End Fed Antennas

One of the most popular antennas today is the end fed 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

 

impedance-transformerThe antenna impedance matching components (BOX “Z” above) to match the antenna impedance to the coax line impedance (usually 50 ohms).  For non-resonant end  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-chokeWith end fed antennas, the coax is meant to radiat 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 fed 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-systemThe 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.

 

The “Bullet” End Fed Antenna Matcher

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 (1-31 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 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.

For best results we recommend that the coax feed line be at least 1/4 wavelength on the lowest operating frequency since the coax braid is used as a counterpoise if you don’t use the external counterpoise terminal on the matching unit.  We also recommend a feed line choke at the end of the coax feed line near the radio to prevent RFI common mode current from interfering with the radio – check out the info below on feed line chokes.

 

High Power End Fed Transformers

Need a higher power 9:1 unun for your antenna system?  Check out the high power 9:1 ununs HERE

Complete Antenna Systems

Need a complete antenna system?  Get the Bullet, the antenna wire and insulator all in one convenient package (great for HOA restricted areas, camping and portable operations, etc.) and don’t forget to add the feed line choke:

 Feed Line Choke

Each end fed antenna needs a feed line choke at the radio end of the coax to stop the antenna common mode current (on the coax braid) from getting into the radio when transmitting and also to stop RFI common mode noise when receiving.  The simplest, most cost effective choke is a ferrite ring (F240 size) installed as shown below:

Add the Feed line choke (part # EFFLC-240) to your end fed today and stop the pesky RFI from getting into your radio and causing audio distortion or unexpected operation!

Need a waterproof feed line choke with SO-239 coax connectors for ease of installation and good up to 500 watts?  Use our Common Mode Noise Filter #1 shown below.  Stops transmit RFI and cuts down on receive noise too!


If you run more than 500 watts PEP and need a high power 9:1 unun for your end fed antenna, check out the 9:1 ununs (up to 7.5KW PEP) on the 9:1 impedance transformer page.

Suggested wire lengths:

Bands Covered (meters)
Wire Length (feet) Minimum Coax Length (Feet)
40-30-20-15  35-43, 49-63, 70-85 35
40-30-20-17 35-45, 54-64, 67-77 35
40-30-20-17-15-12-10 38-44, 55, 60, 68-73 50
80-40-30-20-17-15-12-10 68-73, 85, 92, 102, 120-125 65
160-80-40-30-20-17-15-12-10 135, 141, 173, 203 130

Some antenna lengths may require use of the internal tuner on your transceiver or an external tuner if no internal tuner is available. Counterpoise lengths of 1/4 wavelength on bands difficult to tune may be helpful.

Installation

Shown below is a very successful configuration that we use at most hamfests and portable operations:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Good results also occur with the Bullet matching unit as high as possible (use a tree or vertical support) and then extend the antenna wire horizontally or as an “L” (horizontal with vertical end drop).  The antenna may also be deployed as a sloper with the Bullet matching unit at the top (best) with the wire sloping toward the ground (with the end high enough to avoid contact by humans or animals), or at the bottom of the sloper with the antenna wire rising to a higher point.

Typical installations are shown below:

Bullet Configurations

Antenna Length Modifications

For best results, chose a length from the table above as these lengths will form a non-resonant antenna for the amateur bands indicated.  The antenna length should NOT be ¼, ½ wavelength on any frequency that you transmit as the impedance will be very high (or low) and will not transfer through the matching unit at a favorable impedance to your antenna tuner.  The theory of the antenna length is to make the antenna non-resonant on any amateur band so that the impedance at the antenna side of the matching unit is in the range of 200-600 ohms and when divided by 9 will be in the range of your transceiver antenna tuner.

Any length of 50/75 ohm feed line ok (over 35 feet minimum) but longer feed lines over 50 feet may show reduced SWR on some bands due to soil conductivity, nearby objects, etc. Due to local ground conditions, antenna height and feed line length, SWR may vary and an antenna tuner may be required or some bands to bring SWR at end of feed line to acceptable levels.  Use of one or more ¼ wavelength counterpoise(s) connected to the ground post of the matching unit may also improve antenna efficiency and reduce SWR on certain bands.  The first counterpoise should be installed under the horizontal portion of the antenna for best results

Use a good quality 50/72 ohm cable adequate for the power level of your station.  The Bullet-80 matching unit is rated for 500 watts PEP for SSB and 150 watts continuous carrier for AM, FM, digital modes, or 375 watts CW.  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: The matching unit output is DC grounded to bleed off static electricity, however it is not RF grounded as the RF signal (at the coax connector) will see approximately 1/9 of the RF impedance on the antenna terminal of the matching unit (if the antenna impedance is between 200-600 ohms).

CAUTION

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