[Antennas] Hardline Questions

[Donald E. "Buck" Stiles]

Bob,

Regardless of all others factors, the transmitter is looking for a 50 ohm
load but the transmission line is 75 ohm.  It is impossible to achieve below
a 1.5:1 swr.  It may be higher, but never lower...

The may be insignificant at HF, but quite the opposite at VHF/UHF if you are
counting watts.

----- Original Message ----- 
From: "Robert Lay" <w9dmk@crosslink.net>
To: "Donald E. "Buck" Stiles" <n8csp@triton.net>
Sent: Tuesday, October 28, 2003 12:16 PM
Subject: Re: [Antennas] Hardline Questions


> Don't forget, Tim and Don, that the 1.5:1 mismatch may or may not occur.
> First of all, do you know what the antenna impedance is - maybe it's
closer
> to  75 ohms than it is to 50 ohms, in which case the VSWR would be closer
to
> 1:1.
>
> Furthermore, in a typical installation, there is at least 1.5:1 VSWR on
the
> transmission line - generally much higher. The fact that we put a tuner at
> the transmitter end to transform the impedance seen by the rig to 50 ohms
> (thus giving us the "perfect match" to the transmitter), does NOT change
the
> fact that the VSWR on the line has NOT changed at all. It is STILL
> determined by the line impedance and the antenna impedance.
>
> Bob Lay (W9DMK) in Dahlgren, VA
> http://www.qsl.net/w9dmk
>
>
>