Thursday, April 1, 2010

KD8JHJ 1st 40 meter QRP/portable Operation

This first portable outing was really more of an antenna test than anything.  About a month ago I had purchased a Radio Wavz 20 meter End Fed Half Wave antenna with the intention of putting it up at the home QTH.  Upon my initial inspection of this antenna I noticed that although the Radio Wavz sticker on the matching unit said "20 meter" someone had taken a sharpie and wrote "40m" on the cylindrical body of the matching unit.  I put it up anyway on the tower and proceded to check it out with the MFJ-259B antenna analyzer.  To my dismay the best Standing Wave Ratio I could find was 8:1 and no where near the 20 meter band.  I took it down and replaced it with the 30 meter EFHW described in an earlier post.  The antenna sat coiled on the floor of the shack until today when I measured off 67 feet of AWG #12 copper wire that I had left over from a electrical project at my shop.  I soldered on a ring terminal and attached it to the 20 meter matching unit.  I fashioned a couple insulators from 1/4" Lexan polycarbonate for each end of the antenna wire. 
I packaged up my MFJ QRP transceiver and test equipment into a 5 gallon bucket and hopped in the car for the short trip south of town to the public park near our town's fresh water reservoir.  This area has lots of open spaces and trees- perfect.  I tied some string to a 1/2" bolt and on my very first try launched the line high into the bare branches of a tree.  I tied the string to the end of the antenna insulator and pulled it up.  the other end with the matching unit I fixed to a post near my car so that the feed point was about 10 feet off the ground.  For connection to the rig I used a 50' piece of coax. The end result was roughly a 40 degree slope of antenna wire.  I used an online antenna length calculator to figure how long of a piece of wire to cut.  7.060 MHz showed a length of 66.2 feet so I cut the wire at 67 feet and figured I could trim it down once I had it in the air and got a measurement with the analyzer.  As expected with the wire a bit long the resonant point was 6.990 MHz with a SWR of 1.1: 1  This also confirmed the screw up at Radio Wavz with the 40 meter matching unit being miss labeled a 20 meter unit.  I suspect as often happens the antenna was returned as defective and sent back out upon the next order.  Not a big deal because I needed a 40 meter unit anyway for my single band transceiver. 
My plans were to trim the antenna to resonance around 7.060 MHz but of course I forgot the wire cutters.  I decided to let it be for now and give it go.   As I had hoped reception away from town was great and I could here many signals loud and clear.  I called QRL? and sent some CQ's at a few places between 7.030 and 7.060 MHz with no response.  Finally around 7.040 MHz somebody responded with "KD8??".  I sent my call again slowly and then on the second repeat I noticed that my battery pack had reached the low voltage point and could no longer provide the required juice.  I think I then copied something from the other op about my signal dropping off. 
Unfortunately activity was cut short just as things were getting underway.  Overall I came home happy with the experience.  It was fun to select a site and deploy the wire.  Getting the end of the wire up high was no trouble at all.  The best part of all was being outside on a warm spring day.  I can tell already that portable/qrp operations is something I will be doing alot of this summer.  Letting down the antenna and packing up the gear was even quicker than the setup.  This weekend I plan to get out again and if I can remember the wire cutters I will trim the wire down to get the resonant point to the middle of the CW band maximizing the effectiveness of my 5 watts.

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