Delta 15 VLF Antenna

The goal was to produce a permanent free standing version of the Delta 10 Experimental model.  Developing a simple construction method was  the hardest part of this antenna.  Shielding the loop cable from the suns UV rays is important for long term use.  A new method of using plastic through out makes it easy to construct.  Using 15 wire shielded cable allows a no metal shield to be used.  These loops are 47 feet around.  The mast comes apart in the center and tubes, to allow mods or maintenance if needed.  The loops are tuned with capacitors in a small box at the bottom..    I'm sure this could be scaled to different sizes.  

Operating the Delta 15 on the opposite side of the world.  The Perth Australia station

is triangulating a storm in the Indian ocean with Texas USA.    The Texas station is out of 

sight over on the USA side of the world.  Which is directly behind India on the map.

Bottom loop holders in place.

Pre drilled bolts, for loop holders.

Top loop holders in place with top cap.

Holes are drilled through the centers, to feed the loops all the way through.  Gaps in the cable are centered inside here.

Gaps in shield, at top center are taped.

First Results

Preamp gain was lowered to 50 because of over driving the sound card.  The settings shown here produced the plot shown.  Connected to janne Sweden site produced these results.  The strikes in china actually belong in the ocean near Africa.  Its obviously not a problem hitting the half world point of LR 's mirror imaging limit.  The originating LR station is in San Antonio Texas , USA  (green dot).  Sweden (red dot)

Gain of 50 in preamp is still too much.  Makes adjusting tricky.

Later Test

Preamp overload problems results in a straight connection test.

-33db seems to be the very high peaks with max volume.  This plot was captured with only the Delta 15 and sound card.  The buddy station doing translation with me was the Mildensee Germany station of fellow DXer Torsten.  


Gerry, WB5TXA

San Antonio, Texas