A Quick and Simple 2 Meter Ground Plane Project!

If you are just getting experience in building antennas or you are an old pro,here is a simple and fun project! This antenna is perfect for those hams living in the primary coverage area of the repeater for 2 meter use. This antenna is nothing more than the old standby "Droopy Groundplane" and can be used on any band where it's physical size does not pose a problem. Remember that the vertical radiator is 1/4 wavelength long at your operating frequency.

It has no gain but makes an excellent small antenna that can be mounted just about anywhere and with a little planning, can be used mobile on a short mast from the bumper!! Adding a small attachment loop at the tip of the radiator will enable it to be suspended from above for inside use.

The vertical element and radials can be made of #12 copper wire or welding rods, coat hanger, etc. The vertical radiator (A) should be soldered to the center connector of the SO239.The four base radials (B & C) and (D & E) can be soldered or bolted to the SO239 mounting holes using 4-40 hardware. The four base radials then should be bent downward to a 45 degree angle.

The antenna can be mounted by clamping the PL259 to a mast or even passing the coax through a 3/4 ID PVC pipe and compression clamping the PL259. Either way let your creativity work for you. If you plan on mounting it outside,  apply RTV or sealant around the center pin and PL259, and TAPE WELL,  to keep water out of the coax.

Make each radial a 1/4 wave of your desired xmit frequency. Sometimes it helps to add a little extra length to the radials and radiator. This will give you some adjusting room when you adjust the SWR.(If adjustment is needed, clip all radials equally about 1/8 inch at a time while checking SWR, USING LOW POWER). Center the lowest swr on your transmit operating frequency.

Example Calculation:

Freq (mhz)       146
A (inches)         19 5/16 (Note "A" length is to the SO-239 insulator but not critical)

B THRU E (INCHES)   20 3/16

LENGTHS FROM FORMULA ( 234/FREQ MHZ) + 5 % LONGER FOR RADIALS
TRY ONE ON 440 or other bands USING SAME FORMULA AND CONSTRUCTION TECHNIQUES!

ENJOY AND EXPERIMENT!

DON'T TRY IT ON 75 METERS MOBILE......IT' A LITTLE LONG FOR MOST BRIDGES, OVERPASSES, POWER LINES ETC!!!!

simple antenna for 40 Meters

 

Making a simple antenna for 40 Meters is not very difficult. That is, if you have the space. A standard center fed dipole dipole for 40 Meters needs around 67 Feet of space. But, what if you only have space for a 20 Meter dipole, 33 Feet? If this is case, than you have several options.

1. You could just forget about 40 Meters and work the higher frequency bands, 20 Meters on up.

   What? And miss out on all the fun dodging the the short wave broadcasters in the evening.

2. You could create a Inverted-V type of antenna and raise the feedpoint on a mast.

   This is a possible alternative, but for this particular case, you would need a 28 Foot center mast and the apex angle would be less than optimum. This may cause some signal cancelation and give you a radiation pattern that you don't want.

3. You could shorten the dipole arms to fit the space and use a loading/matching coil in the center.

Item number 3 is what this page is about. Jact Sobel, W5VM (which is now assigned to Vernon Dyer), had at one time described a shortened dipole center fed with a loading/matching coil at the feed point. A drawing of which is below.

Initially, this seems to be a different approach than the shortened dipole designs, detailed on my Short Dipole page. But it's really not. If you tilt your head, and cross your eyes a little bit, you might start seeing it as two coils, very close together. In fact, the coils are so close to the center, that they touch..

Assuming that the two coils are an equal number of turns, and that the wires attached to each side are equal in length, the center of an antenna should be a zero current point. this makes a handy place to tie your coax shield. You could wrap several turns of wire around the coil in the center and feed it that way. But I couldn't begin to tell you how many turns to use or what the feed impedance would be. Each turn of the coil, as you move away from center, provides you with a different impedance and a possible match. By attaching the center of your coax to one of the coils turns, you should be able to find a good 50 Ohm feed point. This then gets around the balanced to unbalanced conversion effort (balun), that would be required and you were center feeding or link feeding..

Each element arm is 18 Feet 6 Inches (5.029 M) long. The loading/matching coils consists of 30 turns of 12 SWG enamelled copper wire wound on 2.5 inch (63.5 mm) diameter PVC tube 6 inches (152.4 mm) long. The winding pitch should be about 6 turns-per-inch (25.4 mm). Although the picture doesn't show it very well, the shield of the 50 coaxial cable is connected to the center of the coil. The coax center conductor is connected to a point 2 or 3 turns away from the center, to a point which gives the lowest SWR. This point may take some experimenting, depending on which section of the band you wish to operate in.

Making a slim jim

 

made one of thease on me foundation course thease are the smae plans we used.slim jim using both 300 and 450 Ohm Feeder and have found the 450 feeder to be easier to SWR..

TO swr the Slim jim simply hang the antenna in free space away from metal objects and make sure the Coax runs straight down below the antenna.Then simply move the feed point up or down slightly until best swr is achieved..
.

The slim jim is Basicaly a Half wave vertical with a quarter wave matching stub so you can calculatefor any band by simply working out a halve wave length for the Longestlenghth, 468/f in mhz,and for the quarter wave length 234/f in mhz and answers in feet.To match simply adjust the feed point as on the 2m version.also worth consideration is the J-POLE seen below

A Slim Jim for 4m

 

This antenna is made from a length of 300-ohm ribbon cable, which makes it easily portable, but you have to devise some method of suspending it!  The dimensions quoted in the diagram have been used successfully by some constructors, whilst others have found it to be off-frequency by a few megahertz. This may be due to a parasitic capacitance in the gap between the half-wave and quarter-wave sections, so be prepared to experiment a bit..

2 Meter Slim Jim antenna using 300 Ohm Twinlead

 

Due to popular searches, I’ve included a diagram to make a flexible slim jim antenna. This antenna is useful to increase the range of your portable radio or as a simple QRP mobile antenna for emergency situation.

In order to proceed with this project you need

• about 165 cm (64 inch) 300 Ohm twinlead cable
• RG-58 coax cable (RG-8, RG-213 might be too big for soldering), any length but keep it shorter than 7 meters for portable radio
• Soldering iron
• Wire cutter
• Connector to your Rig (usually BNC type or UHF Male)
• insulating tape

This is an ideal antenna for first timers to build. It is powerful yet simple to construct, once you get the hang of it you would certainly have no problem to construct other variants of Slim Jim antenna using different material.

This exercise would also prepare you in the world of Amateur Radio where real hams homebrew their own antennas.

Important Notes

• Make sure you solder the center conductor to the longest part of the antenna, and the outer conductor (braid) at the shorter side of the antenna
• If you use this on mobile rig, keep transmission power lower than 50watt to avoid the antenna from being burned away.
• Make sure the antenna is held straight for best transmission and reception. Best way to make sure of that is to hang the antenna at a higher place or strap it to PVC pipe or other non-conductive pole

Advantages of 300ohm Twinlead Slim Jim Antenna

1. Easy to construct
2. Has radiation angle almost parallel to the ground which makes your transmission goes farther than 5/8 or ground plane antennas
3. Wideband
4. Portable; Easy to carry, store and deployed
5. Can be use during emergency situation
6. Light and flexible

Moxon Antenna Plan for 27MHz CB and Freeband Operation

 

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

Hamradio Homebrew 2 Meter Square Dipole Plan

 

Here is a plan for homebrewing a 2 Meter Square Dipole plan. The advantage of this antenna is that it is unidirectional, and it takes less space than the regular 2 meter dipole. The calculation included on the diagram below is for building the antenna using copper tubing, you should use MMANA-GAL or other antenna simulation software to come up with new dimension for other materials (aluminium, wire, etc).

Click on the diagram to enlarge it. Hopefully this will help you in brewing new antennas! Original plan taken from KOFF website

VHF or UHF Yagi BALUN Calculator.

 

For the VHF/UHF frequencies, a 4:1 impedance ratio coaxial balun is normally used. Two sections of identical coaxial cable are needed. One section (A) has a convenient length to reach between the antenna and the transmitter.  Its characteristic impedance is Z.

The other section (B) is a half-wavelength long at the center of the frequency of interest.
The "physical" length is found from: 5904/F = L.  The complete formula is:
        L = 5904 * V/ F  in MHz
where;
L is the cable length, in inches F is the operating frequency, in megahertz
V is the velocity factor of the coaxial cable. 
The result is found by multiplying L by V.
To find the "Electrical" length, divide this result by F.
The velocity factors of common coaxial cables are shown in the following table.
Coaxial cable velocity factors
Regular polyethylene 0.66
Polyethylene foam 0.80
Teflon 0.72

Both radio signals and light travel almost 300,000,000 meters (186,363 miles) per second.

When designing a matching or phasing BALUN for a VHF or UHF Yagi, the quarter wave transformer is where these calculations will come to life.   Most coax cables we use in HAM radio have varying velocity factors (VF).  That is; RF signals travel at different speeds through these coaxial cables, depending on the cable type we use.   For example, the coax cable you are using has a velocity factor of .80%.  This indicates that the electrical length is actually 80 percent of of its "free space length".  When making a VHF or UHF BALUN or phasing transformer we must be sure we have included the velocity factor in our computations.

Slim Jim (J Integrated Match J-Pole)

 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

http://please.name.my/111/howto-2-meter-slim-jim-antenna-from-ordinary-wires.html

The 2 meter Omni Samurai Antenna

Homebrew 2 meter Amateur Radio Antenna from Ordinary TV Rabbit Ears antenna

 

Short on a good and reliable antenna for your amateur radio operation ?

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.

http://please.name.my/105/simple-2-meter-amateur-radio-antenna-from-ordinary-tv-rabbit-ears-antenna.html

A J-pole aerial for 50MHz

Figure   shows the aerial in its diagrammatic form. Notice that the aerial is in the form of an elongated letter ‘J’; this shape gives rise to its nickname – the J-pole. The quarter-wave
RF transformer is the lower ‘U’ section below the half-wave element. At the bottom of the U section, the impedance is zero (this may become clearer later) and at the top of the U section it is high, thus matching the aerial impedance. The coaxial feeder cable is connected part-way up the U section, where the impedance is around 50 .

 

A vertical aerial for 70 cm

The aerial element and the coil are made from a single piece of 1.5mm welding (brazing) rod, and the dimensions are given in Figure . Wind the coil around a 4mm rod or the shank of a twist drill. The lower end is filed to a point and then soldered into the centre conductor of a 4-hole panel- mounting BNC socket. (Try to obtain a good-quality BNC socket with
PTFE insulation – the insulation of cheaper sockets is easily damaged.) Trim the element to 427mm (top of element to top of coil) after the wire has been soldered to the socket.
The base coil causes the aerial to be rather  ‘whippy’, so a piece of 5mm plastic knitting needle can be cut to the length of the coil and then forced into it. The radials are made from four lengths of 3mm welding rod. These are bent and soldered into the four mounting holes of the socket, and then cut to the lengths shown in Figure .

The aerial is made waterproof by enclosing it in a 22mm diameter PVC waste water pipe. It is  ‘weldable’, and available at plumbers’ merchants, usually by the metre. A coupler is slotted to take the radials (Figure ). Filethe BNC socket as required, so that it slides inside the coupler until the radials poke out of the slots. Cut a length of plastic tubing which is 30mm longer than the aerial, and push it into the coupler. You will then need a plastic bung or screw-top to waterproof the top end.

Two & Six Meter Beam antenna

 

Four element, two meter beam, elements can be tubular aluminum, solid aluminum, or for low terrestrial noise, use fiberglass elements.  This beam may be installed vertical, or horizontal.For optimum performance and gain, feed with BUX COMM  "VBALUN."

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Four element, six meter beam, elements can be tubular aluminum, solid aluminum, or for less terrestrial noise, use fiberglass elements.  This beam may be installed vertical, or horizontal.

2M J Pole antenna

6 M Base station Di-pole antenna

tennas & Accessories

A Two-Band Fan Dipole

 

A two-band dipole can be constructed by connecting together the feed point two dipoles for even harmonically related bands. It is fed with 50-ohm coax with or without a balun. The best example of this is 80 and 40-meter dipoles connected together. Both dipoles are cut for half-wave resonance on each of the two bands. They are fed together and the ends of the wires are spread apart. If the ends are close together, there will be interaction between the dipoles. In such an antenna system, both dipoles must be carefully pruned for lowest SWR one band at a time. The lower band will be tuned first since the shorter dipole will not interact with the longer one. Each dipole has a low antenna resistance on the band for which it is resonant. RF energy follows the path of least resistance, and it automatically selects which dipole will receive power. The remaining antenna will have a high impedance. High impedance will block RF. Such an antenna will have a narrower bandwidth than a single band dipole, but close to the resonant frequency of each dipole, a tuner will not be needed. To connect many dipoles for multiple bands is possible, but it is not recommended because multiple wires are prone to interact and it will be impossible to achieve a low SWR on some bands. However, on the two band model, the 40-meter dipole will resonate close to 15 meters, the 80-meter dipole will resonate close to 10 meters, and working four bands with this set-up is possible. Some hams are using this antenna successfully with a tuner on all bands, although the signal on 20 meters suffers somewhat because of high SWR.

Figure - Two-Band Fan Dipole for 40 and 75 Meters

The Double Bazooka Dipole

 

The double bazooka is claimed by its users to be broad-banded, a quality especially interesting for those hams operating on 75/80 meters. Tests done at the A.R.R.L. have shown the double bazooka is only slightly more broad-banded than a regular dipole, probably due to the use of a large conductor (coax) for the center part of the antenna. The double bazooka will not transmit its second harmonic, and its users say it does not need a balun. Other users say it is quieter than a regular dipole.

The center of the antenna is made from RG-58 coax. To find the length of coax needed, divide 325 by the frequency in MHz. The coax forms the center part of the double bazooka and a piece of number 12 wire on each end completes the antenna. The length of each of the end wires is found by dividing 67.5 by the frequency in MHz. To increase the bandwidth some builders use shorted ladder-line in place of the number 12 wire, which makes the end pieces to be electrically larger.

The feed-point of the double bazooka is unique. At the center of the coax dipole, remove about 3 inches of the plastic covering, exposing the shield. Cut the shield in the center and separate it into two parts. Do not cut the dielectric or the center conductor. Leave the center conductor with its insulation exposed. On the feed-line strip off about 3 inches of outer insulation, separate the shield from the center conductor, and strip about 1 inches of the insulation from the center conductor. To attach the feed-line, solder the two exposed feed-line conductors to the two pieces of the separated exposed shield of the dipole center. It goes without saying: seal the feed-point to prevent water from getting in. At each of the two ends of the coax forming the center of the antenna, the coax is stripped back and the center conductor and shield are shorted together and soldered. The end wires are soldered to the shorted coax ends, run to insulators at the end of the antenna, and the soldered joints are sealed against the weather.

New Carolina Windom Antenna

Windom design for 40m 20m 15m and 10m by K4IWL
http://www.hamuniverse.com/k4iwlnewwindom.html

A simple 6m beam

 

The beam is shown in Figure . The driven element is the one whose centre is fed by the coaxial cable, and lies between the two insulators marked A and the feedpoint at B. The reflector is also anchored at the points A, and lies over the upper half of the frame.

 

The wooden centrepiece is used to support the cross-pieces and to mount the aerial on the mast, using a common shelf bracket. The cross-pieces, known as spreaders, can be wooden canes or dowelling, and are mounted to the centrepiece using cable clips and adhesive. Figure  shows how this is done.

If the aerial is to be a permanent installation, the spreaders should be weatherproofed using a good-quality exterior varnish. The wire elements are PVC covered and fed through holes in the spreaders