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Tuning SWR with high output

Mike Hancock

Mike Hancock

Member
Dec 29, 2016
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Oregon Coast
Howdy all. New member here, and glad to be here. I'm having a problem I'm hoping someone can help me out with.
Ive always been into CB, but recently got a Galaxy DX94HP with 150 watt output. My SWR is about a 1.0 all around. But when I turn the power knob up at all my SWR climbes with it. Simple question, Is that normal? Do I have to tune my antenna to a 0 to use any power at all?

Much obliged
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541Oregon
 

Welcome to the Forum!

I prefer to check my antennas with at least 25 watts because at real low wattage, the readings can be false.

As for the movement in the SWR meter when power is applied, If you have access to an external SWR meter, or better yet an antenna analyzer, This will at least tell you the accuracy of the radio's internal meter.

If it does still move, then usually due to what's called common mode current on the coax which is a back feed of RF current traveling down the coax length. This can be controlled by adding snap on ferrite beads to a 7 ft. of coax coiled making a choke and installed right up right at the antennas coax connector.

If you want to try this for yourself, I /we could give you more specifics on this.

The RF power knob on your radio is really for setting the dead-key power and not really for the final peak power. The peak power may drop some when the dead-key power is backed off but not enough to make any difference.

Your radio should still dead-key around 20 watts at low power and go up from there. It's usually best to measure your peak power and divide that by 4 and that will give you a 4:1 dead-key/peak power ratio. Your radio at 150 watts peak should set the dead-key around 35 watts.
 
Some of the 'peak and tune' artists (if you can call them artists) may have not done the job properly, and the radio is throwing off too many harmonics when the radio is turned up all of the way. Just keep the output level below that zone. Find a better tech - too - IMO . . .
 
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Welcome to the forum Mike! There is one certain truth I would like to tell you, If your antenna is tuned at ten watts it will be tuned at 100 watts, 200 watts or 2000 watts. You are tuning to the frequency not a power level. Unless you have a problem with the output circuits of your radio. If your Tech turn your TVI filter into a slinky you will have a problem. Most certainly a few people will disagree about the antenna tuning. The best way to tune your antenna is with a antenna analyzer. Low SWR does not equal resonant antenna.
 
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Its likely due to how and where your antenna is mounted. Those big coiled antennas work best on the roof. If the coil is below the roofline you're probably going to have issues with the power on.

Do you have a top loaded antenna or something like a mostly top loaded antenna like a FireStick or skipshooter you could try?

Also make sure the mount is making a solid connection to the vehicle body. Sand away the pain, use some dielectric grease on the surface and bolt it up tight. When you turn up the power more RF current will need to flow to the vehicle body. If it can't the swr will change.
 
Do you have a ground strap from the door sheet metal to the chassis of the truck? Hinges make poor conductors. Be sure that your bracket is grounded to the door as well.
 
Thanks for all the quick responses guys! My trucks in the shop for about a week or so. When I get it back I'm going to try a mag mount on the roof. Do you guys think that would be a good idea? I don't know anything about how mag mounts work, ive never used one. I've got a few other antennas. Mainly Wilson trucker antennas and a 102" whip. The antenna I have on it is grounded with straps. I actually even tried using the radio on a dipole with an SWR of 1.5 and even then it climbed. Oh and I always use an external meter, never the internal one.
 

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If it happened with the dipole too I might lean towards the radio having an issue....assuming the dipole is hung up in the clear.

It's hard to say without being there. Either way the swr should be the same at all power levels. 2 watts or 2000 watts.
 
Mike Hancock said:
Thanks for all the quick responses guys! My trucks in the shop for about a week or so. When I get it back I'm going to try a mag mount on the roof. Do you guys think that would be a good idea? I don't know anything about how mag mounts work, ive never used one. I've got a few other antennas. Mainly Wilson trucker antennas and a 102" whip. The antenna I have on it is grounded with straps. I actually even tried using the radio on a dipole with an SWR of 1.5 and even then it climbed. Oh and I always use an external meter, never the internal one.
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If you do try a magnet mount, avoid the autopart store cheapy ones, because at your radios max power levels I have heard of them melting the "center load coil"!
 

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