This post will be a bit of a rant. I recently got a Dell Precision M4800, a professional mobile workstation.
It comes with software preloaded called Waves MaxxAudio, it provides some of the same features other notebooks include that can “make audio sound better”.
I’ve been comparing the sound output with MaxxAudio enabled, and MaxxAudio disabled. And while it does sound somewhat better while on. The audio still sounds terrible for some strange reason.
I turned the audio enhancement off, and the audio that came out sounded like a megaphone. I instantly knew something was up. So I stuck the audio from the headphone jack straight into a calibrated audio spectrum analyzer and found that:
1. When MaxxAudio is ‘off’, It isn’t actually off. The mids are boosted, and bass/treble cut off to make the audio sound much worse than it should be
2. When MaxxAudio is ‘on’ It boosts the bass and treble to levels where music begins to sound nothing like what it was intended.
So what I did next was uninstall the realtek driver, and rebooted my PC. Music sounds much better now, not distorted, and full of adequate sub bass that i’m used to hearing from a semi-decent DAC.
Now, I really expected better from Dell. I find this completely unacceptable in a professional notebook. Audio coming out of the speakers, when audio enhancements are “off” should not be tampered with at all.
My advice is, UNINSTALL THIS CRAPWARE the moment you get it. Use the stock driver provided by microsoft. Wave audio’s enhancement software is nothing but a scam and a battery/CPU hog.
This is the only way to make the speakers and headphone jack sound normal again.
A new radio system is being deployed in my city. New talkgroups pop up every day, need a way of logging them for review later so I can identify the unknown ones and submit the info (X City Police Dept) into the RadioReference Database
A means to record police dispatch calls in my city, so I can recall them when my local news paper publishes their “police blotter” section.
Program a script that records the calls so I can listen them to later, a pretty web interface is optional
Two essential pieces of software were written by me. LogRecorder (Available here) and the main ScanEyes application
The ScanEyes application is run in Apache with PHP without the need for a SQL server.
LogRecorder is a PHP script that runs in php-cli.exe (no web server) It polls sdrsharptrunking.log for file changes every 150ms and spawns an audio recorder if an active talkgroup is picked up by Unitrunker.
LogRecorder tells sox.exe to write an mp3 file containing call audio to a specific folder ‘YYYY/MM/DD/UNIXTIMESTAMP_TGID_TGNAME_RID_RNAME.mp3’
EverythingSearch by Void Tools indexes these files and when a user queries ScanEyes, the query is sent to es.exe with the search term. The resulting data is manipulated into various tables and charts.
Here is a diagram of the entire setup, including extra features I’ve built into the server for, for example, streaming live audio with low latency. This entire setup runs at about 7% total CPU utilization for a Core i5 4670K during idle. Main culprits for CPU usage are SDRSharp, 5%; and Unitrunker, 2%.
There are two pieces of hardware in this setup, two SDR dongles. One talks to Unitrunker, another talks to SDRSharp.
Beginners explanation of trunked radio
Unitrunker listens to the control channel and gives a birds eye view of the entire radio system. It shows all the talkgroups on the radio system (Talkgroups are like virtual channels, unlike traditional analog radio, talkgroups are not bound to a particular frequency, rather grouped into a pool with other channels, sharing or competing for a group of frequencies. When an officer keys up their trunked radio, the voice signal can be on any voice channel defined by the control channel. The control channel tells all the other radios what talkgroup to listen to)
Unitrunker has plugins that allow remote tuning of the active control channel. By default, every talkgroup has the same priority, so it’s first come first serve. Unitrunker has 2 features, priority, and lockout. Lockout mutes the talkgroup so it is never listened to, and priority gives a talkgroup more priority over others. Useful for example, when you want to hear SWAT traffic over FD traffic.
remote.dll is a plugin that writes the current listening talkgroup to a file. SDRSharp is a piece of software that acts as a virtual radio, you can tune it to what ever frequency you want, and it will communicate with the second SDR to receive radio signals.
SDRSharp has a plugin that listens to remote.dll. This way, unitrunker can tell SDRSharp what channel to listen to, to get voice out. SDRSharp will then output this sound to a virtual audio cable. Virtual audio cables act as pipelines for audio from one program to another. In this case, we are taking the audio from SDRSharp, and putting it into our digital voice program.
P25 is a radio communications protocol that usually carries voice traffic. If you were to listen to P25 straight from the speaker, you would not hear voice, but digital noises like this. These noises can be decoded into regular voice by a program called DSD. All DSD needs is an input and output audio device and you’ll get clean listenable audio.
Listenable talkgroups along with all data is set through unitrunker, locking out a talkgroup causes LogRecorder to not record the call in the first place.
User and talkgroup prototype feature in unitrunker allows a user to prioritize newly added talkgroups, or lock them out, if only known talkgroups want to be logged.
Responsive design works on tablets, phones as well as desktop browsers
Users can create playlists to share via email, reddit, G+, or Facebook.
The playlist URL contains a gzipped encoded call ID (no DB required)
When playlists are called, every file is played back in chronological order
I’ve decided not to open source my work until an experienced PHP developer can review my code from a security standpoint. I’ve taken all possible measures to deter hackers, focusing mainly on input sanitization. That said. If you find anything on sdrscan.com, I’ll pay you via paypal to report these vulnerabilities to me.
Until then, I will allow other users(persons) to run this software provided that they don’t share it, or use my code elsewhere without my permission. Also, I doubt this will ever happen, but if a company would like this software, you can contact me directly.
As it stands right now, this software uses licensing servers with key validation.
This was my first large scale PHP project. I’ve learned a lot along the way, which has caused some code discrepancies. For example not having a database out of pure laziness to learn MySQL. As I learn new things, I will begin to incorporate or update those features.
One of my new projects is figuring out how to automate my Pioneer VSX-822-K AVR. There have been posts before on how to do this with telnet for higher end AVRs (VSX-1022). But there doesn’t seem to be any documentation on mine.
My plan is to make a PHP web interface for controlling it because:
1. The Pioneer Control App for Android is laggy and crappy
2. I can control it from a web browser as well
The VSX-822-K uses port 8023 for telnet commands. Only some of the commands that worked with the VSX-1022 worked with the 822. Many of the function commands are changed. I went through every possible FN combination below. This information doesn’t seem to be available anywhere else but here.
10FN Video H
15FN DVR/BDR H
25FN BD H
44FN Media Server
49FN Game H
TO get the rest of the commands like tuner preset+/-, I installed Shark for Root on Android. This application is like WireShark in that it captures packets to and from the device. I then opened the AVR application and made sure I pressed every button that was available.
But then I remembered that the app downloaded device specific data when I first opened it. I went on a hunt inside ESFileExplorer for the related application files. I found them in /data/data/jp/pioneer.avsoft.android.controlapp
I zipped that up for inspection.
And then I found the jackpot
Every command the AVR uses, implemented in HTML and JS, by japanese programmers at Pioneer Electronics. I can’t blame them for using HTML, It’s easy, but it’s not responsive at all. No wonder the app was laggy.
After sifting through the code, here’s what I got out
PWR0 Power on
PWR1 Cold standby
PWR2 Network standby
MUT0 Mute on
MUT1 Mute off
?GAP Prints OSD info
FU: Function up
FD: Functon down
10FN Video H
15FN DVR/BDR H
25FN BD H
44FN Media Server
47FN DMR (doesn't do anything?)
49FN Game H
PO Power On
PF Power Off
VU Volume Up
VD Volume Down
MO Mute On
MF Mute Off
MZ Mute toggle (doesn't work?)
##PR (30 avail)
0100SR Advanced Surround
12PB Skip Reverse
13PB Skip Forward
40PB iPod Control30
Some other things to note:
The AVR only allows one telnet session at a time, otherwise it will refuse the initial connection.
The remote is a huge pain in the ass to use, if you want to change settings you have to go into the internet radio function menu, just to get the 80’s style menu to open.
What’s worse is the menu goes from digital in the CPU, to analog in the DAC (so it can be outputted to composite video), THEN it gets converted back to digital for use in HDMI. It looks really ugly to say the least.
When you are using SDR# you are looking at a chunk of radio spectrum. Standard radios only have the ability to process one signal at a time, you now have the ability to not only hear, but also see the signals.
Your sample rate is your bandwidth. If you only want to see 1MHz of spectrum, choose 1.0MSPS. Higher sample rates above 2.4MSPS are not recommended
Interference from very strong signals will show up as mirrors that run in the opposite direction of the actual signal or only appear at the edge of the screen.
Interference from very strong signals will show up at intervals corresponding to your MSPS rate
If you have a signal at 100MHz, and your sample rate is 1MSPS
You will see a duplicated signal at 101MHz, 99MHz, 98MHz, and 102MHz.
If you have a signal at 100MHz, and your sample rate is 2MSPS
You will see a duplicated signal at 98MHz, 96MHz, 102MHz, and 104MHz.
The two display methods of SDR#
What is the FFT and Waterfall?
FFT: Top half of the screen
Waterfall: Bottom half of the screen
How to enter frequencies into SDR#
Type it into the VFO
Click on the bottom or top half of a number
Drag the waterfall or FFT
Use your scroll wheel
Eliminating the center signal spike
If you want to get rid of that DC spike in the center, enable Correct IQ
Decoding digital tips
For decoding digital signals
max out the volume, use WFM, change frequency step to 6.25KHz, and change the bandwidth to fit perfectly around the signal’s envelope.
Set your sample rate to .900000001 MSPS (I personally have had the best results with this)
Also uncheck the filter audio box, chances are, your application will want a clean signal coming from SDR# to decode digital data properly.
If you are decoding time sensitive information (Trunked radio decoding), turn down your audio latency so it is low enough to where the audio doesn’t pop from buffer underruns, but is fast enough so that the beginning of conversations aren’t cut off.
Keeping things organized
If you are going to be using your SDR for multiple uses, like HF, VHF, and Digital. Duplicate your SDR# folder for each instance. This will save configuration time, so you won’t have to change modulation, volume, or Gain every time you want to listen to different modes.
When to use AM
If you do not have an upconverter, there are only very few times you will use AM,SSB,USB,LSB,DSB,CW,or RAW. These include
Listening to Airband (120MHz)
Listening to CB Radio (26-27MHz)
12 and 10meter ham bands (24-30MHz)
Low tech gadgets that run on 27 and 49MHz (RC Cars)
Remote controls that run on ~400MHz (Car door unlocks)
some low tech ISM devices 902-928MHz (home automation, weather sensors)
Otherwise use NFM or WFM
Common interference in the home
If you use Wi-Fi or Ethernet in your home, you may see lots of interference in the 140-160MHz range, when browsing these ranges don’t use Tuner-AGC unless you have already locked onto a signal you want to listen to. If you are just browsing, keep the gain somewhat low to avoid overloading the device.
When to use AGC
Use AGC when you are aware that checking the box may lead to visible interference, only use AGC when you are sure the frequency you are on, is the only signal you want to listen to.
Tuner-AGC seems to work better than RTL-AGC at picking signals out from noise
Generally RTL sticks need calibration. If you are only listening to FM Radio, calibration probably isn’t needed, but for narrow and more precise signals, it is required.
It is recommended to wait several minutes before calibrating, when the temperature of the dongle warms up, the frequency could shift 4+ppm.
Calibration is calculated in ppm (parts per million) AKA Hertz per MHz
so, if your correction is 50ppm, a signal at 1,000,000Hz(1MHz), will be 1,000,050Hz(1.00005MHz)
Remember that this scales the higher in frequency you go. So at 900MHz, the correction will not be 900,000,000/900,000,050
It will be 900,045,000. At 900MHz, a difference of 45 KHz is huge, especially for narrow signals like voice.
When calibrating your dongle, always opt for using a higher frequency reference point.
Calibrating to a local NWS station (162MHz) is good, but calibrating to a local GSM tower, or trunked radio control channel is much preferred.
Getting a clearer picture
If you are listening to narrowband signals, it may be helpful to get a clearer view of the signals you are looking at.
When you first start using SDR# turn your contrast down to a level where:
no signal = blue
weak signal = light blue
med signal = orange
strong signal = red
Note, while gain controls how the signal is heard and viewed, contrast is only visual.
This mod allows your GPU to disable its fans when the temperature is cool enough.
Flash at your own risk, I use this myself, but I can’t take responsibility for fried or bricked cards.
Use nvflash to update. Consider using a piece of software to throttle the fans according to temp levels (EVGA Precision X works)
I oftentimes see people asking why there is so much interference on their SDRs. Most visible interference is in fact not caused by real signals, but caused by the RTL dongle overloading.
Eliminating visible interference
The first to troubleshooting interference is turning off any type of AGC. AGC maxes out the gain slider which makes nearby strong signals to appear where they shouldn’t be.
37.2 dB is a good level
Change your sample rate. Understanding the sample rate is quite easy. 0.25 MSPS will only show 250khz of spectrum on your waterfall/FFT screen.
It isn’t recommended to use 0.25 MSPS because this can cause interference on frequencies every 250KHz. Take for example, a frequency on 850MHz and 850.250MHz. If you set your sample rate to 0.25MSPS, and either the signal is too close, or your gain is too high. Both 850MHz and 850.25 will mix causing bad decodes. The same can be found up to 10 iterations of 250KHz past the original signal. To see this, find a strong signal, set your gain high. Center it on your waterfall/FFT display, and increment the frequency by 1MHz. You will see the same signal every 1MHz, slowly decreasing in strength as you increase the frequency. Now use 2.048MSPS, you will notice mirrored interference every 2.048MHz
.9000001 MSPS is recommended for digital modes because it provides a small enough chunk of spectrum for visually inspecting the signal, and it doesn’t cause even overlaps. So instead of 849MHz, 849.5 849.75 interfering with 850MHz, interference will only occur every 900KHz, which has a lesser chance of overlapping interference.
How to eliminate real interference
Real interference is caused by any type of RFI near your SDR receiver. Simply moving the dongle and antenna away from the source of noise (computer, TV. AVR) will lower interference.
To go even further, you can add a ferrite core, or an RF shielded case around your SDR to block unwanted signals.