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Daily Archives: Feb 16, 2012 08:44

HamSphere on Android

LayOut managers

I have now explored the Android development suite a little more. As you may know, Android is purely based on Java.

The UI design is based on a quite clever XML based concept. But the LayOut management reminds me very much of the initial Java development back in 1996 when Java first saw its light. Actually the Android people have deprecated one of the most tempting Layout Managers called “AbsoluteLayout”. The reason why this manager is deprecated is that Android phones come in so many shapes and sizes. It is virtually impossible to make a “fixed pixel” application for a mobile phone, so I really do not understand why the fixed position Layout was there in the first place. OK, so what are the alternatives then?

The standard Layouts are:

FrameLayout

FrameLayout is designed to display a single item at a time.  You can have multiple elements within a FrameLayout but each element will be positioned based on the top left of the screen.  Elements that overlap will be displayed overlapping.  I have created a simple XML layout using FrameLayout that shows how this works.

LinearLayout

LinearLayout organizes elements along a single line.  You specify whether that line is verticle or horizontal using android:orientation

RelativeLayout

RelativeLayout lays out elements based on their relationships with one another, and with the parent container.  This is arguably the most complicated layout, and we need several properties to actually get the layout we want.

TableLayout

TableLayout organizes content into rows and columns.  The rows are defined in the layout XML, and the columns are determined automatically by Android.  This is done by creating at least one column for each element.  So, for example, if you had a row with two elements and a row with five elements then you would have a layout with two rows and five columns.

What Layout to choose for HamSphere?

I have been playing with all of the above, but the Layout Manager that feels the most tempting is the TableLayout. Howevere it may cause the app to look a bit “off” in some phones. The Relative Layout could possibly work if I use the frame outer edges as reference. We’ll see.

Kelly

 

HamSphere Technology

Quite often I get a question about HamSphere and how it works.

Not many operators realize that HamSphere is constructed on real radio concepts such as local oscillators, mixers, filters, agc’s, balanced modulators, carrier wave suppression etc.

About 10 years ago I started contemplating a crazy concept of simulating SSB-signals on the Internet. Of course back then the CPU power was not enough to achieve such thing, but eventually in late 2007 I started writing the first  embryo for HamSphere on a 4-core Intel server.

The concept is simple. I give each logged in Ham a digital local  oscillator (LO) that can be tuned between 1-99 kilohertz. The LO is then modulated with Amplitude Modulation (AM) by the operator’s  microphone audio. The AM signal is fed through a carrier wave  suppression module leaving a Double Side band (DSB) signal.

The DSB signals from all operators on the system are mixed in a mixer and re-sampled at 192 kHz. That output of that mixer is the ”HamSphere”, which is a melting pot with all signals mixed together.

On the receiver side I inject the LO (1-99 kHz) into a balanced  direct mixer which is also fed with the “HamSphere” signal. The product of that mixer creates an (Intermediate Frequency) IF which is actually carrying the audio product. The IF is then filtered with  a 3.8 or 2.8 kHz filter to get rid of the digital artifacts and then fed to the speaker.

This whole digital concept above is acting like a real shortwave radio or actually a SDR (Software Defined Radio).

The “HamSphere” is constantly reshaped using real so called  QSB-envelopes that I have prerecorded from real shortwave signals on different bands. That is how I can explain the QSB (fading) on the signals that you hear on HamSphere.

Another concept of HamSphere is the fact that when you swirl the VFO know the voices turn into ”Donald Duck” voices, just like a SSB receiver. Well, the reason for that is that it is the same thing, except HamSphere uses Double Side Band instead.
Below I have pasted a diagram of the HamSphere system.

73
Kelly
5B4AIT
www.hamsphere.com

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