SWHarden.com

The personal website of Scott W Harden

How to Destroy a Radio Operator

March 10, 2010
amateur radio

After priding myself on my ingenuity a few weeks ago for documenting my homemade stealth indoor apartment antenna for 40m and 20m, it seems that the green movement has contrived a plan to cripple my successes. So far I’ve made a few dozen contacts in Morse code with my humble little setup (~20 watts of power, direct conversion receiver, indoor homemade antenna). The photo shows some QSL cards I’ve gotten. Anyhow, my apartment manager decided that my apartment needed to have solar panels added to it. It’s too early to tell for sure, but spinning the dial a few times and hearing *nothing* makes me think that it dramatically impacted my reception (and likely transmission) in a dramatic way.

There are the QSL cards I got so far:

I think the AJ4VD station has been effectively shut down!

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Overseas QRP Transmission

March 9, 2010
qrss python obsolete

While working on the spectrograph software I’m trying to complete this spring break, I happened to capture a cool signal from Italy. IW4DXW was sending some cool signals that I captured around 10.140 MHz. See how his call sign is written “visually” on the spectrogram? I thought I’d post it because it’s an encouraging sign that my software is going in the right direction. Also note the numerous QRSS FSK signals around it! So cool.

__I sent an email to the operator and he responded __with station information:

Hi Scott! Thank you so much for nice report. This is a short description of my homebrew beacon. The audio source is a normal MP3/WAV player. The file (.WAV) of my hell message (8x8 char) is generated using Chirphel (program by DF6NM) with a fmax~=800Hz and BW=5Hz, and processed with Csound to obtain the phase relation R = L + 90° between channels (hilbert function). A 10.140MHz oven xtal oscillator (adjusted for +880Hz) is a PLL reference used to obtain a x4 frequency. This clock with the 2 audio channels are applied to a “Softrock style” SSB phasing modulator (double H-mixer with 74HC4053 ic).

The LSB output signal (10.140,080MHz @ ~ -3dBm) is amplified by a 2N2222 (driver stage) and a 2SC2314 (linear PA stage ~1W P.E.P. max, but 100 – 200 mW of average power). I’m using a 30m dipole (inverted vee @ about 50 feet). 30 meters looks good today! My signal heard in VK2 too…

Greetings from north Italy, dear Scott!

73
Riccardo, IW4DXW

__200mW? That’s awesome! __Maybe one day I’ll build something cool like that! I will now return to the programming project that has been eating-up my spring break.

Here’s a screenshot of what I’m doing now I’ll keep for the future memory of this break. Yes, I’m on a Windows machine. I’m at the W4DFU radio club station (they have nicer computers than I do!)

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Dynamic Logo Generation with Python

March 7, 2010
python obsolete

I’m working on a software project and I’d love the startup screen to be unique. I want the splash image to be generated programmatically. I have to generate it from the script, but how can I reliably print text on an image with fonts vary across operating systems? Keep in mind many OS’s don’t have “arial.ttf”, or no truetype fonts at all!

First, I created a 2D binary array to represent the alphabet using pixel fonts such as this as a reference. The word I’m trying to create is “QRSS VD” (the name of my program). I store the data in strings, as seen below. I use 1’s to mark pixels, and spaces to mark empty spaces.

data="""
1111 1111 1111 1111   1  1 111
1  1 1  1 1    1      1  1 1  1
1  1 1111 1111 1111   1  1 1  1
1 11 1 1     1    1   1 1  1  1
1111 1 11 1111 1111    1   111
"""

Once I think it looks nice, I replace the spaces with zeros to make it take up a lot of visual space…

data2="""
1111011110111101111000100101110
1001010010100001000000100101001
1001011110111101111000100101001
1011010100000100001000101001001
1111010110111101111000010001110
"""

Then I further obscure it by replacing linebreaks with a different symbol, such as the number 2, then break the lines so they’re not lined up…

b="1111011110111101111000100101110210010100101000010000001001010012"
b+="1001011110111101111000100101001210110101000001000010001010010012"
b+="1111010110111101111000010001110"

The result is a pretty cool way to obscure the text. I don’t know why you’d want to, but if you want to make sure that no one goes in and changes the letters around (at least without making them think pretty hard about it) you could look at ways to further encrypt this data stream. From here, I create an image using the Python Imaging Library, setting pixel values to 255*b[x,y] (so 0 stays 0 and 1 becomes 255, perfect for an 8-bit image). After enlarging, here’s the result:

Now let’s make it a little bit less pixelated. It’s not a cure-all method, but blurring it up a little with a bilinear filter helps a lot…

Then I apply the code below which applies a cool colormap to the pixel values. I’ll provide cleaner code for this later (I have a really cool way of generating colormaps and saving them as arrays of RGB tuples). Then I go through and plot some random sin wavs on top of it. Sweet! Here are 6 images generated from the program run 6 times. Notice the randomness of the sine wavs!

__A different image is generated every time the script runs, __and it requires no external files (bitmaps or fonts) and should work well on all operating systems.

from PIL import Image
from PIL import ImageOps
from PIL import ImageFilter
from random import randint
import scipy


def genLogo():
    colormap = [(0, 0, 129), (0, 0, 134), (0, 0, 139), (0, 0, 143), (0, 0, 148), (0, 0, 152), (0, 0, 157), (0, 0, 161), (0, 0, 166), (0, 0, 170), (0, 0, 175), (0, 0, 180), (0, 0, 184), (0, 0, 189), (0, 0, 193), (0, 0, 198), (0, 0, 202), (0, 0, 207), (0, 0, 211), (0, 0, 216), (0, 0, 220), (0, 0, 225), (0, 0, 230), (0, 0, 234), (0, 0, 239), (0, 0, 243), (0, 0, 248), (0, 0, 252), (0, 0, 255), (0, 0, 255), (0, 0, 255), (0, 0, 255), (0, 2, 255), (0, 7, 255), (0, 11, 255), (0, 14, 255), (0, 18, 255), (0, 23, 255), (0, 27, 255), (0, 31, 255), (0, 34, 255), (0, 39, 255), (0, 43, 255), (0, 47, 255), (0, 51, 255), (0, 54, 255), (0, 59, 255), (0, 63, 255), (0, 67, 255), (0, 71, 255), (0, 75, 255), (0, 79, 255), (0, 83, 255), (0, 87, 255), (0, 91, 255), (0, 95, 255), (0, 99, 255), (0, 103, 255), (0, 107, 255), (0, 111, 255), (0, 115, 255), (0, 119, 255), (0, 123, 255), (0, 127, 255), (0, 131, 255), (0, 135, 255), (0, 139, 255), (0, 143, 255), (0, 147, 255), (0, 151, 255), (0, 155, 255), (0, 159, 255), (0, 163, 255), (0, 167, 255), (0, 171, 255), (0, 175, 255), (0, 179, 255), (0, 183, 255), (0, 187, 255), (0, 191, 255), (0, 195, 255), (0, 199, 255), (0, 203, 255), (0, 207, 255), (0, 211, 255), (0, 215, 255), (0, 219, 254), (0, 223, 251), (0, 227, 248), (2, 231, 245), (5, 235, 241), (7, 239, 238), (11, 243, 235), (14, 247, 232), (18, 251, 228), (21, 255, 225), (23, 255, 222), (27, 255, 219), (31, 255, 215), (34, 255, 212), (37, 255, 208), (40, 255, 205), (44, 255, 203), (47, 255, 199), (50, 255, 195), (54, 255, 192), (57, 255, 189), (60, 255, 186), (63, 255, 183), (66, 255, 179), (70, 255, 176), (73, 255, 173), (76, 255, 170), (79, 255, 166), (83, 255, 163), (86, 255, 160), (89, 255, 157), (92, 255, 154), (95, 255, 150), (99, 255, 147), (102, 255, 144), (105, 255, 141), (108, 255, 137), (112, 255, 134), (115, 255, 131), (118, 255, 128), (121, 255, 125), (124, 255, 121),
                (128, 255, 118), (131, 255, 115), (134, 255, 112), (137, 255, 108), (141, 255, 105), (144, 255, 102), (147, 255, 99), (150, 255, 95), (154, 255, 92), (157, 255, 89), (160, 255, 86), (163, 255, 83), (166, 255, 79), (170, 255, 76), (173, 255, 73), (176, 255, 70), (179, 255, 66), (183, 255, 63), (186, 255, 60), (189, 255, 57), (192, 255, 54), (195, 255, 50), (199, 255, 47), (202, 255, 44), (205, 255, 41), (208, 255, 37), (212, 255, 34), (215, 255, 31), (218, 255, 28), (221, 255, 24), (224, 255, 21), (228, 255, 18), (231, 255, 15), (234, 255, 12), (238, 255, 8), (241, 252, 5), (244, 248, 2), (247, 244, 0), (250, 240, 0), (254, 236, 0), (255, 233, 0), (255, 229, 0), (255, 226, 0), (255, 221, 0), (255, 218, 0), (255, 215, 0), (255, 211, 0), (255, 207, 0), (255, 203, 0), (255, 199, 0), (255, 196, 0), (255, 192, 0), (255, 188, 0), (255, 184, 0), (255, 180, 0), (255, 177, 0), (255, 173, 0), (255, 169, 0), (255, 165, 0), (255, 162, 0), (255, 159, 0), (255, 155, 0), (255, 151, 0), (255, 147, 0), (255, 143, 0), (255, 140, 0), (255, 136, 0), (255, 132, 0), (255, 128, 0), (255, 125, 0), (255, 121, 0), (255, 117, 0), (255, 114, 0), (255, 110, 0), (255, 106, 0), (255, 102, 0), (255, 99, 0), (255, 95, 0), (255, 91, 0), (255, 88, 0), (255, 84, 0), (255, 80, 0), (255, 76, 0), (255, 73, 0), (255, 69, 0), (255, 65, 0), (255, 62, 0), (255, 58, 0), (255, 54, 0), (255, 51, 0), (255, 47, 0), (255, 43, 0), (255, 39, 0), (255, 36, 0), (255, 32, 0), (255, 28, 0), (255, 25, 0), (255, 21, 0), (253, 17, 0), (248, 14, 0), (244, 10, 0), (240, 6, 0), (235, 2, 0), (230, 0, 0), (225, 0, 0), (221, 0, 0), (217, 0, 0), (212, 0, 0), (207, 0, 0), (203, 0, 0), (198, 0, 0), (194, 0, 0), (189, 0, 0), (185, 0, 0), (180, 0, 0), (175, 0, 0), (171, 0, 0), (166, 0, 0), (162, 0, 0), (157, 0, 0), (152, 0, 0), (148, 0, 0), (144, 0, 0), (139, 0, 0), (134, 0, 0), (130, 0, 0), (134, 0, 0), (130, 0, 0)]

    def red(val):
        return colormap[val][0]

    def green(val):
        return colormap[val][1]

    def blue(val):
        return colormap[val][2]

    def colorize(im):
        r = Image.eval(im, red)
        g = Image.eval(im, green)
        b = Image.eval(im, blue)
        im = Image.merge("RGB", (r, g, b))
        return im
    b = "1111011110111101111000100101110210010100101000010000001001010012"
    b += "1001011110111101111000100101001210110101000001000010001010010012"
    b += "1111010110111101111000010001110"
    b = b.split("2")
    im = Image.new("L", (33+15, 7+13))
    data = im.load()
    for y in range(len(b)):
        for x in range(len(b[y])):
            data[x+6, y+6] = int(b[y][x])*255
    scale = 15
    im = im.resize((im.size[0]*scale, im.size[1]*scale))
    data = im.load()

    def drawSin(width, height, vertoffset, horizoffset, thickness, darkness):
        for x in range(im.size[0]):
            y = scipy.sin((x-horizoffset)/float(width))*height+vertoffset
            for i in range(thickness):
                if 0 <= y+i < im.size[1] and 0 <= x < im.size[0]:
                    # print x,im.size[0],y+i,im.size[1]
                    data[x, y+i] = data[x, y+i]+darkness

    for i in range(5):
        print "line", i
        drawSin(randint(5, 75), randint(-100, 200), randint(0, im.size[1]),
                randint(0, im.size[0]), randint(3, 15), 70)
    for i in range(10):
        im = im.filter(ImageFilter.SMOOTH_MORE)
    im = colorize(im)
    return im


im = genLogo()
im.save('logo.png', "PNG")
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Spring Break Software Project

March 6, 2010
qrss

Wow, I can’t believe I took-on such a massive challenge this week! Ironically I’ve worked harder and learned more in the last 4 days than I have over the last 9 months of dental school. This is an incredible feeling of accomplishment. My program, coded from scratch, polls the sound card continuously and makes extremely large spectrographs. It’s not finished, but it’s working. I’m impressed!

The image above is the actual-size display of the image below. The image below was actually cropped to less than 3,000 pixels high, whereas the original is over 8,000 pixels high!

Note from Future Scott (ten years later, August 2019):

I remember this day! It was the first time I completed a big software project, and it was a great feeling. It motivated me to continue working on software for years to come. I also got a kick out of this quote from early-dental-student Scott: “I’ve worked harder and learned more in the last 4 days than I have over the last 9 months of dental school.”

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Animated Realtime Spectrograph with Scrolling Waterfall Display in Python

March 5, 2010
python obsolete

My project is coming along nicely. This isn’t an incredibly robust spectrograph program, but it sure gets the job done quickly and easily. The code below will produce a real time scrolling spectrograph entirely with Python! It polls the microphone (or default recording device), should work on any OS, and can be adjusted for vertical resolution / FFT frequency discretion resolution. It has some simple functions for filtering (check out the de-trend filter!) and might serve as a good start to a spectrograph / frequency analysis project. It took my a long time to reach this point! I’ve worked with Python before, and dabbled with the Python Imaging Library (PIL), but this is my first experience with real time linear data analysis and high-demand multi-threading. I hope it helps you. Below are screenshots of the program (two running at the same time) listening to the same radio signals (mostly Morse code) with standard output and with the “de-trending filter” activated.

import pyaudio
import scipy
import struct
import scipy.fftpack

from Tkinter import *
import threading
import time
import datetime
import wckgraph
import math

import Image
import ImageTk
from PIL import ImageOps
from PIL import ImageChops
import time
import random
import threading
import scipy

# ADJUST RESOLUTION OF VERTICAL FFT
bufferSize = 2**11
# bufferSize=2**8

# ADJUSTS AVERAGING SPEED NOT VERTICAL RESOLUTION
# REDUCE HERE IF YOUR PC CANT KEEP UP
sampleRate = 24000
# sampleRate=64000

p = pyaudio.PyAudio()
chunks = []
ffts = []


def stream():
    global chunks, inStream, bufferSize
    while True:
        chunks.append(inStream.read(bufferSize))


def record():
    global w, inStream, p, bufferSize
    inStream = p.open(format=pyaudio.paInt16, channels=1,
                      rate=sampleRate, input=True, frames_per_buffer=bufferSize)
    threading.Thread(target=stream).start()
    # stream()


def downSample(fftx, ffty, degree=10):
    x, y = [], []
    for i in range(len(ffty)/degree-1):
        x.append(fftx[i*degree+degree/2])
        y.append(sum(ffty[i*degree:(i+1)*degree])/degree)
    return [x, y]


def smoothWindow(fftx, ffty, degree=10):
    lx, ly = fftx[degree:-degree], []
    for i in range(degree, len(ffty)-degree):
        ly.append(sum(ffty[i-degree:i+degree]))
    return [lx, ly]


def smoothMemory(ffty, degree=3):
    global ffts
    ffts = ffts+[ffty]
    if len(ffts) < =degree:
        # ly.append(fft[i]-(ffty[i-degree]+ffty[i+degree])/2) return [lx,ly] def graph(): global chunks, bufferSize, fftx,ffty, w if len(chunks)>0:
        return ffty ffts = ffts[1:] return scipy.average(scipy.array(ffts), 0) def detrend(fftx, ffty, degree=10): lx, ly = fftx[degree:-degree], [] for i in range(degree, len(ffty)-degree): ly.append((ffty[i]-sum(ffty[i-degree:i+degree])/(degree*2)) * 2+128)
        data = chunks.pop(0)
        data = scipy.array(struct.unpack("%dB" % (bufferSize*2), data))
        ffty = scipy.fftpack.fft(data)
        fftx = scipy.fftpack.rfftfreq(bufferSize*2, 1.0/sampleRate)
        fftx = fftx[0:len(fftx)/4]
        ffty = abs(ffty[0:len(ffty)/2])/1000
        ffty1 = ffty[:len(ffty)/2]
        ffty2 = ffty[len(ffty)/2::]+2
        ffty2 = ffty2[::-1]
        ffty = ffty1+ffty2
        ffty = (scipy.log(ffty)-1)*120
        fftx, ffty = downSample(fftx, ffty, 2)
        updatePic(fftx, ffty)
        reloadPic()

    if len(chunks) > 20:
        print "falling behind...", len(chunks)


def go(x=None):
    global w, fftx, ffty
    print "STARTING!"
    threading.Thread(target=record).start()
    while True:
        # record()
        graph()


def updatePic(datax, data):
    global im, iwidth, iheight
    strip = Image.new("L", (1, iheight))
    if len(data) > iheight:
        data = data[:iheight-1]
    # print "MAX FREQ:",datax[-1]
    strip.putdata(data)
    # print "%03d, %03d" % (max(data[-100:]), min(data[-100:]))
    im.paste(strip, (iwidth-1, 0))
    im = im.offset(-1, 0)
    root.update()


def reloadPic():
    global im, lab
    lab.image = ImageTk.PhotoImage(im)
    lab.config(image=lab.image)


root = Tk()
im = Image.open('./ramp.tif')
im = im.convert("L")
iwidth, iheight = im.size
im = im.crop((0, 0, 500, 480))
# im=Image.new("L",(100,1024))
iwidth, iheight = im.size
root.geometry('%dx%d' % (iwidth, iheight))
lab = Label(root)
lab.place(x=0, y=0, width=iwidth, height=iheight)
go()

UPDATE: I’m not going to post the code for this yet (it’s very messy) but I got this thing to display a spectrograph on a canvas. What’s the advantage of that? Huge, massive spectrographs (thousands of pixels in all directions) can now be browsed in real time using scrollbars, and when you scroll it doesn’t stop recording, and you don’t lose any data! Super cool.

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