Off Center Fed (OCF) Dipole Baluns

1101114670 - Off Center Fed (OCF) Dipole Baluns
+3

50:200 (4:1) CUBE™ Unun, 1.8-61 MHz, 1500/5000 Watts PEP, End Fed, Vertical, Monopole

CU-4-1500
$109.95
In stock
1
Product Details
Input ohms/Output ohms: 50/100-400
Frequency Range < 2:1 SWR (MHz): 1.8-61 (1.5KW), 1.8-31 MHZ for 5000/5000HD
PEP Power Rating (watts): 1500/5000
Insertion Loss (dB): .15
Input Connector: SO-239
Output Connector(s): Wingnut/Eyebolt
Transformer Topology: Broadband Ferrite
Hardware Type: Stainless
Enclosure Size: 4" x 4" x 2"
Antenna Compatability: verticals, slopers, monopoles

Purpose. The CU-4-1500 is used as a 4:1 (200 ohm unbalanced load to 50 ohm unbalanced source) broadband transformer for 50 ohm coax cable rated at at 1500 PEP into 200 ohms unbalanced load from 1.8-61 MHz. Excellent for 43 foot verticals and also slopers (51', 85' or 119" work great)

USE: The top connector is for the 200 ohm unbalanced output, and the side connector is for a ground rod or radial connection.The SO-239 input connector shield/ground is shared with the ground connector.


For best results use a feed line choke between the CU-4-1500 and the coax input to isolate the coax from becoming part of the antenna. Our Maxi-Choker (MC-1-3000) is an excellent companion for this unun.

The CU-4-1500 is also useful for end fed OCF antennas utilizing a 4:1 unun and a coax feed line choke to set the antenna length for the "short" side of the OCF.

CU-4-5000 is in a 4" x 4" x 2" NEMA enclosure and weighs 3 pounds and is specified for 1.8-31 MHz - rated at 5KW PEP

CU-4-5000HD is in a 4" x 4" x 4" NEMA enclosure, contains 50% more ferrite cores then the 5000 and weighs 4 pounds and is specified for 1.8-31 MHz - rated at 4KW continuous duty, 5K+ PEP

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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