FlexControl hysteresis problem

Paul W5PF

My Flex Control knob has a lot of hysteresis. That is, if I am tuning the vfo in one direction and then turn the knob in the other direction I have to make from 1/8 to 1/4 turn before the vfo responds. This makes it very hard to fine tune digital stations with the FlexControl. I am running SSDR 1.0.24 on a Win7 Pro machine. The FlexControl is connected to SCAT not through DDutil. Anyone else have this problem? Thanks, Paul W5PF

John W9KXQ

Paul, I have had the same problems and found it very hard to work a contest by the "Hunt & Call" method due to this. I expected that they would be addressed in time but as of the last update, it had not as far as I can tell. I am running the same SSDR & Win7 Ultimate on a 32 bit machine. Hopefully someone else has a fix. 73 John W9KXQ

WA6FXT Mike

I see this also; however, it seems to come and go. Hmmm

Tim - W4TME

The issue is most probably command queuing coming from the FlexControl. As you rotate the knob, the shaft encoder switches opens and closes, sending three byte commands down the USB/Serial connection to the PC which then formulates an appropriate FlexLib command that is set to the radio to tune the radio X number of tune steps in a particular direction. There is also an acceleration algorithm that senses when you are turning the knob faster and informs the radio to execute multiple tuning increments in one radio tuning operation. So as the commands are being sent to the radio, the serial/USB interface has a FIFO buffer that queues these three byte serial command data. If you are rotating the knob at a moderate rate, this buffer will queue commands, so that when the knob stops sending data, there is still data in the queue that gets processed. In addition, if you are rotating the knob at a moderate to fast the acceleration algorithm in in play so when you stop rotating the knob in one direction, the amount of frequency changes the radio executes as the FIFO command buffer flushes will be greater, amplifying the effect you are seeing. So, what can you do to mitigate this? One option is to change the size of the com port FIFO buffer to a smaller size. The following HelpDesk article is PowerSDR specific, so just do step 2 ( http://helpdesk.flexradio.com/entries/22185687-How-to-Mitigate-FlexControl-Latency) If this does not help, the other issue could be the USB interface the FlexControl is plugged into. It is is sharing a controller with other devices, like a mouse, keyboard or printer that can effect the data rate. You can try connecting the FlexControl to a different USB port when SmartSDR is not running.

Paul W5PF

Tim, thanks for the explanation. I will see what I can do with the buffer and maybe try another port. I am using a usb wireless mouse. The mouse wheel seems to tune the vfo without the hysteresis. Paul W5PF

Stu Phillips - K6TU

I would be very interested to know the CPU type in the PC and also what the typical CPU utilization is when running SmartSDR and then also with running SmartSDR and tuning the FlexControl. Does this problem occur when the slice is on the edge of the panadaptor and so when tuning the FlexControl, causes the pan adaptor to scroll? Also check that SmartSDR is using Maximum Hardware Graphics acceleration... the only time I have seen the issue described above is when the CPU is almost maxed out - usually because there isn't an adequate graphics controller in the machine or for some reason, SmartSDR doesn't detect and use it. This latter case can occur when there is some form of virtual screen driver in the way - using remote control packages like logmein can cause this. Note that at present, SmartSDR does not seem to implement accelerated tuning with FlexControl. Stu K6TU

Paul W5PF

Stu, Tim et.al.; When you asked the questions about slice position, cpu usage etc. I had a more careful look at when the problem occurred. To make a long story short, the set **** holding the knob to the shaft was loose. I tightened it up and the operation is very smooth now. Mechanical hysteresis I guess! Paul W5PF

Tim - W4TME

BIG GRIN :-)

Ken - NM9P

What size wrench do I need to adjust the set ****? I have tried several and haven't found the right one yet.....I have a different problem with the knob.

Paul W5PF

According to the box mine are in it is .028 in. It is the smallest I have.