RF Choke basics

 

RF Choke. To make a choke, all you need to do is wind a portion of the coaxial transmission line to form a coil. A choke balun made of coax is most effective when a single layer is close-wound on a form, such as 4in. plastic drain pipe or 6in /150.0mm. "schedule 40 (4.5 inches / 114.3 mm)" PVC pipe. The table below lists values for each HF amateur band. Form size and number of turns are optimized for each band.

Single Band RF Chokes
(most effective)

Band
(meters)

Form
(inches)

Coax
RG-213

RG-8

Coax
RG-8X
RG-58

160
80
40
30
20
17
15
12
10

6 in.
6 in.
6 in.
6 in.
4 in.
4 in.
4 in.
4 in.
4 in.

8 turns
8 turns
8 turns
8 turns
12 turns
12 turns
6 turns
6 turns
6 turns

5-6 turns
5-6 turns
5-6 turns
5-6 turns
7-8 turns
7-8 turns
4-5 turns
4-5 turns
4 turns

I recommend one choke near the antenna feed point, and another one about a quarter wavelength down the line, before the coax enters your radio shack.

If you intend to use your dipole on its odd harmonics (more than one band) then use the following table to construct your RF chokes.

Multi-Band RF Chokes

Freq. Range (MHz)

COAX: RG-8, RG-58, RG-59, RG-8X, RG-213

3.5 - 30
3.5 - 10
14 - 30

3.05 m. (10 ft.), 7 turns
5.49 m. (18 ft.), 9-10 turns
2.44 m. (8 ft.), 6-7 turns

rf chokes

 

 

Remember To:

Take your ham radio antenna down at least once a year (twice or more if you have had severe weather) to check for damage (frayed ropes, damaged coaxial shield or connection, etc).

 

 


 


Summation:

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