Spacedoggys WB 2010 Build Diary
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Re: Spacedoggys WB 2010 Build Diary

by Lcstyle on Tue Nov 01, 2011 2:31 pm

spacedoggy wrote:ok, I got by power stabilised, and resumed work on this.

2 questions:
-What do i need to check to get the 1300 to lock?
-the 2700 locking at 20.4V seems a little high, is this ok?


_____________________________________________
*using formula 3.3*((X/10)+1)=Y
where X is Kohm
and Y Voltage limit of the sweep test


Good question, I can't get either VCO to lock. Probably a problem with the feedback circuit.

2700 locking at 20.4 high? What freq are you trying to lock at?
For the ROS2700-1819+: 3.3((64.9/10)+1) = 24.717V (Max Vtune for ROS 2700 is 25V)

Again if the voltage is too high for a lower freq lock then it is probably a problem with the feedback circuit, which is probably the most difficult circuit to understand / tune.

Anyone with in depth knowledge on this particular aspect care to chime on on possible steps to troubleshoot? Specific values for measurement across points, etc. Please feel free. Technically speaking you would need an oscilloscope with double the bandwidth to sample VCO output, i.e. for 1300 you need a scope with at least 3 ghz bandwidth etc.

Good luck!
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Re: Spacedoggys WB 2010 Build Diary

by TheFallen on Wed Nov 02, 2011 3:26 am

Actually a Spectrum Analyser would be of more use. That way you can see the peak sweeping over the frequency range, or at least you should.
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Re: Spacedoggys WB 2010 Build Diary

by Lcstyle on Wed Nov 02, 2011 8:37 am

The only way to really test this is to run the feedback circuit in an open loop, (disconnect the VCO from the tuning portion).

Take a variable dc supply and apply it to the VCO tuning input, Vt.

Program up your synth chip, check the ref osc is running, check the phase polarity (especially if running an active loop filter).

Now sweep the VCO slowly with your dc supply. If the programming is right, you should see the voltage on the output of the loop filter suddenly flip state as the VCO freq crosses the desired output freq.

that is a phase lock loop, when it goes over (deviates to far from your tune point) it will reverse phase to make the VCO come back, and this repeats over and over again thus keeping the VCO locked in tune.

More here:
http://mobiledevdesign.com/standards_re ... frequency/
http://rfdesign.com/mag/howtodebug1.pdf
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Re: Spacedoggys WB 2010 Build Diary

by Lcstyle on Thu Nov 03, 2011 8:59 am

TheFallen wrote:Actually a Spectrum Analyser would be of more use. That way you can see the peak sweeping over the frequency range, or at least you should.


Yes, you do need a tool that can help you visualize what is happening. You could spend upwards of 5 thousand dollars US on a Spectrum Analyser for a project who's parts cost no more than 300 dollars, or you could spend about $400 US on a high freq 3ghz frequency counter which will do the exact same thing (for testing purposes) (just display the information in a different way).

http://www.jameco.com/webapp/wcs/stores ... 2145422_-1
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Re: Spacedoggys WB 2010 Build Diary

by spacedoggy on Thu Nov 03, 2011 1:36 pm

$400 is expensive for something that does so little, for almost as much one could get a USRP1 software defined radio and use GNU radio software to scan the frequencies.

All this is out of my price range until i win the banned.
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Re: Spacedoggys WB 2010 Build Diary

by Lcstyle on Thu Nov 03, 2011 2:36 pm

spacedoggy wrote:$400 is expensive for something that does so little, for almost as much one could get a USRP1 software defined radio and use GNU radio software to scan the frequencies.
All this is out of my price range until i win the banned.


I suggest you forget about all this if you hit the lotto.

Disclaimer: IANAL
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Re: Spacedoggys WB 2010 Build Diary

by DimaGS on Tue Nov 27, 2012 2:21 pm

Hi Spacedoggy,

I'm new also in electronics and I'm working on this projet in my school. I'll been doing the modifications too, I want to jam the 4G frequency so I'm using the ROS 2700 et I'm thinking to change the power switch. Exactly which component have you used to replace the original MIC2514? Or you haven't change it at all? I hope yu can help me, I need a power switch which can works with 18V. Thank you so much and greetings.
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