Corruption of SAM SB audio

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Paul
Posts: 355
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Corruption of SAM SB audio

Post by Paul » Sun May 27, 2018 5:38 pm

Sadly, not a new problem for me as this has occured occasionally in the past and I have managed to "cure" it by fiddling with the SAM/HP filter settings menu, although quite how I have managed this is rather opaque, but always returning to SLOW mode.
Gain/Gain reduction settings , volume and antenna choice do not seem to be related.
If anyone has any useful suggestion on how to resolve this, I would be most grateful.
This current occurrence is associated with the latest Windows 10 update, which produced a plethora of unwanted effects, some of which I have identified and hopefully sorted out to my satisfaction.
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g1hbe
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Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Corruption of SAM SB audio

Post by g1hbe » Sun May 27, 2018 10:05 pm

What's actually happening - ie what does it sound like? I notice from your screenshot that your noise level is high and I can't see the level of the incoming signal as it is hidden behind the SAM box. However I think the SNR is very poor, possibly 3dB? I think under those conditions it would be difficult for any SAM system to lock.
EDIT - I've just noticed you have the gain to minimum.

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Andy

Paul
Posts: 355
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Re: Corruption of SAM SB audio

Post by Paul » Mon May 28, 2018 5:15 am

Thanks yet again Andy. I'm pretty sure that in this case you are on the money.
However, somehow or other, it's back to normal again, but I've also had all sorts of issues with the latest teration of Windows 10 (knocking them off one-at-a-time).
Histoically - thanks also for previous advice regarding getting myself an HF preselector - have it going, but only on Port A with the Wellbrook as although the Hi-Z Port works well with a longwire, I'm still unhappy with the loop's performance on it (and with the preselector - really problematic) - I do intend to revisit this over time.
Connection to this Port is via an approx 8" pigtail, terminating with an SO239 (longwire connected via a PL259 or the loop with BNC plus adapter).
The loop itself is on an aluminium mast, about 6' up, attached to a wooden fence post (no earth) and at present only about 1 yard from the house (the best I can manage at the moment) - so a short run of RG58 only.

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pgoelz
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Joined: Fri Jun 02, 2017 11:05 am

Re: Corruption of SAM SB audio

Post by pgoelz » Fri Jun 01, 2018 2:46 pm

Paul wrote:Histoically - thanks also for previous advice regarding getting myself an HF preselector - have it going, but only on Port A with the Wellbrook as although the Hi-Z Port works well with a longwire, I'm still unhappy with the loop's performance on it (and with the preselector - really problematic) - I do intend to revisit this over time.
Connection to this Port is via an approx 8" pigtail, terminating with an SO239 (longwire connected via a PL259 or the loop with BNC plus adapter).
The loop itself is on an aluminium mast, about 6' up, attached to a wooden fence post (no earth) and at present only about 1 yard from the house (the best I can manage at the moment) - so a short run of RG58 only.
FWIW, I am using a Wellbrook with excellent results. It is connected to the HiZ port with a 9:1 balun (not sure if that ratio is needed but it was the only balun I had). In my case, the Wellbrook is up about 10 feet and about 10-15 feet away from an aluminum sided house. Performance is VERY good over the entire 100KHz to 30MHz range.... in most cases it outperforms a fan dipole on the roof (another 10 feet higher and in the clear). I could not possibly ask for more. The only caution is to make sure the ADC is not in overload. I run the input attenuation at one notch above the maximum setting (ie., almost minimum gain) and rarely need to touch it.

BTW, the Wellbrook works equally well into port A but I needed the coaxial ports for other antennas.

Note that I did try the Wellbrook indoors on the second floor of the (aluminum sided) house and performance was very poor. I wanted to try it in the attic (above the siding) but because the loop is glued to the preamp housing, I could not disassemble it to get it through the small hatch to the attic.

I'm curious why you feel you need a preselector. Do you have issues with extremely strong local signals? I find that as long as the ADC does not indicate it is in overload, the only issue I have with strong signals is occasional IF AGC pumping in the presence of VERY strong inband signals (local CW operators in the ham bands in particular).

Paul

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Paul
Posts: 355
Joined: Fri Feb 17, 2017 9:52 am
Location: SW UK

Re: Corruption of SAM SB audio

Post by Paul » Sun Jun 03, 2018 5:13 am

Thanks Paul
That's very helpful, in that you find it equally good on Port A when compared to the HI-Z port, although I saccept that the latter is to be preffered by properly equipped VLF (at least) enthusiasts.
Also your ADC overload comment is interesting, as this was a regular Wellbrook associated occurrence for me using SDRuno V1.22.
I have very recently been experimenting with V1.23 on my RSP 2 and so far, I have experienced no ADC overload events, which is probably a result of lower cpu demand.
I hope that this will remain the case....
Thanks to the back-room guys!

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pgoelz
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Re: Corruption of SAM SB audio

Post by pgoelz » Sun Jun 03, 2018 10:19 am

ADC overload is a function of the incoming signal strength, not the CPU load. The ADC sees all signals within the current bandwidth and the strongest signal must not exceed the maximum that the ADC can handle. If the ADC indicates overload, just reduce the incoming signal strength with the gain slider. Note that the default gain slider function is ATTENUATION, not gain. So to reduce the signal strength you would raise the slider.

Paul

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