NanoVNA SWR display of trimmed comm radio antenna
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NanoVNA SWR display of trimmed comm radio antenna |
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Navigation & Acknowledgements |
3 pictures on this page - scroll down to see the rest
tuning comm radio antenna with NanoVNA: 2021-03-09 Panasonic DMC-FT1
NanoVNA display after the final trimming of the comm radio antenna. The frequency sweep is from 115MHz to 140MHz to give good display resolution. The copper tape dipoles are each now about 486mm long compared to the target length of 490mm in Annex C of the manual. Here the display markers are at 118MHz, the bottom of the aeronautical band, showing SWR (the green trace) of 1 to 2.23. The comm radio spec calls for an antenna SWR of better than 1 to 3 across the band, so this is satisfactory. The yellow trace is the return-loss in dB, for those who prefer to think in those terms. The process of antenna trimming and checking SWR has taken so long that although I started with a full charge, the NanoVNA battery has gone down quite a bit, as shown by the symbol at top left.
tuning comm radio antenna with NanoVNA: 2021-03-09 Panasonic DMC-FT1
NanoVNA display after the final trimming of the comm radio antenna. Here the display markers are at 138MHz, the top of the aeronautical band, showing SWR (the green trace) of 1 to 2.26. The yellow trace is the return-loss in dB.
tuning comm radio antenna with NanoVNA: 2021-03-09 Panasonic DMC-FT1
NanoVNA display after the final trimming of the comm radio antenna. Here the display markers are at 126.25MHz, where the SWR (the green trace) is at the minimum of 1 to 1.01. The yellow trace is the return-loss in dB. The manual Annex C suggests to aim for minimum SWR at 127.5MHz, but the network analyser allows a better approach by aiming for the same SWR at each end of the band.
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