Common mode choke construction

[KOA4705]

A common mode cross wound choke. I used 12 turns of RG-58 on a FT-240-43 core.
The plot shows impedance vs frequency. Frequency swept from 3.5 Mhz to 30 Mhz,
vertical scale : 1K ohm/ div, top is 10K ohm. Marker at 10 Mhz shows the choke has
a impedance of 9.5K ohms.

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Added in 4 days 4 hours 21 minutes 59 seconds:

A common mode cross wound choke. I used 12 turns of RG-58 on a FT-240-43 core.
The plot shows impedance vs frequency. Frequency swept from 3.5 Mhz to 30 Mhz,
vertical scale : 1K ohm/ div, top is 10K ohm. Marker at 10 Mhz shows the choke has
a impedance of 9.5K ohms.

Impedance data:

Freq(Mhz) R X Z Phase(Degs)

3.50 1892 j3456 3940 61.3
3.80 2150 j3537 4140 58.7
4.00 2330 j3614 4300 57.2
7.00 4800 j3860 6160 38.8
7.20 4947 j3851 6270 37.9
7.30 5003 j3894 6340 37.9
14.00 8952 j1578 9090 10.0
14.25 9090 j1358 9190 8.5
14.35 9090 j955 9140 6.0
18.00 9300 -j1943 9500 -11.8
18.10 9320 -j2384 9620 -14.3
18.20 9390 -j1996 9600 -12.0
21.00 8063 -j4305 9140 -28.1
21.25 8052 -j4408 9180 -28.7
21.45 7800 -j4687 9100 -31.0
24.90 6320 -j4938 8020 -38.0
25.00 6252 -j4991 8000 -38.6
28.00 5240 -j5168 7360 -44.6
29.00 5000 -j5140 7170 -45.8
30.00 4714 -j5038 6900 -46.9

[Gunner357]

Looks Good

[MDYoungblood]

Looks good but have you done research on snap beads? They are what most of use on our coax (RG8/U size) or a air choke of 5 wraps @ 4 1/2"dia.

3's

Greg

[KOA4705]

Looks good but have you done research on snap beads? They are what most of use on our coax (RG8/U size) or a air choke of 5 wraps @ 4 1/2"dia.

3's

Greg

Hi Greg, What snap beads are you thinking of using, 31 or 43 material etc? From what I remember each snap bead provides a specific impedance vs frequency. For each additional bead add to the coax, the impedance value will sum.
(RG8/U size) or a air choke of 5 wraps @ 4 1/2"dia. I can make a impedance measurement and post it. I would expect resonance to be at the top end of the HF band.
Joe

[MDYoungblood]

I have both 31 and 43, the 31 mix seems to be the most common. I have 6x 43 mix on my CB antenna coax at the feedpoint, my 6m has 3x 31mix at the feedpoint. I use the air chokes on the rest of my antennas, various diameters and wraps. Just looking to help with stray RF and maybe curb some EMI.

3's

Greg