s.a.r.b.question

I have an aero. search and rescue beacon transceiver from a Govt.
surplus store.
When I connect the homemade(bike spoke) ant. to the casing(at the same

time it is connected to the proper ant.input site) it changes to
receiving a different air to ground conversation,than if I don't
connect it to the casing.I presume it must be changing the frequency of

transmission received.
Why/how does this occur?.
Thanks.

 

Thanks for the info.,Tom.
When I 'earth' the ant. to the body it also cancels the interference
with our tv channel reception.I works ok for my purposes,just intrigued
why earthing the ant. to the body changes conversation recieved.
I'm thinking of using a 50ft wire to extend ant. to see what I
receive.
Hartly