-
Notifications
You must be signed in to change notification settings - Fork 1
/
index.html
194 lines (159 loc) · 7.25 KB
/
index.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
<!DOCTYPE html>
<html>
<head>
<title>Morse Expert 1.14</title>
<link rel="stylesheet" type="text/css" href="main.css">
</head>
<body>
<center>
<h1>Morse Expert 1.14</h1>
<h2>Morse Code Decoder for Android</h2>
<i>Copyright © 2020 Alex Shovkoplyas VE3NEA</i>
<br/><br/><h3>freeware</h3>
<br/><br/><br/><br/>
<img src="VerticalScreen.png">
</center>
<br/><br/>
<h2>Overview</h2>
<p>Morse Expert decodes Morse Code audio to text. Optimized for decoding weak, fading signals in the presence of interference, especially on the Amateur Radio bands. Optionally highlights Ham callsigns and keywords. The audio may come either from the built-in microphone or from another device, such as a radio, via an audio cable. Decoding is performed using the same algorithms as used in
<a href="http://dxatlas.com/CwSkimmer/">CW Skimmer</a>.
</p>
<br/><br/>
<h2>Download</h3>
<p>Download the program from Google Play by clicking on the button below:
<br><br>
<a href='http://play.google.com/store/apps/details?id=com.ve3nea.morse_expert&pcampaignid=pcampaignidMKT-Other-global-all-co-prtnr-py-PartBadge-Mar2515-1'><img style="max-height: 60px; width: auto;" alt="Get it on Google Play" src="en_badge_web_generic.png"></a>
</p>
<br/><br/>
<h2>Discussion Group</h3>
<p>Join the <a href="https://groups.google.com/g/morse-expert-for-android">Morse
Expert for Android Google group</a> to discuss the program and request support.
</p>
<br/><br/>
<h2>Specifications</h2>
<p>
<table>
<tr><td>Waterfall Bandwidth: <td>200-1200 Hz
<tr><td>Decoded Frequencies: <td>300-1100 Hz
<tr><td>Keying Speeds: <td>12-45 WPM
<tr><td>CW Pitch: <td>Auto
</table>
</p>
<br/><br/>
<h2>What's New</h2>
<p>
<h3> Morse Expert v.1.14</h3>
<ul>
<li>Support of Android 15
</ul>
<h3> Morse Expert v.1.13</h3>
<ul>
<li>Small bug fixed
</ul>
<h3> Morse Expert v.1.12</h3>
<ul>
<li>Stability improved
<li>Pause Decoding button added
<li>Premium Version available: ad-free, user-selected text colors
</ul>
<br/><br/>
<h2>Text Selection Mode</h2>
<p>
A long-click on the decoded text switches the app to the text selection mode. Use the selection handles to adjust your selection,
then use the Selection menu to copy, share or save selected text. Decoding is suspended in the selection mode, tap outside of your selection to resume decoding.
</p>
<p>
The Save command saves decoded text to the this folder on your phone:
<pre>Android/data/com.ve3nea.morse_expert/files/</pre>
<p>To copy the file to your PC, connect the phone to your machine with a USB cable.</p>
<br/><br/>
<h2>Frequency Lock Mode</h3>
<p>By default, if there is more than one signal in the passband, the decoder switches automatically
between the signals. A tap on the waterfall display locks the decoder frequency, and the green triangle
<img src="GreenTri.png" />
changes its color to yellow
<img src="YellowTri.png" /> ,
indicating the lock mode. A second tap on the waterfall disables the frequency lock.
</p>
<br/><br/>
<h2>Ham Radio Mode</h2>
<p>The Settings screen allows you to switch between the default, <em>General Text</em> mode,
and the <em>Ham Radio QSO</em> mode. In the latter mode, the app performs extra processing of the decoded text to
improve word segmentation and highlight the callsigns and special words, as shown on this screenshot:
</p>
<center>
<img src="HamMessage.png">
</center>
<!--
<br/><br/>
<h2>Record Signals Command</h2>
<p>
This menu command is available only in the beta version of the app. It saves the next 20 seconds of decoding data to a binary file that the you can send to the author to illustrate your report.
</p>
-->
<br/><br/>
<h2>Reducing Echo</h2>
<p>
Morse Expert can decode audio from the microphone, but acoustic echo picked up by the mic may degrade decoding accuracy, or even completely destroy decoding.</p>
<p>I used the
<a href="https://www.youtube.com/watch?v=_J8YcQETyTw">Morse Letters</a> video uploaded by someone to YouTube to test the effect of the echo.
The first screenshot was taken with the aduio played back via a speaker and picked up by the microphone,
the second one was taken when the audio was fed to the smartphone through a cable, as described in the next section. The tails after every Morse element visible on the first screenshot made decoding impossible, while the audio fed via the cable was decoded perfectly.
</p>
<center>
<img src="Echo.png">
</center>
<p>
I strongly recommend the use of a cable, but if this is not an option, try to place the phone's mic as close to the speaker as possible, to minimize the echo.
</p>
<br/><br/>
<h2>Audio Adapter</h2>
<p>
Many consumer electronic devices, as well as Amateur Radio equipment, output the <i>Line-In</i> level signas, about 600 mV r.m.s. Such signals need to be attenuated to the <i>Microphone</i> level (a few mV) before they are fed to a smartphone. DC decoupling is also often required, in particular, because Android devices
<a href="https://source.android.com/devices/accessories/headset/plug-headset-spec">apply DC</a>
to the Mic pins to detect the presence of an external audio source.
I used the circuit shown below to feed the audio from my shortwave transceiver to the phone, with excellent results.
</p>
<center>
<img src="Schematic.png">
</center>
<p>
To build the attenuator, I used resistors salvaged from an old TV, and the 4-contact audio connector was cut from the broken earbuds. Such earbuds are sold for less than $1 on Ebay. Ironically, the connector alone costs several times more.
<p>
I put the components on a tiny PC board, as shown below, and protected the circuit with a heat-shrink tube.
<center>
<br/>
<img src="Attenuator.png">
</center>
</p>
<h2>Ground Loop</h2>
<p>
It is not recommended to connect the audio and USB cables to the phone at the same time since noise pickup may increase greatly due to a ground loop formed by the two cables. Check the input signal level shown on the status bar above the decoded text, and make sure that it is within -50..-20 dBFS. Higher levels (-20..-1 dBFS) indicate insufficient signal attenuation, ground-loop noise, or other problems.
</p>
<p> If you need to have both cables connected, e.g., to keep your smartphone charged, use an isolating transformer to break the ground loop. I have discovered that the ground loop is eliminated completely usingng the "Audio Aux Noise Filter Ground Loop Isolator" that I bought on eBay
for $5:
<center><img src="isolation_transformer.jpg"/></center>
</p>
<br/><br/>
<h2>Using Morse Expert With a Radio</h2>
<p>
The best way to connect your phone to the radio is via the ACC connector on the rear panel of the transceiver or receiver. Another option is the Headphones jack
on the front panel - this also works, though it is less convenient.
</p>
<center>
<img src="Radio.png">
</center>
<p>
To fix the phone on top of my radio,
I use a smartphone holder made from a paper clip. I was very proud of my invention until I discovered that it was a well-known trick :)
</p>
<center>
<img src="Holder.png">
</center>
<br/><br/>
<hr>
<table width="100%"><tr>
<td><a href="mailto:[email protected]">My email</a><td><a href="http://www.dxatlas.com">My other software</a></td>
</table>
</body>
</html>