2m/70cm Dipole antenna


James Glenn Jr:

     Does anyone know how to make a dual band dipole antenna for 2m/70cm?

Dale Hunt:
There are many ways to do it.

First of all, a 2m dipole may have a low enough SWR
when used on 70cm that it will work as is.  The
radiation pattern may not be optimum, but it still may
be adequate for your needs.

Second, you can put dipoles for each band in parallel.
This is a standard method for the lower bands, and will
improve the pattern over that of just a 2m dipole.

You can do this by taking a length of 300 ohm twinlead
(something over 24" long) and cutting the wires and
insulation in the right places so that each half has
a quarter wave wire for each band, joined together
by the plastic dielectric where the wires are parallel.

Now, you can take that same structure made from twinlead
and connect the 70cm wires to the OPPOSITE side of the
feedline from the attached 2m wire.  If you can get
this to work (I haven't tried it myself yet) it should
give you standard dipole performance on 2m and a bit
of gain over a dipole on 70cm, with a cleaner pattern
than either of the other two options.

tom lish II:
take a piece of coax with one end that has a connector.  take the other end and strip off the outer plastic with out cutting the shield at a distance of a little more than 19 1/2 inches bare.. make a hole in the shield with a pen or something and pull the center conductor out from inside the shield.  cut these both to 19 1/2 inches from the point where they split. you tape the center to a window pointing  up, the shield pointing down and tape the coax going away from the center at a 90 degree angle (makes a sideways T on the window for repeater use) for at least 1/4 wave length ( 19 1/2 inches)

this is a half wave dipole for 2 meters and can also be mounted horizontal for ssb work and make a T from pvc pipe and mount it in there for a handy cheep outside antenna.

with a little luck and perhaps triming  a quarter inch or so from the ends it willl resonate on 440 mhz  also, I think on the 3rd harmonic.

basically a free antenna.

ya like that one, try this :

get a piece of cardboard and some metalic tape ( like they use on air conditioner ducts these days) or copper tape from a glass supply house.

tape a section 19 1/2 inches long to either side of center  in the middle of the cardboard. punch a hole and use a piece of coax here ( drop through the center to run at the 90 degree from the dipole )  and some aligator clips to connect to the dipole center.

now go up about 8 inches or so and put a 36 inch piece of tape  parallel to the dipole ( director), and go 8 inches behind and tape a 41 inch piece of foil tape  in parallel to the dipole (Reflector.).

thumbtack this to the end of a broom stick and run the coax down the broom handkle to your radio. ( or you can use the dipole you made above and some pieces of wire and do the same thing).

instant rotatable 2 meter antenna, you do the math for the one on 440  it is easy..

free antenna s for sale cheep..

73  tom N6AJR

Curt Milton:
There are numerous antennas you can build at these frequencies from common materials.  You did not mention the application - a few thoughts:

(1) handheld - keep antenna light weight, as a heavy antenna will damage how the the BNC connector is attached to the pc board.  same thought for feedlines - use a short piece of lightweight coax before transitioning to RG-58.

(2) mobile - challenge here is mechanical integrity.  unless you are a real good builder, use a commercial antenna.

(3) portable - if you are trying to use FM you really need vertical polarization.   a simple vertical can be made with heavy electrical wire and 2 radials - all attached to a connector.  for SSB you would want gain anyway - think quad or yagi.  

check arrl TIS pages for ideas.


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