The 40M Beam

Ken designed the 40M beam using YO.  It is a 3 element monster that works wonderfully.   For those of you that use YO, we have included the specs below.

It is installed at the top of the 125 foot tower.  We are currently turning it with a Diawa MR-750 rotator with 4 motors.  But, we are having a problem holding the screws in place on the motor.   This part has to be solved, so it is either off to the Big Boy Rotator, or we find a prop pitch motor. 

Corbeil Contest Club 3 el 40 mtr yagi
Height 1440.000
7.000 7.050 7.200 MHz
3 elements, inches
            3.5096    1.5000    1.3750    1.2500    1.1250    1.0000    0.8750    0.7500    0.6250    0.5625    0.5000    0.4375
  0.0000    8.0000   34.0000   61.0000   77.0000   40.0000   37.0000   73.0000   49.0000    3.0000    1.5000    0.0000   56.5814
197.7500    0.0000   72.0000   60.0000   66.0000   30.0000   20.0000   55.5000   20.0000   43.0000    3.0000    0.0000   39.2103
427.0000    8.0000   26.6250   44.0000   60.0000   42.0000   34.0000   94.0000    3.0000   38.0000    3.0000    0.0000   46.3299

    This is the as built 40 mtr yagi.The boom to
element bracket is modeled on a channel piece.  The
matching network is a hairpin match.  the match is a
hairpin using .125 inch rods at 1 inch spacing 38
inches long.  The director has a slightly different
taper schedule from the left to right side and was
modeled both ways to establish the final settings.

March 21,

Mike Walker VA3MW

(3/20/2002) In a long day of very high winds of over 90kph (almost 60mph), the antenna came down (flew would be a better word). The schedule 40 mast broke just above the thrust bearing. The beam is only 6" above the thrust bearing, so the rocking back and forth must have hardened the mast enough to become brittle. Now, the antenna lies 100ft from the tower, upside down, and pointing to Europe. But, we can't reach the feed point. The antenna is in good shape, and we are going to have to figure out how to get down. We may have to do this by building up another tower, putting it in place and taking the beam apart in the top of the trees.

June 18th, 2002

OK, we got it down. We built a tower underneath the beam (56ft). We had to cut the boom in half so that we could lift up the ends. We then lowered it piece by piece. The only damage was that we broke 2 tips. What we learned was not to use an aluminum schedule 40 mast on steel clamps. All the twisting and rocking cut through the mast walls until it broke. Now, we just need to plan a 'hoist' date. Thanks to Paul VA3PC, Bob VA3RTW who helped both Ken and I.

The one picture below from the top of the tower shows the size of the beam. Have a look at those standing around it. This shot is taken from 125ft above the ground. In the other shots, you can see how we managed the temporary tower through the trees. It took us 6 hours to build the tower, take apart the beam and then dismantel the tower.

High Flier