LOG, Loop On Ground, RX Antenna

LOG Antenna

As promised, here are the details on the LOG low noise receiving antenna.   Several of my friends have built this antenna and they are all quite happy with the performance.   My friend Antoine-K3DY worked some ZL’s and VK’s at sunrise on 80M CW using this antenna for receive.  He said the LOG definitely outperforms his home brew active 1M receiving loop.

As you will see, the antenna is simply laid on the ground and forms a square with 15′ of wire on each side of the square.   This square is then coupled to a piece of coax  through a small ferrite coupling transformer.  This transformer is constructed from a Fair-Rite 73 material binocular core which is about 1.5 cm square. I am planning on ordering some cores, so let me know if you want me to order you one.  The new transformer is a 6.25:1 (75-ohm to 470-ohm impedance ratio).  The transformer uses two turns connected to the coax, and five turns connected to the antenna. This core material is optimized for frequencies roughly in the range of the 160m through 30m amateur bands.   That core is quite small, so use fine gauge insulted wire to wind the turns.  Normal cable TV type  of 75 ohm coax is used to feed the loop on the ground.

The author found it not necessary to have a preamp on this antenna.  Even though the signals will be weaker, but without the noise, the overall signal to noise ratio is much improved.  I will however be looking into a suitable preamp design for those wanted to play around with a preamp.

Here are the extra details concerning the LOG antenna as described by the author on the subject.


73, Joe-GMS