Off Center Fed (OCF) Dipole Baluns

4158534878 - Off Center Fed (OCF) Dipole Baluns
+3

Hybrid 1.5:1 Current Balun + 1:1 Current Balun in one enclosure, 1.8-61 MHz, 1.5/5KW PEP - Loop Antenna

CB-1.5-1-1500EB
$139.95
In stock
1
Product Details
MPN: CB-1.5-1-1500/5000EB or TS option
Country/Region of Manufacture: USA
Input ohms/Output ohms: 50 in/75 out
Frequency Range < 2:1 SWR (MHz): 1.8-61 MHz
PEP Power Rating (watts): 1.5KW or 5KW
Enclosure Size: 4"x4"x 2"(1.5KW), 6"x6"x4" (5KW)
Weight (pounds): 3 (1.5KW), 5 (5KW)
Antenna Compatability: Single Band Loop

After many requests we have created a compact, special balun for single band loop (Sky loop or Delta loop) antennas with specific dimension that present a feedpoint of 70-75 ohms. The CB-1.5-1-1500/5000 is a CUBE(TM) enclosure containing a multi-core, broadband 1.5:1 impedance transformer (50 ohm coax input to 75 ohm balanced output) in series with a 1:1 current balun for extra common mode current choking to keep RF current off the outside of the coax braid and on the antenna where it belongs. The extra choking action also means that the coax feed line will not act as a radiator causing unnecessary RF interference (RFI). Rated for full 1500 watts PEP and 1500 watts CW (ICAS), 1KW Digital. 1.8Mhz – 61 MHz.

CB-1.5-1-1500EB is housed in a 4” x 4” x 2” waterproof housing with SO-239 input and stainless steel eye bolts on the side for ease of connection to your wire antenna (or top studs as desired). Top eye bolt acts as an antenna hoist. Also available with top studs for post or wall mounting (Model # CB-1.5-1-1500/5000TS). 5KW models are in a 4 " x 4" x 4" housing.

Loop antennas should be cut for 1005/F(MHz) in total length, where F (MHz) is the lowest frequency to be used. For 3.5MHz this equates to 288 foot perimeter (square, delta, multi-side ok). Vertiucal loops with pointy side up and longer bases and fed 1/4 wavelength down one side have a feedpoint impedance near 75 ohms for which this balun is well suited. A very good DX antenna!

For unbalanced 50 ohm input to unbalanced 75 ohm output use the CU-1.5-1500 or CU-1.5-5000.

Display Note: Product picture is 2:1 balun, 1:1 Unun but actual delivered product is CB/CU-1.5-1-1500/5000 as selected.

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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