[Antennas] Hardline Questions

2003年10月28日 14:14:14 -0500

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" <[email protected]>
To: "Donald E. "Buck" Stiles" <[email protected]>
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
>>>