Best way to feed a vertical?
 

I need to re-erect (after major house remodeling) a 33-foot flag pole
(also known as a 40-meter vertical) and would like to know the best
way to feed it.

Prior to the remodeling, the base of the pipe was held a few inches above
ground and the antenna was fed by simply connecting a 50-ohm coax shield
to a ground rod (with radials, etc.) and the center conductor to the pipe.

I later added an inductor (from memory: maybe 30 turns of B&W with a
diameter of maybe an inch and a half) from the base of the antenna to
the ground rod, hoping it would discharge any static electricity that
might build up. The inductor changed the tuning a little bit but I
never saw any other differences.

Any suggestions?

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

Myron
I presume the antenna is resonant ie about a quarter wave and you feed it
against ground
Ground resistance is likely to be at least 20-30 ohms unless you have lots
of radials and the antenna radiation resistance will be 35 ohms in theory.
So the total load will be 55-65 ohms which is not a bad match to 50 ohms So
you could feed it directly with coax and get away with it.

Richard


mcalhoun wrote in message
...
I need to re-erect (after major house remodeling) a 33-foot flag pole
(also known as a 40-meter vertical) and would like to know the best
way to feed it.

Prior to the remodeling, the base of the pipe was held a few inches above
ground and the antenna was fed by simply connecting a 50-ohm coax shield
to a ground rod (with radials, etc.) and the center conductor to the pipe.

I later added an inductor (from memory: maybe 30 turns of B&W with a
diameter of maybe an inch and a half) from the base of the antenna to
the ground rod, hoping it would discharge any static electricity that
might build up. The inductor changed the tuning a little bit but I
never saw any other differences.

Any suggestions?

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle,
Pistol)

Myron
I presume the antenna is resonant ie about a quarter wave and you feed it
against ground
Ground resistance is likely to be at least 20-30 ohms unless you have lots
of radials and the antenna radiation resistance will be 35 ohms in theory.
So the total load will be 55-65 ohms which is not a bad match to 50 ohms So
you could feed it directly with coax and get away with it.

Richard


mcalhoun wrote in message
...
I need to re-erect (after major house remodeling) a 33-foot flag pole
(also known as a 40-meter vertical) and would like to know the best
way to feed it.

Prior to the remodeling, the base of the pipe was held a few inches above
ground and the antenna was fed by simply connecting a 50-ohm coax shield
to a ground rod (with radials, etc.) and the center conductor to the pipe.

I later added an inductor (from memory: maybe 30 turns of B&W with a
diameter of maybe an inch and a half) from the base of the antenna to
the ground rod, hoping it would discharge any static electricity that
might build up. The inductor changed the tuning a little bit but I
never saw any other differences.

Any suggestions?

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and
cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785)
539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle,
Pistol)