End Fed Long Wire Antennas

One of the most popular antennas today is the end fed long wire antenna due to it ease of installation, portability and stealth in various installations. It can be a condo dweller’s only access to the world of ham radio or the best alternative for a backpacking SOTA (Summits on the Air) mountaintop expedition.

The antenna is simple to deploy, folds up easily for transport, and weighs under a pound, yet, with the proper length of wire, can work the 80-10 meter bands easily with the built in antenna tuner of most current day transceivers. You will need several components for a successful deployment of the end fed antenna and these are shown in the diagram below:

End Fed Antenna Chain - End Fed Long Wire Antennas

 

Impedance Transformer - End Fed Long Wire AntennasThe antenna impedance matching components (BOX “Z” above) to match the antenna impedance to the coax line impedance (usually 50 ohms).  For non-resonant end fed  antennas, the typical feed point impedance is 300 to 600 ohms and a 9:1 impedance transformer (e.g. 450 ohm average antenna impedance to 50 ohm coax, also know as a 9:1 unun).  For do-it-yourself antenna builders, 9:1 impedance transformer  information is HERE

Feed Line Choke - End Fed Long Wire AntennasWith end fed antennas, the coax is meant to radiate as part of the antenna system (serving as the “ground” or counterpoise) and therefore you need to use a Feed line Choke (BOX “FC” above) to suppress the common mode current on the outside of the coax feed line so it does not enter the radio and cause garbled communication.. The Feed line (FC) acts as a stop sign for RF current flowing back on the outside of the coax.  The higher the choking resistance of the feed line choke, the less the coax braid RFI common mode current, and the less noise enters the radio.  Feed Line choke alternatives are HERE.

Radio System - End Fed Long Wire AntennasThe radio station is also a key component of the antenna system and has two functions: transmit and receive.  Matching the transmitter to the coax feed line is often done with an antenna tuner and receiver systems should be installed to maximize signal to noise ratio.  Reducing receiver noise is critical for weak signal reception and the use of coax noise filters AND receiver power supply lines (AC or DC) noise filters is usually needed for optimum reception. Reducing RFI generated by the radio station (you are the SOURCE of RFI) or received by your radio station (you are the VICTIM of RFI) is an important aspect of radio station operations.  Palomar Engineers has many solutions for RFI problems – Click HERE to develop alternative strategies depending on your particular situation.

Want to compare End Fed Antennas?  See: End Fed Antenna Secrets (PDF)

The “Bullet” End Fed Long Wire Antenna

The key to end fed antenna success is the matching network interface between the long wire antenna and the coax feed line and feed line choke at the transceiver.  Palomar Engineers employs a dual core matching system that offers wide bandwidth (1-61 MHz), 500 watt PEP rating, and a connection for a counterpoise or ground if desired.

The antenna can be used as a sloper, “L” with a vertical section and a longer horizontal section, or as a random horizontal antenna between two trees or supports.

Our network matching network is called the “Bullet” because of it shape and its effectiveness at taking down or contacting distant (DX) stations all over the world under the right conditions.  The Bullet uses all stainless steel connectors and a dual core ferrite 9:1 unun for higher power rating then many competitive products.

We sell the Bullet components separately so you can add you own wire type and length or you can purchase a complete antenna system including wire and end insulator.

 

Icom 746/756/765/775/781 Transceiver RFI Reduction Kit, Coax Noise Filter Option, RFI Range 1-300 MHz

SKU RFI-ICOM-756PRO
$89.95
Coax Noise Filter Option
1
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Icom 746/756/765/775/781 Transceiver RFI Reduction Kit, Coax Noise Filter Option, RFI Range 1-300 MHz
Product Details
MPN: RFI-ICOM-756PRO, RFI-ICOM-756DLX, RFI-ICOM-756DLX2
Type: NEW
Country/Region of Manufacture: United States
RFI Suppression Range (MHz): 1-300 MHz
Enclosure Size (inches): n/a
Typical Use:: AC/DC power, RF output x 2, multiple I/O lines

Icom 746/756/765/775/781 RFI kit is designed to be installed on your radio transceiver to reduce Radio Frequency Interference (RFI) caused by common mode current on the coax output of your radio, the AC/DC power, USB, ALC/Send, mouse,mic and additional interconnect cables. Standard 756PRO Kit has 4 ferrite ring filters and 10 ferrite snap on filters and instruction manual or you can choose the optional CMNF-500-50 coax noise filter option for one or two antenna ports.

This kit will help reduce or eliminate:

1. “Hot mic” RFI caused by poor grounding of antennas or common mode currents from linear amps feeding unbalanced (coax fed) antennas without baluns/line isolators.

2. RFI to neighbor’s electronic devices including audio/video systems, computers, telephones, garage door openers, etc.

3. RFI to your other radios, audio/video systems, computers, telephones, etc.

A side benefit is a reduction in noise floor in your receiver depending on the amount of noise being introduced by common mode currents (which are blocked/reduced by the chokes in this kit).

These chokes use a special mix of ferrite core material, Mix 31, that is effective in suppressing radio frequency interference from transmitters and high noise floor on receivers.

The split beads beads are easy to use, don’t require modification of the protected equipment and work in almost all cases, even when plug-in filters fail.

Use of the chokes often helps cure SWR problems between transceiver and a linear amp and between transceiver and antenna tuner or direct to antenna. The DC power line choke helps keep common mode current out of the power line which could cause interference to other devices connected to the same power line if not suppressed.

Purpose. This kit is designed to choke common mode currents going into or exiting from your transceiver. Use of the chokes often helps cure SWR problems between transceiver and a linear amp (if used) and your antenna.The AC/DC power line choke helps keep common mode current out of the power line (or into your radio) which could cause interference to other devices connected to the same power line if not suppressed.

The Deluxe RFI Filter Kit includes the CMNF-500-50 coax common mode noise filter option which is highly effective in suppressing common mode noise carried in (or out) on the coax shield braid external surface.The ring filters used on the coax connector, the I/O cable filters and the DC power supply filter are effective from 1 to 300 MHz.

RFI Kit Part #

CMNF-500-50 Coax Noise Filter

F240-31 Ring

FSB31-1/2 Snap On

RFI-ICOM-756PRO

None

4

10

RFI-ICOM-756DLX

1(*) + DMBC

3

10

RFI-ICOM-756DLX2

2 (*) + Coax jumper

2

10

*CMNF Connector Note:

First CMNF-500-50 comes with Double Male Barrel Connector (DMBC) for connection to chassis of radio.

Second CMNF-500-50 comes with 6 in RG-400 coax jumper for connection to radio since the spacing of the antenna jacks is too close for both noise filters to be connected.

Typical Installation Guidelines

RF I/O:Standard Kit: Ring filter – 8-10 turns of ¼”coax cable thru center

Deluxe Kit: Use CMNF-500-50 Coax noise filter with double male barrel connector or short coax jumper cable

AC/DC Input: Ring filter – 3-7 turns of AC/DC power cable

Send/ALC Amp Cable:Snap On – multiple turns through choke – ½” diameter hole

Band Control: Snap on – multiple turns through choke – ½” diameter hole

Audio I/O: Snap on – multiple turns through choke – ½” diameter hole

Digital Interfaces: Snap on – multiple turns through choke – ½” diameter hole

Note: if you have more I/O cables then ferrite filters, you can put more than one signal type wire through the same ferrite snap on.The ferrites filter the RFI/noise current common to all wires, but do not affect the differential signals internal to the wires.

Also make sure you connect a good RF ground to the transceiver ground post.Use multiple turns wherever possible to increase RFI suppression effectiveness.


For additional RFI suppression, use a feed line choke at the antenna feed point to suppress common current on the coax feed line and a CMNF-500-50 coax noise filter at the radio end of the coax to reduce common mode noise during receive. Typical common mode noise reduction is up to 30 dB or 6 "S" units - now you can hear the DX again!


If you use a linear amplifier use an amplifier RFI kit for additional RFI interference suppression.

Note: Icom 756PRO picture shown which is typical of filters and connection cables for all Icom and many other brand radios with similar I/O ports.

 

Typical installations are shown below:

 

Bullet End Fed Antenna Notes (PDF)

CAUTION

USE CAUTION WHEN INSTALLING ANTENNA AND KEEP AWAY FROM ANY POWER LINE WIRES!