LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #23   Report Post  
Old August 16th 04, 12:06 AM
Roy Lewallen
 
Posts: n/a
Default

Jerry Martes wrote:

I'd submit that, in a practical situation, the mismatch of an antenna for
receiving can be as high as 2:1 or even 3:1 without degrading the strength
of the received signal when the transmission line losses are low. I
thought that, if the receiver is tuneable, the actual impedance the
transmission line presents to the receiver can be 'accounted for. I
thought that, for a given antenna and transmission line, the effects of VSWR
are less important that for delivering power by a transmitter.
Am I wrong when I consider VSWR to be less important for receivers than
for transmitters?

Jerry


It sounds like you (and some other posters) might be confusing the
transmission line SWR with the impedance seen by the
transmitter/receiver, which is often indicated with an SWR meter. The
two aren't the same.

Consider, for example, a 50 ohm antenna and 50 ohm tx/rx, with a 300 ohm
half wavelength transmission line connecting the two. The antenna sees a
perfect match (50 ohms) when receiving, and the transmitter sees a
perfect match (50 ohms) when transmitting. The transmission line SWR is
6:1 when transmitting and receiving. On the other hand, if the antenna
and transmission line are both 300 ohms (+ j0), the line SWR will be 1:1
when transmitting, 6:1 when receiving. And so forth.

The effects of impedance mismatch seen by the transmitter when
transmitting, the impedance mismatch seen by the antenna when receiving,
and the transmission line SWR are three separate issues. Each has its
own effect on system performance, and each needs to be treated
separately. The importance of one or the other depends on the individual
situation.

Roy Lewallen, W7EL
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Inverted ground plane antenna: compared with normal GP and low dipole. Serge Stroobandt, ON4BAA Antenna 8 February 24th 11 10:22 PM
Mobile Ant L match ? Henry Kolesnik Antenna 14 January 20th 04 04:08 AM
Poor quality low + High TV channels? How much dB in Preamp? lbbs Antenna 16 December 13th 03 03:01 PM
QST Article: An Easy to Build, Dual-Band Collinear Antenna Serge Stroobandt, ON4BAA Antenna 12 October 16th 03 07:44 PM


All times are GMT +1. The time now is 04:43 AM.

Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004-2025 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017