Changing Ant changes signal level on different slice?

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I don't think this is a problem but I'd like to understand it better.

I have two panadapters going.  Top is 40m cw.  Bottom is 20m waiting to see if the band opens.

My Ant1 is going from the flex through my SPE 1K amp.  One issue with this setup is that when 40m is selected in the amp 20m is kind of dead due to the amp band pass filters I think.  This is a very good reason with this amp I think to have a separate RX antenna to your TX antenna.  

Anyway I'm sure some of you experts will have a great way to solve this.  I decided to take my second antenna and take it out of the amp output 2 and put it into Ant2 on my Flex6500.

I then went to my bottom pan and slice which are on 40m and simply changed the RX ant from Ant1 to Ant2 and noticed that it brought the base signal level on my supposedly unaffected slice, top pan, slice A up about 10db.  My average noise signal was sitting around -120 and just making the change on the second pan to Ant2 brought the average noise up to about -110. 

This little movie shows the behavior.  Is this normal/expected or something stupid I'm doing?
https://dl.dropboxusercontent.com/u/7578983/Ant2Switch.mp4
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Mark - WS7M

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Posted 3 years ago

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Ken - NM9P, Elmer

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Official Response
It is operating correctly.  the 6500 and 6300 only have on SCU (receiving unit) even though the can have 4 or 2 slices concurrently open.  They are slices of the same receive conversion.  The SCU can only have one antenna connected at the same time.  Switching antennas switches the antenna for the SCU and al the slices that are tapped into it.

Until you get used to it, It can be a bit confusing learning the new paradigm of SCU/receiver Slice/VFO and all the rest.  

For simplicity, imagine the output of a single, really wideband receiver connected to an antenna. picture this output graphically posted on a large,wide school blackboard  That is the SCU.  
In a 6500 you can mark off (sample) up to 4 smaller pieces of that wide bandwidth by placing sticky notes on the blackboard.  Those are the slices.  The slices can be anywhere on the blackboard, along the spectrum received by the wideband receiver.  

You can also tape several different yardsticks (panadapters) which are pictures of a larger section of that wideband receiver.  Now, to really confuse things...you can layer those 2-4 slices on top of 1 to 4 of those panadapters as long as the slice is within the frequency range displayed by the panadapter  (It has to be somewhere on the yardstick).

Now....you can grab a yardstick (panadapter), and move it anywhere on the blackboard.  You can slide it up or down the bandwidth of the wideband receiver and place it anywhere from 50 Hz to 54 MHz (on the 6300, higher for the 6500) neat!  And you can zoom your view in or out and move it anywhere on the yardstick.  i.e.  you can zoom the panadapter in or out from one KHz or so all the way out to 7 MHz on the 6300 and 14 MHz on the 6500.

This is a very visual receiver interface.  and a very powerful package.

And better yet...the 67000 has TWO of these wideband receiver SCU's, and each one can be connected to a different antenna at the same time! This will allow for diversity reception, full duplex, SO2R, and other amazing things whenever the software geniuses deliver them.

Yes,  wish I had a 6700!  But the 6500 does about 99% of everything i want it to do.

Ken - NM9P