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Post by kritic on Nov 3, 2009 12:28:18 GMT -5
My swr is very low--- barely moves the needle but when I switch on my 80 watt amp it will go up to almost a 2:1. Is it normal for the swr to go up when you switch a heater on ??
kritic
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Post by cbrown on Nov 3, 2009 13:46:47 GMT -5
What are you using to measure the SWR? I always recommend an external meter, not the meter built into the radio.
Is this in a base installation or a mobile installation? And what amplifier are you using? Give me some details, and I'm sure I can help you out.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Nov 3, 2009 18:59:04 GMT -5
My swr is very low--- barely moves the needle but when I switch on my 80 watt amp it will go up to almost a 2:1. Is it normal for the swr to go up when you switch a heater on ?? kritic Where are you measuring the SWR? Is the SWR meter before the amp or after? If it's before, you are measuring the input impedence of the amp when it keys, and not the antenna itself. If your meter is after the amp, many times the SWR rises when the amp is on, due to out of band harmonic content reflecting back and power adding in the SWR meter, or a mismatch in the output section of the amp. If you have a low pass filter handy, place that after the amp but before the SWR meter. If the SWR dropps down, then your problem is likely harmonic content. |
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Post by spitfire441 on Nov 4, 2009 5:48:57 GMT -5
My swr is very low--- barely moves the needle but when I switch on my 80 watt amp it will go up to almost a 2:1. Is it normal for the swr to go up when you switch a heater on ?? kritic Where are you measuring the SWR? Is the SWR meter before the amp or after? If it's before, you are measuring the input impedence of the amp when it keys, and not the antenna itself. If your meter is after the amp, many times the SWR rises when the amp is on, due to out of band harmonic content reflecting back and power adding in the SWR meter, or a mismatch in the output section of the amp. If you have a low pass filter handy, place that after the amp but before the SWR meter. If the SWR dropps down, then your problem is likely harmonic content. Also may I add.... If it is the type that needs to be calibrated, You need to recalibrate for the higher power. It could be SWR is the same, the increase in output power, it is showing increased reflected power, try to recalibrate at high power, read SWR again. You need to calibrate at highest power you are going to use......IF it is the calibration type, and it is after the amp. If it is a crossneedle type, what Sandbagger says is true. |
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Post by kritic on Nov 4, 2009 11:51:36 GMT -5
well the thing is the amp is before the meter because it is a dosey 3 meter with swr, power, and modulation. In order to see how much power im out putting it has to be after the amp. So I'm guessing it doesnt hurt to have a little swr when I crank it up
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Post by cbrown on Nov 4, 2009 14:01:55 GMT -5
What is the amp? Some amps are notoriously mis-tuned so they'll show a high SWR.
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Post by spitfire441 on Nov 5, 2009 5:48:39 GMT -5
well the thing is the amp is before the meter because it is a dosey 3 meter with swr, power, and modulation. In order to see how much power im out putting it has to be after the amp. So I'm guessing it doesnt hurt to have a little swr when I crank it up Recalibrate at the high power and SWR should be the same as low power. As you increase output power, you will have a corisponding rise in reflected power. SWR is the same. SWR DOES NOT change with power. Unless your feedline is melting. The reflected power is rising in proportion to output power, the Standing Wave RATIO stays the same. |
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Post by cbrown on Nov 5, 2009 13:44:41 GMT -5
SWR DOES NOT change with power. Unless your feedline is melting. The reflected power is rising in proportion to output power, the Standing Wave RATIO stays the same. Or there is some fault in the system. But I agree - the ratio should always stay the same. |
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