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CB Question


Bos
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I know this came up several times in the past on the old forum, but i can't find an answer in a search over there.

I've just put a new cb in the 90 using the old aerial, so far i've managed to get the SWR to the following

CH UK EU

01 1.8 2.2

20 2.0 2.0

40 2.2 1.8

Which seems well balanced over all 80 channels, but a bit high. If I shorten the aerial the UK values come down and the EU ones go up, as I will use mainly the UK should I lower it and forget about the EU ones or just leave alone ?

The main reason I'm asking is because the range is very poor, it seems to work fine over a short distance vehicle to vehicle, but picks up hardly anything else, If I put it on scan it appears to find (weak)signals but they just come over as noise, and when I do pick up a conversation I only get one side of it (presumably the other is out of range) . Would this be the SWR or do you think I need a new/better/longer aerial ? (currently a 3' springer) .

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Thanks ralph looked at that - bought the cb from there- it's a bit confusing though as it says if ch 01 is lower than ch 40 then shorten the aerial, however it also says to get uk ch20 the same as eu ch20 which it won't be if i shorten the aerial :blink:

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Thanks ralph looked at that - bought the cb from there- it's a bit confusing though as it says if ch 01 is lower than ch 40 then shorten the aerial, however it also says to get uk ch20 the same as eu ch20 which it won't be if i shorten the aerial :blink:

I'd go for the lowest setting on the UK channels only :D

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Shortening the arial raises the frequency at which the SWR 'dip' occurs, it will not lower the value of the 'dip' just move it to a different frequency. Ch40 is higher frequency than Ch1 and UK are higher frequency than EU. Your dip is at the top end of the EU frequency and bottom end of the Uk frequency. Shortening the antenna will bring the dip up into the UK frequencies, at the exppense of the EU ones. Personally that's what i do as i never use the EU frequencies. If you want to lower the SWR values across the whole curve then you need to improve the ground plane and earthing of the antenna.

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This is news to me. I got a liscense in the 80's when they first came out. The post Office told me it was a one off payment (10 quid) no other information than my personal details were necessary. Better be careful how I use it now.

Just a thought, how many people have WiFi & Bluetooth and don't need a liscence, I know it's low power but you can still comunicate peer to peer and you can encrypt it, thats a bit more scary than a bit of chat between trucks. :ph34r:

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Right sorry to bore you all with this again, but I went out today and bought a new aerial and the SWR came down to:

CH UK EU

01 1.2 1.4

20 1.2 1.3

40 1.2 1.3

without any trimming :)

Now the bad news, I wired the radio straight to the (second) battery and it now seems to pick up signals strongly over a good range :) BUT when I turn the ignition on, it immediately picks up a signal/noise - which remains for a while after turning the ignition off again so would I be right in guessing It's picking up interferance from the fuel pump ? and then when starting the engine the interferance gets much worse (making the set unusable).

So my question is how do I go about tracing the cause of the interferance? or can I just fit some supressors somewhere (at random preferably :P ) to sort it out ?

Thanks

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Hello Mark,

Trust you are well after your set back earlier in year :unsure: ?

As yours is a TD5 the interference could well be processor noise from the ECU :angry: ………..I seem to remember that there was a fair bit of info about this on some of the Oz forums …….coz they use HF radio over there in the outback.

I’ll have a search and see what I come up with.

Ian

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Thanks Ralph, I'll try and get hold of a few suppressors.

Feeling ok at the moment thanks Ian, I'll try a few suppressors in various places as per Ralph's advice and see what difference that makes hopefully won't have to mess about with the ECU.

Thanks Both.

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