Hem SAQ Forum SAQ Technical Discussions TX frequenciy audible

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  • #7872 Svara
    Emil Obermayr

    Just a curious question: When you are close the transmitter:

    Are the 17,2 kHz audible to to human ear?

    That is: If you can hear 17kHz at all. That means: not me 😉

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    • #9172 Svara
      Emil Obermayr

      Sorry to pick up this old topic. But I’d like to clarify my question:

      It is clear that an electro-magnetic wave can not be heard directly, no matter of which frequency.

      But the 17200 Hz go through several inductive components, which generates mechanical forces, which should lead to some vibrations. It is the same way you sometimes can hear the 50Hz if some high power devices do vibrate mechanically due to some “loose” inductive components.

      I guess the other components of the transmitter are so loud that an additional “whiste” is hard to detect. But has ever someone reported to hear it? maybe a child?

    • #8614 Svara

      Sorry, typos.
      Last sentence: Animals are able to hear IT.

    • #8613 Svara

      The Signal is Produced by a MECHANICAL tx. So ist could easily be possible that an audible sound ist generated. Anomaly are able top hear that
      QUESTION: IS there an audible acustic Sound?

    • #7954 Svara
      Pat Piscini

      Today, December 25, 2019 at 13:15UTC continuing until at least 13:30UTC I received a morse code signal on AM at 9805khz. The text sent was TIOAAA7. This was being repeated in rapid succession. This sounded like hand sent, as with a straight key, morse code at approximately 15 words pe minute. Signal report was 578 to North Greece New York, about 2km from Lake Ontario, and North West of Rochester New York. There was also what seemed to be a background signal pulsing at approximately 4 cycles per second. Receiving equipment was a Yaesu FRG8800 with a 60 foot shortwave receiving antenna sloping from 2 meters up to 10 meters.
      I do not know if what I was hearing was a harmonic of the alternator or something completely different. The signal was solid copy the entire time I listened, and I unfortunately had to leave home just after 13:30 or I would have continued to monitor the transmission. Pat Piscini, KD2WL, submitted 25 December 2019.

    • #7922 Svara
      N7MSD Mike

      Is not possible to directly hear electromagnetic Waves.

      Actually that’s not quite true: amplitude-modulated microwaves can be beamed into a person’s head and they will hear them. However at lower bands there is not enough coupling. This latter is very easy to prove: stand next to a MW/AM broadcast transmitter’s mast (aerial / antenna), especially a big 50kW one; you might hear the transmission audio from the antenna tuner / coupler (the box right next to the mast) but not actually inside your head. Likewise, if your phone can be forced to GSM (TDMA) mode, make a call and see if you hear clicks inside your head; you won’t.

      At VLF the coupling to a human-sized object is so minimal that even with the power they are running nothing would happen unless you were sloppy enough to touch a live line, in which case you would have bigger problems to worry about! 🙁

    • #7887 Svara

      17,2kHz could be heard by human ear if it was an Audio frequency transmitted by a loudspeaker (at least by young people). However, electromagnetic waves transmitted by huge VLF-antennas, would not be picked uped by the human ear anyhow. For SAQ reception, I Always use a homemade VLF-to-SW RX converter with a ferrite rod as antenna. That works ufb. Best greetings, Regards, DL2GAN.

    • #7880 Svara

      Is not possible to directly hear electromagnetic Waves. What the Humans (and Animals) ear is able to hear are longitudinal (pressure) waves.
      These Sound Waves are mechanical nature and need a Media (Air, Water,…) to propagate. Electromagnetic Waves do not need a Media for Propagation
      (Vacuum!) The low Frequency does not cahnge this behaviour.
      If this would be possible you could hear the 50Hz of the electric power Grid as well. When you hear a Transformer sounding it is the mechanical
      resonance induced by currents to the Transformers core.

      Kind regards,
      73, Roland

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