[Top] [All Lists]

[AMPS] Benefit

To: <>
Subject: [AMPS] Benefit
From: (km1h @
Date: Sat, 14 Mar 1998 15:56:28 EST

>No, it is not erroneous.  This is from an engineering handbook.  A 
>VSWR will reflect 4% of your power.  You can calculate that.  That 4% 
>power goes back down your coax where it weakens do to coax losses.  It 
>then sees a mis-match of some sort when it arrives back at your 
>tuner/pa.  Some of that power is sent back into the antenna tuner/pa 
>some is reflected again to go back up the antenna.  So whatever power 
>no reflected back to the antenna is reduced by the loss in the coax 
>then when it gets to the antenna, 96% of it is sent out and 4% is 
>relected back to do the same thing.  Reflections basically go back and 
>forth continually ad infinitum.  This is why it is called a Standing 
>Is your total power loss 4%?  No, I never did say that.

It was hard to understand what you meant. I prefer to use dB, not some
percentage which is meaningless unless you know all the other parameters.

Saying that 4% goes round and round forever is gross over simplification.

  But SWR does 
>to the loss in your system.

Thats what I TRIED to show later down the page.

>I am willing to go round and round on this one.

Dont bother. When taken in the proper context you are correct.

 I am an RF engineer 
>by degree and trade.  So I feel that my knowledge is sufficient.

So is my son, now going for his MSEE; but no one has questioned your
credentials so why bring it up?
One can be a truck driver and read the charts that are
available...developed by some EE I assume. 

>Fortunately on HF, coaxial line loss is not a huge problem unless you 
>have a monster length feed line.  On VHF and UHF however, losses can 

Basic facts.

>>Here are the published flat and additional VSWR losses for RG-213 per
>>Freq  Flat Loss    Add loss  2:1 VSWR     Add for 4:1 VSWR
>>4 Mhz 0.32dB    <0.1dB                      0.3dB     
>>15    0.8                 0.18                      0.7
>>30    1.2         0.22                      0.9       
>>It would then appear that even a 4:1 VSWR at 20M is of no real
>>consequence for many styles of operating. On 80M I really could care 
>>about  the.3dB when I go from CW to SSB. 
>I don't fully understand this chart.  But the columns aren't aligned 
>properly so I can't read it either.

The chart lines up here even after returning via the reflector; if others
are having a problem let me know. Anyway all I did was copy published
RG-213 loss and then add in the VSWR loss as published in any ARRL
Handbook or Antenna Manual for as long as I can remember. 
Doesn't require no degree to read it either.

SNIP    as the rest is off the cable loss discussion.

73   Carl  KM1H


You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at
Or call Juno at (800) 654-JUNO [654-5866]

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>