I went back and looked at your thread from 2011...
http://forum.tvfool.com/showthread.php?t=13015
The C290 was not panned and openly ridiculed, but larger antennas were suggested.
We failed to respond to your information regarding the connectors you reported using to splice cable together. If I understand correctly, you had used single conductor 'butt-splice' connectors rather than the coaxial 'F-type'. Using the wrong type of connector can produce some odd trouble, including failure of some channels while others seem to make it from one end of the cable to the other. Taped connection are notorious for absorbing and holding water... once there is water in the coax it needs to be replaced.
Have you replaced spliced sections of coax with a single piece of coax, free of any splices?
Have you performed this test:
http://forum.tvfool.com/showthread.php?t=13646 ? If so, what are the results?