I think I understand the term “dispersion” in the optical context and how there 
 could be a similar mechanism at VLF. My main reasons for posting are:

1) an interest is reduced-bandwidth speech systems at cave radio frequencies 
(typically 87 kHz)
2) the resilience of such systems when used in the presence of impulsive 
interference such as LORAN – a problem which is widespread in north-west Europe
3) there are also systems which work at VLF and are intended for subterranean 
location. A typical carrier frequency appears to be of the order of 3 kHz, and 
I wonder if a simple SSB system on 3.3 kHz USB system might give useful range 
(a few hundred metres) for voice communication.
4) Some Australian amateurs have been experimenting with digital voice systems 
(codec2?) on HF and it seems to be possible this approach might also be useful.

John F5VLF

On 3 Dec 2013, at 10:16CET, hvanesce <[email protected]> wrote:

> It might be informative to consider exploitation and mitigation of
> dispersion in approaches to compression for VLF links.
> 
> Jim AA5BW 
> 

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