Topband: Perceivable changes in signal strength

[Mike Chamberlain]

Topbanders go to great lengths to gain the last db of radiated signal.  For
example moving from 8 ten-metre long radials to 64 forty-metre long radials
under a quarter wave vertical over average ground gives approximately 1.4 db
gain according to N6BVs data in Low-Band DXing.  Intuitively we would expect
to be able to audibly detect a difference in signal if a remote station
switched between two such antennas, especially at low received signal level.


 

I'm interested in understanding what change in signal level makes a
noticeable difference for reception - specifically what increase (db) is
necessary to take a signal that is just detectable (by ear) in the noise to
one that  should result in accurate interchange of call sign and reports.
I appreciate that there are several variables to consider, Rx bandwidth,
spectral density of the noise, even selectivity and skill of the operator,
but I'm really interested in an 'average figure of merit'.  I'm interested
in personal observations, measurements or published data.

 

Thanks & 73

 

Mike

G3WPH