Want to get more range from your portable UHF Handheld? Well this is a cheap method and you can also use it it the vehicle with an add-on microphone as a vehicle UHF radio saving you heaps.
What you need
Below is a picture of the type of UHF Radio I have (frontview) followed by the opened unit.
Right firstly the best thing to do is find the ground (GND) point on the PCB (on mine this is shown in the next photo). You can find this by using a Multimeter set to Ohms and connect one lead to the negative point of the battery connections (On above photo large pad area on bottom left) to a pad anywhere near the antenna section at the top left. If you don't have a pad as shown in the next photo don't dismay as most of the large green area is ground plain and all you really need to do is carefully scrape away a little of the green to reveal the copper below and use that.
You will need to grind down the thread part of the BNC Socket to fit comfortably in the case where the original antenna was. Also you may need to grind back the centre connection on the socket to allow you to screw the case together again, you may also need to cut out a little of the plastic case. Make sure it fits when you close the case together before you go any further.
Next solder a small l piece of wire to the centre connector of the BNC Socket and one to the ground out part of the socket case (GND).
Solder the 2 wires to the pads on the board as shown in above photo. Place some 5 minute Araldite in the case and place the socket into this. Remember to work quickly before the glue dries. Close the case and leave to dry.
While the case is drying we can make our "Antenna". Cut a piece of Coaxial cable to around 6" in length and strip back the outer insulation and remove the outer shielding. NOTE: We do not want to connect the outer shield at all on this antenna and only the inner (center) conductor). You only need the GND connection when used in a vehicle and not when used as a handheld. After you have done this solder (or connect depending on BNC Plug you have) the centre wire (conductor) to the centre connection on the BNC Plug. There you have it a simple cheap antenna. You can tidy it up by placing heat shrink or tape over the cable to make sure it secures to the plug and put a cap from an antenna (available free from Dick Smith stores) on the tip of the antenna. This will increase your range to around 10Km in the bush.