Macintosh version of TCalc


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Note: this software is for Macintosh OS Classic not OS X and not Windows.


TCalc+ User Instructions

 
What is TCalc+ ?
TCalc+ analyses the Noise and Intermodulation performance of radio receiver front-ends. It is based on TCALC, a program written in BASIC by Ian White , G3SEK (See Ref. 1). The benefits of the Macintosh user interface have been added to speed up entry and modification.
Individual stages of a receiver are represented in symbolic form. Up to 8 stages can be allocated as either Antenna, Cable, Amplifier, Mixer or Attenuator.
Using Tcalc+
To evaluate a system, first of all use the toolbox to place the desired type of stage into each stage of the receiver, then enter the Gain in dB, Noise Figure in dB (or Noise Temperature in °K) and 3rd Order Input Intercept Point (IP3) for each stage. Finally press Calculate to get the overall results.
Tools and Symbols
Amplifier
The Amplifier tool is used to insert an amplifier into a stage. Select the Amplifier Icon from the tool palette and then click on the stage Icon that you wish to make an Amplifier.
Mixer
The Mixer tool is used to insert a mixer into a stage. Select the Mixer Icon from the tool palette and then click on the stage Icon that you wish to make a Mixer.
Cable
The Cable tool is used to insert a Cable into a stage. Select the Cable Icon from the tool palette and then click on the stage Icon that you wish to make a Cable. Cables can only have a loss in dB, and are assumed to be at a temperature of 290°K. Note that an entry can be made as either a positive or negative value, each will give the same result.
Attenuator
The Attenuator tool is used to insert an Attenuator into a stage. Select the Attenuator Icon from the tool palette and then click on the stage Icon that you wish to make an Attenuator. Attenuators can only have a loss in dB, and are assumed to be at a temperature of 290°K. Note that an entry can be made as either a positive or negative value, each will give the same result.
Antenna
The Antenna tool is used to add the effect of an Antenna connected to the front of the receiver. Select the Antenna Icon from the tool palette and then click on the stage Icon that you wish to make an Antenna.
Cutter
The cutter tool is used to "cut out" a stage from the receiver. Select the scissors Icon from the tool palette and then click on the stage Icon that you wish to delete. The current stage Icon will then be replaced with a straight line joining the other stages.
Starting from the left, you can place an Antenna as the first stage. The Antenna will have an effective Noise Temperature in °K. Note that an Antenna does not have to be included in a system if you do not wish it's effect to be considered.
Radio Buttons allow the noise contribution of a particular stage to be entered in either Noise Temperature (°K) or Noise Figure (dB). Beware! - Once you have entered a value for the noise in one unit, it is not automatically converted to the other unit if the radio button is toggled. eg if NF was entered as 1.5dB and the button was clicked to °K the calculation would now be carried out for a noise contribution of 1.5°K.
The 'Rest of the System" is assumed to have a gain of 0dB. It is represented by a Radio Receiver Icon. Enter its Noise Figure or Temperature and IP3. If you don't want to consider the effect of the rest of the system on the final result then you can enter a NF of 0dB and an IP3 of 100dBm for the rest of the system.
Calculate Button
Click the Calculate Button when you have entered all of the stage parameters that you want to analyse and in a few seconds the results will appear in the Results Box.
Result Boxes
The Results are shown after they have been calculated by pressing the Calculate Button. They show the Whole Receiver IP3 in dBm, the Noise Floor for the receiver in dBm, assuming a bandwidth of 2.5KHz, the Dynamic Range of the receiver in dB and the overall System Noise Figure (dB) including the effect of any antenna.
Note: If you change any parameters or click in an input field then the Results Box will be hatched out to indicate that they may no longer be valid and may need recalculating. Press the Calculate button again to recalculate at any time.
ToolBox
The ToolBox contains the Tools for changing a particular stages type. The ToolBox can be hidden if desired by choosing Hide Symbols from the Symbols Menu.
Summary Page
There is another page of information that can be viewed by clicking on the Receiver Icon. This page shows a summary in textual form of the results as well as the entered values. You can select and copy these to the Clipboard if you wish or alternately export them as a text file. You can return to the front page by clicking on the TCalc+ Logo.
Printing
The Summary Page can be printed out in full from the
Print... item under the File menu. The current date and time will be added to the start of the printed page.
Exporting
The Summary Page can be saved as a text file from the Export... item under the File menu. A dialogue box will allow the choice of filename and destination to be chosen.
The current date and time will be added to the start of the text file. Sorry, the exported text is not in tab separated format but space separated (use your word processor or McSink if you need this).
References
[1] Radio Communication
June 1985 p447-448
by Ian White G3SEK.
[2] The VHF/UHF DX Book 1992
DIR Publishing Ltd.
ISBN 0 9520468 0 6
Front-End Analysis using TCALC p5-18 to 5-20.
Acknowledgements
Thanks are mainly due to David Anderson (GM4JJJ) for asking me to write this and for his continual goading to get it finished (it was originally an excercise in Supercard programming and ended up as a marathon!). Dave also wrote the majority of the explanatory text.

Incidentally the author also has some interesting pages on a homebuilt CNC Router
Neil Gillies Web Page

Neil D Gillies