27MHZ CB SWR

Submitted: Wednesday, Jul 13, 2005 at 11:40
ThreadID: 24679 Views:1594 Replies:3 FollowUps:3
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To anyone who remembers 27 MHZ CB

I finally decided to tune the aerial (z mounted, drivers side, half way back, 80 series Landcruiser) on my Uniden PC 122. The best SWR reading I can get is 2.4:1 and according to the instructions with the meter this is just passable

Does anybody know what SWR is acceptable and would my mounting position contribute to the poor reading?

Any tips appreciated

Leg End
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Reply By: Darryn - Wednesday, Jul 13, 2005 at 12:12

Wednesday, Jul 13, 2005 at 12:12
G'day Leg, acceptable SWR is 1.5:1 or less on Ch 20. With your mounting, check the Z bracket is earthing properly to the vehicle body and the coax is earthing to the bracket. The best way is to get a multimeter and see if there is continuity from the coax plug to a metal part of the body. While your at it check there isn't a short between the coax outer braid and the centre conductor and that the centre conductor is making contact both at the plug and the antenna base. If all these are ok check SWR on Ch 1 and then on Ch 40. If the SWR is lower on Ch 1 than Ch 40 then the antenna is to long and has to be trimmed shorter. If it is lower on Ch 40 than Ch 1 it's too short and you could need another antenna. What sort of antenna is it? If it is a fiberglass whip and it is too long you can carefully cut it back with good side cutters cutting about 3mm/1/8" at a time checking the SWR as you go. Do this on Ch 20 until it comes below 1.5:1 or lower and you should be right for all 40. Any questions ask away.
Regd's Darryn
AnswerID: 120125

Follow Up By: Big Woody - Wednesday, Jul 13, 2005 at 18:44

Wednesday, Jul 13, 2005 at 18:44
G'day Darren,

I read this post and was about to reply but after reading your post I would have written exactly the same thing.

Listen to this man he knows what he is talking about!!!

Cheers,
Brett
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FollowupID: 375242

Follow Up By: Darryn - Friday, Jul 15, 2005 at 12:33

Friday, Jul 15, 2005 at 12:33
Thanks Brett, I haven't done one for years now as I've only got 27mhz in the Cruiser tray and I've had it 8 years with no problems. I wonder how Leg is going with it or has he thrown his hands in the air! Its certainly more complex than just screwing on a Ground Independant UHF!!
Regd's Darryn
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FollowupID: 375538

Reply By: Mad Dog (Australia) - Wednesday, Jul 13, 2005 at 12:30

Wednesday, Jul 13, 2005 at 12:30
2.4:1 isn't good at all don't know how any instructions could say it was acceptable.
Darryn is on the ball and make sure you are checking in an open area with no nearby large objects....ie in the driveway up against the house.
AnswerID: 120128

Follow Up By: nickoff - Wednesday, Jul 13, 2005 at 12:53

Wednesday, Jul 13, 2005 at 12:53
Also make sure yo are using 50ohm coax, not tv stuff, which is 75ohm..and make sure that there isnt excess coax in a coil, as this will affect your readings also...

nick.
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FollowupID: 375173

Reply By: Member - Banjo The First (SA) - Wednesday, Jul 13, 2005 at 16:40

Wednesday, Jul 13, 2005 at 16:40
Got my SWR checked by a pro years ago and have not changed the installation since - not sure of the values - the PC122 XL is a solid unit - pity nobody listens to 27 much anymore - I've been out 2500km in the middle of the day, while mobile on mine. Not being worth a lot, but as new, and installed in the dash, mine is staying put - a back up to the long distance HF.
AnswerID: 120167

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