Data collection and graphing software 
for the PC when connected to the Micro908


Link908 version 2.2.4 is the software program for your PC that collects and plots the SWR and impedance data collected by the Micro908 Antenna Analyst (AA908). Mike Hasenfratz, WA6FXT has worked diligently for several months to create this capability which is of great value to Antenna Analyst owners.

Link908 is a software program that gets installed on your PC and presents a screen link the one shown below to display the SWR, Resistance and Reactance data collected by your AA908 Antenna Analyst during a scan.  You can select to view SWR (red trace), or Resistance (green trace), Reactance (blue trace), or all three!


Understanding the Link908 Screen

The screen capture above shows the results of a 1-10 MHz scan on an N2APB antenna that is resonant at 8.6 MHz. 

There are three distinct regions of the scan:

  1. The "active" region from about 5 MHz to 10 MHz shows the SWR, Resistance and Reactance curves changing in relatively smooth manners, as would be expected as resonance is approached. You see the red SWR curve showing a minimum at the resonant frequency, while the green Resistance curve indicates close to 50 ohms and the reactance is close to zero

  2. The "inactive" region from 1 MHz to about 5 MHz for Resistance (or to about 4 MHz for Reactance) are the frequencies where the impedance is greater than 600 and the R & X values are not able to be computed properly by the Micro908.  So the instrument produces "zero results" at these points where "Z>600" is seen on the LCD display.

  3. The "intermediate" region with the jagged transitions is where the impedance is approaching the Z>600 condition and the readings start to get out of range.  This is normal and to be expected, as with most other forms of instruments approaching its range limitations.


1) Getting Started ...

a) You must have the AA908 version 4.1 (or greater) software loaded.  (See note in next section.)

b) The Micro908 must be connected via a serial cable to the PC running the Link908 software. 

c) You will need to ensure that the serial port setting in the Communications menu is set properly for your PC.  (COM1 is the most common setting for PCs, but yours may be different.)  If you have to change the setting, you must next close and restart Link908 to have the change take effect.

d) You must instruct the AA908 software to send data to the Link908 PC over the serial port during the scan.  That's the only way you can get data to come out of the AA908.   On the Micro908, go to Config, dial up DATA OPTIONS, and select SEND DURING SCAN. Once you exit Config, this setting will be remembered for the next time you use the Micro908 AA908 software.  (Remember to turn it back to "No Data Send" when you are through uploading data to the PC, as the AA908 will scan much faster when it is not logging data.)

2) You should select the desired band you wish to scan, using the the "Frequency Band" setting.  

3) The scan is started from the Link908 screen (Start button) and you will see the "Data Points" counter increment as the scan proceeds.  

4) When the scan is complete, the results will be displayed as selected in the "Display" setting (display SWR, or Resistance, or Reactance, or all three as shown in the example above.)

5) After the scran results are displayed, you may place your mouse over any point along a curve to have the value at that point displayed. If SWR is selected in "Cursor" setting, the display will show the SWR reading when the mouse hovers over a point along the red SWR curve.  If Resistance is selected in "Cursor" setting, the display will show the Resistance reading when the mouse hovers over a point along the green Resistance curve.  If Reactance is selected in "Cursor" setting, the display will show the Reactance reading when the mouse hovers over a point along the blue Reactance curve.  


You must be running Micro908 AA908 version 4.1 (or greater) software to use Link908.  You can download the latest AA908 software from the Software links on the Micro908 home page

You must download and install on your PC the Link908 Installation program: Download Link908 Installation Software

If you area Visual Basic softwaredeveloper, you might wish to play with the Link908 source code that Mike Hasenfratz has made freely available (strictly for personal, non-profit use only): Download Link908 source code  [previous version]

User Notes:

1) Error when pressing Scan: "Error in btnCollectDisplayData_Click routine. Invalid port number"

    Two things to check ...

a) You need to be sure that no other program is using the serial port. You MUST close down TeraTerm, HyperTerm, or any other program that uses the serial port on your PC (e.g., "HotLink" for synchronizing your Palm PDA). These programs conflict with the Link908 program's attempts to control the serial port.

b) Once you change the serial port (in the "Communication" menu) to be the one you have on you PC, just Exit the program and start it up again.  I've found in earlier versions this was necessary and I'm not sure if Mike corrected this condition yet.  Once you do this once, it's good forevermore.

2) Frequency scale of display not as expected

    You must ensure that the Band setting on the Link908 screen is set to the same value as that on the Antenna Analyst.  For example, if you intend to scan the 1-10 MHz band on the AA908, you must also have the 1-10 MHz band selected on the Link908 screen.

3) You must click the Scan button on the PCLink screen

    In order to initiate a scan, you must click the Scan button on the PCLink screen, instead of pressing the Scan pushbutton on the AA908.  Clicking the Scan button on the PC screen will command the PCLink program to automatically start up the scan on the AA908.  You will then see the "data counter" incrementing on the screen, indicating that data is coming over the link to the PC.

More to Come!

The Link908 is an evolving project ... more capabilities will be added as time goes by.  

1) Right now the ability is present to collect the data from the Micro908 over the serial port simultaneously when the instrument is scanning.  Later, when the capabilities are present in the Micro908 to store the scanned data to local SEEPROM memory, the Link908 program will be able to upload and display that saved scan data.

2) Remote Control of the Micro908 AA908 instrument will be possible when another screen gets activated in Link908.  Later on, when pressing the Remote Control button, another screen will present buttons to set Configuration, select modes and a display area will act as a "remote LCD display" so you can copntrol the instrument from your PC keyboard and see results right on the screen!


Mike WA6FXT and George N2APB are available on the Micro908 reflector to answer questions about installation and operation.

Again, thanks very much to Mike WA6FXT for his self-initiated and extensive contribution to this Link908 project!

Back to the Micro908 Kit page

Material and concepts presented on The American QRP Club (TM) website is Copyright 2003 by The American QRP Club, Inc.
These pages are designed and maintained by George Heron, N2APB
Page Last Updated: 
March 27, 2009