Two receive only antennas in close proximity

[andy404ns]

Can two receive only antennas positioned close to one another cause degraded reception? In the extreme case, picture two yagis oriented at 90 degrees to each other with the beam of one nestled between the elements of the other. Not touching, but close. I figure they probably can but the impact wouldn't be perceptible.

 

[mmckenna]

Yes, from what you describe, putting metal boom in between Yagi elements is not a good thing.

 

[iMONITOR]

Can two receive only antennas positioned close to one another cause degraded reception? In the extreme case, picture two yagis oriented at 90 degrees to each other with the beam of one nestled between the elements of the other. Not touching, but close. I figure they probably can but the impact wouldn't be perceptible.

Can you position one higher on the mast and the other lower on the mast? The distance between them would depend on the band/frequencies.

 

[Ubbe]

Radio signals are composed of a magnetic and an electric component. The magnetic one are sensitive to any metal nearby. If you have ever used a magnet compass you probably know that holding any metal close to it will make it read the wrong direction. So antennas can be detuned from it's frequency, change the direction where it is supposed to receive the best from, and degrade the signal when any metal objects are too close it. The distance when it starts to be affected depends of the antenna design and the frequency and in what direction and angle the offending metal are.

/Ubbe

 

[andy404ns]

Can you position one higher on the mast and the other lower on the mast? The distance between them would depend on the band/frequencies.

Unfortunately my mast is a few collar ties in the attic so the antennas run horizontally, not vertically.

Radio signals are composed of a magnetic and an electric component. The magnetic one are sensitive to any metal nearby. If you have ever used a magnet compass you probably know that holding any metal close to it will make it read the wrong direction. So antennas can be detuned from it's frequency, change the direction where it is supposed to receive the best from, and degrade the signal when any metal objects are too close it. The distance when it starts to be affected depends of the antenna design and the frequency and in what direction and angle the offending metal are.

/Ubbe

Thanks for the detailed info Ubbe. I can't get a sense of whether or not such interference as you describe would be noticeable to the average scanner listener. In my head I'm imagining that the impact would be most severe on signals that are already quite weak. I'll pick a few out and see what happens when I move the antennas around.

 

[dkcorlfla]

Attic mounted? Can't you simply make another mount and install it to another rafter? Maybe yards away and maybe a different section of the attic so the lobe of the yagi is more directly pointed at the underside of the roof to cut down on how far the RF has to go through the roof. Seems like a little more work could really improve the results.

 

[andy404ns]

Attic mounted? Can't you simply make another mount and install it to another rafter? Maybe yards away and maybe a different section of the attic so the lobe of the yagi is more directly pointed at the underside of the roof to cut down on how far the RF has to go through the roof. Seems like a little more work could really improve the results.

Yeah this is how my setup is right now. This thread was really more of a curiosity as I was looking at things up there. I did try moving the two that are closest (about 3 feet apart or so) further away and didn't notice anything change.