Poll: If Chosen as our preferred frequency, would you support CB 27/81?

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(1 July 2012, 21:43)The Local Ned Wrote: SWRing in for base antennas is slightly different from mobile ones...dunno where LS is getting that idea from , most antennas can be SWRd in by adjusting a grub screw that alters the physical length of the antenna , which will change the SWR between it and the radio , a SWR of 1:1 is the best possible result , but in my experience it is achieved very rarely.

Groundplanes CAN alter the SWR , but are generally used to 'strengthen' the signals range , an antenna doesnt radiate signals uniformally i.e in a circle , certain directions will have a better range , groundplanes can be altered to try and strengthen the signal in those other directions.

TLN,
Thanks, you are right about adjusting the length of the driven element.

Barneyboy is struggling to get his antenna to work at all, and I'm geussing that raising and lowering the brute is to adjust it for SWR is going to be a fairly big task. Adjusting ground planes ( which it appears he does not currently have) is possibly an easier solution

Ideally you should adjust driver first and then ground planes.... and adjusting the ground planes by raising or dropping them does indeed have a fairly big effect on SWR... That's just my experience, others may know of beter or more simple solutions.

You seem better clued up on CB than me. Do you know the antenna BB is using? I've assumed that its a quarterwave of some sort. Its not a halfwave is it? If halfwave groundplanes will not be needed at all.

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(1 July 2012, 20:11)Barneyboy Wrote: would love to get right one had a midlands cb but could only hear not talk so my money is hear just need a push have a 18 foot on top of 25 foot scaf pole up just need right rig to get and swr meter or some thing about ground plan please help me im comfused

Hi Barneyboy,

While writing my last reply I realised that you have said that your antenna is 18ft long, I reckon that make it a half wave ( 5.5 meters) Very often this sort of antenna does not have groundplanes at all.

Have a look at the manufacturer's mounting instructions and adjust accordingly.

Certainly don't go adding ground planes to it until you are sure it needs them.