Hello everyone.
You're right. The last thing one would want is to transmit long distances via skip at HF. This is not quite the same from 45 - 70 MHz. The main advantage is the long wavelength means non-line-of-sight. The need for LOS is the main problem with Wi-Fi which is also used in regional comms.
There was a general misunderstanding about the bandwidth usage as well. The 7 Mhz band refers to the available TV channel. You are quite right. There are 28 x 250 KHz channels within 7 MHz and we would aim to do this, not 250 kbps over 7 MHz!!
The experimental results were that > 0 dB SNR was obtained at 40 kms with 20 Watts over 250 kHZ baseband bandwidth. This is the key result.
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Hello everyone. You're right. The last thing one would want is to transmit long distances via skip at HF. This is not quite the same from 45 - 70 MHz. The main advantage is the long wavelength means non-line-of-sight. The need for LOS is the main problem with Wi-Fi which is also used in regional comms. There was a general misunderstanding about the bandwidth usage as well. The 7 Mhz band refers to the available TV channel. You are quite right. There are 28 x 250 KHz channels within 7 MHz and we would aim to do this, not 250 kbps over 7 MHz!! The experimental results were that > 0 dB SNR was obtained at 40 kms with 20 Watts over 250 kHZ baseband bandwidth. This is the key result.