[600MRG] "Something's Not Right"

[Frank Lotito]

I still get a feeling that the antenna is not tuned to the fundamental frequency, which is intended to be within the 630 meter band.  Using a shielded dummy load, then the actual antenna circuit, has it been verified that the waveform at the transmitter's output is indeed "sinusoidal looking enough" at the desired transmit frequency?

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Even a low-end single channel X-T analog type 5 MHz scope should be able to ferret this out to verify that the low-pass filter in the transmitter output is indeed doing a good enough job.

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I refer back to a few months ago where this bulletin board discussed "tuning for maximum transmitter current output" or "maximum current at the antenna" as a means to tune a short LF / MF transmitting antenna.  The hazard of this simple "numeric indicator" device tuning is if the transmitter output filter is not adequate, and / or the Q of the transmit antenna high at the second or third harmonic, the antenna could be accidentally tuned to a harmonic instead of the desired fundamental.

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GL 73 Frank K3DZ / WH2XHA
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