Copper Talk » Open Forum » Archived Messages » 2002 » Archived Messages 02/01/2002 to 04/31/2002 » Swr with amp « Previous Next »

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CHUCK
Posted on Monday, February 18, 2002 - 2:11 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I have a kl300p in my mobile and without it on my swr is about 1.5 or lower, but with the amp on it it goes all the way into the red!!! is this normal?
Chuck
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Bigbob
Posted on Monday, February 18, 2002 - 8:36 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

The swr meter works on voltage you increase the voltage and you get more deflection on the needle,you must readjust the meter to the set position with the amp energised then switch to ref. to view the swr,if you don't do this it will always go to the red with the amp on.
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Warlock
Posted on Monday, February 18, 2002 - 9:15 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

You have a bad antenna or poor grounding somewhere.
I'm guessing you did re-calibrate your swr set after turning on the amp>?
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CHUCK
Posted on Tuesday, February 19, 2002 - 4:16 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Bigbob and Warlock, yes i did recalibrate after turning the amp on but i still go up to about 3.5 or so. I am Using a k40, and it is brand new and supposed to be able to handle 1500 watts, but another thing i thought of is i do have a pretty big reflacting area, it is mounted on the roof of my ford explorer. Is the needle just "seeing" this swr or is this actualy harmful to my radio? Thank you for you help.
Chuck
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Warlock
Posted on Tuesday, February 19, 2002 - 8:24 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Chuck,
Try another antenna. Possibly the one you're using has a problem. Also, you don't have something between the magnet and roof do you?
If all else fails buy a Wilson 1k.
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Bigbob
Posted on Tuesday, February 19, 2002 - 10:50 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

If your swr meter is in the radio try a 6' jumper between rad. and amp.if it is after the amp the amp may need retuning new or not,have had to do this.
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CHUCK
Posted on Wednesday, February 20, 2002 - 1:28 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Bigbob, How do you tune an amp?
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Bigbob
Posted on Wednesday, February 20, 2002 - 9:18 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Had it's output checked on a scope by a tech.
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Kraig
Posted on Thursday, March 07, 2002 - 5:15 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Is your meter between the radio and amp, or the amp and the antenna?

If the meter is between the amp and antenna and you have recalibrated the SWR with the amp on you may have bad coax or a cold solder joint in the coax. RG 59 can't take a lot of watts. Change your coax to RG 8X (up to 1000 watts) or RG 213 (up to 2000 watts). Try using 12 ft multiples. I have found this helps a lot also.

If the meter is between the radio and amp, there may be a problem with the amp.

If you haven't checked the SWR between the radio and amp you might want to do this after you have gotten the SWR down between the amp and antenna.
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975
Posted on Thursday, March 07, 2002 - 10:43 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Ok let's clear this up a little. First of all, keep in mind that we are talking about a CB amplifier..... and as we know ALL amplifier generate harmonics, and spurs. What you are seeing is spurs reflected back at the feedline (coax) and the SWR meter is seeing this, therefore, giving you a high SWR reading. This isn't nessasarily a problem, it just means the amplifier is a bit "dirty". (although just because it's dirty doesn't mean it sounds bad on the air) This is VERY common in CB amplifiers particularly mobile broadband solid-state units, because they have no output filtering on the to cut down costs. As long as the VSWR is below 1.7:1 or so with the radio alone, you are fine.