have to get one of the ones that do all the ranges.

I ask here about placement, as no one else that i know in the cfa has a car that they care about the look of, so just put massive antennas on the boot haha. Dont really want that.

 

[snickells]

Yea, its a tricky one Chris, but I'd defiantly look at the Mag-Base. Otherwise, your just drilling through your roof.

 

[Peter_D]

Will having no ground plane still affect RX, or does it only really matter for TX. Also antenna selection is quite small as i have to get one that covers the 160-170MHZ range, where UHF are around the 470MHZ i think. I will have to get one of the ones that do all the ranges.

If your only listening the ground plane doesn't matter but the size of the antenna does. The bigger the antenna or closer to the size of the frequency (wave length) your listening on the better.

As your listening at the top of the 2 meter band your antenna maximum size will be about 2 meters in length anything longer and you'll be getting into multiple wave lengths.

So if your listening at 170Mhz your 1/2 wave and 1/4 antenna lengths are going to be
1/2 - 2.75 feet
1/2 - .33 inches
1/4 - 1.3 feet
1/4 - 16.51 inches
A full wave length antenna might be to long so go for the 1/2 wave length.

With the above antenna you'll be able to listen on UHF also but don't transmit as your antenna is not resonant and you WILL damage your transceiver.

 

[snickells]

And the radio nerds start crawling out of the dark corners!

Seriously though, I hate this shit now. Nothing worse than high VSWR that you cant explain, or a dodgy antenna that you have to re-install.

 

[Peter_D]

Radio nerds can love VR4's also!!!!!!!!!

And the radio nerds start crawling out of the dark corners!

Seriously though, I hate this shit now. Nothing worse than high VSWR that you cant explain, or a dodgy antenna that you have to re-install.

Of course you can explain high VSWR. Bad placement, bad connections in the pl259 plugs, bad cable, bad antenna or a stuffed radio. Check each one at a time and make sure you only trim a bit of the antenna at a time otherwise you'll shorten the antenna to much and you'll have to buy another one.

And I wouldn't consider myself to be a radio nerd any more than I am a computer nerd. I just happen to be a licenced Ham operator and have been for years.

 

[snickells]

Should have guess the Ham connection

 

[Skurfer]

Thanks for the info guys. Going to go have a look around dick smiths tomorrow to see what they have there. Think i will just put it on the bonnet and that should be fine