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When I bought my transceiver, I found out that it only puts out less than half a watt (which can't travel a 1 mile radius from the antenna, according to google). So, I bought a power amplifier. It says it amplifies it to 75 watts, but I think maybe that's a little too many watts for a human to be 1 foot away from the antenna. So, what can I do to make it safer for me to be around the antenna? I read that metal deflects radio waves, so should I make a metal shield to protect myself? Or is transmitting 75 watts on HF is too little to do damage? The antenna is a EFHW antenna.

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Generally, power is not the sole factor determining how far a signal travels. It is frequently possible to hit repeaters more than a mile away with half a watt. If you are not using a repeater, increasing the height of the antenna would help more than increasing the power.

Also, power is not the only factor that determines if the radiation is dangerous. Frequency (which you didn't mention) is a major factor. However, 75 watts is almost certainly not safe at one foot for any frequency.

You can use the ARRL exposure calculator to determine the safe power or distance.

As to how to make this safe, there are multiple ways:

  • Reduce the power. Just because this is a 75 watt amplifier doesn't mean it always outputs 75 watts. It may have an adjustment to reduce the power. Also, likely it has a minimum power input necessary to reach its maximum power output, and likely this minimum is greater than half a watt. So a lower power input may put out less watts. Consult the manual (and an external watt meter!) to determine this.
  • Move the antenna further away. As mentioned above, if you want further distance, a higher location for the antenna would be a good idea, possibly in combination with the higher wattage. So this may be a good idea anyway.
  • Use a directional antenna that focuses the power in a more desirable direction and away from you. However, this may not reduce the danger without also moving the antenna.
  • Putting metal between you and the antenna can help. For instance, if you are using this in a mobile application, if the antenna is on top of a metal car roof, then this would be safer. Note, however, that 50 watts is considered the safe threshold in this situation. At one foot (without a car roof), typically 5 watts is considered safe. Also, if the antenna is inside, putting metal next to it may not help as high power reflections within the room may still be dangerous, and some placements could detune the antenna, which could damage the radio (or amplifier) during transmit. In short, artificially adding a metal object (other than a car roof) is really modifying the antenna, and is just a less controlled way of making a directional antenna.
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