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Changing Ant changes signal level on different slice?

Mark_WS7M Member ✭✭✭
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 **** I'm doing?


  • Mark_WS7M
    Mark_WS7M Member ✭✭✭
    edited March 2017
    Ok I just realized that my system is changing the RX antenna to Ant2 for BOTH slices.  I thought I could have a different RX antenna on each slice. 

    I guess this is a limit of the 6500 only having one SCU.  Sorry about the wasted bandwidth.
  • James Del Principe
    James Del Principe Member ✭✭
    edited January 2016
    Mark, this is an interesting point. Is it possible to set up a receive antenna and assign it to the band you want to monitor? That is, Ant 1 to the 40 meter slice and the receive ant to 20 meter slice?   Worth a try.       73, Jim
  • Mark_WS7M
    Mark_WS7M Member ✭✭✭
    edited January 2016
    Well James that is what I wanted to do.

    My issue was that my SPE amp when on and tuned to 40m has a band pass filter that kind of cuts signals from 20m.  IE I can't see them.

    I wanted to stay in operation on 40 with the amp and setup a second pan/slice to watch 20.  I have a second antenna so I plugged it into the back of 6500 and thought I could switch the second pan/slice to ant2 and leave the first slice/pan to ant1 but it doesn't work.

    I think this is due to the 6500 only having a single SCU.  Those lucky guys that are rich enough to afford 6700s have two SCUs and I'll get that system allows different receive antennas.

    Now what I can do is set both slices to ant2 receive which means I bybass the amp, but TX is on ant1 which goes through the amp.  This works just fine and may do what I want.
  • Ken - NM9P
    Ken - NM9P Member ✭✭
    edited June 2020
    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
  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited December 2016
    You are 100% spot on correct.
  • km9r.mike
    km9r.mike Member ✭✭
    edited January 2016
    Which brings up a question. Even with the flex so2r board for the 6500 and 6300, the second band in use ( the band being scanned for mults ) will be limited to the reception of the single scu correct. In other words, say I have two mono band antennas, one for 20 and one for 15. I am cqing on 15 while simultaneously scanning 20 for mults. If I had a 6700, each of the two scus would be active taking advantage of the better receive capabilities of the monobanders on 15 and 20 respectively. However, if I was using a 6500 or a 6300 with the so2r board, my receive on 20 and 15 is gonna be limited to whatever antenna the single scu is utilizing. The 20m monobander, the 15m monobander or some other general wideband receive antenna correct ?

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