[Lowfer] Loran Lines

[lowfer@mailman.qth.net]

Hi all,

A few comments on LORAN lines, for those that have them, and
those without:

If you measure only 100 microvolts from your antenna at 100 kHz,
don't be sure that you are free from intermod problems.  LORAN
does not have much energy in the carrier.
The energy in one pulse is roughly equal to that of a rectangular
pulse lasting 10 cycles of 100 kHz (100 microseconds) with the same
peak amplitude.  Each two GRI, a master emits 11 pulses of one phase,
and 7 of the opposite.  A secondary station sends 10 and 6.  There
are 4 unbalanced pulses, the equivalent of 400 microseconds of carrier.
On most US chains, 2 GRI is almost 200 milliseconds.  So 100 microvolts
of carrier corresponds to pulses with peaks of 50 millivolts.  The
peaks are 54 dB above the average carrier level.

Several users on the LF list have reported that their receiver noise
blankers do an excellent job of removing these pulses.  If you have
no LORAN lines, try turning the NB off (at a time when QRN is low)
and see if they appear.

The LORAN spec says that at least 99% of the transmitted energy must
be in the band 90 to 110 kHz.  Unfortunately, this means that a
typical 400 kW station can legally emit almost 4000 watts of QRM!

73,

Stewart KK7KA