Antenna tuning

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Antenna tuning

Post by KK4NPS » Sat Nov 10, 2018 8:10 pm

If a antenna is not efficient,
these are made-up numbers, R=37 O=25 and phase angle is 28 and these numbers can be tuned to R=50 O=0 and phase angle is also 0 with a tuner
is the antenna then efficient? I have asked several hams and received a equal number of yes and no answers. My thoughts are that the antenna
would still be inefficient but the tuner will present a tuned antenna to the transceiver only.

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Re: Antenna tuning

Post by k9yli » Mon Nov 12, 2018 3:42 pm

An antenna tuner,, technically a transmitter matching device, just makes the near end of the coax or feeder, appear to the radio output as close to 50 ohms . It does nothing to the antenna. If the antenna is way out of resonance for the frequency desired then its still just an atenuator, no matter what the radio thinks it sees on the input of the 'tuner'
If the antenna is to be somewhat efficient, it must be physically adjusted in length ,etc to match the required frequency.

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Re: Antenna tuning

Post by ku3x » Tue Nov 13, 2018 12:38 pm

You are getting yes and no answers? Oh My !
You can take it to the bank that what K9YLI just told you is spot on !

A tuner is nothing more than a coupling device. An antenna is either efficient or not efficient. If it's not resonant, tune or trim the, "ANTENNA" until
it is matched ( J = 0 ) and then it will be efficient. If you would be using a delta loop and the feed point impedance is 200 ohms and J=0, then the antenna is efficient and you'll need to install a 4 to 1 current balun at the feed point. Even though the antenna is 200 ohms, it is resonant and it is efficient. You are not effecting the efficiency by installing a 4 to 1 balun, you are just making it so you can feed the antenna with 50 ohm coax.

Barry, KU3X

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