End Fed Antennas End Fed Long Wires

Presented at Ham Com 2013

Portable Operations Stealth Applications

Antenna Types Antennas come in two basic types – Resonant and Non-Resonant Resonant types are dipole, yagi, etc. They have a resonant frequency (usually on the band they are designed for) Non-Resonant antennas are long wire, G5RV, etc. They are not resonant on any band and can work on multiple bands.

Antenna Types cont’d There are many different variations of each of these types of antennas. Each type of antenna has advantages, and disadvantages. Resonant antennas have resistance only at resonant, all other frequencies will have an impedance and resistance. If you model antennas it will give the SWR, Resistance, and Impedance at the different frequencies.

Antenna Types cont’d We modeled an 80M dipole 122’ long at a height of 30’ (468/3.8Mhz = 122’). We used EZNEC – this is a popular antenna modeling program that amateur radio operators use. Resonance is defined as Capacitive Reactance = Inductive Reactance (leaving resistance)

80M Dipole – Resonant Freq. 3.875 MHz Resonant Freq. ~ 3.875 MHz – R = 28.26, Impedance 2.24, SWR = 1.77

80M Dipole – Off Resonant Freq. Low 3.80 MHz Resonant Freq. ~ 3.800 MHz – R = 41.74, Impedance 32.82, SWR = 3

80M Dipole – Off Resonant Freq. High 3.95 MHz Resonant Freq. ~ 3.950 MHz – R = 41.74, Impedance 32.82, SWR = 2.77

Antenna Types cont’d Several things to notice. The resonant frequency is at the dip. Here it is at ~ 3.875 MHz. The SWR is 1.77 with a resistance of 28.35 ohms and a reactance of 2.23 ohms so it is very close to the resonant frequency. Why isn’t it 50 ohms? It is too close to the ground – which changes the values. The characteristic impedance of a dipole is 72 ohms.

Antenna Types cont’d Most antennas will contain an impedance that is not at 50 ohms. All antennas will have an reactive component (when it is not at resonant frequency). We usually use an antenna tuner to match the transceiver to the antenna.

End Fed Antenna Most antenna are fed in the middle. Some antennas are fed off-center. The End Fed antenna is fed at the End. There basically two types End Fed antennas: Resonant and Non-Resonant. On a Dipole the impedance is low in the middle and high at the ends. End Fed antenna has a similar type of impedance.

End Fed Antenna cont’d The impedance at the end will be high, so you have to have a matching network to bring the impedance down to a low impedance for the coax. Half Wave antenna usually have a difference impedance when they are close to the resonant frequency. Half Wave and Long Wire End Fed antennas usually use different matching networks.

End Fed Long Wire Matching Unit

Matching Network for End Fed Half Wave

End Fed Long Wire Antennas The matching network is usually made with a toroid core. Common cores that have been used are T106-2, T130-2, FT-140-43. You can probably use just about any toroid that can operate on the frequencies you need. T-106-2 is an Iron Power toroid – 1.06” diameter - # 2 mix

End Fed Long Wire Antennas cont’d FT-140-43 is a ferrite toroid – 1.4” diameter and type 43 mix T106-2 $1 – $1.50; T130-2 $1.60 - $2.00; and a FT140-43 $2.50 – $3.50. Probably any toroid with a TXXX-2 or a FTXXX-43 would probably work. The Mix is just a designation, this is used to determine the frequency range etc.

Winding the toroid The toroid is wound using 9 turns of trifilar winding. Trifilar means 3, so there are 3 wires wound 9 turns on the toroid. This is a UN-UN type device (UNbalanced to Unbalanced). Turns ratio is 3:1, impedance is Turns Ratio Squared 32 = 9.

T106-2 toroid – 9 Trifilar turns

Connecting the toroid Pay attention to the Letters in the above picture. You will have to connect them properly to make the matching network operate properly. Connect the left side Black (b) to the right side Orange (A). Remove the insulation and solder close to the core. Twist the Green wire left side (c) with the Black right side (B) – this will solder to the center of the SO-239.

Connecting the toroid cont’d On the Green wire right side (C) attach a small lug. This will connect to the outside of the SO-239. Solder a large lug to the Orange wire left side (a). This will connect to the Antenna terminal.

Finishing Matching Network The Matching Network should be installed in a weather proof housing of some sort. We have used PVC pipe fitting - 1 ½” Cap and 1 ½” slip plug. We have also used ¾” or 1” plastic LR electrical fittings. This allows more room and you can repair it, if needed.

Matching Network in a PVC Cap and Plug

Matching Network in an Electrical LR fitting

Selecting Long Wire You will need to attach a antenna wire. Select a size suitable for the bands you are going to be operating and your specific surroundings – as a general rule the longer the better. Avoid a length that is ¼ wavelength or multiple ¼ wavelength. Common lengths are shown on the next slide.

For portable operations the 17’ or the 30’ are the most practical For portable operations the 17’ or the 30’ are the most practical. I use a 33’ fiberglass pole and a quad-pod. I can erect the antenna in about 5 minutes.

Operating the End Fed Antenna This antenna does not require ground radials. It uses the coax as the ground. You should use 30’+ of coax for the antenna to work correctly. It may produce some RF back into the shack, if it does – install a line isolator before the coax enters the shack.

Home made Quad Pod with 33’ fiberglass Pole (MFJ 1910) Testing Matching network with a 33’ wire Test SWR with 70’ RG-213 and MFJ – 259B

Test SWR on 30’ wire with 70’ RG-213 using MFJ – 259B (matching network using a T106-2 core)

W5WF permanent installation 33’ Pole W5WF using MFJ-1910 33’ Pole W5WF permanent installation 33’ Pole

Related Information Videos on End Fed Antennas http://www.youtube.com/watch?v=uWkpQ785Pjo&feature=related Video on using End Fed Antenna with MFJ 1910 33’ fiberglass pole http://www.youtube.com/watch?v=yrgU5IMXlQY&feature=related Video comparing a PAR end fed dipole antenna to other antennas These antennas work great using a fiberglass pole. You can use an MFJ 1910 or get one off eBay. (Do a search on eBay for fiberglass poles or look for fiberglass pole by Jackite.)

Material List 1 1 ½” PVC Cap (different enclosure) 1 1 ½” Slip Plug (different enclosure) 1 powdered iron toroid T106-2, T130-2 (FT140-43) 3 24” pieces of 22/20 gauge solid insulated copper wire in orange, green, and black 4 6-32 x 3/8” machine screws 4 #6 nut (for SO-239 connector) 1 SO-239 panel mount connector (4 hole) 1 10-24 x ¾” machine screw and nut

Material List cont’d 2 #10 flat washers 1 #10 lock washer 1 #10-24 wing nut 2 #10 wire lugs 1 #6 wire lug 30’ #14 AWG (16, or 18 gauge will also work) insulated stranded wire antenna

Modification We have added a Ground terminal to the existing design. This will cut out using the coax as the ground. Not sure at this time if this improves antenna operation or not.

End Fed Half Wave Resonant on a particular band No Antenna Tuner is required Usually covers the whole band with less than 2:1 SWR (except 10M) Good for 100 watts SSB/CW – only good for about 50 watts on RTTY/PSK31 Easy to put up

End Fed Half Wave cont’d The matching network is a toroid and a capacitor (like a miniature antenna tuner) The capacitor is made from coax (RG-174) Similar to a PAR EndFedz half wave antenna

Web Site You can get the presentation and the hand out at: www.WB5CXC.com/HamCom13