[AMPS] Have Cake & Eat it too

[Jon Ogden]

Jonathan Kaplan wrote:

>>> In other words, when I tune the AMP
>>> the power meter (a RS model) will either show greater power at
>>> a high SWR or low power at low SWR. But not high power at low
>>> SWR!  What does this mean is wrong? Does it neccessarily
>>> mean the final output into the air is limited, and that the antenna
>>> system is out of tune?
>>
>>If you mean that the meter shows extra high power on frequencies for which
>the
>>SWR is high, this is an inaccurate power reading caused by the meter's being
>>designed to work properly only on a relatively flat (low-swr) line.
>
>Not EXTRA high power. The maximum power showing in any case is about 1Kw,
>which I am told is about expected for 100w drive from a Yeasu Ft-840.

Someone suggested this belongs on Tower Talk - NOT!  It's an amplifier 
related question.

If you have a high SWR, your power meter WILL very likely read higher 
power than would be read under a "normal" SWR condition.  In other words, 
if you are transmitting 1KW and are getting 50% of your power reflected 
back to you (SWR: ~6:1), this "reflected" power will reach your amp, 
tuner, etc and will be reflected back up the line towards the antenna.  
So your power meter will end up reading around 1500 Watts out.  The best 
thing to do is subtract reflected power from forward power.  But then 
again, as others have pointed out, the power meter is not really accurate 
in environs far away from 50 Ohms.

Also, you neglected to tell us what "low power at low SWR" means.  Is 
"low" 1000 Watts?  Or is "low" 100 Watts??

73,

Jon
KE9NA



--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!


Jon Ogden

jono@enteract.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."


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