Why does using the preamp on ten meters create so much wideband RFI with no antenna connected?

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  • Updated 3 years ago
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Attached is what my SSDR panafall looks like with the 10M preamp on and off.  Bad RFI with it on, no RFI with it off, and no antenna connected to the 6300.  Is this typical?
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Posted 3 years ago

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Lee - N2LEE

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Official Response
Are you familiar with how a preamp works and its purpose ?
This is an unterminated input which expects to see 50 ohms, have you tried this with a dummy load ?

An antenna amplifier boosts a radio signal considerably for devices that receive radio waves. Many devices have an RF amplifier stage in their circuitry, that amplifies the antenna signal, these include, but are not limited to; Radios, Televisions, Mobile Phones and Wi-Fi and Bluetooth devices. Amplifiers amplify everything, both the desired signal present at the antenna, and the noise. Typical signal noises include: ambient background noise (electric brush noise from electric motors, high voltage sources from, for example a gasoline engine ignition, or large dispersed currents in the vicinity of the desired reception electric fence). To add, consideration must be taken for the noise generated by the amplifier itself and all other electrical noise which may be generated by the device that is to receive a signal, for example a lot of consideration has to go into mobile phone circuitry design to eliminate as much noise from its own circuitry in order to not disturb the desired transmission signals from its own antenna(ae).