Volume cuts in and out intermitently every second SOLUTION!

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bubblegumpi
Posts: 49
Joined: Fri Oct 14, 2016 11:41 pm

Volume cuts in and out intermitently every second SOLUTION!

Postby bubblegumpi » Wed Nov 09, 2016 11:23 pm

Lately when I listen to the SDR it sounds like someone is turning the sound on and off about once a second. Its unuseable to listen to.

The problem? I had the band width set to 10 MHz. This works some times, but if memory is an issue it will cut in and out. You can tell by looking at the CPU usage bar in the first window.

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dsalomon
Posts: 51
Joined: Sat Oct 10, 2015 1:50 pm

Re: Volume cuts in and out intermitently every second SOLUTION!

Postby dsalomon » Thu Nov 10, 2016 4:17 pm

A large bandwidth SDR takes a LOT of processing power, and not just CPU. The same thing will happen with any SDR that has a large bandwidth. How severe the breakups are depends on several things:

1. Raw processing power, i.e. the CPU and main memory.

2. The USB chipset. This has a rather large impact on how well the SDR performs. Look at many other SDR site forums and you will see a LOT of discussion about which USB chipsets work better than others. In nearly all the reading I've done about SDR sound breakup issues, the vast majority of solutions is to use a USB card with a "better" chipset. There's really no way to definitively state which ones are better than which other ones. Also, having a USB card with one chipset per USB port (vs a single chipset that handles 2, 3 or 4 ports) makes a BIG difference. It really ends up being trial and error with USB cards. My own testing has shown that Renesas chipset based USB3 soundcards work MUCH better than others, at least for my setup. I have two of these in my system: https://www.amazon.com/gp/product/B00HJ ... =UTF8&th=1. They handle the RSP without a problem. They also handle SDRs with 56MHz bandwidth without a problem. I should note that my system has 32GB main memory and a 6 processor fast CPU, so it's a high end system. Even with that raw processing power, I tested many USB cards that did NOT work well, i.e. lots of sound breakups. I tested over a dozen different USB cards, using numerous different USB chipsets. My testing was done to get a Ettus B200 SDR to work reliably. It has 56MHz bandwidth.

3. The USB implementation within the PC. Some are just better than others, and there's really no way to know which is better, or why. You can take the same USB card and put it in two systems with different motherboards, but the same CPU and memory and have significantly different SDR performance. I tried this. I know it matters, but I don't know why.

4. Which motherboard PCI Express slot the USB card is placed in. You have to read the documentation for your motherboard carefully to understand about PCI Express slots and lanes. Which PCI Express slot the USB card is placed in DOES make a difference.

Going through all that I described is, in most cases, significant overkill and unnecessary. However, if getting the very last bit of performance out of your PC makes the difference between sound breakups and smooth performance, then it's nice to know where to look and what matters.

73 - David, AG4F

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F1BJB
Posts: 103
Joined: Wed Jul 15, 2015 4:24 pm
Location: Beauvais France

Re: Volume cuts in and out intermitently every second SOLUTION!

Postby F1BJB » Mon Nov 14, 2016 11:38 pm

Hi
Except for displaying a wide spectrum when you want to listen to a particular signal it is a bad idea
to use an 8 MHz bandwidth.
You increase the risk of overloading the ADC.
If you record the whole spectrum (a great advantage of SDR IMHO) you get very big files.
And of course you use a lot of processing power so your computer cannot do other things
while you listen.

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dsalomon
Posts: 51
Joined: Sat Oct 10, 2015 1:50 pm

Re: Volume cuts in and out intermitently every second SOLUTION!

Postby dsalomon » Thu Nov 17, 2016 4:27 pm

F1BJB -

I respectfully disagree that using a large bandwidth is a bad idea in general. Many people, myself included use SDR exactly because large bandwidths are available. Besides just being better receivers overall when compared to many multiple conversion type receivers, they offer the end user the ability to look at huge chunks of spectrum instantaneously. One of my uses for SDRs it to search large amounts of spectrums for signals, and also to watch moving signals, such as radars that scan across huge areas of the spectrum.

Your comment about increasing the risk of ADC overload can be mitigated by the use of filtering. Also, whether or not ADC overload may occur depends a lot on the RF environment at the user's location. Some users may be in RF quiet areas where allowing in everything may never produce an overload condition. Some other users may be in heavy RF areas where some mitigation must be done all the time to prevent overloading. Simply stating that using 8MHz increases overload risk may have some readers interpreting that statement incorrectly ... that 8MHz will cause negative results. That simply is not the case. Each user needs to independently evaluate his/her specific situation re: what practices to put into place when using SDRs.

Recording the whole spectrum is also not a bad idea. Disk space is cheap these days. If you want to record for later review and analysis, why not? I can get a 4TB external drive for just over $100 at Amazon, 5TB for about $125, 8TB for $250! Using those, I can record a LOT of spectrum over a LOT of time.

Finally, your statement about large bandwidth processing taking up so much processing power that the PC can't do anything else is just plain wrong. Yes, a PC can be built with very low capacity components that might not be able to run an SDR at all. Conversely, a PC can be built to handle MASSIVE computing tasks and running an SDR at 8MHz is no more than a blip on its overall processing abilities. My main desktop PC has a P9X79PRO motherboard, 32GB of memory, a 6-core Intel-i7 processor, a decent nVidia video card, and 2 PCI Express USB 3.0 cards with 4 ports each providing 5GHz of bandwidth PER USB connection (i.e. 40GB total across 8 connections). I run multiple, high bandwidth SDRs (up to 56MHz bandwidth, not just 8MHz) simultaneously and my processor and memory have room to spare for many other tasks at the same time. I do it every day.

So, please don't spread incorrect advice to users who may not know what can really be done. If someone has problems with using their RSP, how about responding with information that could help that person instead of just giving inaccurate, blanket statements. Maybe running at 8MHz IS an issue with your particular PC setup, but that's not the case for everyone, so please don't lead people to believe that everyone will have the same problem.

Best regards - David, AG4F

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F1BJB
Posts: 103
Joined: Wed Jul 15, 2015 4:24 pm
Location: Beauvais France

Re: Volume cuts in and out intermitently every second SOLUTION!

Postby F1BJB » Fri Nov 18, 2016 8:33 pm

Of course if you want to record a 1296MHz EME contest you can use an 8Mhz bandwidth
You will get big wave files that you cannot split or explore with current audio software
You wont be able to play them on many computers.
But you wont get any overload helped a lot here by the directivity of your aerial
Now let's do the same thing at night with the NDB band 250 to 450KHz and a 10m vertical whip
That is a completely different story .
8MHz bandwidth is useless in both cases in the second it is unusable at least with an SDRplay
Using a magnetic loop or front end filtering brings you back to the first case.
My observation is that using a big computer multitasking for SDR is not a too good idea
because they tend to radiate more interference than small ones.

Regards

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