Author Topic: Setting the SWR on a Cobra 29 CB  (Read 6727 times)

Bob_Hataway

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Setting the SWR on a Cobra 29 CB
« on: December 30, 2008, 06:26:18 AM »
I have a Cobra 29 and need to double check the SWR to make sure that I am getting out properly.

It has an SWR switch and a calibrate adjustment.  The problem I have is finding the proper setting to set it on with the adjustment switch.  And what channel do you turn it to so that you set the SWR for the best reception and broadcasting?

Any help will be appreciated.  Thanks and God bless ...

Bob Hataway

krooser

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Re: Setting the SWR on a Cobra 29 CB
« Reply #1 on: December 30, 2008, 09:29:12 AM »
You adjust the SWR by lengthening or shortening the antenna until the SWR is correct.

If you have a fiberglass whip, pull off the rain cap on the end of the antenna and slightly peel back the antenna covering... this will allow you to cut the wire OR pull it out slightly which will raise or lower the SWR.

If you have a coil type antennea simply adjust the steel rod in or out.

IowaSuperTrucker

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Re: Setting the SWR on a Cobra 29 CB
« Reply #2 on: December 30, 2008, 11:23:21 AM »
You are suppose to adjust it with the radio on Channel 20.  If you have the Cobra 29 manual booklet, it describes how to properly adjust the SWR.  Each channel will be slightly different, I never can remember so I keep my manual in my truck with me! :)

Bob_Hataway

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Re: Setting the SWR on a Cobra 29 CB
« Reply #3 on: December 30, 2008, 01:11:17 PM »
I knew about the cutting of the antenae, however, on the Cobra 29 you can adjust from within the radio with an adjustment switch.

I just do not know which of the calibration scales you are supposed to read.

God bless ...

Bob Hataway

JP

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Re: Setting the SWR on a Cobra 29 CB
« Reply #4 on: December 30, 2008, 02:13:22 PM »
No, the "calibrate" on the radio itself will not set the SWR to any level. The calibrate is simply for obtaining a reading from the Cobra's gauge. And like most built-in meters it is not entirely accurate.

Again, the radio itself will merely give you a ballpark figure for the SWR. To use the meter, put the radio in "SWR" mode by flipping the switch. Key the mic. Adjust the calibration knob to wherever on the meter it says. Release the mic and key the mic again. (I believe that is how to do it...)
« Last Edit: December 30, 2008, 02:15:25 PM by JP »
No sheep, no bows on real trucks.

Bob_Hataway

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Re: Setting the SWR on a Cobra 29 CB
« Reply #5 on: December 30, 2008, 03:26:22 PM »
JP, that is how I thought you did it.  I just did not know on the meter when you key the mic you read the calibration.  There are about 3 or 4 different levels on the meter.  There is a calibrate mark on the meter and this is where I set it the last time I tried.  It still does not seem to get out as it should.

BTW, how do you put that photo on your signature?

God bless ...

Bob Hataway

WesV

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Re: Setting the SWR on a Cobra 29 CB
« Reply #6 on: December 30, 2008, 07:28:29 PM »
With the switch on the CAL setting, Key the mic on Channel 20.  On the meter in the upper RH corner you will see "CAL \/" adjust your SWR knob until the needle is centered in the middle of the little arrow.  Now move the switch to the "SWR" setting and key up and take the SWR reading with the 1-4 range on the meter.

Bob_Hataway

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Re: Setting the SWR on a Cobra 29 CB
« Reply #7 on: January 01, 2009, 07:18:41 AM »
Thank you WesV.  That is the information that I needed since I have misplaced my manual.

God bless ...

Bob Hataway

chris142

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Re: Setting the SWR on a Cobra 29 CB
« Reply #8 on: January 01, 2009, 02:50:10 PM »
Ya the radio does not set the SWR it simply tells you what it is. And as already said you put it on 20, put the knob to "CAL", on the right side of the meter is a break in the red with a hard to see arrow. You want the needle there when it's on "Cal" and you key the mic. You adjust it with the calibration knob.

Then put the knob on"SWR" and key the mic again. The needle should stay on the left.

But the meter in the radio is not as accurate as a good swr meter.

JP

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Re: Setting the SWR on a Cobra 29 CB
« Reply #9 on: January 01, 2009, 03:13:48 PM »
With the switch on the CAL setting, Key the mic on Channel 20.  On the meter in the upper RH corner you will see "CAL \/" adjust your SWR knob until the needle is centered in the middle of the little arrow.  Now move the switch to the "SWR" setting and key up and take the SWR reading with the 1-4 range on the meter.

There, that's exactly how to do it. What I said is the best I could remember off the top of my head. :roll:
No sheep, no bows on real trucks.

Bob_Hataway

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Re: Setting the SWR on a Cobra 29 CB
« Reply #10 on: January 03, 2009, 11:39:38 AM »
Thanks to everyone.  I will reset it according to the calibrate arrow on channel 20.

God bless ...

Bob Hataway

Oldrustycars

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Re: Setting the SWR on a Cobra 29 CB
« Reply #11 on: January 04, 2009, 08:52:20 AM »
I'll second that the built in meter isn't very accurate. Mine was way off, in fact. So bad I could have damaged the radio. A $25 meter fixed that, and the Wilson antenna web site has a great page on setting SWR. It's well worth messing until you get it as good as you can. However, it's often not possible to get it perfect, or even close. Make sure the doors are both closed, if you mount antennas on the mirrors. If you have fiberglass doors, like many Macks, good luck.
Find the one thing in life that you don't do well, and then don't do that thing.

JP

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Re: Setting the SWR on a Cobra 29 CB
« Reply #12 on: January 05, 2009, 05:47:02 PM »
If you have fiberglass doors, like many Macks, good luck.

Amen on that one. One of the big keys to a good SWR is ground, ground, ground.
No sheep, no bows on real trucks.