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MFJ-269 Bridge Voltage

Solution

 

To access to the bridge voltage reading the unit should be set first to the TEST mode:

            -  Immediately after turning the power ON, press and hold simultaneously the gate and mode buttons . Wait for the “MFJ Enterprises (c)” message.

            - Release and press again the gate button (without releasing the mode button)

            - Release and press again the mode button (without releasing the gate button)

            - Release and press again the gate button (without releasing the mode button)

            - Release and press again the mode button (without releasing the gate button)

            - Release the gate and mode buttons to place the 269 in TEST mode.

 

The different testing steps are selected with the mode switch button . By pressing four times mode a hexadecimal binary voltage reading should be reached. The calibration frequency considered by default would be 10 MHz. The unit should be set up at that frequency to adjust the voltages.

 

 I do not know if you are familiar with that numeric format. The traditional decimal format  where the numbers consist of a mixture of the ten digits from 0 to 9. We say the decimal system has a base of 10.

The Hexadecimal is base 16. We still use digits 0 to 9, but the letters A, B, C, D, E, and F are used to represent the decimal numbers 10, 11, 12, 13, 14 and 15 respectively. http://www.myhome.org/pg/numbers.html

 

2.) Vz = FFx would be any hexadecimal number from FF0 to FFF (FF0, FF1. FF2. FF3. FF4. FF5. FF6. FF7, FF8, FF9. FFA, FFB, FFC, FFD, FFE, or FFF). Those voltages could be obtained for an "open load" (or simply without any load connected to the antenna analyzer) by adjusting R72.  In the previous paragraph a description of  how to access the test mode was provided.

 

3.) The meaning of Vs = FFx would be understood that is the representation of a hexadecimal number. For this case the load considered hooked up to the analyzer would be a "short" as ideal as possible.

 

4.) By reaching the test mode as previously indicated.

 

Mr. Hung-chul, it is extremely important to connect purely resistive loads at the calibration frequency to obtain an acceptable end. I do not know what kind of resistive loads could you used. On the other hand several combination of attenuators could be considered to perform the calibration. Of course by using different value of  calibration resistive than the one indicated (12.5 ohm, 75 ohm, 200 ohm) loads different binary voltages would be required.

 

Please let me know if you have any question,

 

Sincerely,

 

Joaquin Bonilla ( JB )
Project Engineer
MFJ Enterprises Incorporated

Article details
Article ID: 71
Company: MFJ
Date added: 2017-01-12 14:32:18
Views: 21

 
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