50:200 ohm (4:1) HF Balun or Unun Core Kit, 3-31 MHz, 250 watts

Name: 50:200 ohm (4:1) HF Balun or Unun Core Kit, 3-31 MHz, 250 watts
Brand: Palomar Engineers
SKU: BA-4-250
Price: 19.95 USD
Availability: InStock

Store/Antenna Products/CUBE Impedance Transformers (<1:1, 1:1, >1:1)/50:200 ohm (4:1) Transformers

SKU BA-4-250

$19.95

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50:200 ohm (4:1) HF Balun or Unun Core Kit, 3-31 MHz, 250 watts

Store/Antenna Products/CUBE Impedance Transformers (<1:1, 1:1, >1:1)/50:200 ohm (4:1) Transformers

Product Details

Input ohms/Output ohms: 50 in, 200 out

Frequency Range < 2:1 SWR (MHz): 1-31

PEP Power Rating (watts): 250

Model BA-4-250 is a 4:1 voltage balun/Unun kit (assembly required from parts supplied) used to translate a 50 ohm input up to 200 ohms at power levels up to 250 watts when used with a matched load. With a matched load the SWR will not exceed 2:1 over the frequency range 1.8 to 30 MHz.

The kit consists of a 1.4" diameter ferrite core, two colors of insulated wire. a UHF connector with stainless steel hardware, and an instruction manual with directions to connect the kit as a 4 to 1 balun (balanced coax to balanced antenna like zepp or from 450 ohm feeder line to coax for a tuner) or 4 to 1 unun (unbalanced coax to unbalanced antenna like end fed or random wire).

This balun will also transform at 4:1 for a wide variation of load impedances. Shown below are AIM 4170 SWR results for a 200 ohm load. This balun gives near perfect transformation through 30 Mhz with a SWR under 1.25 . Light blue vertical bars are ham bands starting at 160 meters at left to 10 meters at right.

BA 4 250 SWR 1 31 Mhz png - AM Broadcast RFI Kits

When considering solutions for AM broadcast (550 Khz – 1.8 Mhz) you should consider Mix 77 ferrites available in a variety of shapes and sizes. Choose a size to give the maximum number of turns of the affected wire or cable.

AM broadcast transmits on a low frequency with large antennas. Consequently it takes a large antenna to receive the signals. Typical “antennas” are AC house wiring, phone lines, long satellite or cable TV cables, DSL/CAT5 lines running between rooms, etc. The device wires that connect to these “antennas” need to be choked with as many turns through the ferrite as possible. Some installation examples are shown below on this page.

For AC/ DC power cords and coax cables the F240-77 (2.4″ OD, 1.4″ ID) “Donut” toroid is the most popular. Also available are smaller toroid donuts and Mix 77 beads. Shown below is a graph with 8, 10, and 12 turns through the toroid – obviously more turns has higher choking impedance. Mix 77 toroid products are HERE and Mix 77 small beads (for small wires) are HERE

F240 77 Turns Comparison 1024x648 - AM Broadcast RFI Kits

F240-77 Turns Comparison from .1 – 8.1 Mhz

Shown below is a graph of frequency response verses choking magnitude for a F240-77 in the AM Broadcast band for a 12 turn coil around the toroid. (Same info as above but different frequency range).