P2 Coherent Diversity Issue

w3ub
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P2 Coherent Diversity Issue

Postby w3ub » Sun Dec 27, 2020 3:18 pm

Thetis 2.8.11
Have tried P2 FW from V1.2 to V2.0b

On 80m I have a local broadband noise source, that coherent diversity can null by about 10 dB, which can make quite a difference. I usually run RX1 and RX2 on CTUN, using a 384k sample rate. It works well except for this issue.

If I click diversity on/off/on ... over and over, sooner or later when turning it off the RX1 noise floor is elevated by 40-50 dB. I found that clicking diversity on and off repeatedly could induce the issue. It also occurs when not doing that after some period of time.

Using P1 FW I can't make this behavior happen, but I like to see more BW, the 192k sample rate is not enough.

I have played with this quite a bit over the past few weeks, and can't seem to get coherent diversity stable on a long term basis.

Doug
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w-u-2-o
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Sun Dec 27, 2020 10:17 pm

What hardware are you using?

I'm assuming you have to power cycle the hardware to get it to recover?
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Sun Dec 27, 2020 10:29 pm

A new black 7000.
Yes, I have to cycle things to get it working again.
Doug
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Sun Dec 27, 2020 10:33 pm

That's unfortunate, Doug. It's a limitation of the available firmware on your hardware. If you can't find a version of the firmware that is stable for you that way I'm afraid I don't have a fix.
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Sun Dec 27, 2020 10:52 pm

It's odd for sure. It seems like the additional load of running diversity somehow affects stability. I started running diversity quite a bit, for hours at a time, and found this occasional instability. After playing with it I found that toggling it on and off repeatedly helps to make it recur faster.

I wish there was some way to get 384k sample rate with P1! I assume this has been scrutinized, and 192k is a hard limit?

Doug
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Re: P2 Coherent Diversity Issue

Postby K1LSB » Mon Dec 28, 2020 1:24 am

w3ub wrote:Thetis 2.8.11
Have tried P2 FW from V1.2 to V2.0b

.
.
If I click diversity on/off/on ... over and over, sooner or later when turning it off the RX1 noise floor is elevated by 40-50 dB. I found that clicking diversity on and off repeatedly could induce the issue. It also occurs when not doing that after some period of time.
.
.

Doug

I've experienced the same problem a couple of times before but it's been awhile since the last occurrence, which leads me to suspect that maybe it's a setting somewhere that "sensitizes" the radio to the problem (I typically fiddle with buffer sizes and other stuff so maybe I fiddled with something that "de-sensed" the problem, heck, I dunno).

Mark
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w-u-2-o
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Mon Dec 28, 2020 2:29 am

You can run 384K in PowerSDR with PureSignal disabled.

There's no magic "sensitization". It's a bug in the P2 firmware, possibly related to marginal timing closure in the firmware design.
K1LSB
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Re: P2 Coherent Diversity Issue

Postby K1LSB » Mon Dec 28, 2020 2:47 am

Update: it just happened to me again. I guess I jinxed myself by even mentioning it...darn it! :(
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Mon Dec 28, 2020 12:55 pm

[quote]You can run 384K in PowerSDR with PureSignal disabled.

There's no magic "sensitization". It's a bug in the P2 firmware, possibly related to marginal timing closure in the firmware design. [quote]

I reverted back to P1, and with PS-A not checked the max sample rate available is still 192k. Perhaps I am missing something?

Also, you can't fix a problem if you don't know it exists, so perhaps this P2/diversity issue can go on the FW list to investigate sometime, it may be fixable and different from their efforts in general with P2 non-diversity stability.

Thanks,
Doug
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w-u-2-o
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Mon Dec 28, 2020 3:07 pm

In Setup > Audio > Primary you should be able to change the sample rate to 384KHz. I can do it here.
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Mon Dec 28, 2020 3:28 pm

It is odd, if I start Thetis without starting the receiver, I see other sample rates to choose including 384k. But the moment I start the receiver (with the start/power button) it changed to 192k and that is the max rate available ... with P1 FW. I have tried to turn off PS, maybe it is still on somehow? Or I am missing something obvious.

Doug
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Mon Dec 28, 2020 3:56 pm

Oh, you are using Thetis? I thought you wanted to use a higher sample rate in PowerSDR because Diversity was not stable enough for you in Thetis?

In Thetis you go to Setup > General > F/W Set and with the 7000 you should see sample rates all the way up to 1.536MHz. If you don't then it is probably time to start a fresh database.
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Mon Dec 28, 2020 4:13 pm

Since Thetis works with P1, and diversity is quite stable if I run P1 (and Thetis), I thought that you were saying if I disabled PS, I could get to 384k using P1 and Thetis. If that makes sense ... The problem only occurs with P2 and Thetis.
Doug
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Mon Dec 28, 2020 5:03 pm

Ah, totally my bad, I was brain-locked on P1 = PowerSDR. I forgot that Thetis now supports P1. Duh!

With my brain-lock now sorted out, I've got bad news: Thetis only supports 192KHz sample rate with P1 firmware. It also does not support stitched receivers with P1 firmware (and no need for them with P2 firmware). Release notes are here.
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Mon Dec 28, 2020 5:06 pm

Got it. That is too bad ...

For my own information, what is a stitched receiver?

Doug
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Re: P2 Coherent Diversity Issue

Postby w-u-2-o » Mon Dec 28, 2020 7:34 pm

In PowerSDR you can use the DDCs that are not being used for PureSignal to expand the range of the spectral display. It takes three of them and "stitches" them together to show 3 x 384KHz.
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Mon Dec 28, 2020 7:53 pm

That is sort of what I figured regarding the stitched receivers.

Went back and tried PowerSDR ... have not used it for a few years. Seems like a major step backwards now, but at the time it seemed great! Not going to go down that route.

For now I think I will use non-coherent diversity with RX2 audio along with RX1 audio, using P2 to get the 384k sample rate. If there is a P2 FW bug list, coherent diversity should be on it.

Thanks again Scott,
Doug
w3ub
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Re: P2 Coherent Diversity Issue

Postby w3ub » Thu Dec 31, 2020 1:31 pm

Just wanted to add one thing before I forgot ... I don't think this problem is a fundamental problem with speed/timing, it occurs (for me) only during a transition, either from RX to TX, or more easily reproduced during the transition from diversity on to off, or, or during the transition from off to on.

It seems like things get screwed up only during these transitions, which implies it is fixable.

Doug

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