Antenna selection appears to be erractic?

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  • Problem
  • Updated 3 years ago
Flex Antennas issue

Loss of Receive RF when switching between Antenna 1 and Antenna 2.
Setup: Flex 6700, 5 windows open (number of slices open does not appear to influence antenna switching issue)
    Computer, windows 7 64 bit with all updates
    Mac Computer in Boot Camp mode, dual quad cores, 8G memory, 1TB flash drive
    Flex software v1.5.1.70 s/n 1713-3011-6700-3269

System setup with 3 antennas, two different Rec/Tx antennas on antenna ports 1 & 2, receive only on Rec A.
How to reproduce the issue:
Open 2 slices
Slice 1 20M Receive have Antenna 1 selected, Transmit selected Antenna 1, Select TX
Slice 2 20M Receive have Antenna 2 selected, Transmit selected Antenna 2, do not select TX

Slice 1 select receive antenna 2, complete loss of receive RF, select Rec A, RF returns
Slice 1 select re-select receive Antenna 2,
Slice 2 showing no RF, select TX, Receive RF from Antenna now visible, slice 1 RF remains.
Slice 1 switch between receive Antenna 1 and 2, all appears to function normally
Slice 2 select TX on slice 1, slice 2 looses RF on receive (Rec on antenna on 2 and xmit on 2)

Slice 1 20M Receive have Antenna 1 selected, Transmit selected Antenna 1, Select TX
Slice 2 40M Receive have Antenna 2 selected, Transmit selected Antenna 2, do not select TX
 
Slice 1 select receive antenna 2, complete loss of receive RF, select RX A, RF returns
Slice 1 select Antenna 2,
Slice 2 showing no RF, select TX, Receive RF from Antenna now visible, slice 1 RF remains.
Slice 1 switch between receive Antenna 1 and 2, all appears to function normally
Slice 2 select TX on slice 1, slice 2 looses RF on receive (Rec on antenna on 2 and xmit on 2)
Appears to have the same effect with any selection of bands

ONLY one slice open
Slice 1 20M Receive have Antenna 1 selected, Transmit selected Antenna 1, Select TX

Slice 1 select receive antenna 2, complete loss of receive RF, select RX A, RF returns
Slice 1 select Antenna 1,RF comes back
Slice 1 select receive antenna 2, complete loss of receive RF
Slice 1 select transmit antenna 2, RF returns for antenna 2
Slice 1 select receive antenna 1, RF remains
Slice 1 select receive antenna 2, then select transmit antenna 1, complete loss of Received RF
Slice 1 select receive antenna 1, RF from antenna 1 returns.

I remember being able to switch between receive bands and not having this issue in the past but have not tested for this with the recent updates.
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Watts - K4QJZ

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  • confused

Posted 3 years ago

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Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

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I don't think you have a problem, but I can't tell because a critical piece of information is missing and that is the antenna the panadapter is connected to when you switch antennas on the slice level and the panadapter stops displaying spectrum.

In a FLEX-6700 there is only 2 SCUs and each one can only be connected to an single antenna at one time.  SmartSDR have some very complex RF signal path switching logic to prevent any antenna/SCU signal path switching violations based on the number of antenna/scu permutations the radio can have.

I suspect what you are observing is you are making an antenna switch that is not valid based on the other scu/antenna configurations (like putting attempting to assign 2 antennas to the same SCU) in the logic and the panadapter is being disconnected (default error condition) from the SCU that is providing it digitized data.  Only one ANT type antenna can be connected to an SCU at one time, but either ANT-1 or ANT-2 can be connected to SCU-1 or SCU-2 at any given time.  THis is not the case with RX antennas, as RX-A is always connected to SCU1 and RX-B is always connected to SCU2.  So when you select an RX antenna after attempting an antenna configuration that is a violation and the SCU disconnects, this selection forces a particular SCU to re-associate with an antenna.

I'd like to investigate your antenna switching behavior further based on your one slice open description, because something doesn't sound just right and it is a simpler configuration to debug (fewer variable in play with just one SCU).  So I am going to convert this topic to a support HelpDesk ticket (http://helpdesk.flexradio.com) so we can investigate further.
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Norm - W7CK

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It would be nice to be able to see exactly which panadapter is using which SCU.   I'd like to open a panadapter and assign it to a particular SCU to avoid this problem.  Will this functionality be available in upcoming release Tim?
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Tim - W4TME, Customer Experience Manager

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"It would be nice to be able to see exactly which panadapter is using which SCU."

What is the operational use case for doing this since there is no performance difference between the SCUs?  There is only a "problem" when the radio is instructed to put into a state that is not allowed and even if you were able to see the SCU designation, we are still going to do what is best for the radio.

We allocate SCU resources dynamically and automatically so you don't have to think about it and initiate some type of action, hence the "smart" designation in SmartSDR.  

"Will this functionality be available in upcoming release?"
No, it will not.

There is a way to force a particular SCU to an antenna.  You can do it by using a BNC coax jumper.  Put a 50 ohm coax jumper on the RX-A and RX-B loop.  Open the panadapter, select your ANT antenna and then select either the RX-A or RX-B loop and that will  always associate SCU1/RX-A or SCU2/RX-B  to the ANT antenna of your choice.
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Norm - W7CK

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Thanks Tim.  I guess I'm still having a hard time realizing all that has to take place under the hood!  If I'm understand correctly, If I open 2 slices and select different antennas for each, then each will be on a different SCU.  That helps.... Thanks.