G4AKW

The following GNU radio application adds a waterfall spectrogram to the previous CW filter program. The plot show 4 CW signals in the audio band (lower sideband) at 7023 kHz. The 700Hz signal is filtered and output to the laptop headphones by the CW bandpass filter. The frequency display is shown after the script which is as follows: #!/usr/bin/env python from gnuradio import gr from gnuradio import audio from lpf_bpf_class import Bandpass from gnuradio.qtgui import qtgui from PyQt4 import QtGui import sys, sip     class cw_filter(gr.top_block):     def __init__(self):         gr.top_block.__init__(self)           sample_rate = 44100         out_rate = 8000         kaiser = Bandpass()         cw_flr = gr.fir_filter_fff(1, kaiser.bpftaps)         decimate = int...

  #!/usr/bin/python """ Morse Code Generator. Geoff Robinson, G4AKW, Version 1.0, 4th December 2011. Requirements: Python 2.7, Linux OS, alsaaudio. Usage # python mainmorse.py The basic element of Morse code is the dot and all other elements can be defined in terms of multiples of the dot length. The word PARIS is used because this is the length of a typical word in English plain text, it has a total length of 50 dot lengths. If the word PARIS is sent ten times in a minute using normal Morse code timing then the code speed is 10 WPM. There are 500 dot lengths in a minute for 10 wpm or 1000 dot lengths per min for 20 wpm. The dot length is therefore 60mS for 20 wpm. The python dictionary 'code' and the function convert() converts characters to their dot space equivalents i.e either on or off keying. """ import serial import time, thread import random import sys import sched import wave, struct, math from alsaaudio import * impor...

This antenna is a dipole, each leg approximately 60 ft long (overall length ~ 120ft), fed with open wire feeder (ladder line).  Photo 1 shows the ladder line (constructed from plastic garden plant staples garden centre stuff is usually good at withstanding the outdoor conditions!), and the feed point insulator. A short length of 12 guage wire is used to take the wire tension and support the ladderline on each side of the insulator. The ladder line spacing, around 3 inches in this case, and its characteristic impedance, approximately 500 ohms here, is not important. (Spacing determines the maximum power handling capability (volts) and wire thickness (current)). The ladder line enters the house and is connected directly to the transmatch by two lengths of URM 67 coax stripped of its outer sheath and braid (photo 2).  These two 2 ft lengths take the feedline through two 15mm speed fit Polyethylene pipes through the wall and into the living room.  The impedance at the point ...

After some tests on Topband a few modifications were made. The 40A bridge rectifier failed and was replaced with 50A one mounted on a better heatsink, the problem appears to be the ability to handle the peak repetitive forward current charging the 30mfarrad capacitors -the specs for the rectifier don't show this value - only average forward current i.e. 50A. A front panel transmit/receive switch was also fitted to replace (temporarily) the control from the FT817. The FT817 transmit control line currently does not provide sufficient delay (pretty sure it can be programmed for sufficient lead-in) to ensure the antenna relay is properly made before the amp delivers full power. The final mod was to the microwave oven step/slow start protection circuit. Instead of a 22 ohm series resistor limiting the primary current, the two 50 ohm resistors were connected in series giving 100 ohms which limits the primary inrush current to 2.4 amps (24 amps in the secondary). The protection rela...