Help with SO2R issues

jeffu

I have a Flex 6600 that I am attempting to use in a SO2R arrangement. I have two slices in two different panadapters. One on 6M and one on a 2M transverter. The 6M slice is using Ant 1 for TX and RX. The 2M transverter is using RX_A and XVTA. It is not showing wide, so my expectation is I am on the separate receiver paths as intended. I am using a Mic and speakers plugged into the back of the radio. When in full duplex mode I can transmit on 6M and everything works as expected. When I reverse the TX to the 2M slice I hear my TX audio out of the speakers like the Monitor is full on. This does not happen when I TX on 6M. Turning the Mon on or off does not seem to make much difference. I can switch to digital and transmit on the 2M slice with WSJT-X and it works fine. So appears to be only the mic path. I can change the 2M slice to 10M and it works fine both ways. So seems to be related to the transverter band with mic audio. If I turn FDX off, the problem also goes away. I have tried this on SmartSDR for Mac and Windows with the same results. Seems like I am missing something, but I cannot figure out what it is. Hoping someone has seen this before and can point me in the right direction.

Jeff
K9KLD

KD0RC

Hi Jeff, what happens if you change the 2M side to RX B and XVTB?

jeffu

Hi, thanks for the reply. I changed it over to the B side and it behaves the same.

Jeff
K9KLD

KD0RC

Wow, strange... I wonder if RF is getting in somewhere (a long shot, I know...) What if you disconnect your speakers and use headphones?

Mike-VA3MW

Jeff

It helps if you can post some screen shots for SmartSDR. It is easier to understand.

73

jeffu

I have done some more testing. I unplugged the external speakers and plugged in a set of Heil headphones. I can hear the audio feedback in the headphones. I then took a dummy load and placed it in the XVTA port and turned the drive all but off. The drive was set to 0 dbm max, so turned down there should be very little RF. I also turned the transverter off. Same results. Switched to use the computer speakers and same result. One last test, I did was to set the RX antenna to be XVTA. That makes it go away, but obviously I don't have receive any longer. I wonder if it is full duplexing the split path to transverter and it is hearing it's own IF transmit signal.

Here is a image of the basic setup. I can post more relevant ones if you want to see something specific.

KD0RC

So, just to be sure, you are using 28 MHz as your 2 meter IF, right?

jeffu

Yes, 28 mhz is the IF. Screen capture included.

KD0RC

OK, I just wanted to be sure you weren't using a goofy setup (like a 6M IF...). The last thing I can think of: I see that you are running the Mac version of the software. Do you have a Windows machine available to run SmartSDR from? That will eliminate the possibility that the issue is within the Mac version of the software (possibly a bug in the Monitor function).

jeffu

I have tried with the Windows version as well and it behaves the same.

jeffu

One other test I did was to turn the AGC slider all the way down effectively shunting the receive and I don't hear the audio. I think that helps rule out the monitor path and firms up my thoughts that it is hearing the TX IF signal on the split receive path because it is full duplexing in band on the receive antenna ports. I suspect that behavior may have some uses, but it it is not desirable in this case.

KD0RC

OH, I see what you are saying. It is because you are running split-IF; RXA on receive and XVTR on transmit. The full duplex is letting RXA hear XVTA.

Took me a while to get that...

I just confirmed it is true - While I only have a 6400 (so all of this is happening on the same SCU), I put my first panadapter on my 2 M transverter using RXA for receive and XVTA as transmit. I set up the second panadapter exactly the same way tuned to the same frequency, turned on FDX and heard myself in my speakers!

Do you have a way to run your transverter as a common IF? That way you would just use XVTA and not RXA, and would therefore not get the undesired audio in the speakers.

jeffu

I think I can reconfigure my transverter to single IF, but running split paths on transverters is pretty common, so it feels like that might be a short term solution, but I think we need some input from Flex if there is a possible solution to make this work right. I know of one other ham that that will be headed down this same path with transverters that were specifically built for split IF.

jeffu

I can confirm that if I rearrange my transverter to have common IF, the problem goes away. However that introduces the extra relay switching in the transverter to deal with the common IF.

I found this in the documentation:

When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted along with all other Slice Receivers on the same antenna. Receivers located on different antennas from the transmitter are not muted during transmission.

It seems this is a catch 22 of some sort in the logic. The first sentence indicates that the transmit slice receiver is muted in FDX, but in this case that is not occurring. That may be due to the second part that says receivers on other antennas from the transmit antenna are not muted. So I am guessing due to the split paths, it falls into the not muted category because it is not on the transmit antenna. It seems it should also have options to take into account the case where a receive antenna is bound to the transmit slice and handle that as well.

The question becomes if what I am experiencing is functioning as intended, or could a fix of some kind be done to remedy it?

Jeff
K9KLD

KD0RC

Hi Jeff, I don't think this is a catch 22. The caveat is "on the same antenna". Once you split the IF, you are operating on different antennas.

I agree with you that a new option should be introduced to mute the RX associated with a transverter (RXA/XVTA RXB/XVTB). That way current functionality would be preserved and your issue would be solved.

@Mike va3mw , any thoughts on this?

David Decoons, wo2x

If you want it muted, why not disable full duplex, unless I am missing something.

Dave wo2x

jeffu

I think you are missing that the goal is SO2R. With that you want to hear the audio from the non transmit band while transmitting so you can work both bands. In this case with the split paths on the 2M transverter, in addition to hearing the other band which is desirable, you also hear your own transmit audio echoing back to you which is not desirable.

Jeff
K9KLD

David Decoons, wo2x

Jeff,

based on your last screenshot, you are using XVTRA and RXA ports. Have you tried XVTRB and RXB with slice B?

Dave wo2x

jeffu

Yes, up further in the thread Len suggested the same and it behaved the same. I don't think there is correlation between the slice letter and the letter on the ports if that is where you where headed.

Jeff
K9KLD

David Decoons, wo2x

The only other thing I can think of it is possibly by design with RXA and CVRTRA to have receive when full duplex is enabled (think satellite work). For satellite you would want it to work the way it is currently when full duplex is enabled

In that case an enhancement request submission is probably best bet.

I’m out of ideas.

Dave wo2x

jeffu

I am not a satellite expert, but from what I have seen most of those are cross band and would want similar behavior to what I am expecting. Even if there were some case where you are receiveing in the same band, I can't imagine much use for hearing your own transmit signal / audio on the transmit frequency.

Thanks for trying to help. From what I understand from the documentation mentioned above this ends up with a conflicting logic situation. I agree, I am looking for a response from Flex if this is something that they can update in the firmware to provide for this function. I don't think this is an unusual use case.

Jeff
K9KLD

Mike-VA3MW

There is a lot going on in this thread and I have sort of lost track of what is happening. I really need to see a diagram of the RF layout and a very simple way to recreate the setup with screen shots of SmartSDR. If you want to do that, we are happy to help and then be 100% sure of the layout. You can use DRAW.IO to easily sketch it out. (that is how my mind works :) ).

For my satellite work, I run my VHF on XVTA and UHF on XVTB (no split IF) and I run in FDX.

Keep in mind, that the radio is essentially running on 10M (the 28Mhz IF) so it will be possible to hear the uplink while listening to the downlink if they get close to the same IF frequency. There is over 60db isolation between both sides though. You can't make it totally go away.

KD0RC

Hi Mike, what Jeff is trying to do is SO2R on a 6600 using FDX where one panadapter is on 6 meters and the other is on 2 meters using a split-IF transverter.

With a common-IF transverter in FDX, there is no issue. He can listen to 6M while transmitting on 2M. Because 2M RX and TX are both on the XVTA port, transmitting on 2M does not feed his 2M transmission back to him.

With a split-IF transverter in FDX, his own 2M transmission on XVTA comes back in his speakers via the RXA path. Transmitting on 6 M works just fine because he is transmitting and receiving on the same antenna (e.g. ANT1).

The ask is to have an option that when in FDX, mute RXA when transmitting on XVTA and mute RXB when transmitting on XVTB. This should be an option so as not to upset any existing use cases for the existing FDX split-IF operation of the radio.

I hope that description makes sense...

jeffu

My setup has nothing to do with satellites. That was just a sidebar to what could be a similar use case. I am talking about using the radio to do SO2R operations where I can be transmitting on one band and listening on another at the same time. The 2 bands in this case are 6M and 2M where 2M is provided by a transverter with split path 10M IF. The simple use case is transmitting on 6M and hearing the receive on 2M. This works as intended. The 6M receive is muted while transmitting on 6M and I can receive on 2M and hear that audio. Now when you reverse that and transmit on 2M, you hear the 6M audio as expected, but you also hear your own transmit audio on the 2M side as if the monitor is on. The transmit slice is not muted and because of the separate receive antenna it is hearing itself transmit. This only happens if you are in the split IF path configuration. If you use common IF then it works as expected. Split path IF on transverters is not uncommon.

Here is a link to DRAW.IO map of the RF path showing a 6M antenna attached to ANT1 for transmit and receive. The 2M transverter is using RX_A for the receive path and XVTRA for the transmit path. The radio is in FDX mode. Attached is a screen shot of the slice setup. If you transmit on 2M with any level of receive volume you will hear your own transmit signal audio in a slightly delayed fashion. I believe this is because it is not muting the transmit slice because it is using a separate receive antenna.

Here is the conflicting section from the documentation.

When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted along with all other Slice Receivers on the same antenna. Receivers located on different antennas from the transmitter are not muted during transmission.

Line one says the transmit slice is muted. This does not happen in the setup explained here with the split IF paths. It does work if you change the transverter to common IF.

https://drive.google.com/file/d/1yyhZ6yxNmZENzrYb-5e-IZgJPkPkKtdG/view?usp=sharing

Let me know if you need anything else to help clarify.

Jeff
K9KLD

David Decoons, wo2x

Hi Jeff,

This line you mentioned,

“When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted along with all other Slice Receivers on the same antenna. Receivers located on different antennas from the transmitter are not muted during transmission.”

I interpret that to mean only the transverter port would be muted as that is the “transmitter”.

What you are asking for makes sense though.

73 Dave wo2x

jeffu

@Mike-VA3MW Were you able to look at the information I provided?

Mike-VA3MW

Dave answered it and it is working as designed.

Receivers located on different antennas from the transmitter are not muted during transmission.

Thanks for the diagram, you can just paste them into any reply you are working on. The diagrams are so so helpful.

If you would like us to consider this as a change, I'll need you to open a support ticket so that it is tracked. Just to set the expectation, I don't think you will see a change in the near future and to the best of my knowledge you are the first person to ask for it since the 6000 series came out in 2013.

In your diagram, RX_A is not muted in FDX while transmitting on XVTA. Yes, I can see how this would impact a split IF installation. I guess the easy fix would be to only use XVTA and then add a T/R relay on the XVTA line so that you feed RF into the XVTR while in TX mode. At least there is enough PTT I/O on the radio to make that something pretty easy to do.

jeffu

Thanks for the response. The line that says, When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted along with all other Slice Receivers on the same antenna, implies to me that the slice receiver which is the transmit slice would be muted. I certainly could see the argument for other slices that happened to be using the same receive antenna to not be muted on the second part of that. However I can't think of any reason where you would want to hear your own RF on the on the slice that is doing the transmitting. If you are truly doing split, then you would have another slice that is the receiver and I agree that would not be muted.

I will submit a change ticket for the record. I think this is a valid use case and I am a bit surprised that no one else has come upon it.

kg9ov

@Mike-VA3MW or anyone else from FlexRadio, can this please be revisited and/or brought to engineering for review? How can this be "working as designed" when the 6600 manual and other posts from FlexRadio employees in the forum say otherwise?

From the 6600 manual:

"When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted"


From a post by @Steve-N5AC in https://community.flexradio.com/discussion/comment/16067794/#Comment_16067794

"Receiver must be on different frequency from transmitter: The delay that occurs during filtering is guaranteed to drive someone mad if the transmitter and receiver are on the same frequency. For this reason, we mute the slice that you are transmitting on so you will not hear your own signal. This may seem counter intuitive at first, but it should fit most use cases. For example, if you are chasing DX, you can create two slices, a RX slice on the DX and a TX slice where you will TX up (generally) and when you transmit, you can still hear the DX frequency. You will not hear under your current transmit signal, unless you are in QSK in which case you will hear in-between your transmissions."


From a post by @"Ed.G" in https://community.flexradio.com/discussion/comment/16154911/#Comment_16154911

"With FDX enabled you should be able to listen on ANT1/ANT2 at the same time you are transmitting on XVTR.

The only restriction is that you can't listen to your TX Slice audio unless the RX frequency of the TX Slice is more than 12kHz away (this stops echoes). Does the full-duplex operation with satellites require you to receive on the same frequency as you are transmitting?

If you do need to listen on the same frequency this can be accomplished by using two slices. The slice that is not the TX Slice will receive the audio with FDX enabled."


With the current Flex software (v3.3.32), the actual result is *NOT* as stated in the manual or either of these other forum posts by @Steve-N5AC and @"Ed.G".

From personal experience in several recent VHF contests, I can attest to this issue being able to "drive someone mad" as @Steve-N5AC stated. I don't know about anyone else, but I find it impossible to speak coherently when I am forced to hear my own audio in my ears with 10s of milliseconds or more of delay. If it were like a simple monitor function with NO delay it would be different. But, in the current state, the radio is NOT usable on phone modes in FDX with a split-IF transverter.

-Tony

Mike-VA3MW

Hi Tony

Is there a question I can help answer?

All I can say is that I know hundreds of operators that listen to their satellite downlink in full duplex. It is a standard mode of operating. By listening to my downlink, it allows me to adjust my uplink power dynamically.

I agree, it is strange, but like most things, it was something I had to learn to deal with when doing satellite work. Some people can handle it and for others it drives them crazy.

Just like CW. Once it goes over 20wpm, I hear mush. Others have no issue with it. I guess it depends how your brain is wired.

kg9ov

@Mike-VA3MW, this has nothing to do with satellite or listening to a downlink. Sure, if I were to transmit on one frequency (uplink) and listen on some other frequency (downlink), then I would expect to deal with it. That is *NOT* what is being discussed here. The issue I (and Jeff) have is the *transmit* slice not being muted when in FDX mode. The audio in your ears is coming from your own transmit slice.

I suppose the real question is why does the radio *NOT* function as is stated in the manual and the two posts from other FlexRadio employees that I quoted in my previous comment?

Again, the manual for the radio states "When Full Duplex (FDX) is enabled, the transmitting Slice Receiver is muted" and that is NOT happening.