SimpleCalc

SimpleCalc is a small application that can help you calculate the cascaded noise figure of your EME receiving chain and predict the amount of sun noise your system should be able to detect. From version 1.0.0.2 it can also be used to measure the noise received, it uses filtering on the audio signal from the radio (via soundcard) and presents the filtered data in a separate window.

During installation and debugging of my 70cm EME system, I developed SimpleCalc to help me understand and calculate the noise figure of my system, the effects of changing LNA's, cable losses etc. I also needed a quick and easy tool to help me calculate the expected sun noise I should be able to measure and at the same time, provide an easy way of recording notes taken during measurements and experimentation.

For many many years, the "EMECalc" program by Doug VK3UM (sadly now a Silent Key) has been "The tool" to use for doing this and much more.

In my case, I needed something a little more "light" with only a tiny fraction of the features of EMECalc.

This was how SimpleCalc was born.

DISCLAIMER:

I have tried to make SimpleCalc correct. However, I do not by any means, claim to have the full overview of all the aspects of the math going into making the calculations "super precise". SimpleCalc calculates NF and predicts sun noise, but leaves out a few of the very fine details, details that might get you 0.1 or 0.2 dB closer to "the real truth".

That being said, I think (and hope) that the application makes up for this by being simple and easy(er) to use.

One thing you can be absolutely sure about, is that there are errors in the program :) When you find some, please send me an email of what you see and have done. My email address is on the CV/Contact page.

During the development and testing of SimpleCalc, I got valuable input and suggestions from members of the Moon-Net email reflector for which I'm very thankful!

The main window

The main window of SimpleCalc is shown below.

This is where you enter most of the data for your system.

All the results in the "Results" box to the right are re-calculated every time you change one of the parameters on this (and other) screens of SimpleCalc.

In order to calculate the "Expected sun noise" the program needs a "band specific SFU" value. The program fetches todays and yesterdays measure Solar Flux data from NOAA and uses these to calculate the SFU value for the (ham) band you select. The selection of which site to use for SFU data is done on another screen (see below).

The used SFU value is VERY important as even slight changes in that will have a great impact on the "Expected sun noise" value.

You can find much more information on the SFU values, their usage and what to be aware of by studying the many articles, posts and documents about VK3UM's EMECalc.

In the menu of the main window, you will find functions that allows you to save and load setups from files.

You can also save/load the current settings using the two buttons in the lower left corner.

The "Edit comments" button is explained below.

Update SFU Data window

This window handles all the updating and interpolation of SFU data. As the 5 sites that measure SFU data, only measure these on some specific "non ham" frequencies, we need to do some interpolation of the actual measured values in order to get the SFU value for the ham bands we are interested in.

Currently, I have implemented two different ways of doing this interpolation, "Spline" and "Lines". The Spline method uses a "spline" that goes thru all the measured SFU values to derive the ham band SFU values. The Lines method interpolates the SFU values by "drawing" a line between the two "neighboring" measured SFU values and calculating the needed SFU value.

I made both options available for now, as there are some different opinions on which gives the most correct answer!

The "Lines" method is described here: Determination of Earth Station Antenna G-T Using the Sun....

The SFU update window looks a bit busy at first.

The upper part with the table, lists the measured SFU values from around the world and different times. Red colored columns are data from "yesterday" and orange colored columns are data from "today". Use the column that is closest in time and location to your location and time.

In the yellow column, you can manually enter measured SFU values (for example historic data) and use these as the basis of the band specific SFU values.

To the extreme right, there is a list of the ham bands and their calculated SFU values (derived from the measured SFU values). The band specific value(s) shown there is the value that is used on the main window for the "Expected sun noise" calculation.

If you change the data on this page, the SFU value on the main window are automatically updated.

The graph on the bottom half of the window shows both the physical measured SFU values and also the derived "ham specific bands" SFU values. The blue data is the measured SFU values and the orange data is the derived/interpolated ham band SFU values.

It can sometimes happen that a measurement site does not have data for one or more of the frequencies, this will be shown as "-1" in the data. Depending on the interpolation method used (Spline/Lines), you can get into a situation where there is no valid data for a specific ham band.

Using the "Fetch newest data" button will download the newest data from NOAA, these data are downloaded using FTP from: ftp://ftp.swpc.noaa.gov/pub/lists/radio/rad.txt

When downloading data, a copy of these are saved in the "Documents" folder on your PC in "...Documents/SimpleCalc", the filename is "LastSFUData.txt".

Noise Measurement window

The application has a window that will allow you to measure the noise level currently received. The application uses a soundcard interface to sample the audio, filters this and calculates the RMS value from this. It is VERY important that you DISABLE AGC completely when doing this, only by disabling the AGC the measurements will make any sense. It is also VERY important that the receive chain is linear in the range of the noise measured, clipping/limiting by the receiver will make the measurements invalid!

Using the control to the left, you can select which input to use, the dB per division and the width of the graph in seconds.

Pressing the "Delta = 0" button will take a snapshot of the current measured noiselevel. The "Delta(dB)" number just below the button, will show the delta between the snapshot and current noiselevel.

Comment window

SimpleCalc has a built-in "documentation window". The "Comment" window allows you to keep a log of what you measure, the conditions when you did the measurement etc. Basically you can enter whatever text you want. The contents of the comment window will be saved along the entered data on the main window and SFU window if you do a "save config" from the menu on the main window.

The comment window lets your enter text, change font, add colors etc., pretty much like "Wordpad" or other (simple) text editors.

Download

SimpleCalc runs under Windows operating system. There are no installation to be done. The program consists of a single .exe file, simply download this, copy it to a folder and execute it from there.

SimpleCalc will create a configuration file in the folder it is located in, this file contains all settings you do in the program.

2024-10-02 SimpleCalc - Version 1.0.0.1

2024-09-27 SimpleCalc - Version 1.0.0.0

Release notes

2024-10-02 - Version 1.0.0.1

The antenna gain was limited to only 40 dBi by mistake. Changed to 60 dBi. (Thanks Roger W3SZ)
Added a "user defined frequency" entry field on the main page. User can enter a frequency in MHz and have the program calculate (interpolate) a SFU value for that (thanks Bob K6ZZ)

2024-09-27 - Version 1.0.0.0

This is the initial release

Carsten Groen's (OZ9AAR) personal place