Hello all,
I believe it is time to put things into the right perspective.
Technically speaking, NDB's are obsolete.
However in practice, they are not.
NDB's are in widely use in the offshore industry for guiding helicopters
to offshore installations and special purpose offshore vessels.
New work ships build today and equipped with a heli-deck carry also a NDB.
When America is not your best friend, it seems sensible that for
aeronautical direction finding, you won't rely on the US GPS system.
NDB's are very reliable and cheap to maintain and not easily wiped out all
together, so the system has good redundancy.
For that reason it can be understood why some countries ask for some
protection for this service.
Regarding the NIB issue, the EIRP of most NDB's is in the same class as
the EIRP of the amateur license for 472-479 kHz.
The NDB band covers 190 kHz to 1740 kHz and that includes the MW broadcast
band.
Many Russian NDB's transmit in the range 530 - 1250 kHz and though many
powerful broadcast stations reside in the same frequency range, this does
not seem to pose a problem.
The requirements for the service area of a NDB is a fieldstrength of 70
uV/m at the borderline.
So to cause noticeable interference, the offending signal must be rather
strong.
Many NDB's share the same channel, apparently without problems.
Unless you actually live in or near the service area of a NDB in the
472-479 kHz frequency range, the NIB regulations won't pose a problem.
It is also interesting to note that quite a few offshore NDB's in the
Norwegian part of the North Sea operate between 530 and 600 kHz.
So this NIB requirement won't spoil he fun!
73,
Roelof Bakker, pa0rdt
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