LinkBack Thread Tools Search this Thread Display Modes
Prev Previous Post   Next Post Next
  #1   Report Post  
Old June 2nd 11, 10:49 PM posted to rec.radio.amateur.homebrew
external usenet poster
 
First recorded activity by RadioBanter: Dec 2007
Posts: 133
Default Killing an RF amp with high VSWR: ZlZ0 vs. ZlZ0?

Something I've wondered for awhile now is this: Since you get the same VSWR
with a load both higher than or lower than your "expected" load (we'll call
this Z0, and the actual load Zl), either Zl/Z0 or Z0/Zl respectively, is one
siutation more likely to kill an amp than the other?

When ZlZ0, you tend to (ignoring phase effects here) end up with a higher
voltage sitting on the finals than when Zl=Z0... but less current than the
matched case. With ZlZ0, it's typically lower voltage but higher current.
Based on what I know from, e.g., power supply design, there's usually more of
a margain from overvoltage than there is from overcurrent, in that you can
often find parts that inherently withstand a 2:1 or better overvoltage margain
with just a bit of extra cost, whereas overcurrent will tend to overheat the
power devices and getting rid of, e.g., 2-4x as much heat (vs. matched case)
can require significantly greater heatsinking which often isn't cheap.

In the extreme case, I'd expect that far more amps will blow when shorted than
when open-circuited. But I don't really have much experience in this area...
so... could anyone comment on what you tend to see in real designs? Perhaps
also compare and contrast tube-based amp with solid-state ones?

Thanks you,
---Joel

 
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
killing cars with high RF? KE5MBX Homebrew 17 March 5th 07 10:35 AM
killing cars with high RF? KE5MBX CB 107 March 3rd 07 06:50 PM
killing cars with high RF? KE5MBX General 8 February 19th 07 04:01 AM
killing cars with high RF? KE5MBX Antenna 26 February 17th 07 08:13 AM
Caculating VSWR from rho and rho from VSWR Owen Antenna 69 June 27th 05 01:53 PM


All times are GMT +1. The time now is 03:58 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