Dipole antennas and baluns

[Conrad Cardano]

Hi

I see with a half wave dipole, they use a 1:1 balun.

If I made a fullwave dipole, what balun should I use?

I am interested in 55.3 MHz for meteor detection.

Thank you for helping.

[Alex P]

A "Full Wavelength Dipole" = two half wavelength segments means you will be feeding at the max Z point ~ 2500 ohms.

SO, a 49:1 Z ratio = 7:1 Turns ratio on the matching transformer ( 'balun' )

Alex

[Conrad Cardano]

Thank you, Alex.

That’s helpful.

Conrad

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[Mike Otte]

Conrad,

Don't go there!

Make a halfwave dipole.   Don't use a  unun ,  extra stuff You don't need.

Impedance will be about 70 ohms which will match  TV coax .  RG-6  or RG-59

Formula is  for lengthen feet   =  468/ freq  in Mhz    so 468/ 55.3 =  8.46 ft  over all length when assembled, so make them longer to start

You are not transmitting so most any piece of plastic with holes in will hold together the junction of the coax and the wires.  The ends can be held with just strings.

Solder junctions would be nice junctions but i have done a lot with wire nuts.

1-2 meters off of the ground.

a  9.73 ft reflector wire  laying on the ground  beneath the dipole will increase your gain.

73

Mike w9ys

On Sat, Nov 15, 2025 at 8:48 AM Conrad Cardano <cardan...@gmail.com> wrote:

Thank you, Alex.

That’s helpful.

Conrad

On Saturday, November 15, 2025, 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

A "Full Wavelength Dipole" = two half wavelength segments means you will be feeding at the max Z point ~ 2500 ohms.

SO, a 49:1 Z ratio = 7:1 Turns ratio on the matching transformer ( 'balun' )

Alex

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[Conrad Cardano]

Thank you, Mike

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[Lester Veenstra]

Was not following the thread enough to catch the frequency, but a half wave dipole, or odd multiples, will gatch to 50 ohms at particular heights (details available) or more commonly when at the appropriate angle rather than a straight (180 deg)

Still is a bit” height above ground” dependent but in general a more reliable 50 ohms,

In HF up to 6m.  At VHF the Discone antenna is a variation on the angular dipole theme

 

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)

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