Download - End Fed Antennas End Fed Long Wires
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