G3YSX wrote:

Also if you think back to the RSGB convention, there was one
paper that suggested that we are massively overestimating the
efficiency of our antennas. If that work holds up, then we will have
to drop power to conform to the licence ERP condition......

I think this is the wrong way round -

G3YSX > Yes, I did get it the wrong way round. I meant to say that small 
antennas
are more efficient than we calculate.

if we are overestimating efficiency, that means we are getting less ERP than we 
think we are,
and would have to increase power to reach the 1W ERP limit. ERP is essentially 
defined in terms of the field strength at some
distance that is produced by an antenna, and available field strength 
measurements tend to show that using the radiation
resistance/antenna current formulae do indeed overestimate the ERP by about 0 - 
10dB. Prof. Mike Underhill's work suggests small
antennas may be more efficient than we think, but the experimental evidence 
does not support this, at least in the context of typical
amateur LF installations.

G3YSX> I thought that the Puckeridge test showed this, ie that your smaller 
antenna had a higher
field strength than you expected.

Stewart G3YSX