Amateur Radio / Ham Radio
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Some of the sad realities of Amateur Radio / Ham Radio


The Laughing Policeman
Wireless Society

Amateur Radio /  Ham Radio

Hello. My amateur radio ("Ham") website pages were previously located here.

Thanks for visiting - but I no longer operate and do not encourage you to waste your time and money getting licensed and buying equipment to enter the 'hobby'.

My view is that amateur radio is dying for many reasons including so many operators who just treat amateur radio a "CB", have no interest in technical aspects or the original intent of the licence - i.e. experimentation and construction, they just want to open a box or packet, plug whatever it contains and use it as, or with, their "CB". Operators who think that VOIP services - Hamsphere - is actual "radio", when in reality it's just a telephone call, not to mention a few ignorant operators who just want to talk to their mates on their "CB" / personal wireless intercom, and cannot be bothered to answer CQ calls (when you know that they're there and listening and certainly that they can hear you), or operators who are quite happy to talk to un-licensed (pirate) operators on the 'ham' bands.   All these aspects, and more, have left me totally disillusioned. It really is a crock of old ham.

Finally, for me, amateur radio is doomed due to interference from so many types of unregulated sources; PLT/PLC; Internet Over Mains Wiring; Sky-Q; LED lighting; Solar Power systems and inverters; Switch Mode Power Supplies (SMPS) and iPhone chargers (etc) and many more RF Interference QRM emitters that are probably too numerous to mention.

The RSGB have admitted this to me and that there is absolutely nothing that they or anyone else can do about the increasing pollution of the radio bands with interference - they can't get Ofcom to help. Ofcom are certainly not in any way interested in a small handful of weak signal enthusiasts, and dismiss the pastime as "Hobby Radio" - and who can blame them really.

Perhaps I should say that I am sorry for being so negative, but I won't, so please disregard any words of encouragement that you may have previously read on these old pages - which is why  I have removed them entirely.

Instead, I strongly encourage you to please spend your money on something that will give enjoyment without the frustration of hamateur radio.  I'd suggest a nice TV and a Home Cinema Surround System:




Best wishes. March 2016
----------------------------------


Who's afraid of the DTI (Ofcom) UK amateur radio - LOL
Bob (Robert) Hitchcock - Former G1MTT


Laughing Policeman costs radio ham 9500 - LOL
Bob (Robert) Hitchcock - Former G1MTT - Worcestershire


"Tuning In" - BBC Television Arena Programme 1994
BBC Arena presents a series of films about those people who are fascinated or obsessed with what those [radio] waves are doing." Broadcast in 1994 on BBC2. Introduced by Dilly Barlow.
00:00 TUNING IN (directed by Alex Marengo) featuring several British radio amateurs and their radio stations: G0RPR, G0LUH, Surrey Radio Amateur Club G8TB/p, G4WYJ, Chet Atkins WA4CZD (sk in 2001), G3KTZ, YU4GJK
24:39 THE TEDDY BEAR'S PICNIC (directed by Mary Dickinson)
26:49 WHAT IS A RADIO WAVE? (presented and directed by dr. Fisher Dilke)
33:34 WIRELESS WORLD (directed by Steve Carson) featuring Gerald Wells of the British Vintage Wireless Museum (http://bvwm.org.uk/)


INFORMATION:

Download  dB_power_and_voltage_information_sheet document

SIGNAL METERS


"S" Reading
Received voltage using
6 dB "S" point spacing
Received voltage using
5 dB "S" point spacing
Received voltage using
4 dB "S" point spacing
Received voltage using
3 dB "S" point spacing
S1
0.2 V 0.5 V 1.26 V 3.1 V
S2
0.4 V 0.89 V
1.99 V 4.4 V
S3
0.8 V 1.58 V 3.15 V 6.3 V
S4
1.6 V 2.81 V 5.0 V 8.9 V
S5
3.2 V 5.0 V 7.92 V 12.5 V
S6
6.2 V 8.89 V 12.6 V 17.7 V
S7
12.5V 15.8 V 19.9 V 25.0 V
S8
25 V 28.1 V 31.5 V 35.4 V
S9
50 V 50 V
50 V
50 V
S9 +10
158 V 158 V
158 V
158 V
S9 +20
500 V 500 V
500 V
500 V
S9 +30
1581 V
1581 V
1581 V
1581 V
S9 +40
5000 V (i.e. 5 mV)
5 mV
5 mV
5 mV
S9 +50
15.81 mV
15.81 mV
15.81 mV
15.81 mV
S9 +60
50 mV
50 mV
50 mV
50 mV
Information calculated & compiled by M0MTJ


It is often accepted that the "S9" point represents a received signal of 50V (microvolts), although some equipment may specify that S9 should be calibrated at 100V which muddies the water a little.

Convention often states that each "S" point below S9 this represents a gradation of 6dB (decibels), though this is a contentious statement as some would argue that gradations of 5 dB or 4 dB might be more typical in 'real world' S meters. S meters cannot therefore be wholly relied upon for laboratory standard accuracy and in reality merely provide comparative values.

Above is a table that shows what the actual received voltage would be on a perfectly calibrated Signal Meter using with S9 representing 50uV and the often accepted 6 dB per "S" unit calibration and comparing this with the 5dB and 4dB per "S" unit calibration. While these are not laboratory grade specifications it can be helpful to use a table such as this to provide an idea of the RF voltages being received.

As a very rough rule of thumb a receiver may require about 0.5 uV (microvolts) of RF input to produce a signal to noise ratio (S/N) of around of 20 dB.

+ 3dB  =  2 x the power or 1.4 times the voltage - about 1/2 an "S" point
+ 6dB  =  4 x the power or 2 x the voltage or approximately 1 "S" point
+ 9dB  =  8 x the power or 3 x the voltage
+10dB = 10 x the power or 3.162 x the voltage or approximately 1.5 "S" points
+20dB = 100 x the power or 10 x the voltage or approximately 3 "S" points





DECIBELS:

The decibel is not a measure of a particular electrical unit and therefore figures that are expressed as a decibel are completely meaningless unless they are related to a particular reference. A decibel is actually one tenth of a Bel and is derived from the logarithmic ratio of two voltages or current or power levels: One of these levels must be measured to act as the reference point in order that the other level (or levels) can be expressed as dB relative to that point.

So; Decibels (dBs) represent a RATIO of one voltage to another, or one power to another at the same impedance. Decibels can be either a positive figure representing gain or a negative figure representing a loss.

dBW = 10 x log of Watts

Watts =  antilog of (dBW 10)

dBV = 20 x log of Volts

Volts = antilog of (dBV 20)


Here is a table of decibel relationships:

Voltage Loss Power Loss dB Voltage Gain Power Gain
1.000 1.000 0 1.000 1.000
0.981 0.977 0.1 1.012 1.023
0.977 0.955 0.2 1.023 1.047
0.966 0.933 0.3 1.035 1.072
0.955 0.912 0.4 1.047 1.096
0.944 0.891 0.5 1.059 1.122
0.933 0.871 0.6 1.072 1.148
0.912 0.832 0.8 1.096 1.202
0.891 0.794 1.0 1.122 1.259


1

0.794 0.631 2.0 1.259 1.585
0.708 0.501 3.0 1.413 1.995
0.631 0.398 4.0 1.585 2.512
0.562 0.316 5.0 1.778 3.162
0.501 0.251 6.0 1.995 3.981
0.447 0.200 7.0 2.239 5.012
0.398 0.159 8.0 2.512 6.310
0.355 0.126 9.0 2.818 7.943
0.316 0.100 10.0 3.162 10


1

0.200 0.0398 14.0 5.01 25.1
0.178
0.0316
15.0
5.62
31.6
0.100 0.0100 20.0 10 100
0.7079
0.001
30.0
31.62
1000
0.01
0.0001
40.0
100.0
10000

Information compiled by M0MTJ


dBs are added to represent the total gain or the total loss, while the gain or losses that are expressed as fractions must be multiplied.

e.g. a power gain of 2.5 dB is dealt with thus: 2.0 dB plus 0.5 dB i.e. 1.585 X 1.122 =  1.778


Examples:

+ 3dB  =  2 x the power (or twice the loss, for example when dealing with feeder losses) or 1.4 times the voltage
+ 6dB  =  4 x the power or 2 x the voltage or approximately 1 "S" point
+ 9dB  =  8 x the power or 3 x the voltage
+10dB = 10 x the power or 3.162 x the voltage or just over 1.5 "S" points
+20dB = 100 x the power or 10 x the voltage or just over 3 "S" points

Transmitter Power

Transmitter power is often expressed in Watts, but in amateur radio it is common to find transmitter power expressed in dBW. This is the power in decibels relative to one Watt.

e.g. if a transmitter is quoted as having an output of 6dBW then that would be the same as saying that the power is 4 watts. If a transmitter is quoted as having a power of 14 dBW the 10dBW figure (i.e. 10 watts) is multiplied by the 4dBW figure (i.e. 2.5 watts):  10W x 2.5 =  25 Watts.

Here is a table showing the conversion between dBW and Watts:

dBW Power in Watts
dBW Power in Watts
0 1
16 40
1 1.25
17 50
2 1.6
18 63
3 2.0
19 79
4 2.5
20 100
5 3.2
21 126
6 4
22 158
7 5
23 200
8 6.3
24 251
9 8
25 316
10 10
26 398
11 13
27 501
12 16
28 631
13 20
29 794
14 25
30 1,000
15 32
40 10,000




VSWR

Chart Showing Percentage of Forward and Reflected Power at Various VSWR's:
 

VSWR Forward Power
%
Reflected Power
%
1.5 : 1 96 4
2 :1 89 11
2.5 : 1 82 18
3 : 1 75 25
3.5 : 1 70 30
4 : 1 64 36
4.5 : 1 60 40
5 : 1 56 44
6 : 1 50 50
7 : 1 44 56
8 : 1 40 60
9 : 1 36 64
10 : 1 33 67






COAXIAL & OTHER FEEDER CABLE LOSSES COMPARED

When using an antenna at its resonant frequency  the VSWR should be very low and losses at HF should also be very small. However when it is anticipated that an HF antenna will be used for wideband, non resonant, operation (e.g. a popular all band 'Doublet') the VSWR could be significantly higher and losses in coaxial cable will be higher  than with a resonant aerial.

e.g. at 28 MHz when using an antenna with an SWR of 9:1 it may be perfectly possible to match the antenna system to the transmitter using an Antenna Matching Unit ("ATU"), but if using a 20 metre length of RG58 coaxial cable the losses could be around 3 dB - in which case 100 watts of transmitter power would only result at 50 watts reaching the antenna terminals.

Alternatively if Twin Feeder is used to feed an antenna such as an All Band Doublet where high VSWR will be expected the loss at an SWR of 9:1 would only be about 0.3 dB which would equate to over 90 watts reaching the antenna terminals!

Below are four tables that compare feeder losses at various frequencies with SWR's of 1:1, 3:1, 6:1 and 9:1.


( * = approx)
With an SWR of 1:1 at antenna
 Losses in dB per 100 metres at various frequencies
Cable Type: 3.5 MHz 10 MHz 30 MHz 50 MHz 144 MHz 432 MHz
RG174 *
5
10
15
21
33
59
RG58 2.5 4.3 7.7 10 17 32
RG8 Mini / RG8-X 1.7 2.9 5.4 7.1 13.2 26.5
RG8 1.06 1.8 3.2 4.2 7.6 9.1
RG213 1.1 2.0 3.5 4.7 8.4 15
Ecoflex 10
1.2
2.8 4.9 8.9
Westflex 103 0.6 0.9 1.7 2.7 4.5 7.5
450 Ohm Twin 0.17 0.29 0.51 0.67





With an SWR of 3:1 at the antenna
 Losses in dB per 100 metres at various frequencies
Cable Type: 3.5 MHz 10 MHz 30 MHz 50 MHz 144 MHz 432 MHz
RG58 3.4 5.5 8.9 11.3 19.1 34.3
RG8 Mini / RG8-X 2.4 3.9 6.6 8.4 14.5 27.7
RG8 1.6 2.6 4.2 5.4 8.8 15.7
RG213 1.7 2.8 4.6 5.8 9.7 17
Ecoflex 10 ! ! ! ! ! !
Westflex 103* 1 1.5 2.5 3 5 9
450 Ohm Twin 0.28 0.47 0.8 1.03





With an SWR of 6:1 at antenna
Losses in dB per 100 metres at various frequencies
Cable Type: 3.5 MHz 10 MHz 30 MHz 50 MHz 144 MHz 432 MHz
RG58 4.9 7.1 10.7 13.1 20.9 36.1
RG8 Mini / RG8-X 3.7 5.5 8.3 10.1 16.4 29.5
RG8 2.5 3.8 5.8 7 10.7 17.5
RG213 2.8 4.2 6.3 7.6 11.5 19
Ecoflex 10 ! ! ! ! ! !
Westflex 103* 1.6 2.2 3.2 4 6 10
450 Ohm Twin 0.49 0.82 1.37 1.73





With an SWR of 9:1 at the antenna
Losses in dB per 100 metres at various frequencies
Cable Type: 3.5 MHz 10 MHz 30 MHz 50 MHz 144 MHz 432 MHz
RG58 6 8.4 12.1 14.5 22 37.5
RG8 Mini / RG8-X 4.7 6.6 9.6 11.5 17.1 30.1
RG8 3.3 4.9 7 8.3 11.9 18.9
RG213 3.6 5.2 7.5 8.8 12.8 20.4
Ecoflex 10 ! ! ! ! ! !
Westflex 103* 2 2.6 3.8 4.5 6.5 10.5
450 Ohm Twin 0.71 1.16 1.88 2.34



Losses are given a dB per 100 metres. For other lengths divide dB loss figure by 100 and multiply by the actual length in metres.

These loss figures are for the cable only without connectors and do not take into account termination and other losses.

ECOFLEX 10

 ! = I do not have full data for the ECOFLEX 10, but it is included here due to its attractive physical properties: The big plus for these cables is they are extremely flexible - whereas W-103 is easy to damage with repeated movement such as with a rotator or /p use with portable masts etc, Ecoflex 10, it is claimed, should be much more resilient and therefore long lasting due to its flexibility.  More information from  http://www.diodecomms.co.uk
Download the Ecoflex Product Brochure in PDF format here 



Information compiled from various sources. References:

http://www.ocarc.ca/coax.htm

http://www.timesmicrowave.com/cgi-bin/calculate.pl

http://www.kc7hxc.us

http://whwestlake.110mb.com/

http://www.diodecomms.co.uk

Coaxial Loss Calculator and Power Compensator : A Microsoft Excel based calculator which is a valuable tool to simply and quickly calculate coax lengths and losses. You can download Coaxial Length Calculator for free but you will need Microsoft Excel to use it or another spreadsheet program capable of using Excel. By Steve Burrows M5BXB  -  http://www.m5bxb.com/coaxlengthcalc.htm

RG58 CQ125; RG8X Belden 9258; RG8 Belden 8237; RG213 Belden 8267
* Westflex103 unconfirmed estimated loss at higher SWR's
             


RESISTOR COLOUR CODE CHART & CAPACITOR INFORMATION

Please visit my separate page for RESISTOR COLOUR CODES & CAPACITOR INFORMATION Here>




British / Imperial Standard Wire Gauges  - S.W.G  converted to diameter in millimetres and inches

Standard Wire Gauge - British / Imperial - converted to diameter:

Wire Gauge
S.W.G.
Diameter in
Millimeters
Diameter in
Inches
0 8.23
0.324
1 7.62
0.300
2 7.01
0.276
3 6.4
0.252
4 5.89
0.232
5 5.38
0.212
6 4.88
0.182
7 4.47
0.176
8 4.06
0.160
9 3.66
0.144
10 3.25
0.128
11 2.95
0.116
12 2,64
0.104
13 2.34
0.092
14 2.03
0.080
15 1.83
0.072
16 1.63
0.064
17 1.42
0.056
18 1.22
0.048
19 1.02
0.040
20 0.914
0.036
21 0.812
0.032
22 0.711
0.028
23 0.609
0.024
24 0.558
0.022
25 0.508
0.020
26 0.457
0.018
27 0.416
0.0164
28 0.375
0.0148
29 0.345
0.0136
30 0.314
0.0124
31 0.294
0.0116
32 0.274
0.0108
33 0.254
0.0100
34 0.233
0.0092
35 0.213
0.0084
36 0.193
0.0076
37 0.172
0.0068
38 0.152
0.0060
39 0.132
0.0052
40 0.121
0.0048
41 0.111
0.0044
42 0.101
0.0040
43 0.091
0.0036
44 0.081
0.0032
45 0.071
0.0028
46 0.060
0.0024
47 0.050
0.002
48 0.040
0.0016
Information compiled by M0MTJ





American Wire Gauges  - A.W.G. converted to diameter in millimetres and inches

American Wire Gauge - converted to diameter:

American Wire Gauge
A.W.G.

 Diameter in
Millimeters

 Diameter in
Inches

0000 (4/0)

11.684

0.4600

000 (3/0)

10.404

0.4096

00 (2/0)

9.266

0.3648

0 (1/0)

8.252

0.3249

1

7.348

0.2893

2

6.544

0.2576

3

5.827

0.2294

4

5.189

0.2043

5

4.621

0.1819

6

4.115

0.1620

7

3.665

0.1443

8

3.264

0.1285

9

2.906

0.1144

10

2.588

0.1019

11

2.305

0.0907

12

2.053

0.0808

13

1.828

0.0720

14

1.628

0.0641

15

1.450

0.0571

16

1.291

0.0508

17

1.150

0.0453

18

1.024

0.0403

19

0.912

0.0359

20

0.812

0.0320

21

0.723

0.0285

22

0.644

0.0253

23

0.573

0.0226

24

0.511

0.0201

25

0.455

0.0179

26

0.405

0.0159

27

0.361

0.0142

28

0.321

0.0126

29

0.286

0.0113

30

0.255

0.0100

31

0.227

0.00893

32

0.202

0.00795

33

0.180

0.00708

34

0.160

0.00630

35

0.143

0.00561

36

0.127

0.00500

37

0.113

0.00445

38

0.101

0.00397

39

0.0897

0.00353

40

0.0799

0.00314


UK Source for Silver Plated PTFE (Teflon) covered wire for winding higher power baluns:
http://wires.co.uk/acatalog/ptfe_covered.html
14awg / 16 swg or 0.16 mm dia wire
12awg / 14swg 0.2mm dia wire and larger toroid for higher powers.





Toroid Dimensions - typical physical dimensions of iron poweder toroidal cores


Core. OD
(in)
ID
(in)
HGT
(in)
Mean lgth.
(cm)
Cross
sect.
(cm2)
T12 .125 .062 .050 .75 .010
T16 .160 .078 .060 .95 .016
T20 .200 .088 .070 1.15 .025
T25 .250 .120 .096 1.50 .042
T30 .307 .151 .128 1.83 .065
T37 .375 .205 .128 2.32 .070
T44 .440 .229 .159 2.67 .107
T50 .500 .300 .190 3.20 .121
T68 .690 .370 .190 4.24 .196
T80 .795 .495 .250 5.15 .242
T94 .942 .560 .312 6.00 .385
T106 1.060 .570 .437 6.50 .690


Core OD (in) ID
(in)
HGT
(in)
Mean lgth.
(cm)
Cross
sect.
(cm2)
T130 1.30 .78 .437 8.29 .73
T157 1.57 .95 .570 10.05 1.14
T184 1.84 .95 .710 11.12 2.04
T200 2.00 1.25 .550 12.97 1.33
T200A 2.00 1.25 1.000 12.97 2.42
T225 2.25 1.40 .550 14.56 1.50
T225A 2.25 1.40 1.000 14.56 2.73
T300 3.00 1.92 .500 19.83 1.81
T300A 3.00 1.92 1.000 19.83 3.58
T400 4.00 2.25 .650 24.93 3.66
T400A 4.00 2.25 1.000 24.93 7.43
T500 5.20 3.08 .800 33.16 5.46

information from:  http://www.bytemark.com

Balun using  T200-2 toroid (17 turns of e.c.w.) or T200A-2 toroid (13 turns of e.c.w.) for 400 watt H.F. Balun.
T400-2 Toroid (14 turns of e.c.w.) for 1000 watt H.F. Balun.




WINDOWS  ALT Codes

Alt + 0153..... ... trademark symbol
Alt + 0169.... .... copyright symbol
Alt + 0174..... ....registered trademark symbol
Alt + 0176 .........degree symbol
Alt + 0177 .......plus-or -minus sign
Alt + 0182 ........paragraph mark
Alt + 0190 .......fraction, three-fourths
Alt + 0215 .........multiplication sign
Alt + 0162.......the cent sign
Alt + 0161.......... .upside down exclamation point
Alt + 0191.......... upside down question mark
Alt + 1.......☺....smiley face
Alt + 2 ......☻.....black smiley face
Alt + 15.....☼.....sun
Alt + 12......♀.....female sign
Alt + 11.....♂......male sign
Alt + 6.......♠.....spade
Alt + 5.......♣...... Club
Alt + 3.......♥...... Heart
Alt + 4.......♦...... Diamond
Alt + 13......♪.....eighth note
Alt + 14......♫...... beamed eighth note
Alt + 8721.... ∑.... N-ary summation (auto sum)
Alt + 251.....√.....square root check mark
Alt + 8236.....∞..... infinity
Alt + 24.......↑..... up arrow
Alt + 25......↓...... down arrow
Alt + 26.....→.....rght arrow
Alt + 27......←.....left arrow
Alt + 18.....↕......up/down arrow
Alt + 29......↔...left right arrow


CTRL Key combinations

CTRL + ALT + $ =    Euro symbol
CTRL+C: Copy
CTRL+X: Cut
CTRL+V: Paste
CTRL+Z: Undo
CTRL+B: Bold
CTRL+U: Underline
CTRL+I: Italic

More Keyboard Shortcuts for Windows at:  http://support.microsoft.com/kb/126449
 


'END FED' AERIALS (ANTENNAS) 

The VK2ZOI "Flowerpot Antenna"  - A physically end fed Half Wave "Coaxial Dipole" for 2 metres and 70 centimetres

For 2m and 70cm FM I use a mounted on a lightweight aluminium telescopic pole on the apex of the hose. The base of the antenna (the bottom of its radiating element) is approximately 11 metres above ground level. This antenna is based on the Controlled Feeder Radiation principle (CFR) and is described by VK2ZOI on his website. Also known as a "Coaxial Dipole". My version is described below.

Also seen in the photograph are the ropes that support the H.F. wire aerials.

Dual band home-brew
                                      omnidirectional vertical antenna
                                      for 2 metres and 70 cms
Home brew dual band vertical antenna for 2 metres and 70 cms
(Coaxial Dipole / Controlled Feeder Radiation Antenna / 'Flowerpot Antenna')



VK2ZOI has produced some extremely interesting and potentially very useful dipole antenna designs. The designs could form the basis for a great home-brew antenna project since it is physically end fed and can also be made into a dual band aerial for 2 metres and 70 centimetres, so forming the basis of a viable alternative to buying an expensive commercially manufactured 'white stick' antenna.

The final dual band version works very well and can form the basis of a viable alternative to commercially made 'white stick' antennas, because there's nothing better than using your own home-brew antenna!

Physically, the feeder cable enters the antenna at the bottom end, so it looks like an end fed aerial. VK3TWO / VK6TWO describes it as a "Coaxial Dipole".  'Electrically' it is a simple dipole. The RF is travelling 'inside' the bottom 'element' and doesn't 'feed' the antenna until where the coax is cut - in the centre of the antenna, as shown in the diagram below. Where the outer braid is cut (electrically the centre feed point), the RF then radiates like a simple dipole, via the top radiator (coax core), and via the outside of the coax - the bottom half of the dipole. The top radiator is thinner than the lower radiator (hence why the lower radiator is slightly shorter than the upper radiator). The coiling of the coax is simply forming an RF choke (high impedance point), to stop the RF continuing down the outside of the braid, thus electrically it 'appears' to be the end of the radiating element.



I purchased a 3 metre length of 25mm diameter conduit from B&Q, our local DIY centre and ordered some 25mm end caps and heatshrink from ebay. I already had some good quality RG58 for the feeder and main 2 metre radiating element and some aluminium foil for the 70cm sleeve dipole.

First of all I cut the RG58 cable to form the 2m radiating section and choke coil. Because the UK's 2m allocation of 144 to 146 MHz is narrower than the 144 to 148 MHz available in Australia, I varied slightly from the design shown. The centre of the UK's 2m band is about 1% longer in wavelength, so I decided to make both the top and bottom measurements 1% longer.

I therefore stripped 460 mm of the outer sheath and braid from the cable to form the top 1/4 wave element of the dipole. I then measured down 450 mm and marked the point where the lower 1/4 wave element would finish and the choke coil would start.

Next I attached a thin nylon cord to the top of the top radiator, the coax inner.

I then cut the 3 meter length of 25 mm conduit down to about 2.3 metres and drilled a hole where the coil would start, wound 9 turns of RG58 cable from that hole and marked the position of the lower hole. I then removed the coaxial cable and drilled the second, lower, hole.

I then pushed the radiating section of RG58 into the top hole and fed it up towards the top of the tube, stopping when the marker tape reached the hole. I then wound the coil and pushed the remainder of the RG58 through to lower hole and fitted a PL259 plug on the end.

I pulled the top of the radiator wire tight using the nylon cord and pushed the end cap on. The antenna was then ready to be tested on the 2 metre band. I found that the resonant frequency was rather too high, just above 146 MHz, so I pushed an additional 10 mm of coaxial cable into the upper section of the tube - therefore making the lower 1/4 wave section of the dipole 460 mm long - the same as the top section. I tightened up the choke coil winding again and performed another test.

This time the resonant point was just over 145.000 MHz - near enough the centre if the UK's 2 metre band. That was perfect, so the 70 cm sleeve element was then added - this is a 235 mm long tube of kitchen foil positioned exactly at the centre (feed) point of the 2 meter dipole within the tube.

The SWR was tested and found to be acceptable across both the 2m and 70cm bands.

I then fitted the end cap, applied the heatshrink to the coil and to the aluminium foil sleeve. I noticed that when the antenna tube was moved around the cable inside rattled around making a noise that may be rather annoying to anyone near its final location.

To help hold prevent the cable from rattling I pushed up 4 or 5 small pieces of foam material up the tube from the bottom to rest at various positions along its length. With these pieces in place the cable was certainly silenced, however it may have had a deleterious effect on the SWR.

With the antenna now in its finished physical state I naturally checked the SWR again to compare against the performance in its semi-complete state. I was pleased to find that the SWR was still fine across the 2m band, in fact the SWR was a little lower. However the SWR at the edges of the 70cm band was considerably higher - 1.8 at 440 MHz and about 2.2 at 430 MHz.

I conjectured that the heatshrink covering the foil sleeve dipole may have caused the change in response so I removed it, but the SWR was little different and the bandwidth on 70cm was now disappointingly narrower than expected and hoped for.

Although I cannot say for certain, because they cannot now be easily removed, but it may be possible that the pieces of foam may be the culprits for the difference.

While the bandwidth could not be improved, I decided to move the centre point of resonance down a little by increasing the length of the sleeve element from 235 mm to 245 mm. With that adjustment the SWR was now approximately 1.6 at 430 MHz but rising to 2.0 at 440 MHz. (Unfortunately I forgot to note the exact figures down in all cases).

When the antenna was connected to the 20 meter length of Westflex-103 back to the shack, the SWR reading were as follows:

2 Metres - SWR
70cms - SWR
144.00
1.3
430.00
1.2
144.50
1.2
431.00
1.4
145.00
1.2
432.00
1.4
145.50
1.2
433.40
1.0
146.00
1.2
434.00
1.3


435.00
1.8


436.00
1.6


437.00
1.0


438.00
1.5


439.00
2.0


440.00
2.1



The SWR readings in the shack for 2 meters are lower than at the feed point, which is presumably due the losses in the feeder. The SWR readings for 70 cms look rather erratic, with a strange peak at 435 MHz, while the 430 MHz figure is lower than at the feed point of the antenna, and the 439 and 440 MHz figures are disappointingly higher than hoped for. The peculiar readings are likely due to feeder effects.

However the SWR at 433.4, in the FM simplex portion of the band, is very low.

The completed antenna was mounted to the aluminium mast by utilising brackets of the Watson W50 antenna. The brackets had to be reversed so that the narrower diameter of the 25mm tube could be held in place by the V Bolt, while the circular section that previously fitted over the base of the W50 now slid over the mast, which was coincidentally a similar diameter.

I made a small addition to the design in the form of a second small 150mm length of of the 25 mm conduit glued to a coupler section. This is slid into place at the bottom of the antenna to provide additional weather protection to the joint between the W-103 feeder and the RG58 of the antenna - which itself is covered in self amalgamating tape.

Shown in the table below are some signal comparisons with the Watson W-50 antenna; both were mounted on the same mast in the same position and at a height of approximately 7 metres above ground level. Becuase the S-Meter of the transceiver is not calibrated in absolute values, the figres are for relative comparison only - also bear in mind that a typical S Point represents 6dB - therefore the accuracy of these readings will be coarse and  might be considered to be +/- 3dB - that's a rather wide variation.

Despite the relative crudeness of these comparisons, the results do seem to indiacte that the VK2ZOI antenna is marginally or slightly better than the W-50 on 2 metres and marginally worse on 70cms. I am quite pleased with this result and beleive that this antenna really could replace the need to buy an expensive commercially manufactured antenna.

My only concern with this type of antenna is that there is no path to ground from the top element, as there would be with a folded dipole or a J-Pole type antenna. This may be a cause for concern as far as static build up is concerned.

Signal comparisons

Watson W-50
"Flowerpot Antenna"
2 Metres


Station A
S7
S9
Station B
S5
S6
Station C
S4
S4
Station D
S9
S9
Station E
S6
S6
Station F
S0
S1
Station G
S2
S2
Station H
S2
S3
Station I
S6
S6
70 cms


Station J
S0
S1
Station K
S5
S5
Station L
S5
S4
Station M
S0
S0
Station N
S9
S9
Station O
S6
S6
Station P
S7
S6
  


Please see the photographs below for a visual explanation of this project.  Mike, MMTJ. 05/03/2013


Stages of construction
                                    of the 2m / 70cm dual band antenna
                                    M0MTJ
First stage of construction of the 2m / 70cm dual band antenna
Cutting the 25mm diameter conduit to the desired length and drilling
the two holes allowing the coil to be wound.  MMTJ

Stages of construction
                                    of the 2m / 70cm dual band antenna
                                    MMTJ
Heatshrink applied to the centre of the dipole section and red insulation
tape added to mark the bottom of the dipole where the coil starts.  MMTJ


Stages of construction
                                    of the 2m / 70cm dual band antenna
                                    MMTJ
Thin cord attached to top of the inner conductor of the coaxial cable, which forms the
top 1/4 wave section of the dipole with a piece of heatshrink and a blob of glue.  MMTJ


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
The line isolator choke is formed by winding 9 turns of the RG58
coaxial cable around the 25mm diameter conduit tubing.  MMTJ


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
The thin cord that holds the 1/4 wave radiator in place is located in the
notch and will be trapped in place when the end cap is fitted.  MMTJ


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
After testing, the coil was covered in heatshrink to prevent water entering the plastic tube. 


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
The foil sleeve dipole for 70cms is covered in heatshrink.


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
Oops. Lesson learned. When applying heat to the heatshrink I held the tube above the ground and the plastic of the
tube started to go soft and bend out of shape. The buckle in the tube can be seen in this photograph.
Lesson: When applying heat, keep the tube flat on the ground or work bench and roll the tube along as the
heatshrink shrinks into place ensuring that the tube does not distort or bend. 


Stages of
                                      construction of the 2m / 70cm dual
                                      band antenna MMTJ
25 mm end cap sealed in place by heatshrink.

MMTJ - Dual Band
                                      Dipole Antenna
The completed antenna in place, mounted at the top of my aluminium push-up mast. The fixings used are the
brackets from the Watson W-50 antenna which have been reversed so that the smaller diameter PVC tube
is held in place by the V Bolts.


MMTJ - Dual Band
                                      Dipole Antenna
Photograph detailing the the fixings. The brackets are brackets are from the Watson W-50 antenna which
 have been reversed so that the smaller diameter PVC tube is held in place by the V Bolts.

For further detailed information and reading, please visit the excellent website of John Bishop VK2ZOI here:
http://vk2zoi.com/articles/half-wave-flower-pot/





6 Metre Half Wave Coaxial Dipole - An end fed CFR Dipole antenna supported by a 3 metre long fibreglass fishing pole for 50 MHz

In 2014 I decided to remove the 4 Metre J-Pole antenna from my push-up mast due to the fact that the band is relatively quiet and that I only have the 5 watt Wouxon handheld transceiver for 70 MHz.

I decided that having a good, full size antenna, for the 6 Metre band would be more useful and potentially more rewarding since it can be used with a 100watt HF radio that covers 50 MHz.

The choice of antenna was an easy one. With the great success of the "flowerpot antenna", I decided to build a version for 6 Metres.

Similar designs of Coaxial Dipole antennas had also been featured in recent editions of the RSGB publication RadCom during 2012 and 2013. The antennas in RadCom are described as Controlled Feeder Radiation (C.F.R.) Dipole antennas - the tuned choke at the feed-point controlling, or choking off, the common mode current that would otherwise flow down the outside of the coaxial feeder cable causing E.M.C. issues on transmit, high S.W.R. reduced efficiency and noise on receive. See references below

The advantage of this design is that it can be physically end fed, so there is no feeder cable to route away from the centre of the dipole. Electrically, however, the feed point is at the centre of this dipole aerial, as explained earlier.

Rather than fit the antenna inside a PVC pipe, as with the previous dual band 2m / 70cm antenna described above, I decided to use a lighter weight and less conspicuous 3 metre long fibreglass fishing pole as the support. The completed radiating element simply being taped to the fishing pole.

I cut a length of MIL spec RG58 cable, about 4.5 metres long, to form the bottom half of the radiating section and the choke coil, leaving enough to form a short length (about 30 cm) of cable below the choke coil on to which is soldered a PL259 plug.

The choke consists of 15 turns of the RG58 coaxial cable wound on a 50mm diameter plastic former cut from the empty tube of a cartridge gun that previously contained silicone sealant - allowing a 30cm tail on to which the PL259 plug is fixed on one side and and about 1.31 metre length on the other side that will form part of the radiating element.

The half wave radiator therefore consists of a quarter wave bottom section of the RG58 cable and a quarter wave top section consisting of a length of multi-strand (single conductor) P.V.C. covered antenna wire.

A quarter wavelength at the mid point of the 6 Metre band is:  300 51 MHz = 5.88 metres 4 = 1.47 metres

Due to velocity factor the actual length of the quarter wave sections will be shorter. With the materials that I used, I found that a factor of about 87% was about right, the 1/4 wave length being 1.29 metres.

The top tip of the bottom 1/4 wave section of the coaxial cable is stripped of about 2 cm of outer sheath and braid leaving the length of braided section, measured from where it exits the coil, 129 cm long. The inner conductor is then stripped of 1cm of insulation. This is effectively the centre point of the dipole. To this point is soldered the 129 cm length of the P.V.C. covered aerial wire to form the top half of the antenna. In practice, use a slightly longer length of wire, and then fold over the excess to for the 129 cm length - this can then be used to adjust for lowest SWR at 51 MHz.

The length of the radiating section was therefore about 260 centimetres, plus about 13 centimeters for the coil former giving a total length of 273 cm. This allows about 27 cm of the bottom section of a 3 metre fishing pole to be used to fix to a supporting pole or mount - e.g. to the top of an aluminium mast.

Drill four small holes in the choke former so that when the fishing pole is placed through the centre of the former it can be fixed to the pole using two cable ties.

The radiating section (coax and PVC covered wire) is fixed to the top section of the fishing pole with good quality insulating tape.

The aerial can now be temporarily fixed to the mounting pole using suitable brackets - taking care not to crush the delicate fibreglass! Connect the PL259 plug to the antenna feeder cable using an SO239 back-to-back coupler and test the SWR with an antenna analyzer or SWR bridge. The lowest SWR should be centred on 51MHz and be low - less than 1.5. My reading was 1.2.

If the point of lowest SWR is significantly away from 51 MHz and/or the SWR at the band edges is too high (i.e. over 2) then length of the radiator will need to be adjusted. If the point is too low in frequency, the antenna is too long and will need to be shortened. If the point is too high in frequency, the antenna is too short and will need to be lengthened.

Adjustment can be achieved by pulling the coax through the coil to make it longer, or pushing the coaxial cable back into the coil to make it shorter. Also ensure that the coil winding are adjusted to that they remain tight and neat. The top PVC covered wire section will also need to be lengthened or shortened accordingly by adjusting the folded over section.

Note that in practice, to obtain the very lowest SWR, the top PVC covered wire section may need to be slightly longer by perhaps 1 or 2 centimetres. This is probably due to the fact that the velocity factor of the PVC covered antenna wire is a little greater than the coaxial cable.

Once the antenna is adjusted correctly, ensure that the wires are securely taped to the fishing pole. Connect the permanent antenna feeder to the aerial using the SO239 coupler and weatherproof the joint thoroughly using self amalgamating tape. Use the very best quality coaxial cable possible to ensure lowest loss. I use Westflex 103, but consider MIL Spec RG8 or RG213 as the minimum standard.


6 Metre End Fed
                                        Half Wave Antenna
50 MHz Coaxial Dipole / Controlled Feeder Radiation Antenna / 'Flowerpot Antenna'
A physically end fed fed half wave dipole antenna for 6 Metres


Choke Coil - 6
                                        Metre End Fed Half Wave Antenna
Choke Coil - 15 turns of the RG58 coaxial cable on a 50mm diameter former



VHF Band II Broadcast Band antenna for 88 to 108MHz -
Physically end fed, Coaxial Dipole / Controlled Feeder Radiation Antenna (CFR Dipole) for VHF broadcasts


I used a 2 metre long length of 25mm white plastic pipe, strengthened with with a 2 metre length of 21.5mm overflow pipe pushed up the inside.

The radiating element is made from good quality 75 Ohm coaxial cable. Since VHF/FM broadcast tuners are designed to be fed with 75 Ohm coaxial cable, use high quality, low loss double shielded satellite grade coaxial cable for the feed between the aerial and the radio tuner. Use satellite F type connectors and joiners for lowest loss.

The top half of the radiating section is 670mm of the centre conductor (or a length of multi-strand PVC covered wire). The bottom half of the dipole is 650mm of the complete coaxial cable - choked off at the bottom by the coil section.  The top part is held in place by a a short length of thin nylon cord, trapped in place by the top PVC cap.  The cap itself is sealed on the outside by some self amalgamating tape. 

The choke coil is 22 turns of the 75 Ohm coax wound around the 25mm pipe. Tightly spacing the windings of the coil will minimize the bandwidth covered but provide the lowest SWR at the centre point.  A looser winding of the coil will widen the bandwidth covered, but lowest SWR achieved will be a little higher.

Once the tuning of the radiating elements, coil winding and band coverage has been checked with an Antenna Analyzer, the coil section should be covered with heat shrink, taking great care not to overheat and deform the plastic pipe.

The actual final dimensions (as shown below) may well need some adjustment in length due to differences in cable and type of pipe used. However, with the dimensions shown, I achieved a minimum SWR of 1.3 at 97.4 MHz. The band edges at 88MHz and 108MHz were at an SWR of around 3.8 to 4.0 - which is probably OK for broadcast band reception.  The frequency of lowest SWR can can be changed, if desired, by changing the lengths of the radiating sections - slightly longer for a lower frequency and slightly shorter for a higher frequency. 

VHF Band II Broadcast Band
                                      end fed vertical for 88 to 108MHz
Coaxial Dipole for the 88 to 108 MHz Band II Broadcast Band
An effective, cheap and simple vertical antenna that is fed at its base





RSGB RadCom Articles:

The Controlled Feeder Radiation Dipole. Peter Dodd. RadCom, September 2012, page 22.

More On The CFR Dipole and Coax Chokes. Peter Dodd. RadCom, October 2012, page 54.

VHF CFR Dipoles and More on Common Modes Chokes. Peter Dodd. RadCom, January 2013, page 24.

The HAK Chokes Coaxial Dipole. Encouraging results from 2m to 20m. Peter Grant. RadCom, April 2013, page 22.



VK3TWO / VK6TWO Comments:
 
Many years ago when I was working for a Service Centre, by accident we broke a commercial white stick antenna whilst using it for a task it wasn't intended for. I found that inside the fairly expensive commercial antenna the basis for the design was very similar to the coaxial dipole (as I call them).

Our local repeater club calls them "pogo sticks", which I can only assume is due to the coax coil resembling the spring of a pogo stick. This design had RG213 being fed inside an aluminium tube (the bottom radiator), and the outer braid was then terminated to this. The inner of the coax, then terminated to an identical aluminium tube which was of course the top radiator. Where this design largely differs, is that there was also a 1/4 wave stub of coax running parrallel with the bottom radiator (note that this was for single band operation, not dual band). The whole lot then slid inside the typical white tapered fibreglass housing. I didn't cut open the bottom mounting section to see how it was choking the RF, but I assume it had a handful of ferrites inside the metal base (an alternative way of making the RF choke).
 
The repeater group has built probably hundreds of these and sells them for $40 at local hamfests. We had a 'Jig' made so that all of the measurements were 'pre-marked' etc, and allowed us to mass manufacture them. Last year, we had planned the typical 'working bee' to make about 30 of them, but this time we had a very expensive Anritsu Sitemaster at our disposal. We discovered that the whilst the design we'd used for decades had a good SWR, it actually was far from optimal. With a heap of 'trial and error' (and with excellent visibility of what was really going on via the Anritsu - not just SWR) we were able to fine tune the design.
 
From memory, we actually needed more turns of the coax than we had been using (10.5 turns from memory), and our cutting measurements altered slightly. As to be expected, the number of turns was largely dependent on the size of the conduit being used, even changing from 25mm to 30mm etc.
 
We took several screenshots of the final SWR plots etc. These showed that the bandwidth of this antenna as VERY wide from an SWR point of view. I'll see if I can dig some of them up for you if you'd like.
 
73, Heath, VK3TWO / VK6TWO
MEngSc, GDipCompSc, DipEE
www.spooktech.net

http://www.warg.org.au  - The West Australian Repeater Group Inc (WARG) is the largest amateur radio club in Western Australia (VK6).





D.I.Y. J-Pole Antennas - A really simple, quick and very cheap 'home brew' project J-Pole Antennas

J-Pole antennas for 2 meters, 4 metres, 6 metres and 10 metres :


While experimenting with antennas in the garden in the summer of 2012 I thought that it would be good to have a hand-held radio in the shed to do some monitoring and make a few contacts. To improve upon the performance of the 'rubber duck' antenna I quickly made a J-Pole antenna for the 2 metre band.

It is made from a 47cm length of 450 ohm Wireman ladder line as the 1/4 wave matching section, plus a 97cm length of stranded wire as the 1/2 wave radiator. It is fed with 3 metres of Mil spec RG58 c/u coaxial cable that is soldered to the 1/4 wave matching section's impedance matching point at 3.5 cm from the bottom. The coax feeder is wound around some PVC tube to form a choke. The completed antenna is taped to a 2.2 metre long fibreglass fishing pole that I purchased from Poundland (for 1.00). It took about 20 minutes to make followed by some testing and adjustment with the antenna analyser. The fishing pole is lashed to the shed with some cable ties.

This simple antenna works pretty well, but being so low down signal strengths are not huge, but it's pleasing to get on the air with something so simple and cheap!

2m
                                          J-Pole antenna by M0MTJ
The Shed Antenna - a 2m J-Pole by M0MTJ
Note the simple choke balun at its base made by winding 8 turns
 of the coaxial cable around a small off cut of white PVC water pipe.

J Pole antenna feed
                                              point
The feed point of a J-Pole antenna made from Wireman 450 ohm ladder line.
For the 145 MHz antenna this feed point is 3.5 cm from the bottom of the ladder line section which
is on the right hand side in this photograph. The coaxial cable used in this case was Mil spec
RG58 c/u. But any good quality, low loss 50 ohm coaxial cable could be used. The wire
radiator section is connected to the same conductor of the ladder line as the coaxial cable's
centre conductor. For my antenna, fixed to a fibreglass fishing pole, the radiator wire was
97cm in length. 

J Pole antenna -
                                              connection of the radiator
                                              wire
Photograph showing the point where the PVC covered wire that forms the half wave radiator section
is soldered onto the top of the 450 ohm ladder line that forms the quarter wave matching section.



Inspired by DK7ZB. The J-Pole is a very effective antenna and being made of wire it is very light weight making it quite easy to fix in different positions. If you have problems installing a permanent antenna then making a wire antenna that can be easily supported on a lightweight push up telescopic fishing pole can make an ideal alternative.

The formulas to make a J-Pole antenna from 450 Ohm Wireman ladder line in this way are:

Length of 1/4 wave impedance matching section (450 ohm ladder line) Wavelength x 0.223
Length of 1/2 wave radiator (any reasonably strong PVC covered stranded wire) Wavelength x 0.471
The point at which the coax is connected to the 450 ohm ladder line will be about 5 to 10% of the length of the ladder line section up from the bottom.

The wavelength at mid point of the 2 metre band (145.00 MHz) is found by the quick calculation 300 145 =  2.068 metres

So, to make a practical antenna:

The 1/4 wave section of 450 ladder line will be  2.07 x 0.223 = 0.47 metres long
The 1/2 wave wire radiator will be worked out as 2.07 x .471 = 0.975 metres long
The connecting point of the coax will be about 3.5 cm from the bottom of the 1/4 wave section. The optimal point may have to be found by some experimentation - as will the best length for the wire radiator.

The length of the wire radiator will be affected by surroundings. For example I fixed the wire to a fishing pole. The proximity of the fishing pole has the effect of electrically lengthening the wire; so using a 97.5cm length of wire fixed to a pole I found that it resonated (as expected) at a lower frequency, it therefore had to be shortened until the point of resonance (indicated by lowest SWR) was around 145.00 MHz. This should be done in the antenna's expected final position since the J-Pole is quite sensitive to its surroundings, so if these checks are done near the ground, once it is raised into its final position the SWR will have changed and the adjustments will have to be done again.

I found that 3.5 cm was good for the 2 metre band antenna, but for the 10 metre band version of the antenna a little more experimentation was required:

The VSWR reading may not be especially low, even though the point of resonance for the wire radiator may have been found. For the 10 metre band antenna at this this stage was about 1.7 indicating that the connection point of the coaxial cable to the 450 ladder line needs to be adjusted. The ladder line is used as an impedance transformer, transforming the very high impedance (hundreds of ohms) of the half wave wire radiator down to the 50 ohms required by the transceiver and the coaxial feeder cable. This connection point therefore affects the impedance of the antenna, the higher up the matching section it is the higher the impedance will be, and visa versa.

Once the length of the wire radiator has been set, the connection point can be moved up and down the ladder line until lowest SWR is achieved. A few centimetres of the PVC insulation has to be carefully scraped away from the copper conductor on each side of the ladder line using a craft knife. The inner conductor of the coaxial cable is quickly tack soldered on the side that is connected to the 1/2 wave wire radiator. The coaxial cable's braid is quickly tack soldered to the opposite side of the ladder line at this point, ensuring that both points are equal distance from the bottom. At this point temporary croc clips could be used, but I preferred a quick solder joint.

With radiator trimmed for resonance, the connection point of the coaxial cable can then be moved up or down the ladder line little by little;  un-soldering and re-soldering the coax to the ladder line until a lowest possible SWR is achieved, indicating that the antenna is near the ideal 50 ohm impedance.

Once the ideal point is found the coaxial cable can be properly and permanently soldered to the ladder line.

6 Metre
                                          Band J Pole on the antenna
                                          analyser
6 Metre Band J Pole on the antenna analyser - it's getting close!

Each J-Pole took about 20 minutes to physically make out of the wire components. However the testing and adjusting took a bit more time. I used an antenna analyser which saved having to key the mike every time when using a basic VSWR bridge and causing unnecessary QRM, but even so, hoisting the fishing pole up and down numerous times took a little more time:

10 Meter J-Pole. For the 10 metre band J-Pole antenna this took perhaps another 20 or 30 minutes until I was satisfied with the adjustments. It may take a little longer if using an SWR meter.

6 Meter J-Pole. For the 6 metre band antenna the radiator wire had to be trimmed a little and the feed point adjusted to 6 cm, taking about 10 additional minutes to complete.

4 Metre J-Pole. For the 4 metre band, centred on 70.37 MHz

2 Meter J-Pole. For the 2 metre band antenna the wire radiator took a couple of attempts to get it to the correct length when attached to a fishing pole, but the feed point was spot on first time at 3.0 cm, again taking about 10 additional minutes to complete.

Here are some suggested dimensions for the 2 metre, 6 metre and 10 metre band versions, when supported by a fibreglass fishing pole:

Wire J-Pole Antennas
1/2 Wave Radiator
1/4 Wave Section
 Feed Point
2 Metre Band Antenna
0.975 m
0.47 m
3.0 cm
4 Metre Band Antenna
1.90 m
0.95 m
6.1 cm
6 Metre Band Antenna 2.815 m
1.33 m
6 cm
10 Metre Band Antenna 4.96 m
2.45 m 15 cm


N.B. The 1/2 wave wire radiator section will be shorter than calculated when fixed to a fibreglass pole or other object.

To re-cap, the 1/2 wave section should be adjusted for resonance and the feed point position adjusted for minimum VSWR.

Sealing and waterproofing. Once the antenna is complete and has been checked and tested all the bare joints should be sealed against the weather with liquid electrical tape and self amalgamating tape. The coax should also be secured against the ladder line with a nylon cable tie as a strain relief to prevent the soldered feed point joints from breaking.

These J-Pole Antennas were inspired by DK7ZB - http://www.qsl.net/dk7zb/J_Pole/wiremanjpole.htm
















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