[Milsurplus] Dwindling resource

[CL in NC]

The info on receiving with the R390 in the VLF band I appreciate.  I have a tuner to try with mine that I built years ago that is identical to the HA 10 circuit wise, as the SX117 had a jack on the back to bypass the RF amp and go direct to the mixer for VLF, but you needed extra crystals for the lower band that plugged into the receiver.

Technology moves on, not necessarily for the good of safety but for the 'modern is better' approach.  The FAA is in a full blown effort to shut down every government owned or maintained NDB/LOM site they can, with maybe a couple left in the upper Midwest like ND, and Alaska for the time being.  There are still many located in other countries though, not sure of their plans.  GPS has supplanted the simplicity of the RDF, even thought to actually need to locate where your are when you have no clue with an RDF in an aircraft is quite involved as to flying a certain pattern.  Anyway, the FAA had hopes of putting everything in the GPS basket, but there have been some big hiccups along the way.  One biggie was reflection off water on an instrument approach, where the glide slope signal would come and go or vary, the AF's higher power satellites did not help that at all.  The also decided to leave quite a few VOR's on the air after considering the attack scenario on the satellite system which would render all airnav blind.

Many local airports and counties have maintained their NDB's that we can still enjoy DX'ing, it is still the simplest most bullet proof way to find an airport you are heading to except for looking out the window and knowing your surroundings.  There are even places that are still installing them.  Most are low power though, 25-50 watts, with minimal antennas, a 25 to 50 ft vertical wire with a  25 to 50 ft single wire cap hat.  Funny though, I had an LOM in Greenville, SC that was 50 watts to a 50ft wire and 50ft cap hat right along side the highway.  I got more SWL reports off of that one than either the 400 watter at Spartanburg with a 250 ft vertical and massive counterpoise, or Greer, with 400 watts and a 100ft vertical wire and 3 wire 100ft cap hat.

One of the best resources for interesting BC and VLF band tuning devices and antennas, including passive null tuners to eliminate signals on top of the ones of interest, is the National Radio Clu.  They have quite a few publications devoted to nothing but stuff below 1.710MC, with occasional foray into HF crystal sets.

Charlie, W4MEC in NC