On Thu, 11 Oct 2001 "Mike" <W4EF@dellroy.com> writes:
> Yes, of course, but switch over to a 50 ohm reference and then
> mover your 50 ohm VSWR meter along the length of the line.
> At 1/4 wavelength from the 35 ohm load, the 50 ohm VSWR will
> be 160/50 = 3.2:1. Move another 1/4 wavelength (total 1/2
> wavelength) from the load and the 50 ohm VSWR will be 50/35 =
> 1:43:1 VSWR.
HUH? Where did you get 160 Ohms?
The formula for a 1/4 WL transmissionline transformer is
Zin X Zout = Zo^2 (Zo squared)
Zout = Zo^2 / Zin = 50^2 / 35 = 2500 / 35 = 71.4 ohms
at 1/4 WL from the 35 ohm load for a 50 ohm cable.
SWR = 71.4 / 50 = 1.43, same as at the load, ignoring losses.
OH wait, I see, you are assuming a 75 ohm coax.
Then the IMPEDANCE 1/4 WL from the 35 ohm load is
160 ohms but the SWR = 160 /75 = 2.13, same as at
the load (75 / 35 = 2.14).
SWR is a function of the LOAD impedance AND the LINE
impedance. You can't just arbitrarily change the reference
impedance unless you also change the line impedance.
IF you placed a 50 ohm line after 1/4 WL of 75 ohm line
with a 35 ohm load, THEN the SWR in the 50 ohm line
would be 160 / 50 = 3.2 as you stated, but the SWR in
the 75 ohm line is still only 2.14
IF you place a 50 ohm line after 1WL of 75 ohm coax
the SWR = 50 / 35 = 1.4 in the 50 ohm line and is still
2.14 in the 75 ohm line.
Using a REFERENCE impedance that is different from
the LINE impedance is MEANINGLESS.
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Administrative requests: towertalk-REQUEST@contesting.com