jpole antenna

[kf5rqk]

can a jpole antenna be mounted to a metal pole and how high in the air is sufficient,

thanks

 

[ko6jw_2]

Yes it can be mounted on a metal pole. It should be high enough to be clear of obstructions. The higher the better.

 

[W4FLP]

How can you (or should you not?) mount two vertically polarized antennas on the same mast? I have a specialized 70cm vertically polarized antenna on top of a mast and would like to add a 2m J-pole but am not sure that will work to be so close to the other antenna? Thanks.

 

[nd5y]

How can you (or should you not?) mount two vertically polarized antennas on the same mast? I have a specialized 70cm vertically polarized antenna on top of a mast and would like to add a 2m J-pole but am not sure that will work to be so close to the other antenna? Thanks.

You can't mount a j-pole up against a mast. If you don't want to move the existing top mounted antenna then the easiest thing is to add a cross arm or bracket that is at least 1/4 wavelength long and mount a vertical dipole on the end so it is at least 1/4 wavelength from the mast.

 

[W4FLP]

So ballpark would be that it would need to be 234/ 140 (MHz) = 1.67 ft away from the mast? Maybe round up to about 2' ?

 

[prcguy]

I would go a minimum of 1/2 wavelength and preferably more. At 1/4 wavelength from the mast you will be making it into a 2 element beam with gain away from the mast and a null toward the back of the mast. At 1/2 wavelength it will have a clover leaf pattern with four gain lobes and four nulls. At one wavelength away from the mast you will have eight gain lobes and eight nulls but they will begin to mellow out and be more omni directional.

This is the age old problem for commercial tower owners trying to fit more antennas and revenue on the tower.

So ballpark would be that it would need to be 234/ 140 (MHz) = 1.67 ft away from the mast? Maybe round up to about 2' ?

 

[W4FLP]

Well... ok.... maybe I'll take it over to the chimney which is about 25' away

 

[majoco]

A J-pole or a 'slim-jim' can be mounted on a metal pole - but it must be isolated from it.

Slim Jim vs. Traditional J-pole Antenna

Real measurements of a Slim Jim antenna and traditional j-pole antenna reveal the truth about their respective gain and pattern.

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