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From: jmaynard@thesis1.hsch.utexas.edu (Jay Maynard)
Newsgroups: rec.ham-radio,rec.radio.shortwave,sci.electronics
Subject: Re: VLF Aircraft Radio Beacons
Keywords: VLF Beacons
Message-ID: <4377@lib.tmc.edu>
Date: 28 Nov 90 12:23:24 GMT
References: <4251@radio.oakhill.UUCP>
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In article <4251@radio.oakhill.UUCP> charlie@oakhill.UUCP (Charlie Thompson) writes:
>Does anybody know what output power NDB's utilize?  I can hear
>the CW identifier from them as much as 200 miles away and I am
>trying to determine whether this is excellent reception or just
>typical. My antenna is a homemade 'active' whip which is about 10
>feet long. I was told that NDB's are low power in order to minimize
>interference between beacons operating on the same frequency in
>different geographical locations.

The output power of NDBs vary widely. NDBs are divided into four classes:
1) HH - high power homing beacon, over 2 KW. These have a designated service
   radius of 75 nautical miles at all altitudes.
2) H - medium power homing beacon, between 50 watts and 2 KW. 50 NM.
3) MH - low power homing beacon, less than 50 watts. 25 NM.
4) LOM/LMM - compass locator beacon. These are located at the outer marker
   (LOM) or middle marker (LMM - these are rare) of an Instrument Landing
   System. LOMs and LMMs have a service radius of 15 NM, though their power
   output isn't specified in my reference.

Unfortunately, the only way to find out what class a given NDB is in is to
figure out where it is, and then look it up in the Airport/Facility Directory
for your area, available for $3 (I think) at your friendly neighborhood pilot
shop. The classes above are also described there.
-- 
Jay Maynard, EMT-P, K5ZC, PP-ASEL | Never ascribe to malice that which can
jmaynard@thesis1.hsch.utexas.edu  | adequately be explained by stupidity.
         "With design like this, who needs bugs?" - Boyd Roberts