What’s
New in cocoaModem 2.0 v0.29
Kok
Chen, W7AY [w7ay (at) arrl.net]
Last updated: December 1, 2006
Click here
for the previous (v0.27/v0.28) What’s New page.
What has changed in v0.29 ?
An audio output equalizer is added to the PSK, Wideband RTTY and Hellschreiber interfaces.
An AppleScript is added to select between Hellschreiber mode, together with the Applescript to transmit a Hellschreiber text stream.
Fixed a contest log output problem.
Audio Equalizer
When using one of the wideband interfaces (PSK, Hellschreiber and Wideband RTTY interfaces) cocoaModem outputs a constant level audio tone, defined by the output level slider.
Some transceivers (specifically the Yaesu FT-1000MP in AFSK mode) have a transmit audio response that is not flat across the audio spectrum. This causes the RF output power to vary depending on which part of the waterfall you have clicked as your transmit frequency.
cocoaModem 2.0 v0.29 adds an interface in the form of a sheet that allows you to define an audio passband that is not "flat." The equalizer sheet is brought up by using the Open Equalizer button, shown below for the PSK Config Panel:
The Open Equalizer buttons for the Wideband RTTY
and the Hellschreiber interfaces are in the Transmit tab of
their Config Panels :
When the Open Equalizer button is clicked, the
Equalizer Sheet drops from the title bar of the Config
Panel.
There is a column of text fields to enter numbers that
correspond to the relative output power from the
transmitter when it is modulated by a constant level audio
tone at the specified frequencies. The PSK, Hellschreiber
and Wideband RTTY interfaces have independent tables that
are save to your plist file.
Until you change them, all of these numbers are initialized
with 1.0, defining a flat audio response.
You can either use a well calibrated audio oscillator, or
use cocoaModem itself to create the test tones for
measuring the RF output from the transmitter.
The easiest way might be to use the "FM Hell 105" mode in
the Hellschreiber interface. The PSK interface is not
suitable since the envelope is not constant and some power
meters will not read the proper peak power. An RTTY signal
is too wide to give good readings for a response that is
uneven.
If you are using cocoaModem to measure the transmit audio
response of your transmitter, do the following:
- connect the transmitter through a good RF power meter
which in turn is connected to a dummy load,
- select the Hellschreiber interface, choose the FM
Hell 105 mode (Feld Hell is unsuitable since it is not
constant power, and FM Hell 245 is too wide),
- open the Equalizer sheet to make sure that a flat
response is selected (column of all 1.0s),
- in the receive section of the Hellschreiber Config
Panel, choose a frequency offset of 0 and select the USB
mode,
- click on the waterfall at 400 Hz, click on transmit
and record the RF power output from the transmitter. Use
a power that is sufficient to get good accuracy from the
power meter and make sure the dummy load specifications
are not exceeded
- repeat the power measurement for 600 Hz, 800 Hz, 1000
Hz, 1200 Hz, 1400 Hz, 1600 Hz, 1800 Hz, 2000 Hz, 2200 Hz
and 2400 Hz, making sure the ALC never comes on. If it
does, reduce the power and repeat all readings.
- Reopen the Equalizer sheet and enter these power
numbers into the "Power (measured)" column.
The plot on the right of the Equalizer sheet should show the computed equalizer curve (reciprocal of transmitted power).
Apply the same numbers to the PSK and Wideband RTTY Equalizer sheets if you use the same transmitter.
After applying the Equalizer, you can try sweeping the Hellschreiber waterfall again; you should notice a much flatter response. You can fine adjust the numbers, if you like. It should be relatively easy to flatten the response to 0.25 dB if the original response is flat to within 3 dB. cocoaModem limits the equalization to 3 dB worth of change.
Hellschreiber AppleScript
With Hellschreiber, you can now select Feld, FM105 and FM245 as the modulation modes, e.g.,
set modulation of transceiver 1 of hellschreiber modem to FM105
The set stream AppleScript is now included for Hellschreiber. (get stream makes no sense of course since Hellschreiber is a facsimile mode.)
Contest Log Bug Fix
Xcode 2.4 introduced a new library which caused Cocoa strings to no longer print to the Unix stdio interface with a Cocoa object specifier.
This caused some strings in the cocoaModem2.0 v0.27 contest log, specifically the contest name string, to not get written out properly. As a result, when the log is read back into cocoaModem, the contest interface could not find the proper contest template to load.