Off Center Fed (OCF) Dipole Baluns

440580552 - Off Center Fed (OCF) Dipole Baluns
+3

Snap On RF Choke/Isolator - 1/4"/6mm cable, RG-58/59/06/LMR240 - 3-300 MHz, -5/10/15 Bead Option

SNO31-1/4-5
$16.95
In stock
1
Product Details
Brand: Palomar Engineers
MPN: SNO-1/4-5
Effective Frequency Range (MHz): 3-300
PEP Power Rating (watts): same as coax cable rating
Choking Impedance Range (ohms): 5 bead: 500-1000, 10 bead: 600-1800, 15 bead: 1000-2100
Common Mode Attenuation (db): 5 bead: 16-22db, 10 bead: 17-25db, 15 bead: 21-27 db
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 1/4″ Cable – RG-58, RG59, RG-6, LMR-240, etc

For 1/4” cables use five FSB31-1/4 split beads for 80-10 meters (3-30 mHz) or ten FSB31-1/4 split beads for 160-10 (1.8-30 MHz) meters or use 15 FSB31-1/4 for even higher choking for 1-10 MHz.

Typical Impedance per split bead: 10 MHz: 100 ohms, 25 MHz: 163 ohms, 100 MHz: 275 ohms, 250 MHz: 275 ohm

Select 10 bead version for 160 meter use. Minimum recommended total impedance is 500 ohms at frequency of interest.

The beads clamp to the cable and may be operated as is for indoor use. However, it is strongly suggested that they be covered 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.

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.

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Testimonial

Hi Bob,

Radio: Flex-6700 running barefoot -10 to 100 Watts max.
Antenna: MFJ-1216 – 160/80 meter OCFD wire antenna with matching network.
Elevation: Over 60 feet AGL – fully extended.
Installed: Mid November 2013

I operate mainly on the digital modes running less than 50 Watts.  All of the sudden after a few days operating with this antenna, I start to have RFI and my radio was acting up; such as changing bands, SWR changing values, radio failures and turning off. However, when I used my Hy-Gain 18 HT vertical on the same band none of the abnormality occurred.
I contacted MFJ and confirm that what I was noticing was a failure of their “matching network” AKA balun.  They offered no solutions. Then I contacted Palomar Engineers and bought the 1:1 new toroid RF beads.  I called Palomar Engineers and I happened to talked to you directly; regarding the on going issue with the MFJ antenna. I found out that the 1:1 balun was not what I needed (I was miss-informed by MFJ that it was 1:1 matching network.)
You offered to make the required balun 4:1 and the rest is history.

Here are my findings:

  1. No more RFI displayed on the monitors.
  2. Radio not acting up or turning off.
  3. The SWR at 160/80 meter is 1.2:1
  4. No antenna tuner required.  (radio goes to Bypass automatically.)
  5. Worst SWR is on 10 meter with a 2:1 but still usable, with antenna tuner 1.5.
  6. One happy OCFD user!

Thanks to Palomar Engineers design and engineering for solving this issue.

73, Ernest – W4EG