Are AM loop antennas unidirectional?

[dxer720]

I've got a stock AM loop antenna connected to my radio & I notice as I rotate the loop horizontally, that a given signal seems to come in better in only one direction, instead of the bidirectional reception I thought all AM antennas had.

My question is: Do loop antennas actually have a unidirectional recieve pattern or am I hearing things? If they do, can I some how, make this pattern more pronounced?

 

[rbrucecarter5]

I've got a stock AM loop antenna connected to my radio & I notice as I rotate the loop horizontally, that a given signal seems to come in better in only one direction, instead of the bidirectional reception I thought all AM antennas had.

My question is: Do loop antennas actually have a unidirectional recieve pattern or am I hearing things? If they do, can I some how, make this pattern more pronounced?

They are bidirectional - the have the same response at 0 and 180 degrees. They have a sharp null and broad lobes. Enhancing the nulls can best be done by substituting a tuned box loop antenna.

 

[kenglish]

They can have a very slight difference (front to back) just due to slight mechanical differences in construction.

I think that a Vertical "sense" antenna can be added, which would create a cardioid pattern. I've seen this done with shielded-rod "bidirectional" antennas.