Dimensions
A- 392.09 cm (154 3/8 inch)
B- 58.62 cm (23 1/16 inch)
C- 11.25 cm (4 7/16 inch)
D- 73.4 cm (28 7/8 inch)
E- 143.27 cm (56 7/16)

Gain, Radiation Pattern (mounted at approx 30feet)

Gain : Approx 10-11dBi (30 feet above the ground)
Freq range : 27.300 MHz – 28.300 MHz

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The main advantage of Moxon rectangle antenna are :

• Compact and Small
• Has considerable gain
• It can eliminate noise on HF band
• Easy to construct
• Suitable for HF operation (mid-low radiation angle)

Refer here for 10 meter Moxon Antenna Plan for Amateur Radio operation (28.2MHz-28.8MHz) : 10 Meter Band Compact directional antenna, Moxon

Here is the details of its construction. Click on the photograph to enlarge it.

KakiBiawak @ Astra Antenna in action

Materials used to contruct the antenna

• 8mm aluminium tube, 20 feet
• 6 feet length of 3/4″ PVC plumbing pipe
• Ordinary household plug box

We use a plan taken from LB Cebik (W4RNL) website, first covered in : 10dBi – 6 element OWA Yagi-Uda Antenna for 2 meter band

Here are the photos of the antenna in construction :

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Tools used

The total cost of the yagi construction was RM25 (USD 8.50) for the materials alone. Later we put it on a cheap tv antenna rotator which cost us another RM40 (USD 13.5)

Here are the video of the antenna mounted on ordinary TV rotator :

Antenna Performance
The antenna has 1.3:1 reading (20watt) tx on 145.575MHz. 1.1:1 on 145.0MHz and 1.75:1 on 148.0MHz.

Up until now the antenna have recorded a distance record of approximately 180km on 2 meter FM QSO (from Beseri, Perlis to Bukit Merah, Perak) on 5W (51, 53 signal report). Other record includes distance communication between Alor Setar and Parit Buntar (distance 110km) on 10W (signal report 53,53).

The theoritical distance of this antenna if is mounted sufficiently high enough above obstacle is about 400km-500km. We only manage to mount it about 20 feet above the ground

You can find the antenna plan on : 10dBi – 6 element OWA Yagi-Uda Antenna for 2 meter band

Full article – : Homebrew 5/8 Mobile Antenna

For starters… It does not actually sounds like that, I had to lower the voltage because the speaker output is too loud and you can hear that i’m not a good at sending morse too.

Still in progress, I’m still looking to modify it abit and put it in a nice box and attach it with a decent key.

In the spirit of amateur radio/ham, we will homewbrew the equipment using easily obtainable parts from our nearest electronic stores.

Here’s the circuit

We are still thinking of the easiest and cheapest way to homebrew the keyer, but we are considering to use discarded/faulty computer mouse as our first keyer.

As a bonus, we thought of hooking this keyer straight to PC serial port, so we could use it with XChat CWirc plugin to enable us to test our Morse skill on the irc.

With the amount of work i’m having this week, I would estimate that this project would be completed by the end of March. So stay tune for photos!

Step I

First get a ATX PC power supply from the nearest computer store. Price is around RM30-70.

Make sure it could supply sufficient current. Look at the label. We need at least 10-17amp at 12V for a sufficient operation of mobile rig. Lower Ampere rating means that your mobile rig cant transmit with a typical HiGH setting (50w).

Step 2

Look for ATX power connector. It should look like this.

Look for black and green wire at the ATX connector. The wire position is 4th from the top left side of the connector and 4th from the bottom right side from the connector as pictured above.

Cut the black and green wire. Trim all the other wires as we wont need them.

Tie both Black and Green wire together.

Connect both Green and Black wire to bypass the PC Power Supply unit. Insulate it with some tape. and switch on the power supply. If the fan is running, that means you’ve successfully completed this step!

Step 3.

Turn off the power supply. Look for HDD, CDROM power connector, as pictured above.

Cut all wire from the connector.

Separate 2 black wires and one yellow wire. Combine both black wires together.

Look for an extra mobile rig power connector, this can be obtained from electronic shops car accessories, or car battery shop.

Connect the yellow wire (+12 volt DC) to the positive terminal at the power connector as pictured above. Connect both black wires together and put it to the negative terminal as picture above too.

Step 4

Cut all unnecessary wires, connector, and leave the power supply with just the rig power connector like this. It will look much more presentable and neatly prepared.

You can test the output voltage of this power supply by testing it with Voltmeter/Multimeter. Here you can see that the power supply output voltage is about 12V, which is suffiecient to power a mobile rig (13.8V +/- 15%).

Step 5

Finally, connect the power supply to your mobile rig to power it up. Enjoy your QSO!

FAQ: Nice, but my mobile rig require 13.8VDC to operate, this PSU only supplies 12V, it won’t work
Actually it can work. Mobile rigs requires 13.8 +/- 15% VDC to work (check your rig manual). and that gives a range about 11.7V – 15.8V of stable voltage potential. So a 12V power supply with sufficient current (15A and above) is definitely sufficient to power the mobile rigs.

Acknowledgments
This howto has been translated directly from Malay version original article published in Forum Anak Perlis written by me.

You can refer there for a complete malay version of the guide if you find the English version is confusing.

This how to will show you how to build a 2 meter slim jim antenna from ordinary insulated copper wire commonly used for carrying AC (alternate current) electricity in your household.

Slim Jim construction basic
I am not only going show you the measurement of slim jim antenna for specific frequency, but I’m going to show you how to calculate slim jim antenna by your own using the basic formula below.

The figure above shows that the longest side of slim jim is 3/4 wavelength long and the shorter side of the slim jim consist of 1/2 wavelength and 1/4 wavelength long seperated by a gap.

The feedline (coax cable) is normally connected 1/20 wavelength from the bottom of the slim jim antenna with the center conductor connected to the longest side and the shield/braid is connected to the shorter side.

Building the Slim Jim antenna
This guide assume you want to build a slim jim antenna that centered on 146MHz.

Calculation
The formula for calculating wavelength in metric system is 300/(freq MHz)

Using the formula from the figure, we have :

300/146 = 2.055 M
Wavelength = 205.5 cm

Wavelength x copper wire velocity factor = 205.5 cm x 0.94
= 193.17 cm

3/4 wavelength = 193.17 x 0.75
= 144.88 cm (57″)

1/2 wavelength = 193.17 x 0.5
= 96.585 cm (38″)

1/4 wavelength minus gap = 193.17 x 0.25 – 2.6 cm
= 45.69 cm (18″)

Coax tap = 193.17 x 1/20
= 9.6 cm (3 3/4″)

Building Materials

• 3/4″ diameter PVC (20mm) – 6 feet (180 cm)
• ordinary insulated copper wire for carrying altenate current (AC) – 11 feet (3.40 meter)
• Cable ties

Tools

• Soldering iron
• Glue gun
• Somthing to make a hole on PVC pipe

Wire Slim Jim Building Steps

• First take the PVC pile and measure it according to the 3/4 wavelength formula above (144.88 cm).
• Make two holes at the opposite side of the pipe. This hole is used for putting the copper wire through the pipe. Repeat this step 144.88 cm away from the top hole. Both of these holes will hold the copper wire.
• Insert the wire through the hole until both end reaches each other on one side of the PVC pipe. Then measure the length of the wire and cut the wire on that side so the setup resembles the figure above.
• Cut the wire insulation (but leave the wire uncut) 1/20 wavelength away (9.6 cm) from the bottom of the PVC pipe, again refer the figure above.
• Solder the center of the coax cable at the longest side of the slim jim (3/4 wavelength part) and the braid/shield at the shorted part of the antenna.
• Test the antenna using SWR meter to ensure that its SWR is at minimum or within acceptable level.
• There you go, you’ve build yourself your own 2 meter Omnidirectional Slim Jim antenna for less than USD2 (RM 6.00)

2 Meter Wire Slim Jim Antenna in action

Here’s how to make a simple 2 meter amateur radio antenna from ordinary tv antenna (Rabbit Ears Antenna).

For your information these antenna can be bought from local tv store at around RM4 a piece (less than USD2).

The best thing about these antenna that it has terminating point (screw) which you can screw in your coax cable to each dipole leg, as shown in the (rather blurry) photo.

After that, extend the telescoping element to the desired length to match your transmitting frequency.

Usually amateur radio operator working on 2 meter VHF would use antenna with vertical polarisation. In this case, you need to spread the dipole to vertical position like pictured above, connect it to your transceiver and be amaze by its transmitting (or receiving) power.

Main Advantage of This Antenna

1. Embarassingly easy to construct
2. Lightweight
3. Can be adjusted to any frequency, because of its adjustable telescopic element

As you can see, the rabbit ear tv antenna can also make a good antenna during emergency situation. Its adjustable telescopic elements made it easy to reconfigure the antenna to transmit on different frequencies.

ps : You can use this dipole calculator, if you unsure about the dipole length.