Not sure of your interference RFi frequency? Then try using each of the mixes on your RFI problem to determine which one works the best. This Ferrite Ring Mini-Combo Pack is a convenient solution for troubleshooting RFI/EMI from unknown frequencies or multiple frequencies that require multiple suppression mixes. Included in this combo pack are three 2.4″ OD/1.4″ ID ring toroids as follows:
Mix 75 effective from .15-10 MHz including AM Broadcast band – quantity: 1
Mix 31 effective from 1-300 MHz for general purpose – quantity: 1
Mix 61 effective from 200-2000 MHz for cell phone, WIFI, HDTV, Cable TV interference – quantity: 1
Individually wrapped and labeled with effective RFI frequency range for easy identification
The ring toroids are useful for AC/DC common mode choking with multiple turns as shown below
AC Cable on F-240 Toroid – 7 turns |
DC Cable on F240 – 4 turns |
The ring toroids can also be used on coax or signal lines as shown below:
RG58 12 turns on FT240 |
Ethernet Cable on F-240 Toroid – 7 turns |
For RFI/EMI wrap as many turns as possible (usually 6-12) for higher choking (under 30 MHz). For over 25-100 MHz, 1-3 turns om Mix 61 is usually sufficient. Chokes can also be cascaded in series to offer a broader frequency range.
50 ohm coax to 75 ohm balanced output baluns are useful for low (< 1 wavelength) dipoles exhibiting 75 ohm characteristic impedance or for matching to balanced ladder line whose endpoint impedance is near 75 ohms.
50 ohm coax to 75 ohm CATV coax connections are easily done with a 1.5:1 unun with SO-239 connectors on input and output. Likewise 50 ohm coax to unbalanced verticals or loads near 75 ohms can be matched with a 1.5:1 unun.