[Milsurplus] Radio Ranges - Ruminations on the LF/MF band.

[Mike Morrow]

Sheldon wrote:

>Radio ranges were before my (pilot) time, but I wonder if
>anyone happens to have the older nav charts for the
>Augusta, GA area, if there was a radio range TX site to
>the south of the city, possibly feeding either Daniel
>Field or Bush Field.

LF/MF ranges still survive as non-directional beacons, rather than those directional A-N beacons that disappeared in the US more than 40 to 50 years ago.  I don't know how much longer NDBs will survive, as ADF sets are rapidly being replaced by GPS units even in small private aircraft.

Today, in the vicinity of the airport that you mention, the following URL gives the details of all the radio communications and navigation aids, including several NDBs:

http://www.airnav.com/airport/KAGS

DX'ing NDBs is a fringe activity, yet I can't resist tuning a LF/MF receiver around whenever I'm in a new area of the country.  Most only run about 25 watts.  NDB and VOR IDs can be identified at:

http://www.airnav.com/

The light aircraft radio sets in the late 1930s to early 1950s generally had a receiver covering 200 to 400 kc, and often 540 to 1500 kc, and a 10 watt AM transmitter on 3105 kc (later changed to 3023.5 kc, which is a SAR frequency today).  I've always been interested in this era of aircraft avionics, where one simple set of this type provided air-to-tower comms on 3105 kc (and maybe on 6210 kc), tower-to-air comms (most often on 278 kc), LF/MF navigation using the directional beacons on the day, and beacon and BC band homing if an optional simple fixed loop were installed.  Those were simpler days!  

One such popular and top-line set was the 1945 GE AS-1B, which cost $200 in 1946.  Thus, even this simple gear wasn't all that cheap...that's equivalent to more than $2000 today.  A lower-cost option was just to carry one of the small, simple 200 to 400 kc beacon receivers that were available post-WWII from several sources...portable units like the Motorola Airboy, or panel mounted units like the Bendix PAR-3A.  These were often dry-cell powered and cost about $30 ($300 in 2006 dollars).  At least that allowed navigation via the directional beacon system and monitoring of control tower frequencies and weather info.

Judging from how many of these light aircraft sets have survived today, they must have competed well against all those surplus BC-1206 type units.  Maybe that was because because few of the private aircraft had 28 vdc electrical power required by the BC-1206.

I hate to see the LF/MF band turn into unused territory.  In particular, I really miss the maritime Morse activity that took place between 420 and 520 kc.  Up to about 20 years ago, I kept a receiver at the bedside tuned to 500 kc.  There was interesting listening in the wee-hours of the night from all over the world!

Most of us can likely remember picking up LF/MF Morse or beacon signals on the common BC band radios of more than 40 years ago, especially those AA-fives.  The images of those beacon and maritime signals tended to show up at the transmitter frequency plus two times the receiver IF frequency of 455 kc, thus high in the BC band.

Mike / KK5F