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Author Topic: Sherwood Engineering Receiver Test Data  (Read 2265 times)

K6BRN

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Re: Sherwood Engineering Receiver Test Data
« Reply #30 on: March 20, 2021, 03:35:37 PM »

Ron:

Yes, I'm surprised.  But then, I'm not aware of the limits and "gotcha's" in your approach, either.

A good algorithm designer (subsystem engineer) will also have a very big bag of mathematical and instruction shortcuts that approximate the DSP funtion they are implementing, with reasonable and acceptable losses.  Which makes performing more with less very possible.

I still think building and demonstrating an AM BCB receiver is a good challenge.  It's very do-able without needing too many shortcuts, and the end product would make a fun project.

Best Regards,

Brian - K6BRN
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #31 on: March 20, 2021, 03:42:17 PM »

Just for chuckles, we can compare it to a Flex-6600, too.  The Flex crew includes some very good DSP designers.

Flex wishes they had the designer of the Airspy working for them.
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #32 on: March 20, 2021, 03:48:16 PM »

Yes, I'm surprised.  But then, I'm not aware of the limits and "gotcha's" in your approach, either.

As I said, it's fully compliant (as in bit perfect). The only limit is bandwidth. DVB-T2 is used for 1.7, 5, 6, 7 and 8 MHz channels, and the X15 can only do up to 5 MHz.

You can inspect the source code. It's all open source.

https://github.com/gnuradio/gnuradio/tree/master/gr-dtv/lib/dvbt2

https://github.com/gnuradio/gnuradio/tree/master/gr-dtv/lib/dvb
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K6BRN

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Re: Sherwood Engineering Receiver Test Data
« Reply #33 on: March 20, 2021, 03:54:36 PM »

"Flex wishes they had the designer of the Airspy working for them."

Really?  Did you ask them?  If not, why not be proactive and give them a call.  Maybe if you get both parties together you can arrange a commission - this happens a lot in my business.  And the commissions are usually hefty because the consulting fee the expert charges is usually hefty, as long as they make a commensurate difference.

Flex has a nice big military contract right now and I'm sure they could use a savant to massivly improve their products, if he or she was truely capable and had a good track record of doing so.  A win-win situation for all, in the end.

Brian - K6BRN
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K6BRN

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Re: Sherwood Engineering Receiver Test Data
« Reply #34 on: March 20, 2021, 03:57:21 PM »

"As I said, it's fully compliant (as in bit perfect). "

Excellent! Has it been implemented, built, tested and demonstrated?

The AM BCB challenge would still be a fun project.

Brian
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #35 on: March 20, 2021, 04:17:56 PM »

Excellent! Has it been implemented, built, tested and demonstrated?

Here it is running in Linux. Taking about 3/4 of the cycles in each of the two armv7 cores.

« Last Edit: March 20, 2021, 04:20:59 PM by W6RZ »
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K4FMH

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Re: Sherwood Engineering Receiver Test Data
« Reply #36 on: March 20, 2021, 05:03:06 PM »

I'm tempted to Amazon Rob Sherwood an Airspy HF+, just to shut up the naysayers. Based on testing from others, it would probably place next to the FTdx-3000.

You’d be better served to contact Rob to see if he’s interested in testing the AirSpy HF+. I’ve already offered him one and a couple from SDRPlay but he declined.

All of his measurements are for receiving AND the ranking is ONLY made on narrow dynamic range. This does not necessarily mean it’s the overall best Rx. He ranks them this way for his own interests: that of a CW contest op. To say that this Rx is ranked here and is better than that Rx is ranked lower ONLY pertains to narrow dynamic range.
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #37 on: March 20, 2021, 05:13:07 PM »

All of his measurements are for receiving AND the ranking is ONLY made on narrow dynamic range. This does not necessarily mean it’s the overall best Rx. He ranks them this way for his own interests: that of a CW contest op. To say that this Rx is ranked here and is better than that Rx is ranked lower ONLY pertains to narrow dynamic range.

I got the 84 dB 3rd order dynamic range number from this link.

http://www.dc4ku.darc.de/AIRSPY_Test_English.pdf
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #38 on: March 20, 2021, 05:22:26 PM »

Here's the Beagleboard-X15 processing 1.5 Msps of bandwidth, decoding wideband FM and generating an FFT panadapter and waterfall. It could do more bandwidth, but my X15 is headless and I'm using X11 forwarding over SSH (which takes a lot of cycles).

Modern CPU's are very good DSP processors.

Video:

http://www.w6rz.net/fmx15.mp4

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N2DTS

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Re: Sherwood Engineering Receiver Test Data
« Reply #39 on: March 20, 2021, 05:41:40 PM »

I looked it up and the 6700 has double the sample rate of A/D converter over the 6400.
That may be why its #2 on the list.
Direct Sampling SDR 245.76 Msps – 16 Bit for the 6700.

Direct Sampling SDR 122.88 Msps – 16 bit for the 6400.

I would think they are different chips...


I wonder how the Flex 6700 does so well, does it have some sort of filter before the A/D converter or just a super A/D converter?

There are only two ADC's used by direct sampling radios from Icom and Flex. The LTC2208 and the AD9467. That's it. And they have very similar performance.

The reason that radios test all over the place on the Sherwood list is due to semiconductor device to device variability. Just look at radios with more than one sample on the list. The IC-R8600 is simultaneously at the top of the list at position 4 and at position 20. Same goes for Flex products. The 6700 is at both position 2 and 22 (below the IC-7300).
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N2DTS

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Re: Sherwood Engineering Receiver Test Data
« Reply #40 on: March 20, 2021, 05:43:08 PM »

Maybe the airspy guy can get flex to help him get an ethernet interface going instead of the high latency usb crap.


Just for chuckles, we can compare it to a Flex-6600, too.  The Flex crew includes some very good DSP designers.

Flex wishes they had the designer of the Airspy working for them.
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #41 on: March 20, 2021, 05:49:43 PM »

I looked it up and the 6700 has double the sample rate of A/D converter over the 6400.
That may be why its #2 on the list.
Direct Sampling SDR 245.76 Msps – 16 Bit for the 6700.

Direct Sampling SDR 122.88 Msps – 16 bit for the 6400.

I would think they are different chips...

Same chip. It comes in two different speed grades, 200 and 250 Msps. 3rd order dynamic range isn't really a function of sampling rate.

https://www.analog.com/media/en/technical-documentation/data-sheets/AD9467.pdf

« Last Edit: March 20, 2021, 05:53:32 PM by W6RZ »
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W6RZ

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Re: Sherwood Engineering Receiver Test Data
« Reply #42 on: March 20, 2021, 05:55:57 PM »

Maybe the airspy guy can get flex to help him get an ethernet interface going instead of the high latency usb crap.

I'm not a fan of USB either, but Ethernet adds a lot of cost because you need a CPU to run the protocol stack.


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N2DTS

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Re: Sherwood Engineering Receiver Test Data
« Reply #43 on: March 20, 2021, 06:27:43 PM »

The airspy gets quite bad reviews.
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N6YWU

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Re: Sherwood Engineering Receiver Test Data
« Reply #44 on: March 20, 2021, 09:53:02 PM »

I'm not a fan of USB either, but Ethernet adds a lot of cost because you need a CPU to run the protocol stack.


The Hermes Lite 2 SDR runs its 1 Gb/s Ethernet stack on a state machine inside an FPGA, no CPU in the box.  Open source, so you can read the Verilog.  About twice the price of an SDRPlay, but you get a full duplex QRP transceiver in exchange.
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