I’ve been searching for information regarding the radiation angle and the gain of slim jim antenna, but found none of it. So I decided to build the model of the antenna inside the ever useful MMANA-GAL software to get the information I needed myself.

From what I can surmise, the slim jim has a slightly lower radiation angle than vertical dipole antenna and is easier to mount, thus it is suitable to use for point-to-point communication VHF-UHF operation. It has a gain of about 2.8dBi-3.2dBi in free space and 4.8-5.8dBi when mounted at about 30feet from the ground. Here’s the result of MMANA-GAL :

Tags: Add new tag, amateur radio, antenna, Ham Radio, hamradio, homebrew, slim jim, slimjim

Here’s another 11 meter Moxon Antenna plan suitable for 27MHz CB, Freeband and lower 28MHz Amateur Radio operation band.

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

Tags: 10 meter, amateur, amateur radio, antenna, diy, hf, hobby, homebrew, moxon, moxon antenna

I think many of you might have heard about this particular 2 meter VHF antenna. Called
“Antenna ASTRA” which derived from the name of one of the most popular Amateur Radio Society in Malaysia.

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

KakiBiawak @ Astra Antenna in action

Tags: antenna, astra, diy, homebrew, malaysia, marts

Watch this video for ideas to homebrew Morse Keyer for CW operation.

Tags: cw, diy, electronics, homebrew, morse, morse keyer

Here are few photos that 9W2AZV and I have taken during the course of building our 6 element OWA yagi with 10dbi gain.

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 :

‘ Read the rest of this entry »

Tags: amateur radio, diy, hamradio, homebrew, photos, radio, tutorial, yagi

I never built 5/8 antenna, commonly used by mobile station. However, I found a good plan which you may use to homebrew a mobile antenna yourself. The plan is usable for constructing antenna for HT too :

Full article – : Homebrew 5/8 Mobile Antenna

Tags: amateur radio, diy, homebrew, mobile

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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.

Tags: amateur radio, cw, diy, hamradio, homebrew, morse, morse code

As promised in the previous post,Simple Morse Practice Oscillator Circuit has been completed. Sorry, I cant do anything much with the photo quality as it was taken using my stupid mobile phone.

I promise to include a Youtube video demonstrating its sound and operation. Next, I need to get a decent casing and some cheap morse keyer to go with this oscillator. I might be planning to make one that could interface with CWirc too.

Tags: amateur radio, cw, hamradio, homebrew, morse, morse code

This will be my next homebrew project, a morse practice oscillator circuit. 9W2AZV and I are going to build this as we are preparing ourselves to perfect our Morse code sending/receiving skills.

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!

Tags: amateur radio, cw, diy, hamradio, homebrew, malaysia, morse, morse code

Slim Jim (J Integrated Match J-Pole) is probably the most easiest and powerful 2 meter antenna to build provided you have the exact measurement and material to build it.

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

Tags: antenna, diy, Hobbies, hobby, homebrew, slim jim, slimjim