John Melton G0ORX/N6LYT

Thursday, October 31, 2013

Receiving Slow Scan TV

I installed DroidSSTV on my Android HTC Phone and decoded SSTV simply by using the microphone on the phone and placing it near the speakers on the Nexus 7. Have not tried transmitting SSTV yet! Does a surprisingly good job.

Click on images to see full size

Wednesday, October 30, 2013

New version of HPSDR for Android

I have made a number of changes to UI that will be in the next Alpha release of the Android code.  The initial screen runs discovery by default and shows the devices detected just the same.

A long touch on the device brings up the device configuration screen. Below you can see it does not all fit on the Nexus 7 so needs to be scrolled to see all of the options.  The Alex option at this level now is only Yes/No to show if it is present. I have moved the Alex configuration onto the radio screen for each band.

There is now the addition of Tranverter Configuration.

Clicking on Add Transverter brings up the following screen to enter the details. The name is what will show in the band selection.  The start and end frequency and the oscillator frequency must be entered.  The oscillator frequency is used to subtract from the desired frequency with the result sent to the HPSDR system.

Clicking on an existing entry brings up the following screen to allow an update or deletion of the entry. Note I am using an older Microwave Modules transverter and the 116MHz oscillator is slightly off frequency so I have adjusted for this in the value entered.

A tap of the discovered device starts the radio running.

A local repeater GB3MH on 2 Mtrs.

There is a Debug button that displays the current CPU Load.

The Configure button brings up the configuration dialog for the current band.

It allows you to set the TX Level and the Alex antenna configuration (if Alex is present).  Note that for other devices (Hermes, ANAN) I am working on the changes needed to match the back panel labelling.

The TX Level lets you set the maximum drive so that the RF Gain at its maximum is not overloading the amplifier.

You change bands by tapping on the band selection and it will popup the list of bands and tranverters. Tap on the required band.

The AF Gain button lets you set the AF Gain. Note that this is not the same as the volume control on the device, it is setting the gain of the audio signal from the DSP code.

The RF Gain button lets you set the RF Gain.  The percentage is the percentage of the range set by the TX Level setting in the Configuration dialog. The TX Level should be set on each band so that when the RF Gain is at 100% the output is at the maximum required for the amplifier.

I have also added a squelch option. The squelch button brings up the squelch dialog that lets you enable/disable the squelch using the checkbox and set the level. Note that this is for the current band.

Friday, October 18, 2013

A quick update on the Android HPSDR Radio

The Alpha test has been progressing well. The application now has transmit capability (voice only at the moment).

Some screen shots of the latest GUI (not the one currently in Alpha)

Monday, August 26, 2013

Updated version 1.05 published for Alpha test

I have updated the alpha test version to 1.05. It can take several hours to propagate through Google.

This has some major code structure changes in preparation for implementing transmit.

New buttons to increment/decrement the frequency in 10/100/1000 Hz increments. Holding the button down auto repeats. Makes fine tuning much easier. Still can be changed by dragging left/right.

New Buttons to change up/down the band (still can be changed using the fling up/down).

Tuesday, August 20, 2013

Android HPSDR - DttSP and FFTW3

Android HPSDR

I have managed to port DttSP and FFTW3 to Android and interfaced it to Java using JNI.

Running on a Nexus 7 it just about keeps up at 96000 but has problems at 192000.

The audio is both sent back to the HPSDR device and played out on the audio of the Nexus 7. Currently it is receive only.

Still needs some more work to resolve a few minor problems and to implement transmit and add configuration options to allow more control of HPSDR and Alex.

Code is not on the repository yet. Once I have fixed a few minor problems and implemented a few more features I will upload all the source code.

Saturday, February 16, 2013

Android application working directly with HPSDR

First cut at an Android application working directly with HPSDR.

It will discover devices (note I have 2 devices on the network) and let you select which one to use.

No waterfall yet but the panadapter display is working and it can decode AM, LSB, USB and CW.

Change bands by flicking up/down and change frequency by dragging left and right.

All the code is in Java including the DSP code.  The demodulation code is based on the series of articles 'Signals, Samples and Stuff: A DSP Tutorial' by Doug Smith, KF6DX/7 as implemented by JI3GAB, Takafumi Inoue.

There was a good over-the-pole path to New Zealand on 20 Mtrs when I recoded this.

Tuesday, January 22, 2013

More Nexus 7

I now have the panadapter display working.  Examples below are running at 9600. Next is to get the demodulation working and some audio output. Currently all the DSP processing is in Java using JTransforms.

Medium wave 909 KHz (BBC Radio 5)

20 Mtrs

Discovery Screen