Want to build a box to power and control LNB - need help/suggestions/collaborati - Page 1
Forum section: electronics / projects

author: Bicurico
author_rank: Super Contributor
timestamp: October 21, 2016, 08:40:40 am
content: Hi,I developed an alternative software for the "138M-4.4G USB SMA Source/Simple Spectrum Analyzer/Signal Generator" sold at eBay.More info here:https://www.eevblog.com/forum/testgear/presenting-my-new-software-for-the-sma-spectrum-analyzer-138mhz-4-4ghz/andhttp://vma-satellite.blogspot.pt/One of the problems I have with it, is that I (and possibly others) want to monitor the spectrum of satellite dishes using common C-band or Ku-band LNB's.These normally use 13V/18V (sometimes 14V/18V, doesn't matter) to switch V/H polarisation and 0kHz/22kHz t switch L/H band.On top of this, DiSEqC commands, modulated in 22kHz, are used to switch accessories like multiswitches, motors, etc.Right now, I use the Loop-Through connector of a satellite dish to feed the SMA Simple Spectrum Analyser. WARNING: You need to use a DC blocker to do that! Do NOT connect the device directly, as you will kill the ADF4350 IC.What would really be great, would be a small device with the following features:1) SMA Input Connector to attach the SMA Simple Spectrum Analyser2) F-Type Connector to attach the LNB3) Internal rechargeable battery to drive the LNB4) LED's to show 13V/18V and 0kHz/22kHz (let's forget about DiSEqC in the first version)5) 2 buttons to switch 13V/18V and 0kHz/22kHz6) Built-in DC blocker on the SMA connectorThis would be the minimum specs.The better (second) version, should:1) Connect through USB/RS232 to the PC2) Allow remote setting of polarity and band3) Support DiSEqC commands from PCThis would be the final version.My problem is, that I have much to little electronics knowledge to build this myself and I need help:1) How to I generate 13V/18V from i.e. a 12V battery?2) How to I generate a 22kHz Signal and mix it on the F-Type connector?3) How to best make the buttons and LED work?4) How to make the DC blocker? Is a simple diode enough? What type?I am not considering the 50 Ohm/75 Ohm impedance issue, as I think it is irrelevant precision-wise. Am I overlooking anything?Anyone interested in this project?Basically, I would like to build something similar (equal) to this:http://shop.sat-kabel.de/mess-und-prueftechnik/messgeraetezubehoer/geraeteschutz-aufbewahrung/26/akkuteil-au-spm?c=12Regards,Vitor

author: bktemp
author_rank: Super Contributor
timestamp: October 21, 2016, 08:52:50 am
content: Here you can find some DiSeqC specifications and example circuits. Most of them is for the LNB/multiswitch side, but inserting power is done in a similar way then extracting power.http://www.eutelsat.com/de/unterstutzung/technische-unterstutzung/diseqc-spezifikationen.htmlFor generating the 13/18V supply voltage and also the 22kHz tone you could use this ic:www.ti.com/product/tps65233

author: Bicurico
author_rank: Super Contributor
timestamp: October 21, 2016, 09:43:07 am
content: Hi,Thanks a lot for your reply! I already knew the Eutelsat links, but they are kind of complex and old.But you really went on full win with your TI link!I just ordered this evaluation board:http://www.ti.com/tool/tps65233evmIt is exactly want I needed! And no hardware development, soldering, etc. at all.Regards,Vitor

author: VE2UM
author_rank: Contributor
timestamp: October 21, 2016, 11:04:17 am
content: Just to get sure you won't toast your SDR by sending DC transients....The DC blocking capacitor is not enough, since LNB DC ON/OFF and 13-18V transients may pass through the capacitor, add a shunt inductor (5 - 6 5mm dia turns of AWG22 wire will do) directly on the SDR connector. Keep leads as short as possible.Normand

author: Jane
author_rank: Frequent Contributor
timestamp: October 21, 2016, 07:55:22 pm
content: Also STMicroelectronics makes a chip for LNB. That is LNB21P or LNBH21 which is a quite often used in satellite tuners and those LNBP/LNBH21 make also from 12V inputs those 13/18 V on output.AS you can see in the picture there is a tuner( in a metalic cover) which is soldered on PCB board where LNBP21 controls LNB.