Fixed spelling errors, added links to lowpass filters.

README

@@ -32,7 +32,7 @@ Example usage:
   worst case frequency domain performance of the transmitter.
     sudo PiCW --freq 10.140e6 --ditdit --wpm 60
 
-  Transmit an continuous tone at 10.140 MHz
+  Transmit a continuous tone at 10.140 MHz
     sudo PiCW --freq 10.140e6 --test-tone
 
 ******
@@ -68,6 +68,8 @@ Radio licensing / RF:
   P1 label is pin 1 and its 3rd and 4th neighbour is pin 7 and 9 respectively.
   See this link for pin layout: http://elinux.org/RPi_Low-level_peripherals
   Examples of low-pass filters can be found here:
+  http://www.qrp-labs.com/LPF
+  http://www.qrp-labs.com/ULPF
   http://www.gqrp.com/harmonic_filters.pdf
 
   The expected power output is 10mW (+10dBm) in a 50 Ohm load. This looks
@@ -85,20 +87,22 @@ Radio licensing / RF:
   component of 1.6V, DO NOT short-circuit or place a resistive (dummy) load
   straight on the GPIO4 pin, as it may draw too much current. Instead, use a
   decoupling capacitor to remove DC component when connecting the output to
-  dummy loads, transformers, antennas, etc. DO NOT expose GPIO4 to electro-
-  static voltages or voltages exceeding the 0 to 3.3V logic range. Connecting
-  an antenna directly to GPIO4 may damage your RPi due to transient voltages
-  such as lightning or static buildup as well as RF from other transmitters
-  operating into nearby antennas. Therefore it is RECOMMENDED to add some form
-  of isolation, e.g. by using a RF transformer, a simple buffer/driver/PA
-  stage, two schottky small signal diodes back to back.
+  dummy loads, transformers, antennas, etc.
+
+  DO NOT expose GPIO4 to electro- static voltages or voltages exceeding the
+  0 to 3.3V logic range. Connecting an antenna directly to GPIO4 may damage
+  your RPi due to transient voltages such as lightning or static buildup as
+  well as RF from other transmitters operating into nearby antennas. Therefore
+  it is RECOMMENDED to add some form of isolation, e.g. by using a RF
+  transformer, a simple buffer/driver/PA stage, two schottky small signal
+  diodes back to back.
 
   In transmitting Morse code, the CW carrier must be turned on and off.
   To avoid abruptly turning the carrier on and off, the drive strength
   of the GPIO pin used for transmission is gradually increased from 0 to
   16ma with the idea being that this will reduce the frequency spurs created.
   Specifically, the current is increased up to maximum current by following
-  a raised cosine curve.
+  the shape of a raised cosine curve.
 
   Furthermore, a random amount of time domain jitter is added to the turn on
   and turn off ramps to again reduce the spurs created by the turn on/ off
@@ -169,9 +173,8 @@ History/Credits:
   and double amount of power output was implemented.
   https://github.com/threeme3/WsprryPi
 
-  James Peroulas <james@peroulas.com> added several command line options, a
-  makefile, improved frequency generation precision so as to be able to
-  precisely generate a tone at a fraction of a Hz, and a self calibration
+  James Peroulas <james@peroulas.com> AB0JP added several command line options,
+  a makefile, improved frequency generation precision, and a self calibration
   feature where the code attempts to derrive frequency calibration information
   from an installed NTP deamon.
   https://github.com/JamesP6000/WsprryPi
@@ -179,6 +182,6 @@ History/Credits:
   Michael Tatarinov for adding a patch to get PPM info directly from the
   kernel.
 
-  James Peroulas <james@peroulas.com> created PiCW.
+  James Peroulas <james@peroulas.com> AB0JP created PiCW.
   https://github.com/JamesP6000/PiCW