[Elecraft] Measuring SWR (Long)

[Roger D Johnson]

For an interesting discussion..."What happens to the power that's reflected?"


On 4/9/2019 3:42 PM, Al Lorona wrote:
> There's always a lot of discussion about measuring SWR, low SWR values, SWR lights not lighting up, etc. Here's something that might give you a better 'feel' for SWR.
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> Imagine that you measure your forward power at 100 W and your reflected power at only 1 W. You'd probably be very happy about this. Congratulations, your SWR would be 1.22 to 1.
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> Pause for a moment and let it soak in that an SWR of 1.22 is fabulously good. Once you get to this point, below which we're dealing with reflected power that's less than 1% of your power, or four-hundredths of a dB, it's not worth doing any more to your antenna system to improve it. No trimming, cutting, raising, lowering, hanging stuff from it, adding remote tuned things, nothing. You're done for the day and can now get on the air!
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> If the reflected power were 4 W, which would still look pretty small on the meter, the SWR would be 1.5 to 1.
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> A lot of people might be bothered by an SWR of 1.5, but really this is still very good and it's probably not worth going back up to the antenna to mess with it any more. Most importantly, the station on the other end cannot possibly hear the difference between your 1.2 and 1.5.
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> At this point you may be saying, "Yeah, but my rig/amplifier/other thing isn't happy unless the SWR is below 1.5 to 1, so I would still have to do more work."
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> Okay, that's fine, but my point is that the absolute number 1.5 nonetheless represents a system that is working quite well.
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> Let's allow the reflected power to increase all the way to <gasp> 10 watts! At that point, your SWR would be about 2 to 1. Sounds pretty bad, but surely if you were stranded in the desert and had to use your KX3 and a wire to get help, you'd be happy to have a match this good.
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