Some questions

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Michal Demin

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Mar 21, 2011, 1:48:45 PM3/21/11
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Hello,

I just received rfexplorer from seeedstudio. I have some questions
about the operation:

1. sweep time - How long does it take for one sweep to finish?
RBW is unknown. I would guess 100 or so steps per scale. 200us
settling time. That gives 20ms/sweep ?

2. Are FW sources going to be released ?

3. Is there description for the serial protocol ? I guess that not
everybody has windows to work with :)


Michal

Ariel Rocholl

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Mar 21, 2011, 2:07:32 PM3/21/11
to rf-ex...@googlegroups.com, Michal Demin
Hi Michal,

All good questions. See below

2011/3/21 Michal Demin <michal...@gmail.com>

Hello,

I just received rfexplorer from seeedstudio. I have some questions
about the operation:

1. sweep time - How long does it take for one sweep to finish?
RBW is unknown. I would guess 100 or so steps per scale. 200us
settling time. That gives 20ms/sweep ?

Sweep time is a function of settling time (which is higher as you select a narrower span) and sweep steps, which is constant=112.

I have a prototype GUI which optionally display #sweep/second and RBW on screen, I can make it available in the near future as a beta for testing if you have interest. It will become part of baseline firmware at some point.
 

2. Are FW sources going to be released ?

PC Client source code will be available for download in a week or two, I'm just working on wording for GPL requirements.

The embedded Firmware won't be publicly released because include some commercial libraries that are incompatible with GPL. I'm working on a couple of ideas to extend RF Explorer in a way that can be hacked and still be compatible with licensing requirements. It will probably take the shape of a programmable extension module, interacting with the main RF Explorer MCU.
 

3. Is there description for the serial protocol ? I guess that not
everybody has windows to work with :)


Sure, I will publish that together with PC Client open source. I will offer full support to any effort on connecting RF Explorer to other OS like Linux, MacOS, Android, WebOS, you name it. An advantage of using a serial interface is the universal nature of the connection. The only limitation may be the Silabs CP2102 driver availability for the specific OS, but Linux and MacOS are well covered as far as I was told.
 

 Michal

Regards

--
Ariel Rocholl


Michal Demin

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Mar 22, 2011, 1:19:02 PM3/22/11
to Ariel Rocholl, rf-ex...@googlegroups.com
Hi Ariel,

I would be glad to test the firmware :-).

Another question: How do the different algorithms work? (max, normal, avg)

If I select 32 iterations, the display update rate is slower. I guess
that you calculate the
32 iterations first and then display the data.

Would it be possible to store the 32 sweeps in circular buffer and do
calculation/displaying
each time new sweep data is available ? It would make the GUI more "responsive".

Michal Demin

Ariel Rocholl

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Mar 22, 2011, 1:52:30 PM3/22/11
to rf-ex...@googlegroups.com, Michal Demin
Hi Michal,

I will let you know whenever the beta firmware is available. I will be very interested in your feedback.

As for the iteration algorithm, it does actually update the screen at the same speed as in the realtime (normal) mode. But what you see is expected: as the calculator averages (avg) or store peak values (max), the new incoming data has a lower weight on the overall result, and that is why you visually get the sense of longer refresh cycles. You can see that very well in the PC Client: where the realtime curve is updating very fast, the average is not, and that isn't because of a slower refresh rate but because of calculator weighted data visualization. The golden rule is: the more data goes into the calculator for an average, the less impact a single sample will have and data will move slower but more consistently towards the averaged value.

The average calculator is great to cancel white noise, typical in the RF spectrum floor. The max calculator is great to keep a temporary peak for longer time and also to more precisely get the shape of a fast-changing signal in the spectrum. None of these would be possible in the normal mode...

If you are interested in deeper understanding on how a Spectrum Analyzer average calculator works, I suggest to look in the Application Note 150 from Agilent, it is the best guide wrote ever in the subject. Look for reference 5952-0292 in www.agilent.com. Pages 26-38 are good background for your questions.

Thanks

2011/3/22 Michal Demin <michal...@gmail.com>



--
Ariel Rocholl


Ariel Rocholl

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Apr 14, 2011, 12:44:52 PM4/14/11
to rf-ex...@googlegroups.com, Michal Demin
Hi Michal,

The new beta firmware includes a sweep speed screen indicator. Let me know if that fulfill your requirement.

Cheers
Ariel
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