Signal on ground wire

Discussion in 'General Electronics Chat' started by Robin Mitchell, Aug 2, 2013.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    Hi everyone!

    I have been trying to construct an AM receiver. Now the transmitter is no problem, infact it works very nicely. The only problem im having is that when I measure the ground wire with an oscilloscope I find that the AM signal is present on this wire. Im sad to say I dont have a schematic which im personally using but this is as close to the design as it gets
    [​IMG]

    Has anyone encountered any similar problems?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,498
    2,364
    What are measuring with respect to?
    Is the common of the supply actually connected to earth ground?
    (Shades of a Cats Whisker radio)
    Max.
     
    Last edited: Aug 2, 2013
  3. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    Puzzling question. Assuming the ground wire of the oscilloscope is connected to the ground wire of the circuit, then you measure the ground wire with the oscilloscope probe, you should have zero in both AC and DC. Something is missing here. Please elaborate.
     
  4. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
    732
    199
    Well the GND on the oscilloscope is connected to the same ground in the AM circuit. After some other tests I think my transmitter is interfering with the power supply and scope.

    tomorrow, transmitter far away as well as the radio circuit using a battery as opposed to the PSU :p

    Im sorry if I cant give any more info, i feel bad just for asking
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,974
    3,220
    If you are radiating the AM signal with an antenna then the ground current from the antenna radiation current is going through the ground return until if finds earth ground. The voltage that you see would likely be due to that current.
     
Loading...