Wideband Signal on <30Mhz Possible?

[Lord of nothing]

Hi
Does it is possible to transmit a Wideband Signal on <30Mhz?
Like https://de.wikipedia.org/wiki/Olivia_MFSK
Are there any commercial "Wide Band" Mode in use? The only I know is DRM (?!) Radio who get broadcast von Radio Romania and from Saudi Arabia.

[David Hess]

Sure, why not?  There are practical difficulties with a channel bandwidth which is a large part of the carrier frequency but it is not impossible.

Olivia MFSK however is still a narrowband transmission mode as it is required to stay within the bandwidth of an SSB voice channel or smaller and is typically 1000 Hz.

[Lord of nothing]

Do you know a (Commercial Used) Mode who is Wideband on <30mhz?

[David Hess]

The best real example that I know of off hand was the old VHF television channel 1 which was between 44 and 50 MHz.  It was removed in 1948 making VHF television channel 2 the lowest channel.

An internet search show that the military is looking into something and has done tests with a 24 kHz bandwidth in the HF band but that is hardly wideband.

It would not surprise me if some nations use wideband HF direct sequence spread spectrum for some secret communications systems with a bandwidth of at least 100s of kHz.  The limitation with small installations is antenna tuning.

[Lord of nothing]

Here the lowest who currently (by law) could be TV Transmitt is 47,0 - 68,0 MHz

[T3sl4co1l]

https://en.wikipedia.org/wiki/Duga_radar

There are a number of similar systems in operation around the world, don't know if their frequencies are published though.  Likely they're all frequency agile or hopping, these days, so you don't get incessant interference on any given channel/band.

Tim

[xaxaxa]

You probably want to use OFDM since it is unlikely the antenna/channel characteristics will be constant across a wide fractional bandwidth; OFDM plus a suitable error correction scheme can deal with frequency-selective fading and the bad frequency response of your antenna.