Saturday, February 6, 2010

Antenna Testing

Yesterday the 5th of February and into today a large winter storm passed across the eastern United States.  We received about 8 inches of snow with temperatures in the 20s.  Strong winds caused drifting 3 to 4 feet high.  Great weather for ham radio.  For two weeks I have been testing a new antenna at a location about 1 mile from my normal QTH. (QTH is the Q-signal for "My Location Is")*  The Antenna is an end fed half wave wire.  Its length is about 66 feet long with the feed point up 30 feet up.  The wire slopes to a tree in the back corner of the property and is oriented north-south.  The brunt of a transmitted signal radiates outward perpendicular from a horizontal wire antenna.  This set up yields even lobes of transmitted energy to the east and west.  The antenna's physical length make it resonant at 7 MHz or the 40 meter amateur band.  The 40 meter band is my favorite area of the radio spectrum to operate.  We say in ham radio that "40 meters is always open to somewhere".  During the daylight hours contacts can be made out to about 600 miles and at night signals easily travel 2000 miles or more.  My other antenna is a multi-band vertical and as such it is very sensitive to vertically polarized man made noise or static QRN.  (Q-signal for Static)*  The vertical antenna was my only antenna for the first 16 months that I have been a ham.  The first thing I noticed about the horizontal wire antenna was that the noise level or background static was much quieter than while using the vertical.  CW and digital signals seem much louder and with the noise floor lower it is much easier to copy weak signals.  I have only read about these differences in vertical and horizontal antennas and it is cool to validate these traits through my own testing.  Initial transmissions were done using my 5 watt 40 meter CW QRP transceiver feeding the antenna through 75 feet of RG-8X 50 Ohm coax cable.  My first three contacts were K2TPZ in Baltimore, MD 340 miles point to point distance.  K4LTY in Charlottesville, VA 240 miles point to point and KE5REJ in Cabot, AR 640 miles away.  After these sucessful QRP contacts I was looking forward to hooking up this antenna to my primary rig an Icom IC718 HF transceiver.  On the 1st of February with the Icom in line and output power at 37 watts I established contact with WA5OLT in Arlington, TX.  Will and I had a nice 25 minute chat in Morse Code, our signals easily traveling the  964 miles between us.  This morning I had a QSO (radio contact) with KC2UQA Ira in Medford NJ.  Using our straight keys we exchanged signal reports, descriptions of our station equipment and of course the weather conditions.  Ira reported that the winter storm was now full fury at his QTH. The end fed half wave antenna is working great for the casual operating that I prefer.  Once the weather warms up I plan to get the far end of the wire higher up in the tree. The antenna will be in more of a horizontal position and it will be interesting to see if this change will affect the performance.  

To facilitate antenna connections at my station I use an Alpha Delta 4 position coax switch pictured above.  This switch allows 4 different antennas to be connected and the rotary switch allows me to select any of the four positions.  Currently I only have the 40 meter end fed (right connector in picture) and a dummy load (left connector).  The middle connector is the jumper cable to the transceiver. 

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