Impedance also has a reactance component. A 2:1 SWR could be a 25 ohm 0
reactance load or a 100 ohm zero reactance load as you state. But there are
also an infinite number of values of real and reactive values that can give
a 2:1 SWR. Impedance is R + jX where R is the real part of the impedance
and X is the reactive part of the impedance. So it is not as simple as it
sounds.
Carl Moreschi N4PY
121 Little Bell Dr
Hays, NC 28635
www.n4py.com
 Original Message 
From: "dbp tds.net" <dbp@tds.net>
To: <tentec@contesting.com>
Sent: Saturday, January 08, 2011 11:37 AM
Subject: [TenTec] TT Eagle tuner spec: SWR v. impedance range?
> Hi
>
> I do not believe that "there is no such thing as a stupid question. You be
> the judge:
>
> The Eagle spec sheet for the antenna tuner says: "Matching impedance
> range:
> 10:1 SWR typical".
>
> Impedance is measured in Ohms, (Z). Impedance is not a ratio, its'
> associated SWR is a ratio. I think this spec would make more initial sense
> if it read from like "10 Ohms to 1500 Ohm's". That to me is an impedance
> range.
>
> What does a 10:1 SWR actually mean? A 50 Ohm dummy load gives a 1:1 SWR;
> and a 100 Ohm load gives a 2:1 SWR as does a 25 Ohms give a 2:1 SWR, 12.5
> Ohms is a 4:1 ratio. 200 Ohms is 4:1, 400 Ohms then gives an 8:1 SWR. That
> is considering the designed output Impedance of the transmitter is 50
> Ohm's. (Back when a TX ouput was designed for 75 Ohm's then a 75 Ohm
> antenna
> yielded a 1:1 SWR).
>
> So, should I assume (hate that word) that the Eagle tuner "Matching
> impedance range: 10:1 SWR typical" could mean a tuning Impedance range
> from
> 25 to 400 Ohm's? If that is the case, I want an external tuner that will
> match maybe from 10 to 1500 Ohm's I*mpedance to use with the short whip
> (LoZ) or end fed longwire (HiZ) antenna. Just thinking of easy antennas to
> throw up in a portable situation.*
>
> *What say you?*
>
> *73 de dave in NH*
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