Topband: Waller Flag Question

[Arthur Delibert]

The on-line materials about Waller Flags says that a modest size WF would need about 40 dB of gain to boost the signal to a usable level.  One of the postings says that cascading two preamps of 20 dB each seems to add extra noise, and they talk about developmental work being done on a single preamp of 40 dB.  

Is there now such a 40 dB preamp?  Is it made commercially?  Alternatively, are there plans on-line somewhere?  Has someone actually used it in a high-RF urban/suburban area, with multiple 50 kW AM BC stations?  With what results?

Many thanks.

Art Delibert
KB3FJO