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Air Bender
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Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 12:20pm 20 Feb 2011

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My 9 year old son has picked up a UHF radio that he is planing to install in the cubby as soon as we have the wind mill charging a battery. His main aim is to be able to pick up a couple of hand helds around town at a distance of about 4 klms, also he has a couple of mates on farms about 20 klms away and a repeater on a mountain about 40 kls away which is in line of site if we can get the antenna up above the trees. Being a newby to radio i was wondering if we need to buy a proper base antenna or could we get away with a cheep one on a long pole.

All the best Dean.

Robb
Senior Member

Joined: 01/08/2007
Location: Australia
Posts: 221

Posted: 11:23pm 20 Feb 2011

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A 1/4 wave ground plane may be all you need. You should be able to make one of these pretty easy.

Ground plane calculator

An example. You will need to scale down the size for UHF. The above calculator with give you the size.

I think the more important question is do you want your 9 year old to have one of these. I would get your self acquainted with local uhf CB culture by listening to it for a few weeks your self prior to deciding.

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 09:53am 21 Feb 2011

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Thanks Rob that should be helpfull. i have heard there is a bit af a bad CB culture in the cities but being in a rural country area am hoping it would be a bit better here, i may be wrong. i will ask around some of the locals and find out what it is like before i go ahead. But i am afraid he pretty much has his heart set on it. If it is bad i may put in an antenna low enough not to pick up the repeater.

Thanks Dean

isaiah

Guru

Joined: 25/12/2009
Location: United States
Posts: 303

Posted: 09:19am 03 Mar 2011

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you may be able to make a antenna out of a mobile cb antenna by taking the loading coil out and trimming the stinger. We have done this here in the states for 2 meters. we also made dipoles out of brazing rod. 18.6 inch if I remember right.
There may be some on ebay

URL=http://www.motherearthnews.com/Renewable-Energy/1973-11- 01/The-Plowboy-Interview.aspx>The Plowboy Interview[/URL>

rockabye

Newbie

Joined: 12/02/2011
Location: Australia
Posts: 4

Posted: 06:17am 08 Mar 2011

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If you are new to CB licensing information on CB radios can be found here.

http://www.acma.gov.au/WEB/STANDARD/pc=PC_1265

Assuming you have a mobile or car type UHF radio a simple independent ground plane antenna may be suitable. I've seen designs using a panel mount female N type connector as the base section.

The outer 4 mounting holes become the ground plane section by connecting solid wire about 16cm long to each one and angling them down by 45 deg. Then a matching N type connector with a single 16cm wire soldered to the centre pin can be screwed on.

A coaxial 50 ohm cable of about 5 metres is then connected to the base section of the new antenna at one end and a connector that matches the one on your radio at the other end. Make sure there is no shorts between the inner and outer when finished.

You will need to mount it on a pole some it clears the roof by a metre preferably.

Everyday is a chooseday

KiwiJohn
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Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 08:12pm 08 Mar 2011

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The most simple antenna you can make is a 'zep', loosely modelled on the ones used by Zepplin airships.

To make one, first determine 1/4 wave at the frequency you are using then strip off the copper outer of your coax for that length leaving 1/4 wavelength of the inner insulation exposed. Thats it! You have a simple 1/2 wave end fed dipole antenna!

You hang this vertically.

It will be a little better if the entire length of the coax is an even number of 1/2 wave lengths (total including the bit sticking out the end) but that is rather 'iffy' to calculate as the wavelength in coax is shorter than in air, about .65 or something depending on the coax.

JohnEdited by KiwiJohn 2011-03-10

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 10:12am 16 Mar 2011

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Thanks everyone,
I have only a very basic knowlage of electronics and radio waves ect. but i am never to old to learn, especialy when i have a young son to keep up with, so i think it is higly desirable for us to build one ourselves instead of just going out and buying one ready to go of the counter, especely when we can build one out of things that we can find around the shed at home. So hopfully we can put something basic together initualy and then he can tinker with it from there. What he has got hold of is UHF CB 5W radio out of a car. I have just finished puting together a shunt regulator for the wind mill which i have just bench tested and it worked first time {sometimes i am just lucky] so a 12 volt power suply is not war away. All your ideas have been greatly apreciated and I am shore we will be able to put something together that will work.

Thanks Dean.

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 10:13am 22 Jun 2011

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Finally the we have wired the cubby to the windmill and the antenna is being built.
things take a while to happen around here but eventualy things get done.

At the moment we have cd player lights and uhf radio wired in.

rabio is installed next to a comfy chair.

The antenna is built and just needs to be mounted on a pole.it is built to a plan identical to the one that Rob linked me except from using alumimium for the bottom elements it uses bronze welding rod. the calculator link was very handy as this plan i found does not have the correct size for our frequency in its table.
We have a 6 m lenth of 3/4 inch gal pipe to mount it on, with the cubby being 2 meters of the ground this will give us a hight of 8 m which will just put it up above all the house roofs within our local area.
if the weather is kind the antenna will be up in the next couple of days.

I think I might start using the cubby more than the kids.

All the best Dean.

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:24pm 22 Jun 2011

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Hi Dean

Looks like you are making a comfy dog house under the guise of a cubby house. when will she wake up.

All the best

Bob

Foolin Around

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 12:18am 23 Jun 2011

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Bob you have seen through my guise.
It started a few years back when it was decided i needed to build a fort platform for the kids to play on.

But from the beginning i left plenty of room for expansion and it has slowly grown over time.
Next thing to be wired in.

My son and I have gone halves in this LCD HD 12 volt DC TV with in built DVD player.

Soon we will need to rev up the windmill a bit

All the best Dean.

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 09:09am 24 Jun 2011

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Hi all

It is good to finish a sucessfull project and this has been one of them.
The antenna is up and we have transmited and received to 40 km so far. It has only been up for a couple of hours so our full range is not known yet but it is as good or even better than what we set out to achieve so thanks to every one who helped out.

Antenna is tested with a multi meter before it goes up and checks out OK. Early on I discovered a short in the coax conection to the plug with the braid touching the end pin socket. So it is well worth doing regular checks as you go along they can save you alot of worK and time later on.

The finnished antenna project. All up it cost us $45. For stay wires we used cheap tie wire as the pole is connected to the side of the cuby and the stays are just to prevent it swaying in strong winds.

All the best Dean.

brucedownunder2
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Joined: 14/09/2005
Location: Australia
Posts: 1548

Posted: 09:48pm 24 Jun 2011

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Hi Dean ,,,,

Just a word of warning ,,27Mhz ,channel 35 ,is sometimes worked by some of the foul mouth operators I've ever heard.. So best get your little fella to stay on just a couple of channels with his known mates.. Keep away from 35 . and remember channel 16 is a call channel , so just use it for that purpose ,,or he'll get foul mouthed again ,. My brothers and I keep to 30,31,32 and a couple other channels when we've established contact.. Free Skypt telephone service through your computer is another way to establish a contact with your friends .

Nice kids , mate ,,I remember when my 2 were that size...lots of fun..

Regards, Bruce

Bushboy

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 12:17am 25 Jun 2011

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Thanks Bruce

I have these concerns as well, as he informs he already knows all the swear words.
But even so the ground rules have been laid down and if he misbehaves, it will be disconected.

All the best Dean.

Robb
Senior Member

Joined: 01/08/2007
Location: Australia
Posts: 221

Posted: 01:13am 29 Jun 2011

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I think the brass should be better than aluminium

You did seal the whole thing up so water cant get into the plug and down the cable? Neutral cure silicone should do fine.

Thats one cool playhouse

Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206

Posted: 01:42am 29 Jun 2011

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Hi Robb

I did seal it well with silicone as i read somewere that water can get down the cable.
Your posts and your links have been a great help, lots of thanks.

All the best Dean

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