Here are the photos of my homebrew 2 meter VHF antennas. One is 6 element OWA yagi and another is a 2 meter Slim Jim for omnidirectional operation
The homebrew slim jim antenna was previously featured on my blog as well as its plan. The OWA Yagi 6 element antenna plan can be obtained from this post : 6 Element OWA Yagi Antenna for 2 Meter band plan
Here are some of the photos taken during Kota Setar Amateur Radio Club (Kelab Alor Setar) Family Day on 8 March 2008. Below are the repeater maintenance activity taken on top of Gunung Keriang Hill during that day.
Btw, the guy in the blue shirt maintaining the repeater is 9W2USF, Handle: Amiruddin.
Gunung Keriang Repeater Team
You can get the rest of the photos here – RGK Repeater Gunung Keriang Photos, all of the photos taken from 9W2DOT website
Here is a guide to modify your PC power supply unit to power up your mobile rig. If its done correctly you can have a cheap (regulated) VDC power supply solution for your mobile rig to operate at home.
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).
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.
Continue reading “How to turn PC Power Supply to power mobile rigs”
For those who are wondering, I am a licensed Amateur Radio operator and my callsign is 9W2WTF. I live in the northern part in Malaysia, in a town called Alor Setar.
As an amateur radio operator I usually monitor local repeater (145.525 MHz -0.600, tone: 103.5) and local simplex on 145.425 MHz mostly during night time.
I use an Icom v8 and Icom IC V8000 as my communication equipment. My hobby includes antenna homebrewing and finding the most energy efficient way to transmit as far as possible using the least power.
That’s all for now. Thanks for visiting. I can be reached at [email protected], or [email protected]
73 to all 🙂
Ever wonder how much power is loss in your coax cable feedline? Here is a website which helps you estimate power loss in your antenna feedline according to your choice of coax cable.
For example :
If you are transmitting on 145 MHz frequency with 65 Watt of power using 15 meter RG-58 cable, the maximum effective power radiated by your antenna is just about half of the transmitting power (36.156 MHz).
But when you switch to RG-8 cable, the loss would be significantly lower, and your antenna would radiate 54 Watt of power.
Since the power loss is significant, it is advisable that you consider the choice of your feedline before setting up your station. In emergency or QRP situation, every 1 Watt counts.
If you have no other choice other than to use RG-58 cable, it is advisable to put your antenna as high as possible with the shortest amount of cable possible. This will save your rig a lot of hard work, and may actually get your signal to travel further than before
How much power loss in your feedline ? Check it at Coax Cable and Line Loss Calculator website
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.
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″)
- 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
- 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
There are a lot of confusion rise from the term use to describe UHF connector, commonly associated with Amateur Radio rigs.
Actually both PL-259 and SO-239 are collectively known as UHF connector.
Pictured above is commonly called the UHF male connector. Usually come in two version, one for lighter cable like RG-58, and another for heavier braid coax RG-8, RG-213.
Also known as UHF female. If you bought a mobile or base amateur radio rig, yours are likely to have this kind of connector.
Both PL-259 connector and SO-239 fits together and is collectivly called the UHF type connection.
So hope that would clear up confusion associated with SO-239, PL-259 connector. Both of them are known as UHF connector but with different names for male/female jack. That’s all for today folks!
Due to the enourmous size of 3 element Yagi and the current working condition on 10/11 meter band, I decided to accept the advice of 9W2RZL and thinking of constructing a directional antenna right after I obtain the 11/10 meter rig (which is maybe around April).
Moxon antenna might suit my need as it is :
- has gain of around 5 dBi
- Compact and Light weight
- Easy to construct
- designed for 50 Ohm impedance
- Great F/B ratio, useful for blanking noise
Here is the plan for the 10 meter Moxon antenna, centered on 28.5 MHz frequency.
- A – 382.43 cm (150 1/2 inch)
- B – 57.13 cm (22 1/2 inch)
- C – 11.02 cm (4 3/8 inch)
- D – 71.06 cm (28 1/4 inch)
- E – 139.76 cm (55 inch)
These calculation are made for 12 gauge wire using L. B. Cebik Moxon Calculator tool. The Moxon on the above photo belong to Mark Rabel
Here is a 6 element yagi my friend and I have built for experimenting with directional antenna. Theoritically the antenna has about 10dBi gain in its main lobe and a good Front-to-Back ratio, a perfect substitute if you don’t have means to get the popular V24 Silverthunder antenna.
Radiation Pattern Lobes
Dimensions (in inches)
Element, Length, Space from Reflector
Reflector – 40.52, —-
Driver – 39.96, 10.13
Director 1 – 37.38, 14.32
Director 2 – 36.31 25.93
Director 3 – 36.31, 37.28
Director 4 – 34.96 , 54.22
Calculated Center of gravity 23.87 inches
Dimensions (in cm)
Element, Length, Space from Reflector
Reflector – 102.92, —-
Driver – 101.50, 25.73
Director 1 – 94.95, 36.37
Director 2 – 92.23, 65.86
Director 3 – 92.23, 94.69
Director 4 – 88.80 , 137.72
Calculated Center of gravity :60.66 cm
The plan for the antenna has been taken from LB Cebik website. More article will follow that covers our construction of this Yagi antenna along with our reports of its improvement.
The waiting is over for those who’s taken Malaysian Radio Amateur Examination (RAE) 2007-2. The examination result is now available on MCMC website : RAE 2007-2 Result or from local mirror – rae_2007_2_result.pdf
Congratulations to those who has passed the examination! See you on the air!