Re: Spectrum window crash / spot persistence

Patrick Herborn

A quick update.

I got a chance to try the HDSDR test tonight (with SDRPlay ExtIO DLL).

As anticipated, HDSDR also froze/crashed, further pointing toward the DLL as the
cause. That being the case, I tried Steve's config for the DLL and hey presto,
it works! OK, great - a working config, now find out the critical bit....

Steve had LNA gain 2, Low IF, 200kHz IF filter, and 31 IF gain, with a Total
Gain Reduction of 43dB....

First test : try the ADC AGC rather than a static gain. That still worked so
that was good.

Next test : try different LNA gains. That also worked fine - with more gain
it would show ADC OVERLOAD on the SDRPlay config window, and there was
clipping hash in the spectrum, BUT it didn't crash!

Next test : try it with the wider 1.536kHz IF bandwidth. This got rid of
the decimation, again it would show ADC OVERLOAD but not crash, which is
still good.

The final change was back to Zero IF - immediate freeze/crash. Right, it
doesn't like Zero IF!

It looks like the only thing I *NEED* to change in order to avoid
freezes/crashes is to use Low IF.

I tested this in N1MM+ and it was stable running the RSP1A itself,
I haven't tried WB at this time but I would be somewhat surprised
if this didn't fix it.

There is one caveat here.... it was a different rig and I had to run
FM with zero mic gain to get a carrier. Thought this one could be
keyed by MIC UP and MIC DOWN on CW but alas not, and didn't have a
spare key to hand. So it COULD still break, *BUT* given that it
pretty much IMMEDIATELY broke with Zero IF even at 5W, I suspect
that it will behave OK. Fingers crossed! Should get a chance to
test it on the actual rig we should be using for IOTA tomorrow.

If it pans out well (no pun intended ;) ) the use of Low IF could then
make its way into the manual....

Best regards,

Pat. (M0MGO).

On Tue, 23 Jul 2019 07:07:44 -0400
"Tom Wagner (N1MM)" <n1mmtomwagner@...> wrote:

There is a bug on transmit. Try right-click reset radios to start it
going again.

The DLL for SDRPlay can crash when restarted. Don't keep closing and
opening the spectrum window.

If you insist on trying to crash the window by opening and closing, you
can make spots persist in the telnet window.

The db scale is not accurate.  Hiding it to provide more spectrum
display area is intentional.

In some configurations, I prevent the spectrum from displaying during
transmit. This is intentional. Transmitting overloads the SDRPlay and
wipes out signals near the transmit frequency.

SDR Console is a much better SDR receiver & display.  It does not
integrate finding *signals* (the red dots), keyboard (shift up/down to
jump signals), radio control and spot display.

Tom - N1MM

On 7/22/2019 9:11 PM, Patrick Herborn wrote:
Evening All!

Some further updates on this, still using the 18Jul release.

So far I have not been able to replicate the crash with IC-7300, it
looks like the current release is OK for the moment. It does occasionally
reset the waterfall but that is not an issue - the spots stays.

I have had more time with the RSP1A and have more info on that :

With N1MM+ driving the RSP1A, the spectrum display will hang at
occasions around a transmit event. Sometimes it is at the start,
sometimes it is at the end, but it seems to be stable so long
as you don't TX.... if you do, and if it freezes, then it is not
possible to close and re-open the Spectrum window, nor is it
possible to open the SDRPlay ExtIO config window. The only way
to recover is to exit and re-start N1MM+ as a whole - sometimes
this might need Task Manager to kill hung processes. Other times
the frozen Spectrum window will cause a full N1MM+ crash.

Thinking this was a hardware issue I proceeded to add a ferrite
to the USB cable. Unfortunately that did not help, but it did lead
me down a different path. Thinking that the issue was a software
one rather than hardware, and that it was related to the magnitude
of the returned data from the SDR, I tried using Waterfall Bandmap
to provide a spectrum data source to N1MM+....

With WB running, the problem moved. N1MM+ faithfully reported what
WB was sending it, BUT WB itself would hang. It is possible (sometimes
with the help of Task Manager) to restart WB and get the spectrum
going again without having to restart N1MM+ - which is a step in
the right direction, but tedious when WB frequently hangs during TX.

The fact that WB and N1MM+ both freeze is perhaps related to the
fact that WB was "merged" into N1MM+ and hence the source may be
very similar. That could help narrow things down a bit.

As a sanity check, and to "prove" the point that this issue is
most unlikely to be hardware, I tried running with no spectrum
display in N1MM+ and instead used SDRConsole V3 to display the
waterfall. I can confirm that, despite trying quite hard, I was
unable to "break" SDRConsole V3 - no matter how many times I
went to TX, no matter what power or mode, the spectrum data carried
on without any issues at all. WB and N1MM+ could be made to
hang with just 5W in CW! In SDRCV3 one could see the signal
strength rise from -110dBm to -37dBm with 5W, climbing to
-27dBm at 50W as expected, and getting all the way up to
-21dBm at times (the ADC AGC was targetting around -30dBm
so the -21 was brief until the outer AGC loop brings it down).
Thinking about that..... the scale on the Spectrum window
is "limited" to 50dB, so again I wonder if it's possible
that with a signal at least 80dB above the noise floor, could
that cause issues with the spectrum code ? SDRCV3 is setup
to span -140dBm up to somewhere around -20dBm - not much
point in going over that when the ADC AGC loop tries to
keep it down to -30dBm.... but that's a range of 120dB,
more than twice what's in the Spectrum window.

As a further aside - for some reason, unless I open the
config using the < in the top right, the dB scale on the
left, and the key on the right do not get rendered. Doubt
it is related, but it's not working as I suspect it is
supposed to do. When I close the config using > then the
dB scale and the key disappear again. For the avoidance
of doubt, this is in the Landscape mode.

It is possible, I guess, that SDRConsole is initialising the
RSP1A and its driver in a manner which differs from what WB
and N1MM+ do - I have a feeling that SDRCV3 doesn't use the
ExtIO dll - I guess I could verify if it is an ExtIO dll
issue by using the SDRPlay ExtIO dll with HDSDR - if that
breaks then it's an SDRPlay issue, not N1MM+/WB, but if
HDSDR works fine with the ExtIO dll then it narrows it
down further to 1) the hardware config set as the programs
start, or 2) N1MM+/WB getting themselves in a twist with
some aspect of the IQ data.

I'll keep digging - in the meantime if anyone has any further
suggestions for things to try in order to narrow it down, that
would be much appreciated!

Whilst I was hoping to use this setup for IOTA this coming weekend
I am slowly resigning myself to the fact that we will have to use
the older setup with N1MM+ talking to SDRCV3 and SDRCV3 using
OmniRig to talk to the radio. That setup has worked well in the
past, BUT you don't get spots on the spectrum, which is useful
for an S&P station.

Best regards,

Pat. (M0MGO)

Patrick Herborn <pat@...>

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