The “Bullet” End Fed OCF Antenna Matcher - 100/500/1500 Watts PEP/Digital
The key to end fed OCF antenna success is the matching network interface between the wire antenna and the feed line choke on the coax. Palomar Engineers employs a dual port ferrite matching system that offers wide bandwidth (1.8-61 MHz), and a 100 watt PEP power rating.
The antenna can be used as a sloper, “L” with a vertical section and a longer horizontal section, or as a horizontal or sloper antenna between two trees or supports. Great antenna for portable operations like NPOTA, SOTA, Field Day, etc., or for permanent installations like installing in an attic, under the eaves of a house, along a fence, etc. This is a short, effective and easy-to-hide antenna which gives a good account of itself on -80-6 (95' wire), 40-6 (55' wire) or 20-6 (25' wire) meter bands.
We sell the Bullet-4U-100 separately so you can add you own wire type and length (see table of suggested lengths below) or you can purchase a complete antenna system including wire and end insulator. Remember you also need a feed line choke like the easy adjustable snap on SOFLC.
Use a good quality 50 ohm cable such as RG-8X or similar as that size allows multiple (5-6 recommended) turns thru the feed line choke. The Bullet-4U-100 matching unit is rated for 100 watts PEP for SSB and 100 watts for CW/FT8. If the matching unit becomes warm to the touch after transmitting at high power, reduce the power output or the internal matching unit may become damaged.
NOTE: We rate our Bullet baluns (and ununs) VERY conservatively with a 50% duty cycle as used with digital (FT8) modes. Some manufacturers selling low cost baluns may use a 5% duty cycle for their PEP rating to make it appear you get a higher rated balun for a lower price, but you may in fact be getting be getting less. Their 1500 watts PEP really means 75 watts continuous or 150 watts at a 50% duty cycle compared to our 250 watts at 50% duty cycle. Our baluns typically cover a larger frequency range under 2:1 SWR which make your transceiver happy and probably will last longer with less electrical stress.
Remember we over engineer our products, to out perform our competition - just compare the weight of our products to theirs and you will know we put much more into our products so you don't have to worry about power saturation failure at a critical moment.
Often it is difficult to slip beads on a cable because of a plug or connector. Split beads solve this problem. They come in two halves that fit over the cable. A plastic snap cover holds the two halves together and holds the assembly on the cable.
For RFI use, mix 31 is effective from 1-300 Mhz, mix 43 works from 20-250 Mhz, Mix 61 is for 200-2000 Mhz, and mix 77 favors .1-20 MHz. These frequencies are those of the interfering signal to be eliminated, not the operating frequencies of the equipment to be protected.
Not sure of what sizes you need or solving a RFI problem with devices using multiple size cables? Try the Ferrite Snap On Combo Pack which has sizes from 1/4″ to 3/4″ with either Mix 31 (1-300 MHz) or Mix 61 (200-2000 MHz) or Mix 75 (150 KHz – 10 MHz).
NOW WITH QUANTITY PRICING FOR CLUB , VOLUME PURCHASERS!
Bead dimensions are shown in the picture below and in the table as A, B, C
Ferrite Split Bead Dimensions
Application Notes
Application Note for using these Snap On split beads: How Many Chokes do I need?
You can very effectively increase the choking impedance of smaller cable by using a large hole ferrite bead and wrapping the cable through several times. For particularly difficult common mode current/RFI problems you may need a choking impedance as high as 5-10K ohms. Using multiple beads and multiple turns through each bead will give higher impedances up to a point. At higher frequencies, when the number of turns approaches an electrical wavelength, the choke becomes resonant due to stray capacitance and the inductance of the cable and limits the high end impedance values to less than the above table points.
Some example of ways to wrap cable are shown below.
 FSB-1/4 – 1 turn |
 FSB-1/2 1 turn |
 FSB-1/2 Open Shell |
 FSB-1/2 2 turns |
 FSB-1/2 3 turns |
 FSB-1/2 4 turns |
—–//—–
More examples of split bead use
Ethernet Cable on FSB-1/4
Ethernet Cable on FSB-1/2 – 3 turns for 9X Impedance good filter for 15-30 mhz between 2K-3K ohms choking Z
Three Effective Radio Interference Filters
 FSB-1/4 or FSB-1/2 4 turns for 14-50 Mhz 2K-3K Z |
 FSB-1/2-5 turns for 10-30 Mhz 2K-4.5K choking Z |
 FT240-43 – 14 turns for 3-14 Mhz or use two FT240-43 for 1.8-10 Mhz |
These snap-on chokes are useful for reducing RFI in public address system amplifiers, speaker wires, mic cables, mixer panels, coax cable, telephone wires, computer sound card speakers, dsl/cable connections, remote control heads for ham transceivers (Especially FT-100, FT900, IC-706, IC-7000), AC power cables, DC power cables, home theater cables, video cables, HI Fi cables, guitar amps, linear amp cables, etc.
They are also helpful in suppressing common mode noise/RFI in radio and TV receivers, audio and RF amplifiers. They can also help suppress noise generated by treadmills, exercise equipment, fish tank heaters, oil heater pumps, fluorescent lights, motors, cable modems, DSL modems, computers, and many other electrical devices. Common mode current reduction in computer cables often helps speed up computers.