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Thursday, September 30, 2021

IC-7300 - Strange SWR anomaly

 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?

7 comments:

  1. Hartmut LuedtkeThursday, September 30, 2021 at 11:35:00 PM GMT+2

    Hi Bas,

    if you have this anomaly only when measuring SWR, but not when transmitting normally on frequencies above 28,600 MHz, then I suspect that a filter is not being switched when the swr sweeping goes over the frequency 28,550 MHz.

    Is the swr correct, if you manually select the frequencies above 28,550? Does the TRX switch on the correct filter?

    What happens if you run the swr-sweep with the frequency 28.700?

    73 Ham, DB6LL

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    Replies
    1. PE4BAS, BasFriday, October 1, 2021 at 8:04:00 AM GMT+2

      Hello Hartmut, yes the SWR is correct above 28,500 MHz like I wrote. Yes the TRX switches the correct filter (I guess because TRX does well). Have not tried SWR sweep with center freq. on 28,700 MHz. Have to try and see what happens. 73, Bas

      Delete
  2. Tom-M7MCQThursday, September 30, 2021 at 11:46:00 PM GMT+2

    I have a similar issue on 17M as SOON as I go past 18.110 🤷‍♂️ I’ve ordered a 17M monoband resonant antenna so I can work the band.

    73, Tom, M7MCQ

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    Replies
    1. PE4BAS, BasFriday, October 1, 2021 at 8:06:00 AM GMT+2

      Hope that will solve the problem Tom. That gives me another idea....I didn't try the SWR sweep with my 10m LFA beam...73, Bas

      Delete
  3. GerardFriday, October 1, 2021 at 7:10:00 AM GMT+2

    Have you tried using the “Tune” button on 28.500?
    If so,, what happened then?

    73, Gerard, NL14080

    ReplyDelete
    Replies
    1. PE4BAS, BasFriday, October 1, 2021 at 8:08:00 AM GMT+2

      Hello Gerard, just to be clear I don't use the internal tuner from the radio. My CG3000 ATU is at the feddpoint of the antenna, I suggest you read some previous posts. On the other side, yes SWR is 1:1 on 28,500 MHz like I wrote. 73, Bas

      Delete
    2. PE4BAS, BasFriday, October 1, 2021 at 7:47:00 PM GMT+2

      Sorry Gerard, I have to say....very clear view from you. I notice I still have the internal tuner on! That's why this fault occurs. Tnx! 73, Bas

      Delete

Thanks for your comment. Bedankt voor je reactie. 73, Bas