Thursday, November 7, 2013

New 40-M Wire Vertical Installed

     I've been building a 40-M wire vertical here in the house over the last few days and yesterday I installed it.  It is a 33.3-foot section of No. 14 stranded wire that stands off from the tower about 2-feet.  You can see the 2x2 treated boards that hold the top and bottom of the antenna in the photo on the right.  (Click on any photo to see a larger image.)  The bottom of the vertical is about 27-feet above ground and the top is about 60-feet.  I have two elevated radials attached and both slope down a little (they are not horizontal.)  I wanted to get it as high up in the air as possible because below 30-feet on the tower, everything to the West is blocked by my hill.

     The photo on the left above shows the RF Choke which is about 21 feet of coax wound on a 6-inch form - about 12 turns.  It is about 3-1/2 feet from the feedpoint of the antenna.  It is marked "Coil" in the photo of the tower.

     On the left is a plot of the SWR of this antenna.  The antenna is pretty flat from about 7.1 to 7.2 but at a 1.6:1 SWR.  It seems to be resonant about 7.125 MHz.  I was shooting for 7.025 MHz. and missed that by a good margin.  I'm guessing that the proximity of the tower is messing with the antenna both in the resonant point and in the pattern.  Still, it was easy to put this up (relatively easy - I am WAY out of shape!)

     But, it was good enough for me to have a QSO with K9W this morning on 40-M SSB.  The operator was Hal, W8HC, who was with me on Swains Island last year.  That was HUGE to be able to work him on Wake Island - AND that was a New One for me on 40-M!.  Obviously the antenna does get out as I only had to call twice to work him (at 43 minutes past my SR.)

     Here are some spot checks of the SWR:

7.000 - 2.25:1     7.100 - 1.61:1     7.200 - 1.59:1
7.025 - 2.00:1     7.125 - 1.41:1     7.225 - 1.71:1
7.050 - 1.88:1     7.150 - 1.46:1     7.250 - 1.77:1
7.075 - 1.66:1     7.175 - 1.55:1     7.275 - 1.83:1

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