For 32 bit Windows™
© 2003 Oscar Steila, IK1XPV & Claudio Re, i1RFQ.
"Computer Interface Audio Out Radio" or "CIAOradio" is a Windows program for using a PC equipped with a full duplex audio card as a demodulator receiver plus signal level analyzer for Radio Amateur application. Introduction articles on the use of this program are present at www.antennex.com.
Release 0.96d
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Disclaimer: The CIAOradio program is provided as is without warranty of any kind. User accepts all risks arising out of the use of this software. The use of this program may cause or require reset of PC in case of error. |
All rights reserved You may use this program for personal and hobby purposes only. Any commercial use is expressly prohibited without written consent. You may not attempt to reverse compile, modify, translate or disassemble the software in whole or in part. Disclaimer: The CIAOradio program is provided as is without warranty of any kind. The authors makes no claim of merchant ability or fitness for any particular purpose. User accepts all risks arising out of the use of this software. To use the Full Edition you have to pay the registration fee, thanksUSA: www.antennex.com
Oscar Steila IK1XPV Claudio Re I1RFQThanks go to the following people:
- Bill Miller, K4TYE,
- Anselmo Stiffan, IZ3BGJ,
- Jack Stone, Antennex,
- ..all the others..
You will need:
- a computer with Windows 98™, or Windows 2000™ , or Windows XP™ operating system.
- at least a Pentium™ 700 processor (or better preferred)
- a 16 bit Audio Card that works with Windows in duplex mode: audio input and output at the same time. Simplex audio card with 16 bit resolution can be used, but there is no demodulator output.
- an HF transceiver,or a receiver or rf down converter.
- cable to interface audio signals to Audio Card.
- (option) Antenna switch (relay or diode) driven by COM port of PC
Software
If you are reading this prior to installation, then all you need to do is to request the program file. Normally it will be e-mail'd to you as an archive "CIAOradioXX.zip" just extract it into a dedicated directory. This will create all the necessary directories and files. Nothing is stored in the registry, so deleting the program or upgrading it later is also easy. If you want to uninstall it, just delete the related files. The Full edition has a text registration file containing the user license to be placed in the same directory of executable CIAOradio.exe.The installation does not create a "Start Menu" link, so you will need to locate the executable file CIAOradio.exe and create a shortcut (right click on it), then drag that to the desktop or the start menu.
The help file is located into the same directory of the executable file while all the necessary pictures are placed into a subdirectory called "\IMAGE".
Hardware
Connect the transceiver audio output to the line-in plug of the sound card.This is the easiest solution to use CIAOradio. When you will know more of the program operation and structure then you will be able to use the program with different hardware solutions.
If you want to compare antennas signal you will need to use a switch driven by the serial port, the RTS signal (pin 7) on COM1 or COM2. The circuit required is, for instance, a relays driven by an NPN transistor with a base series resistor.
Menu -> Setup -> Configuration
The configuration menu will ask you to confirm or modify the center frequency label and the serial port (COM) chosen to drive the auxiliary relay.The center frequency has 8 digit, so if you enter 100000000 the frequency displayed will be 00000000. The combo box lists the COMs that have been found in the computer. The OK button confirm the choice
Menu -> Setup -> Sound in
The Mixer program "SNDVOL32.exe" is called by the "Sound in" menu button. The default program is the standard Windows volume utility, recorder input.
Please enable the input path you want to use,both Line or Aux inputs can be used. Microphone input may be used too, but please disable any extra feature like microphone boost or automantic gain control. Here you can adjust the input gain of your board.
Menu -> Setup -> Sound out
The Mixer program "SNDVOL32.exe" is called by the "Sound out" menu button. The default program is the standard Windows recorder input utility.
Please enable the output path Waveout and Speaker output. Here you will adjust the ouput signal volume. Your can use a different sound mixer program, outside of CIAOradio.
CIAOradio main screen shows the frequency spectrum of the audio signal.
The program is controlled mainly by the mouse. Hereafter the different controls.
Frequency screen
The top display shows the rf/audio spectrum in the range 0-24 KHzThe yellow line displays the position of the carrier used by the demodulator, it can be moved with the mouse. Take it with the left button and move the mouse, or click at the desired position.
Frequency display & knob
The frequency can be changed clicking on the frequency display. Clicking the top of the picture will increase it, while clicking the bottom will decrease it.
The tuning knob can be turned using the mouse, take it with the left botton and "rotate" it.
Demodulator filter
The demodulator windows displays the "IF" filter used by the demodulator.
The BandOutput Menu will modify the frequency span of the display.
The green line is the demodulator filter response.
The light blu line is the spectrum of the demodulated signal after AGC.
The red bar displays the level of the demodulated signal.The mouse can modify the demodulator filter shape.
The left bottom acts on the filter limit. You can take the green line limit and move it.
The right buttom of the mouse modifies the shape of the filter in the middle. If the button is clicked and moved in the lower part of the screen the filter is modified with a notch. The same button on the higher part of the screen will eliminate the notch.Demodulators
The selection of the demodulation type is done pressing one of the following buttons
- CW The cw decoder. It uses lsb demodulation with a 350Hz default filter.
- LSB Lower Sideband Decoder. It has a 2.7 KHz default filter.
- USB Upper Sideband Decoder. It has a 2.7 KHz default filter.
- AM Amplitude Demodulator. It has a 10.0 KHz default filter.
- FM Frequency Demodulator. It has a 12.0 KHz default filter.
The main window menubar is:
File menu
FileIn - allows selection of a wave file to be used as input instead of Audio Card, a 48 Ksample, stereo, 16 bit, .wav file is requiredTools menu
The two stereo tacks are used as I+Q inputs.
Exit - closes the CIAOradio program.Off - disables the tools previously activated.Mode menu
Signal Level Trace - open a separate child window that shows the demodulated Signal Level Trace .
Reference input - activates an internally generated input signal made by 10 frequencies of different amplitude (in 10 dB steps). The higher one changes its amplitude during time. It is useful program verification.
Reference output - generates two sinosoidal output frequencies. It may be used to verify that the output path of the Audio Card is not looped back to inputs.
Real - Select the mono input mode. Use this mode with the SSB audio of an external receiver connected to Audio Card. It can be used with a down converter real (mono) in front of the Sound Blaster. This mode can be used for direct ELF reception, connecting an antenna ELF to the Audio Card input
X KHz - Select the bandwidth shown in the Demodulator window. The possible selections are 2,3,4,5,6,8,12,20 KHz.Setup MenuConfig - allows configuration of center frequency display and COM selection
SoundIn - launches "SNDVOL32.exe" to configure audio inputs.
SoundOut - launches "SNDVOL32.exe" to configure audio outputs.
This is the trace of the demodulator output signal level.The menu bar of this windows allow to select:
This menu item selects the bandwidth of the video filter used to reduce the effects of noise and modulation on the trace.
Time Span
It selects the time span of signal level trace.
Switch Rate
It controls the switching rate of external relay.
Amplitude scaleThe diagram amplitude scale can be adjusted using the mouse, moving the two yellow lines to the required amplitude span.
In my knoledge the first ’software radio’ equipment, was created in the late ’70s by Walter Tuttlebee of Roke Manor Research, and it was composed by an Analog-to-Digital converter (ADC) connected to an 8085 processor, with a VLF operating radio section. The first software radio applications were mainly of military kind. The Software-Defined Radio (SDR) is implementing a specified range of capabilities through software-reconfigurable elements. The ideal software radio (SWR) should encompass full software-reconfigurable functionalities ( so as to completely and dynamically redefine the personality, i.e. operational band and mode) of the radio. The global architecture of an SWR includes a wideband ADC that converts a full service band at IF, with programmable digital filters for channel selection and DSPs for demodulation. It is coupled with a corresponding digital-to-analog converter (DAC) and software-reprogrammable functions, allowing to support several and arbitrary radio modes within engineering limits. Such limits include the bandwidth and the dynamic range of ADC/DAC, timing accuracy and the computational power of digital processing hardware.
Ham's have today the possibility to use of SDR or SWR radio technology. The wonderful design made by Gerald Yuongblood, AC50G at http://www.flex-radio.com the design by Moe Wheatley, AE4JY at http://www.moetronics.com and Pieter Ibelings, N4IP at http://www.rfspace.com are masterpiece examples of what can be done today.
Our SDR/SWR project was called: "Computer Interface Audio Out Radio" or CIAOradio.
This Win32 software is designed to use a standard PC with a full duplex Audio Card as demodulator and signal level tracer.
The Audio Card and software installed driver must be of the full duplex type, it must be able to record and play audio signals at the same time.
The program is written to do real time digital signal processing of the audio input from the Audio Card.
A "good" Audio Card has a signal dynamic range of near 90 dB. Using a narrow band analisys some extra range gain can be added (20-25 dB). We can use this software to measure relative signal level in a range of more than 90 dB depending also on the performance of the external converter.
CIAOradio uses a complex FFT to analyze the audio (I&Q) incoming signal.
The demodulators are based on FFT frequency translation and fast convolution. Internal demodulator filter can be real time modified using the mouse. The demodulated audio, after an Automatic Gain Control (AGC) is sent to the speaker output line.
The Signal Level Trace is a screen graphic recorder of amplitude of the signal. Variable Video Bandwith filter and time span allow a precise relative-amplitide analisys. The unit has not an absolute level setting. but the numerical signal processing approach guarantee a quasi perfect relative comparison. Periodically switching the two term of comparison (antennas, receiver ,amplifiers) the program can drive a COM (RS232, RTS) signal to control an external switch.The program is written in cpp using winmm.lib to drive Audio Card. The real time operation and bugs in our software may cause crash in the software execution, requiring a reset and restart of the computer.
We are working to improve the performance of this program. Registered Users will receive notice of new software releases.
If we have an antenna A with known Gain (in dB), we can determine the Gain of an unknown antenna B by switching the antennas to the same measurement instrument. The difference in power received (and therefore, the difference in gain) between the two antennas is shown by: Gm = Ga - Gb.
Knowing Ga and measuring Gm it is easy to compute Gb = Ga - Gm.
This test method is called the " Substitution Method," or sometimes the "A/B Method."The signal used for the antennas could be picked from the air, or locally generated in the Far Field from a third antenna. Naturally, if an on-air signal is used, the incoming signal may be subject to variations due to propagation. The two different source options depend on the room available for the tests, the frequency of the measurements and the equipment available for testing purposes. There is another factor. To achieve more precise results, the A and B antennas have to be placed in the same place one at a time.
This is not always possible, especially in HF, where antennas are big. In HF, the best we can do is to leave both antennas in their place, switch the two antennas continuously and rapidly, and analyze statistically the difference between the received signals.Hardware of the "CIAO RADIO MEASURING SYSTEM ". The switch can be a sensitive relay (as used in our tests) or a diode switch.
It will be driven from the RS232 interface of the PC that will deliver a switching level from -12 to + 12V at low current. The RF to AF converter can have very different architectures, depending on the use and the specs needed. For Ham use in measuring the Gain of the antennas, we have selected two different interfaces:The Line Input of the Audio Card is better suited for the high audio levels available from most SSB receivers.
- 1) An SSB receiver that the Ham uses in his Shack
- 2) A simple Direct Conversion Mixer
The Microphone Input is better suited for the simple Direct Conversion Mixer, whose output is at a much lower level. SSB Receiver hook-up
The SSB receiver should be connected as in figure. The RF input of the receiver will be converted to an audio signal that will be fed to the Audio Card and analyzed from the Ciao Radio Software. To use this configuration, the SSB receiver has to be set as follows:
- A) The AGC must be set as slow as possible with respect to the switching frequency. Otherwise, the AGC will automatically readjust the gain between one antenna and the other, thus negating the test!
- B) Alternatively, the AGC can be disabled. In this case, we need to be certain that the receiver is operating in a linear region. One way to do this is by switching an attenuator in and out in series with the antenna input of the receiver and verifying that the output level change is correct on the screen of the PC.
Unfortunately, the AGC of many SSB receivers is too rapid to allow proper tracking of the switched antennas. While it may be possible to modify the AGC circuitry, many Hams may be reluctant to do so. Also, many receivers do not allow the AGC to be turned off. For these reasons a configuration using a direct conversion mixer is preferred.
Direct Conversion MixerThe following figure shows the block diagram of a Direct Conversion Mixer using a single NE 612 integrated circuit.
This design allows the use of crystals, a VFO, or an external Local Oscillator. This design doesn't suffer from problems of AGC because it doesn't have it , but of course it hasn't to be saturated .
It has no rejection from the image. This design also suffers from medium - poor rejection from harmonics of the local oscillator , but for measuring purpose this could be an advantage.
If we install a Xtal of 3579 Khz ( very easy to find because it is a standard for color burst frequency for U.S. color TV), we could measure signals inside or very close around most of the HF Hams bands.
HARMONIC F0 OL FRX min FRX max HF BAND NUMBER MHz MHZ MHZ mt 1 3.579 3.555 3.603 80 2 7.158 7.134 7.182 40 3 10.737 10.713 10.761 30 4 14.316 14.292 14.340 20 5 17.895 17.871 17.919 17 6 21.474 21.450 21.498 15 7 25.053 25.029 25.077 12 8 28.632 28.608 28.656 10
- - Agust 2003 - release 0.80
- - October 2003 - release 0.90; signal level trace added
- - November 15th 2003 - release 0.95; relay driver added
- - December 1st 2003 - release 0.96; help added
