End Fed Antennas End Fed Long Wires. Presented at Ham Com 2013.

End Fed AntennasEnd 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.

Green

Orange

Black

C

B

b

A

a

c

Antenna Wire 30'

SO-239

End Fed Long Wire Matching Unit

Antenna WireHalf Wave

SO-239

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.

A

BC

abc

T106-2 toroid – 9 Trifilar turns

Green

Orange

Black

C

B

b

A

a

c

Antenna Wire 30'

SO-239

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.

20 40 60 80 100

60M40M20M17M15M12M10M6M

30M20M17M15M12M10M6M 17M15M12M10M6M

½ Wave Dipole

1 Wave Dipole

1 ½ Wave Dipole

Suggested Lengths

28.5' 30' 36' 59'44' 49' 53' 72' 88' 98' 102'17'

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

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

21.0 21.225 21.45

15M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

28.0 28.5 29.0

10M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

50.0 50.4 51.0

6M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

18.1

17M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

14.0 14.175 14.35

20M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

10.1

30M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

7.0 7.15 7.30

40M

50

150

200

100

1.0

3.0

4.0

5.0

2.0

SWR R, Z

0

3.50 3.50 3.50

75, 80M

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

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.

Green

Orange

Black

C

B

b

A

a

c

Antenna Wire 30'

SO-239

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