Welcome to the G6OHM Website

Antenna Designs

 As some of you have gathered i love building antenna's.

The antenna's shown below have been built be me at some time or other.

Like all antenna's they work better if they are mounted high up and in the clear.

They will work in confined spaces or twisted and bent to fit. Sometimes antenna's have to be adjusted to work in

different locations.

What antenna works in one place does not mean it will work well in another.

So don't moan at me because the antenna you have just built does not perform as it should.

The VK2ZOI Flower Pot Antenna !



 VK2ZOI gave a talk I gave at a Hornsby and Districts Amateur Radio Club (HADARC) meeting in early 1993, He (lightheartedly) showed that by placing plastic flowers over this antenna, you can effectively disguise it. This could be particularly helpful if you lived in a mobile home and did not want your neighbours to realise you had a transmitting antenna. Other suggestions were made at the time included making a fake patio umbrella but the name “Flower Pot” has stuck for the last 14 or so years.

 

I have made quite a few of these antennas and they work very well.

The flowerpot works well as a scanner antenna for VHF and UHF  listening.

Like most antennas mount the flowerpot high and clear they work well.

 

My father Les G6SXB uses one when he goes caravaning so here it is the :

 

 

 2m and 70cm FlowerPot Antenna

 

Note size of tube and turns on choke altered to uk tube size

 

                      Someone asked me how much power the Flowerpot will take.

                          My father has run one using 100w on 2m with no problems.

 

                                                             
     

                    My version of the flowerpot sorry for the bad picture the antenna looks bent !

 

 

   

                                   

  Me doing a talk about the flowerpot antennas and halfwave endfeds at Huntingdon Radio Club

                                                       

 

                                               

     My Flowerpot antenna in action in North Wales. I use a 10m telescopic fishing pole to support the antenna.

 

 

         Here's an idea if you cannot get any antennas outside or live in sheltered accommodation. 

                                 

                    

 

 

 

 On the VK2ZOI site ( link below) there is more information on a high gain version of the flowerpot antenna.

Link to VK2ZOI Website

 

                                        

                        David G6ENN operating portable with a flowerpot antenna in the Lake District.
                                               Picture taken by Susan Gordon ( Davids wife )
 
 
    David G6ENN enjoys cycling so decided to try push bike mobile with a Flower Pot Antenna .
               
 
                 
                         
 
 
 
         6m Flower Pot Antenna
 
 
 
                  
David G6ENN has been busy building a 6m Half Wave Endfed. The picture above is Davids  Static  mobile setup.
First results encouraging with David working  through GB3UM and hearing the Beacon GB3BAA on 50.016 MHZ.
 
 
 
Here at 6ohm i use a coax halfwave endfed on 6m . All i did was to wind the choke around a piece of 40mm waste pipe. I then strung  it up horizontal in the roof space.
I have worked a fair amount of DX using this setup. I run about 50w with this antenna with no problems.
 
                                    
 
 
 
 
 
 
                   4m Coax End Fed Antenna
 
 
      
 
The 4m flowerpot is made with 32mm solvent weld tube.I had problems getting VSWR correct.So slid 41mm tube over the 32mm. Rechecked VSWR now ok @70mhz 1:1 @ 70.500  1:6:1 with 8 turns on the choke coil.Might try pulling the choke coil apart this can help broaden the bandwidth.
 
     

Antenna Hoist Idea if you have Problem Neighbours

Here at 6OHM i am very lucky i have good neighbours as regarding putting up antennas.

I am often playing with antenna's so they think i am mad anyway !.

When dad and myself did some work on my antennas we put up this system. So i could play with 

antenna designs.

The idea is to screw in an eyelet into the Fascia board. Run a long piece of nylon rope through the eyelet.

Run your coax to the spot where you want to play with antennas. Allow plenty of spare coax .

Tie your insulator or antenna to the rope and hoist it up.

When finished drop it down. The neighbours can't moan as it is not up for long. Good eh !

 

  

The antenna in the main picture is a 6m Half Wave endfed.I intend to make one for 6m ,4m, 10m, 20m.

HF Coax Endfed Antenna

              The Choke Balun needs to be wound on a former of 6inches or 150mm aprox

Alternatively you can wind the coax onto itself 6inches diameter.

 

Breaking News

I have just made a coax endfed for 10m band. I made the antenna resonant at 29mhz and it works upto 29.600 mhz for the 10fm repeaters and also works ok at 28.500mhz SSB end.


 

 

GM0ONX Inverted L Antenna

I have never been a big HF operator but i do enjoy the odd QSO on 160m,80m,40m,10m.

My first antenna for HF was a nest of dipoles for 40,20,15,10m.

My garden is not very big so a 160m,80m dipole was out.

I came across a design in PW written by GM0ONX.

I talked to my dad Les about the design. ( By the way dads callsign is G6SXB )

Out came the tape measure and we worked out i could shoehorn in a 160m-10m inverted L antenna. 

 

  Here at G6OHM the vertical section is 16ft high and the vertical leg runs 45 deg sideways  to get the antenna into the garden.The rest of the length is horizontal.  

My Inverted L also goes over the roof as in the picture .

 

Ensure when the trap is completed it is watertight. Do not use silicone mastic that has a vinegar smell to it as it will corrode brade and solder joints.

               

 

Link to GM0ONX Site

 

 Earthing & Counterpoise

HF Dipole Antennas

The one of the simplest antennas to make for HF is the dipole antenna.

Take a look at the first drawing.

 To work out the length of a dipole use the calculation 468 divided by the frequency.

This will give you the total length of your dipole.

It is best to cut the antenna for the center of the band in question.

 

Before i put up the Inverted L antenna i used a nest of dipoles .

You can add different lengths  of wire to make a nest of dipoles to be able to  transmit on different bands.

                                     

 

 The A element is for 40 meters (and 15 as the third harmonic), while the B element is cut for and works fine on 20 meters.  The overall  height is about 24 feet.  The spacing between elements is 4 inches.  Element lengths were calculated using the formula 468/F(Mhz) and cut several inches long for any needed adjustment after the antenna was erected.

 

Further dipoles can be added underneath B  to work on 10m and 6m.Just add extra insulated spacers.

 

 For insulators go to your local pound shop and buy nylon chopping board.

Or nick one out of the kitchen !

The insulators can be around 4" x 1 " wide or if you are metric  100mm x 25mm.

Drill a hole each end , one end to tie rope through, the other end your antenna.

 

Next it is a good idea to use a 1:1 balun at the feed point.

The reason for the balun is to stop feeder radiation running down the outside of the coax causing interference to TV or radio.

A simple balun can be made.( See the next section )

 

 

 

70cm Double Quad Beam also known as a Bowtie Beam

  

                      

 

 

 

 

 With adjustment the Double Quad will work well at 446mhz.

If anyone has built a Double Quad antenna send me a picture !

 

I have been sent a picture by my friend Roy M6CKI who has built one of my double Quads and uses it in his upstairs flat.

Roy informs me using a Baofeng UV-5R and 5w he can open repeaters 40 plus miles away. 

                                            

 

 I have also been sent a picture of a double Quad beam being used on 446 mhz. Sorry forgot the

 persons name or handle !

 

                                           

 

 

                                    

            I have been sent a picture of a Double Quad made by Fred M6FCC . Nice one Fred

Trap Dipoles

                    

 

 

 

 Making Antenna Traps

                

 

                                            Coax Traps

 

                  

                                          Traps are wound on 40mm white waste pipe

 

   Consider these figures above as approximate only. Some playing with the turns of the coax may be needed.

TO check the trap for resonance either use a GDO ( Grid Dip Oscillator ) ) or an MFJ Analyzer.

If you are unsure how to do this take a look at the link below.

 

How to Check Traps with an MFJ

 

 

                              

 

                                                


 

              

                              

CJU & IOIO Antenna

While surfing the net for info on Satellite antenna's came across these design. 

The antenna's were designed by EA4CYQ and all the credit goes to him for the designs.

So i made a CJU to see how well it worked. I have to say i was impressed.

I found the 70cm CJU or IO works well on 446mhz as well.

So would be useful for hilltop working or even a simple beam for a roof space.

If you only want a 2m IO antenna just use the dimensions for VHF .

 

 Link to IOIO Antenna design

 Link to CJU Antenna

 

                              

 

6m 2 Element Tape Measure Antenna

NOTE:   ON DIPOLE CONNECTIONS CLEAN PAINT OFF  WHERE BOLTS GO THROUGH TAPE.

ANTRON A99 OR IMAX 2000 CB VERTICAL

This is not another antenna project.

For the last  few years i have been using a Antron A99.

I have been very surprised how good the antenna works between 14mhz to 29.7 mhz.                                           

The Antron is mounted 8 ft off the ground which is about a quarter wave length at 28.500mhz.

I set the ringlets to about three quarters of the way up the threaded section.

The next section is important if you want to cover various bands.

You need to make a choke balun out of your coax that's connected to your Antron A99.

The balun needs to be 8 inches diameter and 12 turns. Cable tie or tape the balun into a tidy loop.                

               

Keep the length from the wound choke balun to the PL259 as short as possible.

With 12 turns i have found the Antron to be a good match between 29.7mhz to 18.150mhz.

On 14mhz i have to use my Kenwood AT-230 ATU to match. With out the ATU i have found VSWR to be 2.0

So before you new licensee's go taking down your Antron A99 CB antenna. Try out winding a balun and give it a

try on the higher amateur bands . You may be surprised at the results.

 

 

Magnetic Loop Antenna

 

I have played around with Magnetic Loop Antenna's on and off for a few years.

The design came from G3YCC so credit goes to him.

The loop is useable between 7mhz to 21mhz.

                          

The diameter of the loop is 1m.

I made mine from some old LDF-250 Heliax, but can be made from RG-213 Coax or 10mm Microbore tube.

 The inner of the SO239 forms a gamma match to the tube, about 9 inches from the earthy connection.I used a crocodile clip on the end This is adjusted for minimum SWR. As show, the loop can be mounted on a wooden support and is fed with 50 ohm coax.

You will need a capacitor of around 200 pf. One of the old type used in wartime radio's.

Please do not think to use one of the plastic type polycon types.

The spacing of the vanes is important. The wider the spacing the more power you can run through the magnetic

Loop Antenna.

DANGER ! It should be noted that there are high voltages  present across the gap of the loop and Capacitor.  Even at QRP levels can be dangerous. Certainly with higher powers, this situation can be LETHAL.      I would  not recommend the use of the loop near where you operate. QRP levels can produce dangerous amounts of RF . Suffice it to say that I know of one local who did use a mag loop indoors and wondered why the paint next to the loop was bubbling (!) Also if sitting close can make your skin tingle like sun burn.

Please make sure no-one can touch the magnetic loop while you are transmitting. RF burns take a long time to heal. I know from experience ! YOU HAVE BEEN WARNED

 Having said all that if used correctly magnetic loops are a useful antenna if you live in a flat and can't get an HF antenna outside. My mate Roy M6CKI uses one in his flat and it works great for him.   

           

Please note magnetic loops have to be returned every time you move frequency as the loop has what is called a High Q

 

.

I have been busy building a magnetic loop for portable work. Covers 7mhz,10mhz,14mhz

See pictures.

 

                                              

 

 

 

 

 6m Delta Loop

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