12:1 Baluns/Ununs

Snap On RF Choke/Isolator - 3/4"/18.7mm cable, 5/10/15 Bead Option, 1-300 MHz

SKU SNO31-3/4-5
$32.95
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Snap On RF Choke/Isolator - 3/4"/18.7mm cable, 5/10/15 Bead Option, 1-300 MHz
Product Details
Brand: Palomar Engineers
MPN: SNO-3/4-5
Effective Frequency Range (MHz): 3-100
PEP Power Rating (watts): same as coax cable rating
Estimated Insertion Loss (db): .025
Input Connector Type: none
Output Connector Connector Type: none
Ground Connector (Y/N): none
Enclosure Size (LxWxH inches): none

Use for 3/4″ Cable LDF-4, Heliax(R), LMR-600, etc.

Use five split beads for 80-10 meters (3-30 MHz) or ten split beads for 160-10 (1.8-30 MHz) meters or use 15 split beads for even higher choking for 1-10 MHz.

Typical Impedance per split bead: 10 MHz: 50 ohms, 25 MHz: 95 ohms, 100 MHz: 195 ohms, 250 MHz: 322 ohms

A minimum impedance of 500 ohms is needed for 50 ohm cable or 10 times the cable impedance for other cables.

The beads clamp to the cable and may be operated as is for indoor or outdoor use. For longer life outdoors to protect the plastic covers from weathering – use electrical tape for best results or heat shrink to ensure longer life. All kits come with instruction manual which covers assembly and application tips.

As you can see from the impedance vs frequency graph, you can very effectively increase the choking impedance by increasing the number of beads on the cable.

Excellent choke size for multi-turn RG-8X or similar size cables


Snap On and Slip on Feed line chokes available in sizes to fix cables with outside diameters of 1/4", 3/8", 1/2", 3/4", 1" - check website for other size options.

12:1 Baluns are useful between 600-650 ohm balanced loads the impedance at the  end of the feed line is 600 ohms (1/2 wavelength feed line), or high impedance feeds for rhombic,  T2FD and traveling wave antennas.

12:1 Ununs are useful between coax and long wires with a load impedance near 600 ohms like a beverage antenna.  Shortwave listener antennas also can benefit with the 12:1 unun and it may provide a better match than 9:1 ununs – this means quieter noise levels and stronger signals so you can hear distance stations easier.