          Welcome to N2PK VNA Software Version 2.01
          -----------------------------------------

  This README file contains information about the software for the N2PK 
  Vector Network Analyzer. Please read this file in its entirety. It is
  recommended that it be printed for quick reference to the programs and
  their features. Also refer to the VNA documents Parts 1 and 2 for VNA 
  hardware details, and Part 3 when it becomes available for additional 
  software and application information.


TABLE OF CONTENTS
-----------------
1.  Release history
2.  Hardware requirements
3.  Operating Systems environments
4.  File contents
5.  Program Installation
6.  Current Working Directory
7.  VNA.CFG file
8.  Data Averaging
9.  Re-usable calibration
10. Programs & Features
11. Program sounds
12. VNA & Program Frequency Resolution
13. Graphics
14. Using the programs
15. Data files & on-screen data display
16. Contact the author
17. Acknowledgements


1.  Release history
-------------------
    Release 2.01
    ------------
    Known problems:
    1. Ctrl+C does not work in PARPORT.
    Corrections:
    1. New calibrations, after the 1st, no longer change the user input 
       frequencies if a CAL file is present.
    2. Maximum number of frequencies no longer decreases on subsequent
       new calibrations - did so in Release 2.00 if a CAL file was present.
    3. Relative phase (approx.) is now correct on re-entry to VFO program
       "S" frequency mode selection. 
    4. Frequencies stored in CAL data files for real time programs are now
       the original calibration frequencies, not the last ones used.
    5. Corrected some memory allocation errors in DDS.
    Changes:
    1. Calibration file names are now named *.CAL instead of *CAL.DAT.
    2. Frequency in REFLR is now displayed to 8 decimal digits as other
       programs.
    3. Frequency entry in the VFO program is not allowed above 100 MHz.
    Additions:
    1. Allows user specified data (*.DAT) filenames.
    2. Adds 'ADCdel' to *.CAL files.
    3. Added the 'Radio' mode to the VFO program, where the RF DDS can be 
       used as a single conversion radio local oscillator and the LO DDS 
       can be used as the radio's BFO.

    Release 2.00 (Aug. 24, 2003)
    ------------
    1. Initial common 'look & feel' release of all programs.
    
2.  Hardware requirements
-------------------------
    The VNA hardware and software are designed to operate with an IBM
    compatible PC with:
    
    a) an IEEE 1284 compliant parallel port. 
    b) a minimum of 1 Mbyte of memory if DOS is used. 
    c) a monitor and a display adapter capable of VGA 640x480 graphics.
    d) minimum of an 80386 processor with an 80287 numeric co-processor
    
    In addition, the 'N2PK VNA' as described primarily in Part 2 of the VNA
    documentation will be required and additional hardware,  as needed, such 
    as impedance bridges, DDS buffer, detector pre-amp, etc. Part 3 will
    describe additional hardware to extend the 0.05 - 60 MHz frequency range
    of the VNA to VHF and UHF in narrowband fashion.
    
    Useful accessory: IEEE 1284 compliant parallel port switch, such as
    the Belkin F1U123. A parallel port switch allows the PC to share one
    parallel port between the VNA and a printer.
    
    The PC and the software here provide all hardware control functions
    as well as data transfer, reduction, display and storage of test 
    results.
    
    The VNA hardware and software has been tested on laptop and desktop 
    systems of various speeds, ranging from 75 to 2000 MHz.
    
    An IEEE 1284 compliant parallel port cable with a DB25 connector
    at each end is recommended, such as the Belkin F2A047-XX, where XX 
    specifies the length. Non IEEE 1284 cables and switch boxes have little 
    signal line impedance and crosstalk control and usage with the VNA 
    may result in software and hardware mal-functions.
    
    It is recommended that the parallel port be capable of 'ECP' or
    'EPP' modes for best performance, particularly on the faster real time 
    programs such as the SWPGEN program. However, in some limited testing,
    it was not found necessary to enable ECP or EPP modes to obtain maximum
    performance.

3.  Operating Systems environments
----------------------------------
    The VNA programs are all DOS based and will function properly in:
    
    a) MS DOS 5
    b) Windows 95
    c) Windows 98
    d) Windows 2000 (requires a direct parallel port access driver)
    
    The programs may also function in other versions of DOS and Windows, 
    such as ME, NT, and XP, but have not been tested. NT and XP will likely
    require a direct parallel port access driver, as does Windows 2000.
    
    There are several direct parallel port access drivers available. The
    only one that has been tested with the VNA is "Direct I/O" at:
    
    http://www.direct-io.com/
    
    As claimed at the above web site, it appears to be quite fast as I see
    no performance difference between native DOS and Windows 2000.
    
    In Windows, multiple copies of the same VNA program or different ones
    can be executing simultaneously. However, this will likely introduce 
    errors in most cases and should be generally avoided. The only known 
    exception is simultaneous use of the VFO and ADC programs in the DEBUG
    directory which interact with different hardware in the VNA. However,
    even with these two programs, it may be possible for Windows time
    sharing, combined with VNA operations in the VFO program, to result in 
    ADC time-outs, which will currently abort the ADC program.

    
4.  File contents
-----------------
    a) VNASOFT.ZIP:
    
       README.TXT
       README.PDF 
       VNA.CFG
       VNAREALT.ZIP
       VNASTORE.ZIP
       VNADEBUG.ZIP


    b) VNAREALT.ZIP:
     
       VNA.CFG
       REFLR.EXE
       TRANSR.EXE
       GRPDELR.EXE
       VFO.EXE
       SWPGEN.EXE

    c) VNASTORE.ZIP:
     
       VNA.CFG
       EGAVGA.BGI
       REFL.EXE
       TRANS.EXE
       GRPDEL.EXE
       
    d) VNADEBUG.ZIP:
     
       VNA.CFG
       PARPORT.EXE
       VFO.EXE
       ADC.EXE
       DDS.EXE
    

5.  Program Installation
------------------------
    The following procedure is recommended for new VNA users and will be
    assumed in the descriptions that follow. However, the procedure can
    be modified to suit individual user preferences, as they develop, for 
    programs used, data storage locations, common or isolated copies of
    the VNA.CFG and *.CAL files, etc. 
    
    In what follows, "X" is the hard drive letter of your choice.
    
    a) Create the following directories:
       X:\VNA
       X:\VNA\DL     (Original download files)
       X:\VNA\REALT  (Real time programs)
       X:\VNA\STORE  (Stored data programs and possibly stored data files)
       X:\VNA\DEBUG  (Hardware debug programs)
       
       You can also optionally create:
       X:\VNA\DATA
       This directory can be specified as the 'current working directory',
       in either DOS or Windows, and will be used to store user data in 
       the CFG, CAL, and DAT files.
       
    b) Copy or move the VNASOFT.ZIP file to X:\VNA\DL. Unzip it there to
       obtain:
       
       X:\VNA\DL\README.TXT
       X:\VNA\DL\README.PDF
       X:\VNA\DL\VNA.CFG
       X:\VNA\DL\VNAREALT.ZIP
       X:\VNA\DL\VNASTORE.ZIP
       X:\VNA\DL\VNADEBUG.ZIP
       
    c) Copy X:\VNA\DL\README.TXT and X:\VNA\DL\README.PDF to X:\VNA for
       quick reference after installation.
       
    d) Copy VNAREALT.ZIP to X:\VNA\REALT and unzip it there to obtain:
    
       X:\VNA\REALT\VNA.CFG
       X:\VNA\REALT\REFLR.EXE
       X:\VNA\REALT\TRANSR.EXE
       X:\VNA\REALT\GRPDELR.EXE
       X:\VNA\REALT\VFO.EXE
       X:\VNA\REALT\SWPGEN.EXE
          
    e) Copy VNASTORE.ZIP to X:\VNA\STORE and unzip it there to obtain:
    
       X:\VNA\STORE\VNA.CFG
       X:\VNA\STORE\EGAVGA.BGI
       X:\VNA\STORE\REFL.EXE
       X:\VNA\STORE\TRANS.EXE
       X:\VNA\STORE\GRPDEL.EXE
       
    f) Copy VNADEBUG.ZIP to X:\VNA\DEBUG and unzip it there to obtain:
    
       X:\VNA\DEBUG\VNA.CFG
       X:\VNA\DEBUG\PARPORT.EXE
       X:\VNA\DEBUG\VFO.EXE
       X:\VNA\DEBUG\ADC.EXE
       X:\VNA\DEBUG\DDS.EXE
    
    The VNA.CFG file in X:\VNA\DL should not be edited to maintain it for
    reference and copying to other directories if errors are made to the
    VNA.CFG files in those directories.
    
       
6.  Current Working Directory
-----------------------------
    All programs will read data from file(s) and, in some cases, will 
    write data to files. These files, as used by each program, are located 
    in the 'current working directory' or simply the 'working' directory.
    
    These files include the VNA.CFG, all the *.CAL, and all the *.DAT files.
    
    In DOS or a DOS box/VDM in Windows, the current working directory is 
    the "current path" (in DOS 6.22 parlance) as can be displayed by typing
    "PROMPT $P$G" at the command prompt. Normally, it would be preferable 
    to change that directory to the one specifically created for VNA use.
    That can be any of the directories created in section 5a above.
    
    If the DOS (box or VDM) current path is changed to the VNA program 
    directory using the DOS "CD" command, then the current working 
    directory will be that same directory.
    
    BAT files can also be used to handle directory management as described
    in DOS documentation.  
    
    When using Windows PIFs or shortcuts, the current working directory 
    will default to the program file directory. There is also an option 
    using the program information file, or 'PIF' as it was called in the 
    early versions of Windows, to define a different working directory. The 
    PIF can be accessed in later versions of Windows by right clicking on 
    the icon or words for a shortcut to each progam or a copy of the 
    program. Then left click on 'Properties', left click on the 'Program' 
    tab, and finally enter the name of the desired directory next to 
    'Working.' 
    
    Of course, the working directory must be created and the files needed 
    or used by that progam must be transferred there. In the case of files 
    written by that program, they will automatically be placed in the 
    designated directory.
    
    There are doubtless many different ways that the DOS or Windows 
    directory management tools can be used with the VNA and its files. 
    
    
7.  VNA.CFG file
----------------
    Each program requires a copy of the VNA.CFG file in its current
    working directory. This file contains information that can be 
    customized by each VNA user. It is an ASCII file that can be viewed, 
    modified, and saved by any text editor, such as Notepad and Wordpad 
    in Windows or EDIT in DOS.
    
    A sample VNA.CFG file, without the optional comments, is shown here:
    
    ---
    Port=0x378    
    Clk=148.340   
    ADCdel=100    
    cfp=1         
    Z0=50         
    Cop=0.039     
    Rsh=0         
    Lsh=0.0       
    Rld=50.013    
    Lld=0.15      
    Cld=0.23      
    Raw=0         
    ---
    
    Here's a description of the parameters:
    
    Port    - The address of the parallel port used by the VNA in hex. Keep
              the '0x' prefix - only the following three digits may be
              different. This value can be obtained from the PC's CMOS 
              memory for DOS, or using Device Manager in Windows.
    Clk     - The actual VNA master oscillator frequency in MHz. It can be 
              adjusted from the sample value by either direct measurement 
              of the master oscillator or indirectly by measuring a DDS 
              frequency using the VFO program and correcting the Clk
              parameter until the measured frequency matches the programmed
              frequency within acceptable limits. To correct the Clk 
              parameter, multiply the last Clk value by the ratio of the 
              measured to the programmed DDS output frequency. This may 
              have to be repeated depending on the number of digits used
              in the calculations.
    ADCdel  - delay in ms between a frequency/phase program and the first 
              ADC read that follows. '10' is recommended for the real time
              programs for improved performance with the possibility of 
              some degradation in accuracy. '100' is recommended for best
              accuracy for any test or debug program.
    cfp     - continuous frequency programming: if set to '1', there will 
              be no 'holes' or interruption in the DDS outputs due to 
              re-initialization between different frequencies, '0' if
              otherwise. Use '1' as a default.
    Z0      - Basis in ohms for measured reflection coefficients and the 
              center of Smith Chart displayed in REFL, generally 50 ohms.
              This can be different than the resistance of the load 
              standard.
    Cop     - Excess shunt (fringing) capacitance in pF of the Open 
              calibration standard beyond the reference plane. 0.039 pF
              represents a flush ground female SMA chassis connector. 
              Lacking a better value, use 0.     
    Rsh,Lsh - Series resistance in ohms and inductance in nH for the Short 
              calibration standard. Both are essentially close to zero thru
              60 MHz for a well constructed flat plane short over the back 
              of a flush ground emale SMA chassis connector. Lacking a 
              better value, use 0 for each.
    Rld     - Series resistance in ohms of the Load calibration standard, 
              usually about 50 ohms. Use an accurately (4 point Kelvin
              probe) measured value, if possible. Lacking a better value, 
              purchase precision 1% or 0.1% meatl film resistor(s) and use 
              the nominal value(s).
    Lld,Cld - Series inductance in nH and excess shunt capacitance in pF
              of the Load calibration standard beyond the reference plane.
              The values shown are estimates for a four 0805 200 ohm 0.1% 
              surface mount resistors, mounted E-W-N-S fashion, between the
              center pin and outer conductor of a flush ground female SMA
              chassis connector. Lacking values for other terminations, 
              use 0 for each.
    Raw     - Set to '1' to append raw data to *.RAW files, '0' if not. For
              general usage, '0' is recommended to avoid accumulation of
              unused data.
   
    The values needed for the open, short, and load calibration standards 
    will depend on the connectors and standards being used. If you use 
    multiple calibration standard sets, a VNA.CFG file can be saved for 
    each set using some descriptive file name and each changed to VNA.CFG 
    as needed prior to testing using them.
    
    Make sure that the common parameters, such as Port, Clk, & cfp, are
    updated in all the various copies of the VNA.CFG as needed.
  
8.  Data Averaging
------------------
    Averaging of measured data is provided in all of the VNA programs that
    collect data.
    
    Since each data point is a vector (i.e. magntude & phase on the complex
    plane), averaging the readings collected for each component of each
    vector can result in signal to noise ratio (S/N) improvements when the 
    S/N is low.
    
    The maximum improvement is when there is essentially no signal. For 
    example, the noise floor in a transmission test can be typically lowered 
    (improved) by about 7 dB when ten readings are averaged. The degree of 
    improvement with averaging will vary as it depends on a variety of
    factors, including the drift in the VNA.
    
    However, since averaging increases the test time in nearly direct
    proportion, averaging should be used only in those cases where it can 
    actually improve accuracy. 
    
    High insertion loss transmission measurements and group delay 
    measurements significantly off the 'nose' of a filter are two test
    examples that may benefit from averaging. Only the most critical of
    impedance measurements will benefit from averaging.
   
9.  Re-usable calibration
-------------------------
    The real time and stored data reflection, transmission, and group
    delay programs all provide the user with the option of saving a
    calibration just performed for later re-use. On subsequent entry,
    each program will offer the user the option of re-using the previously
    saved calibration data. If the subsequent DUTs are to be tested over
    the same frequency range and would utilize the same calibration
    standards, this can be a significant time saver particularly for the
    OSL reflection calibration where the calibration consumes 75% of the
    total test time needed for a single DUT.
    
    Each program will search its current working directory for a previously
    saved calibration file. It will also optionally write new calibration
    data in the current working directory. Note that each calibration save 
    will over-write the previously saved data. 
    
    However, care must be taken to ensure that the original test set-up
    is replicated prior to subsequent measurements. It is also important
    that the VNA be warmed up sufficiently prior to all measurements to
    minimize drift induced errors. Periodic re-test is recommended to 
    verify that the set-up is correct and that drift has not introduced an 
    unacceptable level of error. 
    
    The calibration files are named REFL.CAL, TRANS.CAL, and GRPDEL.CAL.
    They are all ASCII text files that can be viewed to verify contents and
    saved under a new name by any text editor, such as Notepad & Wordpad in
    Windows or EDIT in DOS. They can also simply be copied or re-named as
    desired. In this way, multiple calibration files can be stored and 
    re-used. 
      
     
10. Programs & Features
-----------------------
    On entry, each program displays a description of what it does. Here is
    a summary of each by directory:
    
    X:\VNA\REALT directory programs
    -------------------------------
    This is a collection of real time VNA test programs, as denoted by the
    "R" suffix, that display reflection, transmission, and group delay data 
    to the user as it is being collected at selected frequencies. In 
    addition, there are two programs, VFO and SWPGEN, that collect no data, 
    but provide real time interaction with the VNA RF and LO DDS signal 
    sources.
    
    Each program requires a valid VNA.CFG file in its current working 
    directory. It may be desirable to set the ADCdel parameter in the
    the real time VNA.CFG files to 1 (ms) to provide the best possible
    performance. While there can be accuracy losses by doing so, they may
    not be important to some real time applications, such as adjustments.
    
    The real time programs can also be used to perform preliminary
    measurements in preparation for more extensive and time consuming
    stored data collection. Using the generic VFO capability of all of the 
    real time programs, parameters like crystal resonant frequencies, 
    filter 3 dB frequencies, and group delay peaks can be quickly found
    and then used as the basis for more detailed measurements.
       
       REFLR.EXE
       ---------
       This program measures the complex reflection coefficient from 
       50 kHz to 60 MHz for one port and multi-port networks, such as 
       antennas, amplifiers, and components. A variety of directly 
       measured & derived test data will be continuously updated on 
       screen at 1 to 7 frequencies. Each frequency can be independently 
       controlled while DUT data is displayed. No DUT data will be written 
       to a file.  Calibration data in REFL.CAL can be used and this file 
       can also be written using calibration done here.
       
       TRANSR.EXE
       ----------
       This program measures the complex transmission gain from 50 kHz 
       to 60 MHz for multi-port networks, such as filters, matching 
       networks, and amplifiers. If care is taken to ensure the source and 
       load match required by the DUT, the measured complex transmission 
       gain will closely approximate S21 or S12. A variety of directly 
       measured & derived test data will be continuously updated on screen 
       at 1 to 7 frequencies. Each frequency can be independently 
       controlled while DUT data is displayed. No DUT data will be written 
       to a file.  Calibration data in TRANS.CAL can be used and this file
       can also be written using calibration done here.     
       
       GRPDELR.EXE
       -----------
       This program measures group delay from 50 kHz to 60 MHz for multi-
       port networks, such as filters, matching networks, and amplifiers.
       You will need to enter a 'frequency aperture' which is centered on 
       each nominal test frequency. Typical apertures are 1-10% of the DUT 
       BW. This program can be useful in determining an optimal aperture. 
       Measured group delay is continuously updated on screen at 1 to 7 
       frequencies. Each frequency can be independently controlled while 
       DUT data is displayed. No DUT data will be written to a file.  
       Calibration data in GRPDEL.CAL can be used and this file can also be 
       written using calibration done here. The user can specify either a
       two or four frequency aperture to be used for the group delay
       calculation. The four frequency aperture is slower, but may help
       the user determine the optimum aperture width for a given DUT.
       
       VFO.EXE
       -------
       This program provides independent or coupled frequency control of
       the RF & LO DDS sources. There are two coupled modes. One provides
       the same frequency and relative phase control of the LO DDS phase,
       in 11.25 degree increments. The second coupled mode controls the 
       RF DDS frequency and the offset of the LO DDS from the RF DDS. The 
       frequencies and phase are initially entered numerically and can then
       be changed using the cursor control (arrow) keys. 
       
       This program can also be used to enable the VNA's RF DDS as a local
       oscillator (LO) for a superhet radio where the indicated frequency is 
       actually the radio's tuned frequency. The RF DDS is automatically 
       offset on the high side by the intermediate frequency (IF). The LO 
       DDS can also be used as the radio's beat frequency oscillator (BFO).
       
       The decimal frequency is directly controlled, but the DDS hex tuning 
       words are also displayed. 
       
       The VNA's ADC will not be used. There will be no data on screen or 
       to a file. There will be no program feedback that the DDS's have 
       properly received or executed their commands. The user can do that 
       by independent measurements of frequency and relative phase. 
       
       The VNA test programs are typically limited by distortion in the RF
       DDS output transformer for frequencies below 50 kHz. However, the
       LO DDS outputs are capacitively coupled and negligible distortion
       occurs below 50 kHz. The primary limitation is amplitude loss, but
       this can also be minimized by high impedance loading which may be
       desirable at audio or near audio frequewncies.                                                  
 
       SWPGEN.EXE
       ----------
       This program sweeps the DDS sources and permits real time return 
       loss and insertion gain/loss measurements, and adjustment if 
       desired, of one port and multi-port networks, such as antennas, 
       amplifiers, and other components. The program assumes that the user 
       will supply an external bridge, a log amp, a scope, and trigger or 
       DAC connections from the VNA, as needed, to perform the desired 
       measurements. The sweep center frequency, deviation from the center 
       frequency, the number of frequencies per sweep, the LO DDS phase, 
       and re-trace time are all controllable while sweeping. There will 
       be no data on screen or written to a file. The VNA's ADC will not 
       be used during frequency sweeps. An AD8307 log amp with output 
       offset control can be a useful RF detector when connected to the 
       scope vertical input. A calibrated 50 ohm step attenuator is also 
       useful for setting vertical calibration. Pin 14 of the parallel 
       port DB25, at the VNA, can be used for external scope sync and also 
       beam blanking during frequency re-trace, if desired. In addition, 
       a DAC will be available on the fast detector board to permit 
       horizontal deflection of a scope in X-Y mode. 
       
    X:\VNA\STORE directory programs
    -------------------------------
    This is a collection of stored data VNA test programs designed to
    collect reflection, transmission, and group delay data and store the
    data in files. The user can then view, copy, or import data into other
    programs, such as MathCAD, spreadsheets, word processors and e-mail.  

    Each program requires a valid VNA.CFG file in its current working 
    directory. While it may also be desirable to set the ADCdel parameter 
    in the stored data VNA.CFG files to 1 (ms) to provide the best possible
    performance, the best accuracy here may be more useful as provided with
    the default value for ADCdel of 100 (ms).  It is difficult to provide 
    specific guidelines for setting ADCdel. The user can experiment with
    various values of ADCdel ranging over a suggested range of 1 to 100 
    ms to determine the value that provides the desired balance of
    accuracy and test time for the DUTs of interest.                                        
      
       REFL.EXE
       ---------
       This program measures the complex reflection coefficient from 50 kHz
       to 60 MHz for one port and multi-port networks, such as antennas, 
       amplifiers, and components. A variety of directly measured & derived 
       test data will be displayed on screen, and can also be written to 
       the REFL.DAT file in the current working directory, where 'REFL' can
       be changed by the user. Raw test data can also be optionally written
       to the REFL.RAW file. Calibration data in REFL.CAL can be used and 
       this file can also be written using calibrations done here.
          

       TRANS.EXE
       ---------
       This program measures the complex transmission gain from 50 kHz to 
       60 MHz for multi-port networks (DUTs), such as filters, matching 
       networks, and amplifiers. If care is taken to ensure the source and 
       load match required by the DUT, the measured complex transmission 
       gain will closely approximate S21 or S12. A variety of directly 
       measured & derived test data will be displayed on screen, and can 
       also be written to the TRANS.DAT file in the current working 
       directory, where 'TRANS' can be changed by the user. Raw test data 
       can also be optionally written to the REFL.RAW file. Calibration 
       data in REFL.CAL can be used and this file can also be written using 
       calibrations done here. 
                     
       GRPDEL.EXE
       ----------
       This program measures the group delay from 50 kHz to 60 MHz for
       multi-port networks, such as filters, matching networks, and 
       amplifiers. If care is taken to ensure the source and load match 
       required by the DUT, the measured complex transmission gain will 
       closely approximate S21 or S12. You will need to enter a 'frequency 
       aperture' which is centered on each nominal test frequency. There is
       a balance to be found between resolution and noise in the measured 
       group delay. Typical frequency aperture values are 1 - 10% of the 
       DUT BW. Measured group delay will be displayed on screen and can 
       also be written to the GRPDEL.DAT file in the current working 
       directory, where 'GRPDEL' can be changed by the user. Raw test data 
       can also be optionally written to the GRPDEL.RAW file. Calibration 
       data in GRPDEL.CAL can be used and this file can also be written 
       using calibrations done here. 
       
       This program only uses a two frequency aperture. Use the real time
       GRPDELR program to aid in determining the optimum aperture width for
       a given DUT.                    

    X:\VNA\DEBUG directory programs
    -------------------------------
    This is a collection of VNA hardware debug programs that may be helpful
    in the event of apparent hardware and/or software mal-functions. In
    addition, the DDS program can be used for various hardware performance
    testing.   

    Each program requires a valid VNA.CFG file in its current working 
    directory. 

       PARPORT.EXE
       -----------
       This program assists in verifying the parallel port connections 
       between the PC and the VNA. Connect the VNA, if desired, to the 
       appropriate parallel port to facilitate probing of the port pins & 
       verification of connections. The VNA can be powered ON while 
       outbound pins are toggled by the program. During inbound pin 
       sensing, the VNA is powered off and all connectors to the VNA PCB(s) 
       are removed to permit external forcing of voltages on the inbound 
       pins. Parallel port pins will be referenced here to the DB25 
       connector. Refer to VNA documentation for internal pinouts. Each 
       outbound pin can be toggled between logical 1 (+5V) and logical 0 
       (Ground) continuously and can be monitored on an oscilloscope. 
       Outbound pins will generally be at a logical 0 state with no
       program activity. Pins 1, 14, and 16 are typically at a logical 1 
       state and one can be used as an aid in inbound pin forcing to that 
       state, if needed. Each inbound pin logical state can be sensed and 
       displayed continuously while the corresponding pin can be forced to 
       Ground or +5V to observe the effect. Inbound pins will generally be
       at a logical 1 state with no external forcing. A series 220 ohm 
       resistor between an inbound pin and either a ground pin or one of 
       pins 1,14, or 16, if needed, is recommended to minimize the 
       potential for damage by inadvertently grounding outbound pins. In 
       general, avoid shorting parallel port pins unless you know what 
       you're doing.         
       
       VFO.EXE
       -------
       The VFO program was described above with the real time programs. 
       But, since it exercises only the VNA RF and LO DDS signal sources
       and does not exercise the ADC, it can be useful in hardware debug
       as well.
              
       ADC.EXE
       -------
       This program exercises only the ADC in the VNA without programming 
       the DDS's. Connect the VNA to the appropriate parallel port and 
       power it on now. You will be prompted for an integer to be used to 
       average ADC readings. If this value is greater than 1, then the mean 
       and standard deviation will be displayed. If the DDSs are 
       functional, they can be programmed using one of the other programs
       such as VFO prior to starting this program. Connecting the DDSs to 
       the detector will, in turn, affect the ADC readings here.                                    
       
       DDS.EXE
       -------
       This program is intended to be a general purpose hardware diagnostic 
       tool, a vehicle for non-VNA uses for the hardware, and evaluation of 
       new test sequences. Arbitrary frequency and phase programming can be 
       done for each of the RF & LO DDSs from 50 kHz to 60 MHz with sub Hz 
       frequency & 11.25 deg. phase resolution. Frequencies outside the 
       above range can be programmed, but with degraded waveform quality. 
       Phase is programmed from 0 to 31 representing the 11.25 deg. 
       increments from 0 to 348.75 deg. There are many possible operating 
       modes in this program and its main menu shows the possible options. 
       One way to learn how to use this program is to tee a dual channel 
       scope into the DDS to detector paths, try different program options
       and combinations of options, and observe what happens. The program 
       can optionally write measured data to the following files:
       
       a) ALLDEV.DAT, used to store Allan deviation data of measured
          ADC readings for a range of averaging values that permit a 
          population of at least 100 means to be used to calculate the 
          Allan deviation. 
             
       b) MEANSDEV.DAT, used to store the means (averages) and standard
          deviation of the means for a range of averaging values that
          permit a population of at least 100 means to be used to
          calculate the standard deviation.  
          
       c) PHLIN.DAT, used to store the results of a phase linearity test
          where the vector ADC readings are collected at each of the 32
          possible LO phases.
       
       d) DDSSCR.DAT, used to store the data displayed on screen.

      
11. Program sounds
------------------
    These programs can emit two sounds - a low or a higher pitched beep. 
    
    The low pitched beep indicates a user entry that is in error. 
    
    The higher pitched beep is used shortly after program entry to alert the 
    user that VNA has been detected. After that, it is generally used only 
    to signal completion of some possibly long duration event that would 
    normally then require the user's attention to change the hardware 
    configuration.
    

12. VNA & Program Frequency Resolution
--------------------------------------
    As a result of the 148.34 MHz clock frequency and the 32 bit DDS tuning
    word, the DDS frequency resolution is approximately 0.035 Hz. This is
    the smallest change in frequency that could be observed on an extremely 
    stable frequency counter. Actually measuring this change would also
    depend on VNA clock stability and other factors, which would typically
    mask these small changes.  
    
    However, the programs are provided with 0.01 Hz resolution to permit 
    the decimal frequency to be used to step through all possible DDS tuning
    words. In certain programs, such as VFO, SWPGEN, and DDS, where both the
    decimal frequency and the corresponding DDS tuning word is displayed, it
    will be seen that 3 or 4 steps at 0.01 Hz per step will be required 
    between tuning word changes.
    
    Except for situations where one might be interested in observing DDS 
    spurs, recording frequency to 0.1 Hz resolution will be at the limit of
    what is useful. Even 0.1 Hz resolution, given long term stability and 
    calibration of the VNA cl0ck frequency will generally only be useful for 
    determining delta-f where the two frequency measurements occur within
    seconds of one another.
    

13. Graphics
------------
    The three stored data programs, REFL, TRANS, and GRPDEL, will each 
    display a plot of the measured data vs. frequency after the data 
    collection and reduction is complete. These programs will require
    the 640x480 capable VGA display mode and the EGAVGA.BGI file in the
    current working directory for each of them. Generally, DOS and Windows
    will support 640x480 mode if the hardware does. In Windows, the program
    will go to full-screen to display the plot. 
  
    
14. Using the programs
----------------------
    All programs have specific use instructions, but here's some general 
    comments:
    
    a) 'Ctrl+C' without the Enter key can pressed at most times in the 
       programs to abort the activity in progress and return to the 
       program entry.
       
    b) The contents of the VNA.CFG file in use are displayed shortly after
       program entry. You should review the parameters for the hardware in 
       use, before continuing. In DOS, you will have to exit the program 
       to make the changes to the VNA.CFG file. In Windows, you can make
       the changes to the VNA.CFG in a separate window and then continue
       with the VNA program.
       
    c) Prior to calibration standard and DUT data collection, the 
       measured vector components are continuously updated on screen to
       allow the user to verify that all of the connections are correct
       and that the readings are stable. Familiarization with these
       raw data readings is recommended as it can help spot set-up 
       problems as well as minimizing measurement errors and wasted time.
       
    d) Most programs will check the parallel port designated in the VNA.CFG
       file for the ADC in the VNA which is the only part of the hardware
       that can reply. If the VNA ADC is not detected via certain
       expected responses, the program will allow the user to correct some
       set-up problems such as the VNA powered down or a parallel port
       switchbox still connected to the printer instead of the VNA. If the
       parallel port number is not correct in the VNA.CFG file and if the
       program is operating under Windows, the VNA.CFG file can be updated 
       in an editor window with the correct port number and re-read by 
       pressing 'Ctrl+C' in the VNA program.
       
    e) Many programs allow selection of three frequency entry modes: 
       fundamental, harmonic mixing, and synchronous common LO up/down 
       mixing. The later two modes extend the frequency range of the VNA, 
       in narrowband fashion, beyond 60 MHz. They also require additional 
       hardware to be described later in Part 3 of the VNA documentation. 
       For now, use the fundamental mode.
     
    f) While there are certain timing requirements for the VNA ADC, Windows
       time-sharing has not caused VNA programs to mal-function while they
       are interacting with the VNA hardware in usage so far. However, it 
       is possible that slower PCs or ones with greater time loads imposed 
       by other programs may cause VNA program mal-functions or aborts to
       occur. If aborts do occur, they may be preventable by keeping the VNA
       program in the foreground, and also to ensure that the VNA programs
       are not suspended when in the background.
       
    g) The SWPGEN program, when used with a triggered scope sweep, may have
       some occasional trace aberrations due to Windows time-sharing. The
       DAC, to be described in a future hardware update, can be used to
       drive the scope's beam horizontally in place of the scope's internal
       timebase. Use of the DAC has been found to eliminate the occasional
       aberrations in Windows. Until the DAC becomes generally available, 
       the SWPGEN program can be run under DOS to eliminate any objectionable
       effects of time-sharing.  
       
       
  

15. Data files & on-screen data display
--------------------------------------- 
    The reflection, transmission, and group delay stored data programs
    save the measured results in ASCII text files called REFL.DAT, 
    TRANS.DAT, and GRPDEL.DAT respectively by default. Optionally, the user
    can select either that no test data will be written to a file or the
    part of the filename preceeding '.DAT'. Each of these files will be 
    created in the applicable current working directory if it does not 
    exist, or over-written with its previous contents destroyed, or  
    appended with the new data added at the end of the previous data.
    
    These files can be viewed by most text editors. The text editor can be 
    used to selectively copy & paste certain data from these files into 
    other files or other programs, such as MathCAD, spreadsheets, word 
    processors and e-mail. Alternatively, since the files have comma 
    delimited data and column header fields, they can be generally imported
    directly into a spreadsheet. 
    
    As these files may get quite large, it's useful to periodically review 
    their contents, save the important data, and discard the rest. This
    editing can be done safely with a text editor while no VNA programs are 
    running. Subsequent writing to the file by the VNA programs will simply
    append the new data to the end of the file.
    
    File growth can also be limited by selecting DAT filenames based on
    some user recognizable criterion, such as a short DUT description, that
    conforms to the DOS 1-8 character file naming conventions.
    
    The programs also provide a 'no file name' option for cases where the
    user may want to only view the test data on screen either numerically
    or graphically and does not want the data stored on the hard drive.
    
    In addition, REFL.RAW, TRANS.RAW, and GRPDEL.RAW can be optionally used
    to store the raw measured DUT and calibration standards for user review,
    debug, and additional data analysis as needed. This option is enabled 
    with 'Raw=1' in the applicable VNA.CFG file.
    
    Note that the *.RAW and *.CAL files cannot be named within the programs
    by the user at this time. However, they can be re-named as needed 
    externally.
    
    Here's a brief summary of the key column headers in each of the DAT
    files. Much of this data also appears on-screen as well.
    
    REFL.DAT
    --------
       Date
       Time
       Freq.MHz
       Reflection Coefficient:
          Real         - real part of the complex reflection coefficient
          Imag         - imaginary part
          |rho|        - magnitude
          deg          - polar angle in degrees
          RL.dB        - return loss in dB
       SWR             - (voltage/current) standing wave ratio
       Rs.ohms         - real part of the impedance in series form 
       Xs.ohms         - reactive part of the impedance in series form
       |Zu|.ohms       - magnitude of impedance
       <Zu.deg         - angle of the impedance in degrees
       Q               - quality factor = |Xs|/Rs
       Cs.pF           - Xs expressed as a capacitor in series with Rs
       Ls.uH           - Xs expressed as an inductor in series with Rs
       Rp.ohms         - real part of the impedance in parallel form
       Xp.ohms         - reactive part of the impedance in parallel form
       Gp.mS           - Rp expressed as conductance
       Bp.mS           - Xp expressed as susceptance
       Cp.pF           - Xp expressed as a capacitor in parallel with Rp
       Lp.uH           - Xp expressed as an inductor in parallel with Rp
       Rdgs            - number of ADC readings averaged
       cfp             - value of Continuous Frequency Programming
       Z0.ohms         - reference value for the reflection coefficient
       Cop.pF          - Open cal. standard value from VNA.CFG
       Rsh.ohms        - Short cal. standard value from VNA.CFG
       Lsh.nH          -   "    "      "      "      "     "
       Rld.ohms        - Load cal. standard value from VNA.CFG
       Lld.nH          -   "    "      "      "     "     "
       Cld.pF          -   "    "      "      "     "     "
       DUT Description - Optional user supplied description of the DUT
       
    TRANS.DAT
    ---------
       Date
       Time
       Freq.MHz
       |G|             - magnitude of the transmission gain
       |G|.dB          - magnitude of the transmission gain in dB
       <G.deg          - angle of the transmission gain in degrees
       Rdgs            - number of ADC readings averaged
       cfp             - value of Continuous Frequency Programming
       Z0.ohms         - not used in calcs, for reference only 
       DUT Description - Optional user supplied description of the DUT
    
    GRPDEL.DAT
    ----------
       Date
       Time
       Freq.MHz        - Center frequency of each aperture in MHz
       Apert.MHz       - Frequency aperture used  
       mean |G|        - magnitude of the aperture mean (average) gain
       |G|.dB          - mean gain in dB
       <G.deg          - angle of mean gain in degrees
       delta.deg       - change in measured angle at the aperture endpoints
       GrpDel.Sec      - group delay in seconds.
       Rdgs            - number of ADC readings averaged
       cfp             - value of Continuous Frequency Programming
       Z0.ohms         - not used in calcs, for reference only 
       DUT Description - Optional user supplied description of the DUT
   

16. Contact the author
----------------------
    The author of the software and designer of the VNA hardware is Paul
    Kiciak, N2PK. Please report any program bugs, comments, or questions 
    by e-mail to pkiciak@adelphia.net.


17. Acknowledgements
--------------------
    I wish to acknowledge and thank the following individuals for their
    contributions to the software portion of this project. Harold Johnson,
    W4ZCB, suggested the idea of re-usable calibrations. I initially
    resisted implementing this, but it is now a feature I would not do
    without. Bill Carver, W7AAZ, suggested a simple yet elegant way to
    extend the frequency range of the VNA into the VHF and UHF range. This
    resulted in the "Synchronous Common LO up/down mixing" frequency entry 
    mode that is available in many of the programs. Bill also suggested 
    providing the user with the option of naming the test data files - 
    another feature that should prove generally useful. Jim Tonne, WB6BLD, 
    graciously provided a wonderful jumpstart in the design of the Smith 
    Chart that appears in the REFL program.
    
    Harold Johnson and Bill Carver have also provided a great deal of 
    assistance & feedback generally by building their VNAs and being the
    primary beta software testers.
    
    Harold also now refers to his VNA as "the lab in a box."
