I had a peek at e-bay. This look like a fun kit with a well designed circuit. I might have to get one
Incidentally, the circuit looks like it is from Tony van Roon's web site:
http://www.sentex.ca/~mec1995/circ/aviarx/aviarx.htmlIt
could be a impedance issue. A length of coax will transform the impedance of the load as seen by the source if the impedance of the source, load, and characteristic impedance of the coax don't all match.
This can actually be put to use for matching:
Zo = sqrt( Zs * Zl )
Where Zo is the characteristic impedance of a 1/4 wave long piece of matching coax, and Zs and Zl are the source and load impedances. This is awkward to use, however, because usually Zs and Zl are set in stone, and you can't just order up an arbitrary impedance Zo coax to fit your need.
Is your dipole acting like a dipole? Can you get a peak/null on a distant source by rotating the antenna? If not, then it may be that the whole feed line is acting as part of your antenna. It
could be a balance issue. A balun at the feed point of the dipole
might help here. A receive only balun at this frequency should be easy to achieve, even an old VHF TV balun might be OK.