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PE4BAS Amateur Radio Weblog

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IC-7300 - Strange SWR anomaly

Posted: 30 Sep 2021 01:17 PM PDT https://pe4bas.blogspot.com/2021/09/ic-7300-strange-swr-anomaly.html


To measure an antenna concept like I have you need something different
from an antenna analyzer. Since the ATU needs a signal of at least 10W to
tune the antenna. With an analyzer it would mean I choose a frequency
transmit a signal, disconnect antenna, connect analyzer and note or make a photo from the results, next frequency same thing. This would take at least
a hour to measure all 5 bands. The IC-7300 (and my old IC-706 as well) has
an option to make a SWR graphic. And the outcome from my antenna concept
system is of course different from the pictures you see normally since the
ATU is an integral part of the antenna system.




You see that I have excellent SWR all over the bands. Logically because the
ATU is tuning to minimum SWR on all frequencies. A lot of fun and very fast
to measure with this radio.
The strange thing however is this:

I tried this several times. And you can be shure the SWR is 1:1 at 28.500
MHz and above. But the IC-7300 keeps giving me 1:2 SWR when I use this SWR tool. I think this has something to the with the filter switch which I hear clicking when I tune over 28.500 MHz. Not shure why this is affecting the measurement. Can somebody give me a logical explanation?

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