[Milsurplus] NDB's and LOM's

[CL in NC]

I used to maintain these for the FAA many years ago. Since I was the only ham at the three different field offices I worked at over the years, I also got all the SWL reports, or would that be LWL reports, and had a nice certificate for those that sent a report.  There were still many on the air back then, but few requests for confirmations, until no requests for confirmations.  I think anyone interested has passed on, or they did not bother to send a signal report.  I am sure most field offices rotary filed them, but I liked to answer them.  Over the years, I had stations that ran 400 watts to 250 ft and down, tower heights, or as low as 25 watts to a simple 50 foot vertical wire with single or triple top hat wire.  I had one station I maintained for a local airport, a commercially manufactured product that contained two 25 att transmitters 1KC apart.  Instead of having a circuit, as most did, that generated a 1020Hz or 400 Hz ID signal, it would key the other transmitter that was 1KC off to generate a beat note.  For some reason, the most received NDB I ever had was at Greenville, SC next to the municipal baseball field which was situated right next to a 4 lane highway, and the transmitter was only 25 watts with a 50 ft wire vertical with 50ft single wire top hat.  Of course the counterpoise on all stations was extensive, 160 radials of #6 solid copper minimum, the length determined by the plot size.  There were some 1KW stations left before I retired, I believe in Alaska was the last, but places like Montana and ND had them at one time.  The NDB that still exist for the most part used to be the Adcock directional beacon, that sent the letter A or N depending on the quadrant you were in, and an on course indications was achieved when the A and N superimposed on each other and you got a steady tone.  Many of those stations were downgraded to NDBs by just cutting off the part of the transmitter that generated the other signals sent to the ring of 4 towers around a central tower, and then those other 4 towers were removed leaving only the center one.  NDB's and LOM's are basically the same transmitter, but the LOM, Locator Outer Marker, uses a 400Hz ID tone with normally a 2 letter ID sent, 3 letters are usually NDB's, and were co-located with the 75MC Outer Marker transmitter.  In the late 90's we removed the top 50 feet of one of the beacon towers because the ring transformer that coupled AC to the obstruction light circuit failed and the FAA was too cheap to buy a replacement, so the remaining 195 feet did not need an OB lamp even though from the top of the tower you could almost spit to the Spartanburg Airport.  All of this stuff is being shutdown as more and more navigation in put in the GPS basket, but the FAA has come to realize the danger in that, and has decided to leave certain VOR's on the air.  Air traffic control at first consisted of bon fires on the tops of hills, the radio beacon was the next improvement and have been with us since the early 30's.  One of the Adcock site style transmitters was on the cover of ER Magazine several months back.  I live in an area with frequent power outages, trees, wind, ice storms, and one of the best times to hear those stations is when this occurs.  I listen on a Bendix RDF, and ever during the day, you can hear many signals when all the AC power line crap goes away.  Judging by the fact places like ND or AK only had a couple of the 1000 watters, I would guess that in the air, reception was several hundred to a thousand miles.  The remaining beacons can be found on this site:  https://www.dxinfocentre.com/ndb.htm

Charlie, W4MEC in NC