Outer Limits 4x4 Board

Hi all,

Just a quick one, I heard that you should avoid routing coax near electrical compents etc as it creates interference, I am rerouting my set up at the moment and would like to k now if there is any truth to this so I can route it to suit.

Thanks a heap for yoor help!

Cheers,

Paul

beretta wrote:Hi all,

Just a quick one, I heard that you should avoid routing coax near electrical compents etc as it creates interference, I am rerouting my set up at the moment and would like to k now if there is any truth to this so I can route it to suit.

Thanks a heap for yoor help!

Cheers,

Paul

Not near EFI computer, EFI loom, radio, or heavy cables. Interference issues can run both ways affecting EFI and radio. Radio antenna greater than 1 metre away from car antenna. Run seperate fused power and earth (not fused) to the radio direct from the battery (2nd battery if you have one)using 6sqmm, cable,do not get power from "somewhere under the dash".

So I had it running past the battery and beside a fistful of other live wires and through the firewall among other cables, would that make much difference?

beretta wrote:So I had it running past the battery and beside a fistful of other live wires and through the firewall among other cables, would that make much difference?

Try and minimise the amount of the run that is done next to the other cables. Not absolutely critical, but is the difference between being able to hear faint signals or being "squelched" out.

can you get shielded conduit anywhere?

Sometimes you cant avoid routing near other wiring.

Cool, I am going to run it up the other side of the wall where theres fewer cables etc, hopefully it improves, I had noticed that I seemed to be running out of range a bit early for a UHF and signals were weak, so maybe it has affected it.

Thanks heaps for the help!

DAMKIA wrote: Run seperate fused power and earth (not fused) to the radio direct from the battery (2nd battery if you have one)using 6sqmm, cable,do not get power from "somewhere under the dash".

If you run a seperate earth wire back to the battery, it should be fused as well. If you have a problem with your battery's earth strap, your radio's earth wire will suddenly be conducting a lot of current.

6mm cable is way overkill. Your average UHF radio draws less than 2 amps while transmitting, even a higher powered commercial PMR draws a maximum of 7.5 amps. 4mm would be fine.

Sudso wrote:can you get shielded conduit anywhere?

co-axial antenna cable is already shielded. A good earth at both ends will go a long way towards minimising interference.

The main thing is to keep the coax run as short as possible. If you are running the antenna on the bullbar you should be using a ground independent antenna. if you dont use a ground indepent antenna your range is reduced as you dont have a even groundplane.
Running coax beside everyday power is no problem at all, But it is a good idea to keep it away from high voltages like your coil/ ignition leads etc.

The other main thing about reduced range is the antenna is in the wrong band or out of tune. if you have a antenna that the SWR is bad the radiated power is reduced and the power that is not getting transmitted from the antenna is returned back to the radio, you will notice this from the heat being geterated at the back of the radio where the finals (RF Power Amp/ Final stage amp) are. the best way to test this is by getting a Through Line meter or SWR Meter.


I work in the industry and find that we get alot of drivers coming in saying that there radio is working **** House and that the main reason is the antenna. most people dont understand that there is a direct connection between frequency and the antenna length and inturn think that the bigger the antenna the better it is going to work, this is completly wrong i see drivers putting the good old 27Mhz (AM) antennas on the UHF band (477Mhz) and when i put the through line meter on it i see that the radiating power from the antenna is under 1 watt which mean that 4+ watts are getting fed back in to the radio which if you spoke for to long with the radio like this it would not last long at all.

Hope i have been a bit of help and not just talked aload of crap.

Cheers
Simon..

84zooksta wrote:

The main thing is to keep the coax run as short as possible.

The instructions for my GME antenna said not to change the length of the cable at all because it is "tuned length"

If you are running the antenna on the bullbar you should be using a ground independent antenna. if you dont use a ground indepent antenna your range is reduced as you dont have a even groundplane.

Where are ground independant antenna's ground to and how do you know which type your antenna is?

Coax is never tuned to the right length unless you are making a multicoupling. which is used for when you have multiple transmitters connected to a single antenna and you use Filters(cans) to give isolation. THIS IS ONLY USED AT RADIO SITES eg Repeater sites.

RG58 coax has huge amouts of loss, over 5 meters you have massive DB loss which means you are loosing power through your coax via leakage, if you were to leak 150milliwatts per meter buy the time it get through the whole 5 meters you will be 750+ milliwatts down even before you get to your antenna. so by keeping the antenna coax as short as possible or by using a low loss RG58 coax you will reduce the amout of power loss.

Your most common Ground Independant Antenna is the Elevated Feed Antenna, these are the antennas with a piece of tube that the antenna screws on and are what the police use on there vehicles, Also the other type of Ground independant antenna is the ones that RFI make they are the CD91 series which are the elevated feed ones and also the CD51 Series which are normally used on commercial bands when the antenna has to be mounted on either a mirror or on a gutter mount or fender mount etc.

You can normally tell if your antenna is a ground independant by looking at the bottom of it. It will have either the elevated feed or it will have a are that looks like a bulb. If your antenna just screws on to a base and there is no bulb or something you can normally say it is not ground independant.

If you are unsure you can either give me a model number of the antenna or take a photo and i will help.

just another thing. The large fiberglass ones that electrophone, RFI and polar make are all ground independant and are called colliner antennas and work extreamly well when range is required around hills or on fringe areas.

Hope this helps.

Cheers.

Hi Simon,
Can i ask you a question about what we call "Farmer Aerials" up here, Collinar aerials they would be, about 5ft tall. I see many are damaged/broken on the tip from tree's, sheds and the like. My mate had one which was damaged and i urged him to get rid of it in case it damaged his set. His set slowly over time lost TX strength and i blamed the aerial. He took it to be looked at and was told his diodes had been slowly blowing from the dodgy aerial, hence the drop in power. My question is, how much damage can an aerial sustain before it attracts damage to your set.
I have a Phillips FM900 remote head set which has been converted to UHF. It has switchable TX power from 5watt to 25watt and is an awesome set. I have a base loaded antannae with about a 2 foot centre wound fibreglass tip. I have had to put a layer of shrinktube over the fibreglass because of the old shrinktube getting buggered. I left the old tube on when i did this. will this affect or damage the set?
Thanks for any reply..............Pete!

The whip that you are using can normally take a fair beating.

The main thing that makes the antenna U/S is if the center loaded coil is damaged or if the lengh of the antenna has been changed.

Some antennas can look really good but be bad for the sets. The only way of knowing there is something wrong is if there is a drop in TX range or the receive is reduced or through a SWR meter or thruline meter on it. or for $20 bucks just grap yourself a new antenna.

I like the strong stainless steel whips, They dont seem to break at the bottom and they should never change length on you, it may bend but should be able to be bent back in to shape.


Hope this has answered your question but if not please ask away.

Cheers.
Simon..

just reading about routeing your cable one other point you ight want to know is not to route your cable near your raditor or cooling system because of stray voltage, its when you transmit the cable generates a field around it and can put voltage into your cooling system, which will eat through any aluminium pipes. to chek for this get a volt meter (peferbly digatal) , remove the raditor cap , place the + in the middle in the water making sure not to touch the rad, - place on the battery - post and transmit, if the voltage reading is over .5 of a volt you are to close.

pommy paul

[/quote]If you are unsure you can either give me a model number of the antenna or take a photo and i will help.

Zooksta my GME arial model no. is AE4018K1 Colinear. 4.5db gain
Ground indepentant.

It just says "No tuning required (Pretuned)

Is this referring to the cable length?

Those antennas say no tuning required cos they are ground independant and are desigened for the 477mhz (cb) band so it makes life easy and by cutting the length of the coax you will not change the tuning of the antena but will be improving your setup by reducing the losses through the coax

That antenna is not a Colinear is is called an elevated feed antenna. the whip on the top is a 4.5db gain antenna but when used in the configuration on the elevated feed base it's gain is inreased to 6.5db.

Cheers

I have taken some precautions with my radio installation, but I still used existing holes in the firewall to pass my coax cables and power cables through.
I have an Icom IC-2800H 50/30 watt VHF/UHF transceiver with the antenna mounted on the bullbar and have found no problems with my 2004 Hilux 3.0TD due to where the antenna is or the way the coax has been run.. I also have an Icom IC-F7000 HF radio, but the power for this takes a different path and bypasses the ECU area altogether. The antenna tuner is also at the back of the ute. Once again, I have sent a selcall while driving along (which makes the HF transmit as much power as it can) on several channels with no ill effects to anything eg. no funny engine response, flashing indicators, gauges doing weird things. The UHF antenna is also mounted on the bullbar and the coax follows the same path as the other antenna.

At the moment, we are completing a major radio install in a Country Fire Service command vehicle, a TD Prado. Installed are two GRN radios (low UHF band), a VHF, UHF CB, HF, CDMA car kit, siren unit, headlight flasher module, flashing light bar, a Garmin GPS76, handheld radio battery chargers etc. etc. etc. In the past we have yet to find any installation of this magnitude causing problems with the onboard electronics. However, we once had a Codan HF with a bad earth on the auto tune antenna cause the central locking of a Commodore lock and unlock by itself. Once the earth was fixed, the problem went away.

Check out my radio install pictures here, none of this has caused any problem with my Hilux at all. On the other hand, the transponder in my alarm system messes with my VHF radio on some frequencies...
http://www.users.on.net/~michaelcarey/p ... March2005/
http://www.users.on.net/~michaelcarey/p ... x/May2005/

beretta wrote:Hi all,

Just a quick one, I heard that you should avoid routing coax near electrical compents etc as it creates interference, I am rerouting my set up at the moment and would like to k now if there is any truth to this so I can route it to suit.

Thanks a heap for yoor help!

Cheers,

Paul

Late reply, but anyway.....I rerouted the coax up the passenger side away from electricals and it has made a massive difference in the signal transmitting and receiving, so much so I was very very surprised so I would encourage anyone else to have a serious look at where their coax is run.

By the way thanks for all the help people!

Cheers,

Paul

ill post here to save starting a new thread

does anyone know how to change the output wattage of a philips fm92 (w band), i am buying one and it has been reset to 5 watts and i was hoping to have it variable between 5 and 25.

cheers