Re: [IRCA] Ground Problems at Coos Bay, OR AMer.

[AM-DXer@xxxxxxxxx (Patrick Griffith, N0NNK / WPE9HVW)]

Ground problems can be really tricky. We just ran across a strange one
today while working on the KCKK array. One of the nearby high tension
towers that we detuned seems to give different field strength readings
and require retuning every time we check it. It is close enough to our
DA and tall enough to affect our pattern as we work through the proof of
performance readings. We have noted that the changes seem to correspond
with changes in the weather. Today we had the FIM-41 connected to a
3-wire loop around one of the legs of the high tension tower. Just
standing back and not touching anything we could see the field strength
reading change as the wind blew and as light rain passed through the
area. In disgust I leaned on one of the support members for the tower.
When I did we saw a large sudden change in the field strength. We found
out that shaking various support members on that leg of the tower would
cause large changes in the field strength indications. Now we are
thinking that: 

1. There is poor continuity along the structural components of this
tower which we are guessing is about 30 years old. 

2. These towers are located in a flood plain. On this particular leg the
point where the side support elements connect to the main tower leg has
become covered with silt and is now a few inches below the terrain. We
think the structural elements may have developed intermittent continuity
there due to corrosion. (the connections on the other 3 legs are above
the terrain and seem more stable)

3. The quality of the grounds at the 4 legs of this tower are suspect.
Instead of driving the ground rods into the soil near the tower the
ground rods are all embedded in the cement that anchors each leg. We are
not certain to what extent they extend below the cement into the soil.

The power company was interested enough in our observations that they
are sending a crew out tomorrow to go over this tower with us.

Patrick Griffith, CBT CBNT CRO
Westminster CO
http://community.webtv.net/AM-DXer/

_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx