LET'S GET STARTED
Now you've probably heard of a beam antenna, and maybe you've heard of a J-Pole.
But what's a J BEAM?
It's a vertical directional antenna made of 1/2 inch copper pipe and wood or PVC.
It uses a standard J-pole antenna as the driven element and center support, with two parasitic elements-----a reflector and a director, to provide directivity and gain. See J Beam pattern below. It can be built for around RM25.00 and you can use your old Jpole as a basis for the JBeam. You'll probably need to shorten the main 1/2 wave element by 1 to 2 inches, as the reflector and director tend to couple and lower the resonance of your original jpole toward the lower part of the band. See formulas for cutting to your desired frequency of operation or band . A small amount of trimming on the tip of the main active 1/2 wave element may be needed to get the SWR as low as possible. You shouldn't have to adjust the 1/4 wave matching stub, as this is not strongly affected by the parasitic elements.
Design Details and Drawbacks
The element lengths and spacings are a combination of info from the ARRL Antenna Book section on 2 meter Yagi antennas, and from experiments with a field strength meter and different length elements and spacings.
The reflector and director element spacings are equal at 16 inches. Slightly higher gain with reflector spacing at 18 inches from driven element and director spacing of 14 inches can be had but the antenna may tend to lean with unequal spacings if strong mast mounting is not used.
The bandwidth is not as wide as that of the standard jpole by itself. The SWR tends to rise faster toward the ends of the band, but you get an estimated 7dB
gain and 20 dB F/B (front to back ratio).
High wind loading could potentiallly break off the jBeam at the bottom joint
since the entire structure is supported by that point. You may want to reinforce
The lengths used in these plans are for the upper part of 2 meters and you can use the formulas to design it for your frequency.
1/2 inch copper pipe is used for all elements and standard soldering made with a small blowtorch. A soldering iron is just not hot enough!
Longest element = 58 1/2 inches (add about 2 feet for mast mounting) matching 1/4 wave stub = 20 1/4 inches
(position matching stub toward director for a bit of added gain reflector -
director = 32 inches
stub and main element spacing = 3 inches
coax feed point = 3 to 5 inches from bottom
(use hose clamps for feed point coax attachment connections for easy repair/adjustment)
Center boom is 1/2 inch by 1-inch wood or PVC and about 36 inches long
Measurements should be made as close as possible but are not extremly critical!
Element to boom mounting variations depend on your particular situation and construction materials at hand but insure that element centers are at center of boom Use your own imagination! (see pics for better details)
"One fellow built one with five elements-----just cutting the extra directors shorter by eye-----and was able to work a repeater 35 miles away, with a 5-watt HT holding the antenna, from a valley that's hard to get out of with 50 watts and an omnidirectional antenna at 30 feet!"
J Pole Long element (in Inches) = 8568 / F mhz
J pole Stub (in inches) = 2952 / F in mhz
Reflector (in inches) = 5880 / F in mhz
Director (in inches) = 4704 / F in mhz
Spacing (in inches) = 2352 / F in mhz
Some examples for other bands:
REF : 26.52"
"A PICTURE IS WORTH A THOUSAND WORDS"
Here are two thousand words!
driven element about 2 feet longer at bottom for mast mounting.
Center conductor of coax to longest element, shield to shortest
k-RAMAT atau Koperasi Radio Amatur Malaysia ditubuhkan atas dasar untuk membina satu rangkaian komprehensif peminat radio amatur yang telah sedia ada di Malaysia ini. k-RAMAT juga berfungsi untuk memberi kebajikan kepada semua ahli dalam pelbagai bentuk kelebihan yang akan ditawarkan oleh koperasi k-RAMAT ini. Buat sementara waktu k-RAMAT ini beroperasi di No.22, Jalan BP6/12, Bandar Bukit Puchong, 47100 Puchong, Selangor. Tel: 03-80623370 Fax: 03-80623372. Emel address firstname.lastname@example.org
Maklumat Lanjut ====>> k-RAMAT ( KOPERASI RADIO AMATUR MALAYSIA)
Assalamualaikum & Salam Sejahtera,
Keputusan RAE 2008-2 telah pun dikeluarkan oleh pihak MCMC.
Syabas dan tahniah kepada semua yang telah berjaya, dan jangan berputus-asa kepada yang telah gagal dan cuba lagi di masa depan.
Keputusan boleh dilihat disini
RAE 2008-1 (Result)
Perkara-perkara yang perlu dilakukan setelah lulus RAE
1. Tunggu surat pengesahan lulus daripada MCMC
2. Isi Surat Permohonan Callsign
3. Isi Borang permohonan Apparatus Assignment (A.A)
4. Isi Surat Sokongan 9M2
5. Isi Surat Akuan Sumpah
Dan serahkan pada Pejabat MCMC/SKMM yang berhampiran bersama
RM60.00 (yuran pemprosesan)
RM24.00 untuk setahun (maks 5 tahun shj)
An interface unit allows one to transmit and receive digital modes using a computer sound card. Conveniently, the interfaces below were designed to operate without an external power supply, so before rushing out and spending a fortune on a commercial interface with features you will probably never need or use, consider building your own! I have included here some simple designs that I have built, tested and which work very well considering their simplicity and economy. These circuits will perform well if you intend to run an Internet gateway using the eQSO or EchoLink software. Parts for these circuits (or complete kits) can be obtained from www.modecomponents.co
(1) SIMPLE INTERFACE
This circuit, based on parts typically found in any amateur's "junk box" is an extremely cost effective solution. In this circuit, RTS (the "ready to send" line on the computer) drives an open collector for the PTT. Any general NPN transistor can be used instead of the BC108. It is very similar to the isolated circuit (below), except it does not use audio transformers or the optocoupler, but performs splendidly. (Of course, if you just happen to have a couple of audio transformers, you could add them to this circuit in the same position as in the isolated circuit).
1 x 1k ¼ watt resistors - 2 x 2.2k ¼ watt resistors
1 x 1k Potentiometer Lin - 1 x 2.2uF 50v capacitor - 4 x 0.01uF capacitors
1 x Red LED (High sensitivity type) - 2 x Diode 1N4148 - 2 x 3.5mm Stereo plugs
1 x BC108 Transistor - 1 x 9 Pin D plug ( Com port 1 or 2) & cover
Screened cable - Project Box
(2) ISOLATED INTERFACE
This circuit incorporates two 600-ohm audio transformers (T1 & T2) and an RS232 powered optocoupler IC1. Preferably use an IC socket for IC1, for possible quick replacement! The purpose of the transformers and an optocoupler is to isolate the transceiver from the computer, keeping the interference from the PC to a minimum. Ensure that the screening on the radio and the screening on the PC are not connected together.
Stereo 3.5 mm plugs connect the line in and out on the computer soundcard. Use the tip and earth only as in this application the sleeve is not used.
To control the radio PTT, an isolated signal from the computers RS232 (RTS) line is used. If you have an available DB9 connector on your computer, use RTS (Pin 7) and ground (Pin 5). If you have a DB25 connector on your computer, use RTS (Pin 4) and ground (pin 7).
VR1 is a 1K linear potentiometer used to control the amount of audio going to the MIC and is adjusted for correct audio drive to the radio, usually converting line (0.5v) to MIC (10mV) levels. The 1.2k resistor (from the Line Out) can be changed to a greater value if you are troubled by the pot always being at the bottom or top of the range or alternately by adjusting the computers audio out slider till the correct level is achieved. Operationally, audio levels are adjusted by the computer level controls or are incorporated in the software you will be using.
The LED (high sensitivity type) is used as an indicator when the interface is in the transmit mode.
It is suggested that the finished interface is put in a metal box and that the grounding is taken from the radio side of the circuit.
3 x 1k ¼ watt resistors - 1 x 1.2k ¼ watt resistors
1 x 1k Potentiometer (lin) – 1 x 2.2uF 50v capacitor - 3 x 0.01uF capacitors
2 x (T1 & T2) 600 ohm transformers type 9000 RS Number 208-822
1 x IC1 optocoupler 4N25 RS Number 597-289
1 x Red LED (High sensitivity type) - 1 x Diode 1N4148 - 2 x 3.5mm Stereo plugs
1 x 9 Pin D plug ( Com port 1 or 2) & cover
Screened cable - Project Box
(3) INTERFACE FOR TWO TRANSCEIVERS.
The circuit below, a special version of the Isolated Interface, allows gateway operators to run 2 eQSO Internet Gateways (say one on 2m and another on 70cm) without the need for two callsigns and wasting server bandwidth
from an article by Peter, G4KQU, with his kind permission.