[1000mp] Q: Antenna Tuner, FT-1000MP Mark V Field

[Ian White, G3SEK]

Mark Shaum wrote:

>> > frequently have to do exactly what you have described.  At times I
 >> > have
>> > to use very low output, just a few watts, before the Autotune will
>> > locate a null.  The SWR reading will generally then increase
 >> > slightly as

>Yep!  But I've had instances where even 10W is too high for a null to be
>found when TUNE is pressed.  I'll then key up, slowly advance the RF
>POWER from zero until I begin to get a SWR reading (which is sensitive
>to power output at very low levels) of about 3:1, keeping the HI SWR
>from triggering.  Then hit TUNE.  The initial match found at that point
>then usually holds fine at higher outputs.

The true SWR is the one you see at higher power levels.

When you use very low power, you are "hiding" the problem from the 
auto-tuner, by making the reflected signal so small that it's mostly 
below the conduction threshold of the detector diode.

This allows the tuner to carry on searching without stopping on HI 
SWR... and then the tuner can sometimes find settings that are still 
acceptable when you turn up the power again.  I believe this is called 
"making technology work for you"  :-)


-- 
73 from Ian G3SEK