loop antennas

Mike943

Newbie
Joined
Oct 16, 2016
Messages
2
I have a couple of questions for the learned forum. I have an MFJ 1886 receive only antenna and an RSP 1A SDR. I have set the antenna on an AR 500 High Gain rotator which works fine. What I would like help with is which way do you point the antenna to start?. Say for instance from my home I wanted to listen to a Volmet at Shannon in Ireland, would I take a compass bearing for Shannon and near enough point the antenna edge in that direction and adjust to fine tune the direction and listen. I am really at a loss where to start. With my long wires etc. it was put it up and tune around, but which way do I start east west north south. Sorry to be a bit naive about this, I have searched the internet but not found the definitive answer yet. One other question, are both edges of the antenna the same in receiving, i.e. does it matter which edge is facing to the place you want to receive from. Thank you in anticipation.
 

Mike943

Newbie
Joined
Oct 16, 2016
Messages
2
I have a couple of questions for the learned forum. I have an MFJ 1886 receive only antenna and an RSP 1A SDR. I have set the antenna on an AR 500 High Gain rotator which works fine. What I would like help with is which way do you point the antenna to start?. Say for instance from my home I wanted to listen to a Volmet at Shannon in Ireland, would I take a compass bearing for Shannon and near enough point the antenna edge in that direction and adjust to fine tune the direction and listen. I am really at a loss where to start. With my long wires etc. it was put it up and tune around, but which way do I start east west north south. Sorry to be a bit naive about this, I have searched the internet but not found the definitive answer yet. One other question, are both edges of the antenna the same in receiving, i.e. does it matter which edge is facing to the place you want to receive from. Thank you in anticipation.
Thanks for reply, I am gradually getting the picture. About the edge of the loop either side of the null, are they both the same for receiving, or does it matter. Thanks again.
 

N6ML

Member
Premium Subscriber
Joined
Sep 26, 2008
Messages
1,230
Thanks for reply, I am gradually getting the picture. About the edge of the loop either side of the null, are they both the same for receiving, or does it matter. Thanks again.
The same - hence showing "MAX" off both sides in the diagram.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
13,207
Location
So Cal - Richardson, TX - Tewksbury, MA
Your loop has a figure 8 pattern with broad pickup lobes off the sides of the loop and a null looking straight through the "hole". The pickup pattern is probably 120deg wide on each side and the null is very sharp and narrow. This means you don't really turn the loop to peak or tune in your signal of interest, you orient the null so it doesn't interfere with your signal of interest and you can turn your rotor quite far and see no change in signal level over a broad range.

The null is useful for reducing interference in a specific direction and the maximum null will happen over just a few degrees of rotation. You will probably accidently go through the null the first few times you try it and will have to reverse the rotor and run through it a few times to find the maximum null point.

I've had a loop up for a few years now and after playing with the null I eventually parked the loop in one spot to receive the signals I want over a wide area and I haven't moved it in at least a year now. That's how wide the pickup pattern can be.
 
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