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[TenTec] "Tuning" antennas; baluns

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Subject: [TenTec] "Tuning" antennas; baluns
From: aa4lr@radio.org (Bill Coleman AA4LR)
Date: Tue, 23 Sep 97 22:14:37 -0400
On 9/23/97 4:35 PM, Chester Alderman at chestert@pressroom.com wrote:

>At 10:30 AM 9/23/97 CDT, you wrote:
>>Also, I thought a tuner would correct the L and C to obtain resonance 
>>reason) so you could resonate any object... screen door, gutters, long wire, 
>>etc.  Ok, I probably need to read more.
>I think everyone can find something that can WORK FOR THEM. However, as 
>Stuart explains, a tuner is not resonating the screen door, gutter, long 
>wire, etc., it is transforming the 'real' and 'imiginary' impedance 
>presented at the INPUT of your transmission line, to something that your 
>rig will tolerate.

It if transforms the impedance to something that is 50 ohms or so, then 
it WILL be resonant.

>Hopefully a resistive 50 ohms with no capacitative or 
>inductive reactance. A 'tuner' will do nothing to or for the screen door, 

The problem with a tuner-fed screen door, gutter or long wire (hey a long 
wire might not be bad) has nothing at all to do with whether it is 
"resonant" or not. It has to do with efficiency. A screen door or gutter 
probably has awful losses due to nearby objects. With a tuner, it will be 
just as resonant as a properly cut dipole. No difference.

Again, people are confusing antenna resonance with antenna efficiency. 
They are two very different animals.

>>- - - - - - - - - - - - - - Original Message - - - - - - - - - - - - - -
>>Hello all,
>>Now, to try to summarize a complex subject:
>>The concept of resonance, and tuning to resonance for an ANTENNA, must 
>>changing its Physical Dimensions.  Once you have cut it to some size, it will
>>have certain resonant properties.  No amount of "tuning" of L and C circuits
>>at the shack end of the transmission line will alter the resonant dimension 
>>of the antenna up in the air.  Tuning is defined as affecting resonance; and 
>>antenna resonance depends on its dimensions in terms of wavelengths or
>>fractions thereof. 
>>The only thing you are "tuning" in the Antenna Matching device is actually
>>"adjusting"  the values of the L and C of those tuned circuits.  However, you
>>are MATCHING the transmission line to the rig, 
>>In fact, I hope all will agree or will measure,  that even with an antenna
>>matching device, (which for years was mistakenly called a "tuner"), you still
>>have standing waves on the transmission line, and the matching device is just
>>there to TRANSFORM a complex impedance at the shack end of the line to a 
>>value that more closely matches your transmitter.
>>I hope this helps divide the concepts into their proper areas.  Antennas
>>resonate depending upon their physical structure and dimensions.
>>73, Stuart K5KVH
>I urge everyone who does not have a full understanding of antennas and 
>transmission lines and  tuners (or matching devices) to SAVE Stuarts 
>notes. In the most clear terms possible, Stuart has explained the 
>differences between the three and what you CAN do and what you CAN NOT do 
>with a tuner.

Except that Stuart is also confused about the distinction between 
resonance and efficiency.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Not in a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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