Uhf install

[millsy]

Originally Posted by stoneddoodle

Thanks for all the info guys. After i got motivated this morning after 10 haha, i pulled off the dash and there just happened to be 4 wires hanging there with the old diy clap wire joiners, so it looks as it the last owner may have had a cb and mabey a hf radio. made things soo much eaiser. and there was and easy was through the firewall also that mad it and easy install. Might sitck a few pics up just so for other to have a look at if they have a go at diy install. All up it took a really short hour if that. As for this better earth for the ant, how would i go about doing this in a bit more detail and also do a better earth help wit reception or just stops it blowing the fuse?

Thanks guys

I am assuming you have an earthed antenna. This is the most common type I think. You know if you have one because there will be a base plate under the antenna mount with four sharp claws, one in each corner. They provide the earth connection. Provided all the bolts that hold your bullbar to the chassis of the car have not got a solid layer of rust all over them! These claws are supposed to pierce through the paint on the bracket welded to your bull bar. The other type of antenna is a ground-independant type. These obviously are named that way because they do not need earthing/grounding.

The way the radio shop 'fix-it' man explained it to me is that if the antenna loses its earth connection, or develops a high resistance earth connection due to paint or rust problems, then the output amplifier in the radio cannot transmit all its power properly into the antenna. This is called an impedance mis-match. So apparently the power is reflected back into the power amplifier itself. This causes the amplifier to overheat and so it damages itself - 'burns' itself out and dies.

It is the same thing as having a high SWR value. A high SWR reading means too much output signal is being reflected back into the radio. The lower the SWR the better - the more power to the antenna, and the further your signal travels across the countryside.

So the extra earth wire is my way of insuring that this does not happen. If you have abad earth then you will not be 'getting out' very well, since the antenna is not getting its full complement of current that the amplifier should be giving it. So your output, or transmit signal, will be weaker than it should be, and people will have trouble receiving you. You will not be blowing a fuse, but will run the risk of blowing your output amp!

I have two antenna bases on my car - one on the bullbar, and one in the middle of my fibreglass roof. On the bullbar mount I soldered a ring connector under the earth plate of the antenna - the plate with the four claws. To give it some mechanical strength I wrapped two zip ties around the base and the ring connector, clamping them together. Then the wire coming from the ring connector just goes straight to the negative post on the battery.

On the roof antenna mount, I have a metal plate under the canopy to spread the load of the wind reistance over a larger area of the fibreglass. I have also set up a ground plane with this metal plate at its centre, and four radial wires coming out to the four corners of the roof. A metal roof gives a better ground plane effect, but my four radiating wires are better than nothing!

The clawed earth base that comes with the antenna mount spikes into this metal plate. So I just drilled a small hole into the plate and used a self tapper to screw a small ring connector to the plate. And again, the wire from the ring connector goes to the negative battery terminal.

I am no expert on radios or antennae. Just acting on what I have been told. Would be interesting to see what others have to say about this.

Cheers, Millsy.

[stoneddoodle]

Originally Posted by millsy

I am assuming you have an earthed antenna. This is the most common type I think. You know if you have one because there will be a base plate under the antenna mount with four sharp claws, one in each corner. They provide the earth connection. Provided all the bolts that hold your bullbar to the chassis of the car have not got a solid layer of rust all over them! These claws are supposed to pierce through the paint on the bracket welded to your bull bar. The other type of antenna is a ground-independant type. These obviously are named that way because they do not need earthing/grounding.

The way the radio shop 'fix-it' man explained it to me is that if the antenna loses its earth connection, or develops a high resistance earth connection due to paint or rust problems, then the output amplifier in the radio cannot transmit all its power properly into the antenna. This is called an impedance mis-match. So apparently the power is reflected back into the power amplifier itself. This causes the amplifier to overheat and so it damages itself - 'burns' itself out and dies.

It is the same thing as having a high SWR value. A high SWR reading means too much output signal is being reflected back into the radio. The lower the SWR the better - the more power to the antenna, and the further your signal travels across the countryside.

So the extra earth wire is my way of insuring that this does not happen. If you have abad earth then you will not be 'getting out' very well, since the antenna is not getting its full complement of current that the amplifier should be giving it. So your output, or transmit signal, will be weaker than it should be, and people will have trouble receiving you. You will not be blowing a fuse, but will run the risk of blowing your output amp!

I have two antenna bases on my car - one on the bullbar, and one in the middle of my fibreglass roof. On the bullbar mount I soldered a ring connector under the earth plate of the antenna - the plate with the four claws. To give it some mechanical strength I wrapped two zip ties around the base and the ring connector, clamping them together. Then the wire coming from the ring connector just goes straight to the negative post on the battery.

On the roof antenna mount, I have a metal plate under the canopy to spread the load of the wind reistance over a larger area of the fibreglass. I have also set up a ground plane with this metal plate at its centre, and four radial wires coming out to the four corners of the roof. A metal roof gives a better ground plane effect, but my four radiating wires are better than nothing!

The clawed earth base that comes with the antenna mount spikes into this metal plate. So I just drilled a small hole into the plate and used a self tapper to screw a small ring connector to the plate. And again, the wire from the ring connector goes to the negative battery terminal.

I am no expert on radios or antennae. Just acting on what I have been told. Would be interesting to see what others have to say about this.

Cheers, Millsy.

Thanks for taking the time there millsy to answer, Im going to do what you said and run a wire from the base plate back to the neg on the batt. Last thing i want it to blow my new radio even know it was kind of a cheepy.

Thanks heaps

[Watt]

Hey millsy when i say clamp joiners i meant the ones with the small tunnel through and two little screws so you can feed each end in and screw them down... i also used heat shrink.
The main reason for doing this instead of soldering was the limited wire length i had to work with... I think soldering is always the best option if possible.
I hope my joins don't come loose anytime soon, pain in the arse getting the dash apart again. hahaha.

[millsy]

Originally Posted by Watt

Hey millsy when i say clamp joiners i meant the ones with the small tunnel through and two little screws so you can feed each end in and screw them down... i also used heat shrink.
The main reason for doing this instead of soldering was the limited wire length i had to work with... I think soldering is always the best option if possible.
I hope my joins don't come loose anytime soon, pain in the arse getting the dash apart again. hahaha.

Ah-ha! I reckon those connectors are great. I always fold the wire back onto the plastic insulation, flattened out a bit and wrap it around if I have to get it small enough to push into the hole. That way there is no movement, or very little movement, and the stress of the screw is on the plastic rather than the wire. These two things stop the wire from breaking due to wriggling with the vibrations of the car or other movements.

I do the same thing whenever I use those connectors, like bullet or spade connectors, where you have to crush the connector neck down onto the wire with a pair of pliers. If I can't fit the plastic insulator plus the wrap of wire back onto the plastic, then I at least I try to double the thickness of the wire by bending it back on itself, leaving the insulation outside of the crsuh tube, but still inside the plastic insulation of the connector.

I thought you were talking about those clam type connectors. The ones that have either a little spike or a little U guilotine that makes a slice through the plastic insulation on each side of the wire. You need a pair of pliers to clamp them closed so that the little locking clip on the side snaps over its catch. They are used for making a T junction join onto a length of wiring when you don't want to cut the wire and make three ends to solder together. But I have had problems with these over the years. Like I said, quick and nasty, and then cause intermittent open circuits in the future.

Of course soldering a strong mechanical and electrically good join is a skill in itself.

I was taught correct soldering techniques at uni, and have always made a point of passing these skills on to my students in their electronic work at school.

Many people do not understand how important it is to pre-tin the wires before joining them. And they also don't understand that soldering is not just a matter of shoving the solder onto the soldering iron and melting it so that it drips onto the cold wire! All this does is burn the flux, which goes up your nose and probably causes cancer in your lungs.

The soldering iron should be cleaned and tinned itself. This is then used to heat the wire to be tinned, and with the iron still touching the wire the flux cored solder is touched to the wire, not the iron. The flux (acid) melts first and runs out in front of the melting solder, cleaning the hot wire before the solder runs over the hot wire and makes a good electrical bond.

Hot, flux-less solder dripping onto a cold wire causes dry, crystallized joints which suffer hairline fractures beween the solder and the wire. This causes either a complete open circuit, an intermittent open circuit, or a high resistance connection.

[vk2vbb]

the aerial base needs to be connected to a good clean earth, the spikes on the underside of the aerial base are all that are required to provide the connection to ground, especially on an alloy bar. If however you're using a painted steel mount, remove the paint on the underside to provide grounding. Running a wire directly to the battery fron the antenna base, while providing an electrical connection to earth, doesnt provide a ground plane connection where it is required, at the base of the antenna. The ground plane is an important function of your aerial and without a good ground plane, the resultant higher SWR, or reflected power, will blow the final transistors in your radio. Rule of thumb, when wiring a good quality radio into a vehicle, is to run both positive and negative wires directly to your battery. This way the battery acts as a capacitor, effectively filtering a lot of the electrical noise, otherwise generated in your vehicles wiring harness. I hope this info helps, Cheers, Bill, VK2VBB.

[millsy]

Thanks Bill. Looks like those wires from the antenna mount to the battery negative are not neccessary!

I know I have a good ground plate connection on my roof mount. But people were telling me my signal from the bull bar mounted antenna was not very clear at all. Maybe I just need to do a good scratch with some emery paper to get rid of any paint or corrosion that's preventing a good electrical connection with the metal of the bull bar.

[vk2vbb]

Millsy, grounding an aerial is a funny thing, where people get confused is with an electrical ground, compared to an RF ground. RF energy travels on the outside of the wire, which is why all good radio installations use flat braid grounding straps, like the old style battery negative braid, this gives more RF surface area. All areas on my Triton are bonded with these straps, bull bar to chasis, bonnet to chasis, doors to chasis and tray to chassis, because you can't trust a ground through a hinge or painted surface. The ideal place (although not practical) for an aerial is centre roof, this produces a 360 degree transmission pattern, fairly uniform coverage in every direction. If you mount an aerial on the bull bar, your transmission pattern looks more the shape of a tear drop, across the ground plane, so if the aerial was on the left front bull bar, the maximum radiated power would be in the direction of the right rear of the vehicle. This can be somewhat compensated for, with the use of "Ground independant" antenna's for the higher bands. These are the big white fibreglass style UHF antennas, and they have their own artificial groundplane built into the antenna. The elevated stainless steel whips, that sit up on a solid 20cm base are the same style. With these antenna, the higher and longer the better, to get maximum transmission power above your roof line. All this changes again, on the lower, long distance HF bands, but thats a more complicated issue. Cheers, Bill. VK2VBB

[summerscheifer]

I'm getting a nasty grinding sound from my power antenna motor. From what I read, it's the teeth and I can just remove the top of the antenna, pull the chain out, buy a new one and drop it in. In the mean time, is there an easy way to get to the motor to unplug it? thnaks guys in advance. godbless.