Off Center Fed (OCF) Dipole Baluns

50:300 (6:1) CUBE™ Balun, 1-61 MHz, 1.5/3KW (choose top stud/eyebolt/power rating)

CB-6-1500TS
$109.95
In stock
1
Product Details
MPN: CB-6-1500,CB-6-3000
Input ohms/Output ohms: 50 in, 300 out
Frequency Range < 2:1 SWR (MHz): 1-61
PEP Power Rating (watts): 1500/3000
Weight (pounds): 1500=2#, 3000=4 #

1500/3000 Watt 6:1 CUBE Balun™ – Model CB-6-1500/3000

Model CB-6-1500/3000 is a 6:1 (300:50) balun housed in a NEMA enclosure box (1.5KW in 4″ x 4″ x 2″, 3KW in 6" x 6" x 4") with two top studs capable of input power levels up to 1.5KW PEP watts when used with a matched load. The 6:1 ratio takes 50 ohms input and matches to 300 ohms balanced output from 1-61 MHz with SWR < 1.5:1 under matched load conditions. A great balun for windoms, OCF antennas >60 feet over ground, Hertz and folded dipole antennas, T2FD etc. 8 core, Use “EB” version with side eye bolts for wire attachments for OCF dipole use.

Typical SWR and impedance transformation from 1-61 MHZ shown below:

CB 6 1500 Graph png - Off Center Fed (OCF) Dipole Baluns

This transformer requires a feed line choke to isolate the coax feed line from the antenna. A coax noise filter is also recommended.

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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