Release Notes: AA908_v4.0c
Date: 12/24/2004

This newest software should be used once the Service Pack has been installed.  It depends on proper channel gain with the ERA-3 amp on the DDS card, and with R19,R24,R29,R51 = 71.5K.

Changes since v3k5 ...

1) Changed to using ERA-3 with different gain resistors.  Getting rid of MAV-11 solved
high-end signal level rolloff

2) Changed to "back_to_basics" simplified calibration, adjusting Vr to make SWR=5.4
with 270-ohm load.  Best performing results ever!!

3) Added LCD backlight control circuit (and software timers, Setup menus, etc.)

4) Fixed bug in calculating R (was improperly scaling large denominator)

5) Started measuring and adjusting for A/D offset voltages.  Improved accuracy a bit.

6) Now handling remainder of correction factor generation and use.  Yields best results yet!

7) Fixed cursor adjust too far to left.

8) Straightened out Lite control and EEPROM save/restore

9) Moved cal data to EEPROM Page 1.

10) Fixed power-on pushbutton so timing not critical on release.

11) Added "Stopped" display at powerdown.

12) Made the Default Settings option more sensible and usable.

13) Determine & display reactance sign.  (I'm still not happy with this and more changes will come.)

14)  Reactance Sign Determination -- I diddle the freq (by 1 MHz) when the 
instrument is in Impedance Mode, and when the dial is at rest.  You can see 
this on a scope connected to the load.  Kind of interesting, actually.
[Note: This feature, and the diddling, have been disabled in the current release 4.0c.  We'll
turn it back on when reactance sign results are better.]

15)  L & C Measurements -- Pressing Mode will allow you to select among the different
Modes available for the instrument: Impedance (default), Capacitance, Inductance and VFO.

16)  VFO Mode -- Added a fourth mode called "VFO" which just outputs the 
test signal, without diddling, yielding a signal suitable for external use.

17) All references to that experimental power control feature have been 
removed, so the Micro908 will not randomly go into "stopped" mode, and the 
mysterious interaction with the Sleep pushbutton is gone. Whew! :-)

18) Tone operation is cleaned up a little bit more ... should fix the 
"metronome" effect that some of you guys have noted.

19) The strange readings of "0 +j50" below 8 MHz with 50-ohm load resistor is 
cleared up.  (In some cases, the no-load Vr offset voltage was greater than 
the Vr reading, which was near zero with a perfect match load, resulting in 
a negative corrected sample reading of Sample - Offset  ... not cool.  This 
only showed up after I sampled numerous units and saw what some of you guys 
were noting.)

20) User interface change for the MODE pushbutton.  Instead of using a press-and-hold 
to cycle through the different operational modes of the instrument (Impedance, Capacitance, 
Inductance and VFO), pressing the MODE pushbutton will present the four modes on the LCD 
and the user can turn the dial to display the different modes and press the dial to select 
the desired one.  Thus the user interface is now more consistent with that of the CONFIG 
and BAND pushbuttons.  One further change is that the instrument automatically drops into Impedance mode display upon power-up, after displaying battery voltage and software version number ... again, a much more convenient user interface, as I'm sure you'll see.

I will keep working on improvements, as always, and keep everyone posted. 
Thanks for everyone's kind support and suggestions along the way.

Let us know how this new release works for you.

73, George N2APB
    n2apb@amqrp.org


