VLF-band power line channel sounding

It is commonly asserted that VLF band signals can penetrate distribution transformers. The best evidence for this may be the fact that several UNB-PLC systems are known to work in this band. However, precise quantifications of the channel transfer functions are necessary to determine how well those systems can work, in principal, and thus what is theoretically possible in the VLF band. We present the results of a recent survey conducted at multiple sites at multiple utilities in which broadband VLF signals are broadcast over the power line and recorded at distant points. The transmit and receive points are on separate low voltage networks, connected by at least one medium voltage network, and thus isolated from each other by at least two transformers. Those recordings have been analyzed and the transfer function of the resulting channel inferred with a high degree of confidence. Together with an analysis of the noise power spectral density the signal-to-noise ratio of a VLF-PLC link can be inferred. These findings illustrate the viability of future VLFPLC technologies.