RF Circuit Design Lecture

Nice lecture about RF circuit design from practical point of view, Michael Ossmann is the one created HackRF one which is SDR (Software Defined Radio) RF transceiver board that has wide frequency range up to 6 GHz. Lecture gives tips from one in the field of designing/mastering RF circuit design.

Just note, even this is a practical guide, you still need to have knowledge about the concepts like PCB, Impedance and impedance matching, filters.

I like in this lecture it always mention that take the easiest way to give you the best result, like: Always use integrated circuits, use recommended components from manufacturer for passive elements, always use ready made filters available don’t go for design (except you really can’t find another way), always match to 50 Ohm and choose IC based on that, always match impedance on 50 Ohm.

In future, I may practice some PCB/SBC/RF SDR circuit design so that’s why I started to start learning from in the field masters.

Enjoy the lecture

 

 

Posted on by yassernour 0

Dropbox vs. Ubuntu One

Dropbox and Ubuntu One are Cloud service that provides storage service of folders and enable you to sync them between multiple machines. In old days, i was sending files to myself by emails to have the same files on different machine.

Dropbox offering free 2GB storage with the ability of sharing folders between different users, or publish certain files to the public (like publish certain images and put in a website or blog or send a link to it to a friend). Dropbox can be used on Linux, Windows, MAC and Mobile.

Ubuntu One is nearly the same but offering more free space of 5 GB, but runs only on Ubuntu 10.10 or newer, Windows and MAC OS not yet supported. So they offer more space but make sure all your machines on your cloud should be Ubuntu 10.10+.

Also one of the drawbacks of Ubuntu one is that it doesn’t mention if the data stored are encrypted or not. but as seen on forums most probably not encrypted which is a big issue for a lot of users. While Dropbox encypt data with AES-256 encyption.

So as i have 3 machines, with different distributions and versions (Ubuntu 8.04, Ubuntu 10.10, Ubuntu 9.04 and CentOS 5 + Windows Vista) and for Security (Encryption) I had to go with Dropbox. Sorry Ubuntu.

On Dropbox, Folders and files in your dropbox folder on your home directory are syncronized with all your machines linked to your cloud. Also you can browse the data on your cloud using Dropbox website

Posted on by yassernour 3

Gnome 3 – A New Desktop Experience

Gnome 3 has been released early this month under name Gnome Shell and two distributions have it now to try it by Linux users (Fedora and Suse distributions), I have tried the Fedora Live CD, if you didn’t try it yet, try it and you well see the next generation of Linux Desktops.

Gnome 3 require video card supporting hardware accelerators, so don’t try it with VMware player or Virtual box (I tried but didn’t work) ,in VMware or VirtualBox it will not run Gnome-shell and will run in a fallback mode as any older Gnome versions.

Wireless, sound, webcam work fine from Live CD, I liked many things with the new Gnome, first the maximize/minimize of windows, arrange multiple windows in workspace, switching between workspaces, adding your meetings/tasks in calendar located in panel and a lot more to explore.

From this few minutes experience with Gnome 3, i think Gnome Desktop may hit tablets business with this new desktop (After trying it, think if this desktop could be used with touch screen? I would say yes), as you may notice by trying it.

Here some screenshots instead of words:

Applications in Gnome 3
Windows in Gnome 3
Calender
Workspaces
Wireless Works !!
Posted on by yassernour 3

Wget : Resume broken ISO download

Wget is a free ftp/http downloader available on all Linux distributons and has a windows clone, it has a lot of useful options and it is helpful in a lot of downloading tasks, for example it can be used to download entire website for offline browsing, download specific file types from a webpages. Like source files from a certin website … etc.

One of the benefit i got recently from wget is resume feature, i have been downloading ubuntu iso image using firefox download manager, then at 65% download stoped and firefox tell me download completed (sure it was wrong).

I searched and found -c option to continue/resume broken download. so i got the iso link i was downloading, then i use wget to resume downloading :

wget -c http://us.releases.ubuntu.com//maverick/ubuntu-10.10-desktop-i386.iso

Also one of the greatest feature i use to not starve my other newtork activities (e.g. browsing, other persons bandwidth on local network)) is using –limit-rate to set maximum download speed of wget(in Bytes/sec unit).

wget --limit-rate=40k -c http://us.releases.ubuntu.com//maverick/ubuntu-10.10-desktop-i386.iso

Posted on by yassernour 0

Kill a process using name

This a small post about a linux command make my life easier, when i want to kill a process i was using to get PID then use kill with this process PID, this was require that i do the next long line:

kill < `ps aux | grep process_to_kill | awk ‘{print $2}’ | head -n 1`

Recently, i found the equivalent of this painfull line 🙂 :

pkill process_to_kill

But without the first line i used to use i wouldn’t get familiar with ps, awk, head, tail. But now for sure i will use pkill :).

Posted on by yassernour 5

Lenovo SL510 slow HardDisk problem with CentOS [SOLVED]

It has been a while since i was living with Lenovo SL510 slow performance with Centos 5.3.

I had made a lot of research for this problem, one of the best tool i used to fix problem is hdparm tool, this tool will give you all information and help you tuning harddisk performance.

The problem was CentOS installer find the harddisk drives as /dev/hdx where as a SATA harddisk should be seen as /dev/sdx. Measuring performance of harddisk using hdparm gives:

/sbin/hdparm -t /dev/hda

gives about 3MB/Sec while for SATA HD it should be in range from 50-90 MB/sec.

It turns out that the IDE driver was loading before the SATA driver (ata_piix) (I think in initrd) and that caused the drives to be found as /dev/hdx instead of /dev/sdx and when it tries to load SATA driver it gives


ata_piix 0000:00:1f.2: version 2.11
ata_piix 0000:00:1f.2: MAP [ P0 P2 IDE IDE ]
ACPI: PCI Interrupt 0000:00:1f.2[B] -> GSI 16 (level, low) -> IRQ 16
ata_piix 0000:00:1f.2: 0x1F0 IDE port busy
ata_piix 0000:00:1f.2: 0x170 IDE port busy
ata_piix 0000:00:1f.2: no available legacy port

Adding hda=noprobe hda=none to kernel arguments in /boot/grub/grub.conf file then reboot solves the problem.

Now “/sbin/hdparm -t /dev/sda” gives 65 MB/sec (Amazing) and all partitions now are seen as /dev/sdx.

Now the SL510 performance is great as it should be (Boot in less than 1.5 min), and fast copy and move folders.

Posted on by yassernour 1

Terminator – Make life on terminal easier

Terminator is terminal emulator that allow you to split window into multiple terminals on the screen without using tabs or multiple windows as in gnome terminal. It has the advantage of working in one terminal and seeing all what happens in other terminals.

When you open terminator you can use the following few key combinations to work with terminator:

* Ctrl-Shift-E: To split the view vertically.
* Ctrl-Shift-O: To split the view horizontally.
* Ctrl-Shift-P: For focus to be active on the previous view.
* Ctrl-Shift-N: For focus to be active on the next view.
* Ctrl-Shift-W: To close the focused view.
* Ctrl-Shift-Q: To exit terminator.
* F11: Fullscreen.

enjoy.

Posted on by yassernour 0