Page 1 of 2

Bandwidth Issues on FDM-S2

Posted: Thu Oct 01, 2020 5:20 pm
by W6UV
I'm using an Elad FDM-S2 with SDR-Console v3.0.25. When I start the radio using a bandwidth of 1.536 MHz, everything appears to work normally. If I select a BW of 6.144 MHz when starting the radio, there appears to be artifacts spread throughout the bandwidth and everything sounds very raspy. Below are screenshots taken with the two BW settings. What is the cause of this? Is 1.536 MHz the highest BW that can effectively be used with the FDM-S2?

BW=1.536 MHz, center frequency=770 kHz:
Image

BW=6.144 MHz, center frequency=770 kHz:
Image

Re: Bandwidth Issues on FDM-S2

Posted: Thu Oct 01, 2020 5:23 pm
by G0OFE
I have noticed this kind of thing before, and traced it to when I was using another high traffic USB device at the same time as the S2.

Worth going through what else is using USB ports on your PC, or if using USB2 for your S2, try a USB3?

Re: Bandwidth Issues on FDM-S2

Posted: Thu Oct 01, 2020 5:55 pm
by Simon G4ELI
I can't read the screenshots. Please use the built-in Screenshot option.

Are you on USB2 or USB3?

From the waterfall it does look like packets are being lost.

Re: Bandwidth Issues on FDM-S2

Posted: Thu Oct 01, 2020 8:37 pm
by W6UV
I've attached two screenshots taken with Console itself. The screenshot taken at 132248 was at 1.536 MHz BW and the one with timestamp 132357 was at 6.144 MHz BW.

The system is a AMD Ryzen Threadripper 2950X 16-core CPU @ 4.2 GHz with 128 GB of RAM running Windows 10 Pro version 2004. The FDM-S2 is plugged into a USB 3.1 Gen 2 port. The only other USB devices in the system are a keyboard and a mouse, both plugged into USB 3.1 Gen 1 ports. The graphics boards is a NVIDIA RTX 2060 (and FFTs are computed on the CUDA cores on the GPU).

The issue is worse if the FDM-S2 is plugged into a USB 3.1 Gen 1 port.

Re: Bandwidth Issues on FDM-S2

Posted: Thu Oct 01, 2020 11:11 pm
by Tony_AD0VC
On the off chance that the radio is overloading, try kicking on the attenuator with 6Mhz BW.

Tony

Re: Bandwidth Issues on FDM-S2

Posted: Fri Oct 02, 2020 4:16 am
by Simon G4ELI
Tony_AD0VC wrote:
Thu Oct 01, 2020 11:11 pm
On the off chance that the radio is overloading, try kicking on the attenuator with 6Mhz BW.

Tony
Good idea. Either it's overloading somewhere or there's a USB issue. When the waterfall isn't clean then it's often an indication of bad packets, but with USB 3.1 6 MHz bandwidth is not big deal.

There are some very strong signals there, so it could be overloading.

Re: Bandwidth Issues on FDM-S2

Posted: Fri Oct 02, 2020 4:41 pm
by W6UV
Thanks for suggesting using the attenuator. I gave it a try and it didn't make a difference.

Yes, there are some very strong AM broadcast signals there, but none of the stations are closer than about 35 miles from my location. I do have large antennas, however, so that might be a factor here (the screenshots were made with a big rombic connected to the FDM-S2).

If this is a USB issue, how do I go about diagnosing it? I don't have any other USB devices plugged into the computer with the exception of the keyboard and mouse, and I can't do without those. I've tried moving the FDM-S2 around to different USB ports (all on the motherboard--no hubs here) and it didn't make any difference at all.

The real reason I'm concerned about higher bandwidths is because the FDM-S3 is finally available and I'm planning to get one. It supports bandwidths of up to 24 MHz, but if my setup can't even handle 6 MHz effectively on the S2, I think 24 MHz will be even more problematical. One possible saving grace, however, is that the S3 has a USB 3 interface versus the USB 2 interface on the S2.

Re: Bandwidth Issues on FDM-S2

Posted: Fri Oct 02, 2020 5:50 pm
by Simon G4ELI
With the 6 MHz bandwidth attach a screenshot of the whole 6 MHz, let's see what you've got between 0 and 6 MHz.

Re: Bandwidth Issues on FDM-S2

Posted: Sat Oct 03, 2020 1:55 am
by Tony_AD0VC
Might still be overloading. The built in attenuator is only 12db (regardless of what it says in SDRC). I have seen situations with my S2 where 12 db was not enough. If you have an external attenuator you can use, you might give it a try. I have not see a case where 20db was not enough.

Tony

Re: Bandwidth Issues on FDM-S2

Posted: Sat Oct 03, 2020 11:18 pm
by NN4F
Are you getting the same effect when using our Elad-SW2 software?