not a head scratcher at all.
the meter is expecting a 50 ohm load on the radio side.  the internal tuner 
is altering that load to compensate for the impedance of the antenna system 
and is therefore no longer 50ohms when it is activated.
so, the meter is seeing something other than 50ohms on the radio side and 
gives inaccurate readings because of it.
That's why everyone keeps telling you to turn both the internal tuner, and 
the other tuner off, take the external one right out of line actually, then 
tune the antenna with the meter.
in fact, to be safe, disable the internal antenna tuner in the radio's menus 
so you don't accidentally turn it on at some point.
Physically disconnect the external tuner from everything.
Then, make sure you have a counter poise of some kind for the antenna. 
After that, you can start trimming or adding wire to your quarter wave 
length radiator until you achieve a 1 to 1 match.
You won't hurt the radio if you use 5W to check the swr, no matter how high 
the swr is.
You could key down all day long with no antenna connected at all with 5 w 
and the radio wouldn't be hurt.
Remember, tune in CW mode.
Not AM or FM as the modulation will cause the power to fluctuate and could 
alter your readings for SWR before you reach a 1 to 1, or close match.
As long as the antenna is 3 to 1 or below you will be fine...the internal 
tuner will take care of anything from a 3 to 1 match down and make the radio 
efficient.
73
Colin, V A6BKX

----- Original Message ----- 
From: "mark Torgerson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 27, 2010 2:26 PM
Subject: Re: Question About TW 1 and readings


> Hi
>     The internal antenna tuner is simply to protect the radio. I want =
> to=20
> have the SWR meter reading the true value of the antenna system =
> including as=20
> much of the feed line as possible. Interestingly though, when I take the =
>
> internal tuner off line the SWR tends to jump about two units on the=20
> external meter. Now, there is a head scratcher.
>
> God bless,
> Mark Torgerson
> =20