Is A Slight Tuning Latency (~100 - 300 mS) Typical For SmartSDR/FLEX6500 ?

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  • Updated 4 years ago
(If this is deemed inconsequential then I apologize.)

(Background: I'm running Windows 7-64 bit on a homebrew PC based on an early Intel quad core CPU and an ancient Intel motherboard, with an Nvidia 8800GTX video card. The Win7 'performance test' rates the configuration at 5.9 due to a 3GB memory limitation.)

If I offset my FLEX6500 from a carrier, with the radio receiving SSB such that a beat note is audible, and then quickly turn the FlexControl tuning dial, there is a perceptable delay (my best estimate is between 100 & 300 mS) between the cessation of the dial turning and the beat note frequency stabilizing. The frequency shown on the screen seems to exactly track the dial turning so I don't believe that the latency is a function of the USB link to my PC. I've run the experiment using 1,5 & 10 Hz tuning step sizes and from what I hear believe that the lag is unaffected.

I thought that the delay might be in the GigaBit EtherNet switch that I route everything through and so I temporarily directly connected my PC to the radio but could not tell any difference; the slight lag between the tuning dial coming to a halt and the beat note stabilizing remained the same so far as my ear could tell.

I understand that the FLEX6500 is basically a dedicated LINUX computer intermingled with digital and analog RF hardware and so am wondering if the lag I am hearing may simply be processing delay due to the LINUX OS ?

(This problem may simply be stage-fright on my part - getting used to a new radio environment. When I bought my TenTec Paragon in 1988 I found problems with it and yet it still graces my operating desk .... I got used to it.)

- Paul, WB5AGF
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Paul, WB5AGF

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Posted 4 years ago

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DrTeeth

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First thing to do is turn off the com port buffers, that should help.
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Tim - W4TME, Customer Experience Manager

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Refer to this article on reducing FlexControl latency
http://helpdesk.flexradio.com/hc/en-us/articles/202118458-How-to-Mitigate-FlexControl-Latency

Then update your video drivers.
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Paul, WB5AGF

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Saturday Night
08 Nov 2014

ref a comment in my original inquiry :

" The frequency shown on the screen seems to exactly track the dial turning so I don't believe that the latency is a function of the USB link to my PC."

(Something not in my original message)
I have the spectral display refresh cut back to 10/s; doing that reduces the CPU load down below 10 percent.

I suspect that I need to go learn how to run Wireshark and examine the back-and-forth command/response sequences.

- Paul, WB5AGF
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Jim, KJ3P

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I solved a USB latency problem (in other equipment) by installing a separate good quality USB card in the PC. I only used this card/controller for the target device, since a multi-port USB controller will only run as fast as the slowest device connected (I've been told). Instant wonderfulness! Your mileage may vary, but it's an inexpensive thing to try.

  --Jim, KJ3P

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Paul, WB5AGF

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Sunday Evening
09 Nov 2014

My Intel motherboard provides a bunch of USB 2.0 ports, and that is what I have been using for my FlexControl, but this afternoon I tried moving over to one of the connectors on a PCI Express USB 3.0 card that I recently installed .... no apparent change.

- Paul, WB5AGF