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Problem with discontinuity in balun design at 45 MHz

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kocha

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I have made a balun for a dipole antenna 20-90MHz and I have a discontinuous in the middle frequency at 45MHz, the phase of the antenna is changing in 180 deg and then turn to normal after few MHz (10MHz).
Can anyone have any idea what could be the problem?

regard
 

Re: Balun design problem

need more details. What type of balun and antenna?
 

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    kocha

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Re: Balun design problem

Dipole antennas do not normally operate over two plus octaves. How big is your dipole?
 

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    kocha

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Re: Balun design problem

Azulykit said:
Dipole antennas do not normally operate over two plus octaves. How big is your dipole?
Click to expand...

The antenna is 1.5m long .
The balun is built on PCB with two ferrite core and a balanced resistor parallel to the antenna feed, at the feeding of the balun there is a serial ferrite (bead on lead) for impedance matching.
 

Re: Balun design problem

Several observations:

At 20 MHz you have a 15 meter wavelength. Your antenna is 1.5 meters long. It is electrically small.

I would be inclined to take a pair of your baluns and connect them back to back to see what the insertion loss (s21) is for the pair.

What gain value do you want? What do you expect?

Look carefully at the 180 degree phase step. Could it instead be 360 degrees? If so it is the result of a steep phase vs frequency change and just the result of the network analyzer displaying your phase mod 360 degrees. Just a thought.
 

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    kocha

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Re: Balun design problem

Azulykit thanks for your help so far :)


Look carefully at the 180 degree phase step. Could it instead be 360 degrees? If so it is the result of a steep phase vs frequency change and just the result of the network analyzer displaying your phase mod 360 degrees. Just a thought.[/quote]


what i mean is that the phase is change for about 200 deg slowly and not as a phase mod 360 degrees




what i have


thanks
 

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