Question with swr

Your SWR should stay constant from 1 to 100 watts,i have even keyed 1000 watts and the SWR stayed the same so I'm thinking that you may need to ground your antenna better.

If you speak into the mike while watching the SWR meter and it goes up then you need a better ground.

 

Your system uses an unbalanced line typically called coax. Unbalanced return currents on the shield cause higher SWR readings at higher power levels. An experienced radio operator measures SWR at the lowest power level needed for calibration.

 

CORRECT ....

Most of the time you see SWR change is due to increasing garbarge ( out of band ) a common problem with export radios and amps ...

 

Sounds like neither of you understood what I said. The SWR does not change due to increasing line current from higher power levels. The READING on an SWR meter changes. This is not the same thing as the SWR itself, rather it is a statement of the fact that the meter is not reading correctly due to the current on the shield.

 

now i'm totaly lost

 

I do not see why, this is not that hard to understand and there is a very large amount of posted scientific literature on the subject. When you increase the power level in an unbalanced system the currents flowing on the coax shield cause the SWR meter reading to rise, therefore giving a false reading of SWR. This is why you use the minimum power to measure SWR. An antenna with an SWR of say 1.7:1 at 4 watts still has an SWR of 1.7:1 at 100 watts, yet you will see an increase in meter reading. Only in a perfectly balanced feed would you not see this effect. This is not to be confused with a variance seen by changing conditions such as keying an amplifier where the generator supplying the meter becomes the amplifier output stage instead of the exciter. Obviously under these conditions the input impedance to the meter is changing. It is very simple to extrapolate that since an SWR meter merely indicates the ratio of its input to output impedance the reading will change if there is a change in one of the compared impedance's.

 

Correct, you are fine. You may need to take the advice of Carolina Thunder "you may need to ground your antenna better". This will improve things for you.