Off Center Fed (OCF) Dipole Baluns

1031115103 - Off Center Fed (OCF) Dipole Baluns
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CABLE TV/Satellite RFI Coax Noise Filter, Suppresses 1-60 MHz common mode interference

CMNF-TV
$69.95
In stock
1
Product Details
MPN: CMNF-TV
Country/Region of Manufacture: United States
Filter Power Rating (PEP watts): receiver only
Choking Impedance (ohms): 1000 - 7000
Common Mode Attenuation (db): 21 - 36 db
RFI Suppression Range (MHz): 200 KHz-30 MHz
Insertion Loss (db): .02
# Ferrite Filters: 3
Enclosure Size (inches): 4" x 2" x 1.5"
Typical Use:: Noise filter at radio end of coax next to receiver

CABLE TV/Satellite RFI Noise Filter for AM broadcast & shortwave from 1-60 MHz – Receive Only - F connector I/O - 75 ohm input/output, will pass DC straight thru

Purpose. The CMNF-TV is used to suppress RFI noise and common mode interference on the coaxial input line of satellite and cable TV receivers often caused by nearby transmitters

The filter is designed to have a high RF impedance to noise and interference from common mode currents on the outside of the coax braid while passing RF signal currents on the center conductor and inside of the coax braid to the antenna.

The effectiveness of the filter is dependent upon the amount of common mode noise encountered on the feed line. If your receive system has a large amount of common mode noise current then you should experience a reduction of common mode current which usually as heard as background noise level. Typical choking impedance is shown in the gallery picture.

Got Common Mode Noise? Not Sure - Find out now by clicking link below:

Palomar Engineers Common Mode Noise on Coax User Diagnosis Test 


The filter was quite effective. Was surprised that it actually reduced the noise level
more than the signal so S+N/N improved by 1.9 S units.
Bill
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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