[AMPS] Where to read Reflected Power

[Jon Ogden]

measures wrote:

>The only thing a tuner does is to 
>>essentially act as a buffer between your exciter and your load.  It will 
>>not improve a bad antenna.  If the antenna has a 15:1 VSWR without the 
>>tuner, it still has it with the tuner.  You just don't see it.
>>
>€  Thick sliced bologna.  .  .  If a 15 to one / 750 ohm antenna is 
>connected to a matching network/antenna tuner, the 750-ohms is 
>transformed to 50-ohms +/- j0 ohms. 

Rich, it is NOT bologna!  The impedance at the feedpoint of the antenna does NOT change because you put a tuner in the line.  If you think that it does, I have a bridge to sell you.  The tuner DOES transform the impedance at the tuner to look like 50 Ohms so that it looks proper to you exciter.

Yes, the 750 Ohms is transformed to 50 Ohms, BUT THE ANTENNA IMPEDANCE AT THE FEEDPOINT IS STILL 750 OHMS!!!  You still have that 15:1 VSWR between the antenna and the output of the tuner.

>
> >........I wouldn't worry about your variances in SWR readings.  It's 
>>really just to give you an idea of what kind of power is coming back at 
>>your rig.  Personally, I'd match it so that the PA sees the best possible 
>>match.  This means that your tuner and whatever you have on the output of 
>>your PA are optimally matched.  Who cares what the SWR meter in the tuner 
>>sees.  The output of the tuner is going to have a high VSWR anyhow!  
>>Matching this way will cause you to put the maximum available power into 
>>the tuner instead of reflecting 2.5% of it back to the amp.
>>
>€  However, without a tuner, the 2.5% gets reflected back to the antenna. 
> 

No, that's not correct.  Jim's VSWR of the antenna itself is much worse than that.  The 2.5% mismatch is the mismatch BETWEEN the tuner and the PA when the tuner is tuned for min SWR.  You just didn't read the post carefully enough, Rich.

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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