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Title

Questions, questions, and more questions.

Hello Serg!

Files with schematics - http://www.adobri.com/misc/stm_bt/RF_GrSt.sch and http://www.adobri.com/misc/stm_bt/RF_GrSt.pcb file with PCB of 2.4 amplifier.

If provider will block files use .zip http://www.adobri.com/misc/stm_bt/RF_GrSt.zip

I use ExpressPCB – not best but not bad – most important for me – I get PCB manufactured on a 3 day after order.

Antenna for ground station - http://www.shapeways.com/model/322767/2-4ghz-antena.html , Antenna for Cube Sat - http://www.shapeways.com/model/322768/small-2-4ghz-antena-for-cubesat.html

Pictures: 

antena ..

Antenna

Bluetooth - http://www.nordicsemi.com/eng/content/download/2730/34105/file/nRF24L01_Product_Specification_v2_0.pdf

Power amplifier- http://ww1.microchip.com/downloads/en/DeviceDoc/S71291.pdf

Low noise amplifiers - http://cache.freescale.com/files/rf_if/doc/data_sheet/MC13850.pdf

Switches - http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=788

Voltage regulators 500ma http://www.analog.com/static/imported-files/Data_Sheets/ADP3335.pdf  and http://cds.linear.com/docs/Datasheet/1761sff.pdf 100 ma

All components in database - http://174.6.165.86/dbadobri/Search.aspx

In Australia on two antennas like for ground station with regular wi-fi distance 12km without problem – limit is horizon (or height of antenna mount) – no need for any amplifiers — I think with 20-40mwt for wi-fi distance can be 20-60 km. If to connect Bluetooth that it must work on 1 km. One man claimed that on 4 antennas together (made less fancy made then my – people used cut PVC sewage pipes) he get signal from Mars orbiter.

Schematic which I send in last tests was without regulators 3.3v – for power amplifier and for LNA. I removed them and connect 3.3v from 1amp regulator – regulators works somehow unstable – I think is just some of my mistake with capacitors – I need individual regulators for Bluetooth+PIC and separate supply for a TX and RX

R1 and R2 in power amplifier — I set 2.9V by a separate variable resistor for a voltage reference – conformed value – in original schematic was bug - fixed

С26 — my inserts — otherwise switches does not works – another bug – fixed

С34 — same bug - fixed

L2 — have no idea - in typical application 12nH – but I put 8.2nH

Then I fixed problem in control signals for TX-RX – was stupid bug in tracing.

Then was a bug in soldering on U4 (I believe this is when I baked voltage regulator 3.3 100ma)  

Then was bug with sizes — capacitors size 402 (1мм х 0.5мм) and  resistors 805 (2мм х 1.25мм), but on PCB I placed all sizes 402 – as a result I have to cut spaces for a bigger resistors and 10uF capacitors.

If two antennas used then stable signal is over open air - 500 -670 m. If one antenna will be behind window glass then distance reduced to 120m. If I put amplifiers, then on 500m over glass packets travels fine. Another sign that power amplifier somehow working – with antennas only (1mwt) behind trees no receptions on 100m – with amplifiers at the same spot perfect reception. Also over air 500m is definitely better reception (LED blinking only on packets used in protocol – period of blinking give rough estimates). But power amplifier should give 36 dB – am I right or not – input 1mwt – 36dB output 1Wt (current also shows 350 ma)? If it is 1Wt – than signal must be really strong – even on another side of downtown with reflection I should see reception? With 1mwt I perfectly get reflection from nearest building – with 1Wt – no reflection – only direct open air.

Run with CubeSat prototype at 3AM aroundVancouveris interesting task – all Boms are curious – usual question – Is that technology can be used to get high? At day time it is funny too – tourists 

I also do not understand – first – capacitors on RF-IN RF-OUT? What sizes of traces before and after capacitors should be?

And actually what for that capacitors? – lest assume for decoupling.  Then why on power amplifier it is 1.2pF and for LNA it is 2.4pF? – Frequency of a sample application for a same 2.4GHz, or this picoF just what you have today for soldering? Or this pico depend on width and length of a trace?

Does they depend on a height? No seriously – after soldering a lot of buggers on traces – trace like hatchbacks – does it require to clean buggers or make it bigger – to adjust picoF? Then thickness of PCB – how account this?

And what a hack this L1 – bloody inductor! In recommendation it is stated: “Could be removed (really?!) if -7dB(?!) return (!?) loss (??!) is acceptable (?!)” – What loss? Why loss back? — is it -8 is OK and -6 is very bad? What is ACCEPTaBLE? dB of what? And that documentation is really good – in other specs for a different chips – only pins – event horizon for a creativity – try what you like with combinations 16*15*14*… etc.

Now antenna – I soldered it on J3 over capacitor (1.2?.2.4?) – as on a picture – direct connection of a antenna to a capacitor and without capacitor – What will be proper way to soldering /connect with or without?

Then connection to a Bluetooth – today it is a coaxial 25cm (2.4Ghz length of wave) in a future Bluetooth will be on same PCB but now coaxial – question – from a point of connection length/width of a trace to capacitors should be??? 1/6 or 1/32 of wave’s length. Or nature likes different fractions?

Next – “50om /85 mil” or “50om/120mil” or something even more mysterious – “50om RFIN” “50om RFOUT” – Yes I know – it was a man with a last name Ohm – also Ommm is Tibetan song – and what? 120mil * 3 = 360 +15 = 375 = small bottle in liquor store. But how liquor store related to U=I*R?

May be needs additional amplifier? The power amplifier designed to work for wi-fi. And 1mWt is not enough to work?

Also on schematics present noise canceling QHX220IQT7. But I am fighting with difference noise - in a head mostly. I even did not soldered it.

If you understand – you help will be appreciated. My knowledge is limited in RF area - as you know.

Alex.

 

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