How to assure in SO2R that you really utilize different SCU:s when needed?

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When configuring and running SO2R with a 6700 (dual SCUS:s) in contests you need to be running duplex so that you can transmit on e g 40 m (ANT1) and listen in parallell on 20 m (ANT2) with another antenna. With two SCU:s this is feasible - and the 6700 is connecting ANT1 to SCU1 and ANT 2 to SCU2. So far all good. 
Recently I have wondered how do you make sure this rellay happens. And that ANT2 not is connected to SCU1 in reality? Or have I mistaken something? 
I know from Steves forum posts that it is the RX1 and RX2 that determines which SCU that is associated to each ANT1 or ANT 2.
Reason for my wonder is that in the recent CQ MM contest I could not in parallell listen to  20 m while transmitting on 40m without having the band spektrum wiped out as when you use two slices with the same SCU. 
Or am I missing something in the SCU conceptual set up?
73s Kari 
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Kari Gustafsson SM0HRP, Elmer

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Posted 5 months ago

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WA5YOM

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Have you selected FDX mode?
Tim
WA5YOM
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Kari Gustafsson SM0HRP, Elmer

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Yes
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K3SF

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few things to consider in SO2R.

yes...must have FDX ( full duplex turned on)
yes... separate antenna selected for each slice receiver ( slice A on ANT1, Slice B on ANT2)

BUT
most critical is is to have enough RF separation between each antenna or provide band pass filter for each antenna input so as to NOT overload the SCU that is in receive when transmitting.

the flex radio will cutback power or even shut down transmit if it detect high RF condition on an SCU input and it detects you are the offending transmit signal.

i know from experience that on the 6600M model that a message will pop up saying SCU is overloaded and is shutting down transmit...been here...done that
i needed 200ft ( ~ 70m) of separation of my antenna to eliminate this overload condition
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Kari Gustafsson SM0HRP, Elmer

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Thanks for the inputs.

Eventhough I only have about 70 feet of separation I have good isolation due to HP bandpass filters.

I found one solution to the problem. If I disable TX1 (20 m) while transmitting on 40 m slice B / ANT2 the spectrum om slice A stays intact as it should. And if I use RXA instead of ANT1 spectrum of slice A stays intact when transmitting on slice B/ANT2.

SHOULD IT BE SO?
(Edited)
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Tim - W4TME, Customer Experience Manager

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Whether or not you are using both SCUs is really simple and it has nothing to do with Full duplex (that is an SO2R configuration dependency).

If the RX antenna for two slices are not the same, then you are using two SCUs.  The slices will have to be in different panadapters because that is really where the antenna (SCU) dependency resides.

It makes no difference which antenna port is connected to which SCU as they are identical.

Reason for my wonder is that in the recent CQ MM contest I could not in parallell listen to  20 m while transmitting on 40m without having the band spektrum wiped out as when you use two slices with the same SCU. 

If they are on the same RX antenna, then they are on the same SCU and in full duplex mode (receiving while transmitting), then you are going to get RF energy on 20m because it is the 2nd harmonic of 40m.

The 6700 also does not have contest grade preslectors (bandpass filters) like the 6600, so you may have to add external filters for additional isolation.