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
(within
>>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,
>etc.
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
>>involve
>>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
>the
>>antenna resonance depends on its dimensions in terms of wavelengths or
>>fractions thereof.
>
>YES..YES...YES...YES
>
>>
>>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,
>
>YES..YES..YES..YES
>>
>>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.
>
>YES..YES..YES..YES
>>
>>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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