Is there a known reduced dB level for a third and fifth harmonic of the fundamental, or is what I am looking for not applicable for a radio signal? Please avoid Fourier Transform equations / explanations as it is a Saturday.
Harmonics - dB levels?
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Need more info, is this for transmitter type specs? For newer amateur HF transmitters over 5 watts all harmonics and spurious signals must be at least 43dB down from the carrier. For VHF 30 to 225MHz and over 25 watts all harmonics and spurious must be down at least 60dB from the carrier. Higher order harmonics are typically attenuated more as they get further out from the carrier.
Or are you looking for a different type of info?
Or are you looking for a different type of info?
@prcguy - Okay, that is very helpful. Whether amateur or commercial gear, I was wondering what the dB value would be to suppress harmonic signals. I did not know there was a regulatory amount. For example, if a nearby NOAA WX transmitter was at 162.400 MHz, I was wondering what to expect at 487.2 MHz and if I would have anything at all after suppressed down into the noise floor.
As to the higher order harmonics typically attenuated more as they get further out from the carrier, that really speaks to what I also wanted to know, without additional suppression, and if that can be give a dB value. I don't think it can though due to the distance and power factor.
As to the higher order harmonics typically attenuated more as they get further out from the carrier, that really speaks to what I also wanted to know, without additional suppression, and if that can be give a dB value. I don't think it can though due to the distance and power factor.
A VHF weather transmitter should be 60dB down or more on all harmonics. Some WX transmitters are very high power and its not possible to tell how far down the third harmonic is at 487.2 out of the transmitter when receiving over the air because the antenna will not be tuned there and the harmonics will be further attenuated by the antenna and its radiation pattern for out of band signals.
For a 100 watt transmitter, a third harmonic 60dB down would be -10dBm which could be heard for some distance if the antenna has a good pattern at the horizon. A 400 watt WX transmitter 60dB down would be -4dBm and so on. I would expect a second harmonic to be very close to 60dB down as that is the challenge for the transmitter and filter designer. A third harmonic is naturally further down than the second right at the transmitter plus the low pass filter would be much more effective on a third harmonic, so it should be waaaaay down.
For a 100 watt transmitter, a third harmonic 60dB down would be -10dBm which could be heard for some distance if the antenna has a good pattern at the horizon. A 400 watt WX transmitter 60dB down would be -4dBm and so on. I would expect a second harmonic to be very close to 60dB down as that is the challenge for the transmitter and filter designer. A third harmonic is naturally further down than the second right at the transmitter plus the low pass filter would be much more effective on a third harmonic, so it should be waaaaay down.
Thank you very much.
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