Copyright: Copyright 1995 ValuSoft All Rights Reserved


Contents
Ham Help Table of Contents

Click on the main topic you want to know more about:

dB Tutorial

Return Loss Calculator

Mismatch Error Limits

Log <=> Linear Converter

Fundamental Constants

Registration Information

Order Form

License Agreement

For information on additional topics click on one of the following:

Program Overview

Main Entry Screen

Menu Items

File Menu

Tools Menu

Options Menu

Help Menu

General Entry

Glossary


Program Overview
Ham Help Program Overview

This program helps Ham Radio Operators and Electrical Engineers solve common problems involving Return Loss, SWR, Mismatch Limits, Logarithmic to Linear Conversions, and presents commonly used constants.

For instance, many Ham Radio Operators have SWR meters in their shacks which tells them how well their antenna is matched to their radios.  But, in order to really find out how a particular SWR reading effects you, the reading needs to be converted into Mismatch Loss.  This is the amount of power loss due to not having a perfect match.

Click on the additional topic you want to know more about:

dB Tutorial

Return Loss Calculator

Mismatch Error Limits Calculator

Log <=> Linear Converter

Fundamental Constants

Main Entry Screen

Menu Items

Text Entry


Main Entry Screen

The main entry screen is divided into four sections.  Return Loss Calculator, Mismatch Error Limits, Log <=> Linear Converter, and Fundamental Constants.  Each of these areas are accessed by clicking the mouse on the appropriate notebook tab at the top of the screen.  Alternately, any of the four areas can be accessed by selecting the corresponding item in the tools menu.

Click on the additional topic you want to know more about:

Return Loss Calculator

Mismatch Error Limits Calculator

Log <=> Linear Converter

Fundamental Constants


Menu Items

Along the top of the screen is the menu bar.  Drop down menus can be selected using the mouse or by pressing ALT + <the underlined character> to bring down the menu.  The drop down menu item can then be selected by clicking on it with the mouse cursor or by pressing the corresponding underlined letter.

The menu bar is broken up into four drop down menus:

1.	The File menu for printing, selecting printer font, selecting printer, and exiting program.

2.	The Tools menu allows you to select one of the calculation tools.

3.	The Options menu to set preferences to tailor the program to your needs.

4.	The Help menu lets you display the help system.

Click on the additional topic you want to know more about:

File Menu

Tools Menu

Return Loss Calculator

Mismatch Error Limits

Log <=> Linear

Fundamental Constants

Options Menu

Help Menu


File Menu

The File menu has the following menu items:

Print

Brings up the Print Results dialog box.  Here you can specify what you want to print and how you want to print it.  You can chose one or more screens of results to print.  Next choose whether you want each screen of results printed on a separate page or combined onto a single page.  When you press the Print button the Print dialog box comes up allowing you to set some printing options and allows you a final chance to change the printer by pressing the Setup button.

Print Font

The Font dialog box allows you to choose which font to use when printing.  For most printouts a fixed spaced font instead of a proportionally spaced font will look better.  Using a fixed spaced font such as Courier New will make the number line up better.

Printer Setup

Displays a dialog box that lets you select which printer you what to print to.

Exit

Exits the program.


Tools Menu

The Tools menu has the following menu items:

Return Loss Calculator - Converts between Return Loss, Mismatch Loss, Reflection Coefficient, and SWR.

Mismatch Error Limits - Calculates Maximum SWR, Maximum Phase Error and Mismatch Loss Error.

Log <=> Linear - Converts between Log, Power Ratio, and Voltage Ratio.

Fundamental Constants - Shows physical constants commonly used in electrical engineering.


dB Tutorial

dB is an abbreviation for decibels, which literally means a tenth of a Bell.  dB is a log representation of a ratio of two numbers.  It is convenient to use this log notation because it compresses the range of numbers we have to deal with.  You can see this using the Log <-> Linear converter.  Notice how small changes in dB correspond to large changes in power ratio.  Secondly log notation is convenient because it allows us to add numbers where we would normally have to multiply numbers.  You may remember from your school days: log(A * B) = log A + log B and similarly Log(A / B) = log A - log B.  For example, if we have two amplifier gain stages in a radio and we know there gains are 12 dB and 16 dB and we want to compute the total gain, we simple add the two gains together to get 28 dB.  This is much easier that doing without dB notation which would be 15.849 * 39.811 = 630.964.  Try this yourself by using the Log <-> Linear converter to convert 12 dB to a power ratio of 15.849 then convert 16 dB to 39.811.  Now sit down and multiply the two numbers together to get 630.964.  To check the answer put 630.964 into the Log <-> Linear converter and select power ratio, notice that this converts to 28 dB.

As mentioned before dB is a log notation for ratio of two numbers.  If we want to compute the gain of an amplifier we measure the power coming out of the amplifier, say 23 mW for instance, and the power going into the amplifier, say 3 mW.  The gain is the output power divided by the input power. i.e. 23 mW / 3 mW = 23.667.  This power ratio can be converted to dB by entering 23.667 into the Log <-> Linear converter and selecting power ratio, notice that this converts to 13.741 dB.

But, what if we want to use dB notation but we dont have a ratio of two number we only have one number?  For instance, the output power of your transmitter maybe 180 Watts but you want to represent that in dB.  To do this we reference a known power such as 1 Watt.  Then we have 180 W / 1 W = 180 power ratio referenced to 1 W.  We can use the Log <-> Linear converter to convert 180 power ratio to 22.5 dB referenced to 1 W or 22.5 dBW.  This can also be done in one step by entering 180 into the Log <-> Linear Converter and selecting Watts.  We can then see that is corresponds to 22.5 dBW.

Lets see why we might want to do this.  Suppose we have our 180 W transmitter connected to a coax to our antenna.  We want to know just how much power is getting to the antenna.  If we know that the coax has 3 dB of loss we can compute the power at the antenna input to be 22.5 dBW - 3 dB = 19.5 dBW.  To find out what this is in watts use the Log <-> Linear Converter, enter 19.5 and select dBW.  We can see this corresponds to 89.1 W.  This also shows us just why it is so important to use low loss coax.

See the Glossary for definitions of other dB terms.


Return Loss Calculator

This screen converts between Return Loss, Mismatch Loss, Reflection Coefficient, and SWR.  To use this calculator just type the number to be converted in the first edit box.  Then choose what type of number you are converting from the list box.  As soon as you start typing a number the program recalculates.  You do not have to press enter after you type the number because the program recalculates after each keystroke and anytime the input parameter type is changed.  For any type number the program calculates the equivalent number in Return Loss, Mismatch Loss, Reflection Coefficient, and SWR.

The numbers in the column labeled Nominal are straight conversions of the input number.  Many times when these parameters are measured a directional coupler is used.  Because the directional coupler only has limited directivity, there is some error introduced.  This error leads to uncertainty in the results obtained.  If you enter the directivity of the coupler you used to measure the input number in the Coupler Directivity field, you can read the Lower and Upper limits of what the actual number could be due to uncertainty.

Practical example:

You want to measure the return loss of your antenna and feedline determine what effects this has on your station performance.  You have a directional coupler and a power meter.  The directional coupler has been characterized to have a directivity of 20 dB and a coupling factor of 10 dB.  Connect the through path of the directional coupler between the transmitter output and the antenna coax.  You measure the power at the forward coupled port to be 30 dBm.  This means that the transmitted power is 30 dBm + 10 dB coupling factor = 40 dBm.  Next, you measure the power at the reverse coupled port to be 21.5 dBm.  This means the reflected power is 21.5 dBm + 10 dB coupling factor = 31.5 dBm.  The return loss is the difference in dB between the transmitted power and the reflected power.  Return loss = 40 dBm - 31.5 dBm = 8.5 dB.

Now type 8.5 dB in the Return Loss Calculator and select return loss as the input parameter.  You can see that nominally 8.5 dB return loss corresponds to:

0.661 dB Mismatch Loss

0.376       Reflection Coefficient

2.204:1    Standing Wave Ratio (SWR)

One of the most interesting numbers here is the mismatch loss.  This represents the loss of power due to not having a perfect match between your transmitter and your antenna system.  This shows you that not the entire 40 dBm of transmitter power is going into your feedline.  The amount of power is reduced by the mismatch loss.  i.e.  40 dBm - 0.661 dB = 39.339 dBm in the nominal case.  Now enter the directivity of your coupler, 20 dB, into the Return Loss Calculator.  Now you can see the effects on your measurement of not having perfect directivity in your coupler.  Your return loss could actually be as good as 11.644 dB or as bad as 6.197 dB you don't really know.  Also note how this effects the mismatch loss.  You could be actually loosing as little as 0.308 dB or as much as 1.192 dB due the mismatch.  So the transmitter power actually going into your feedline is between 39.692 dBm and 38.808 dBm.

This same example could be done using a SWR meter and having the Return Loss Calculator convert SWR to mismatch loss.  Many SWR meters don't tell you what the directivity of the coupler they use inside of them but SWR meters work on the same principle.

0.661 dB mismatch loss may not seen like enough difference to worry about but take a look at the example for the Log <=> Linear Converter to see what this means in terms for Watts.

If an error occurs because the input number can not be converted, such as when a reflection coefficient greater than 1 is entered, the words "Math Error" will be displayed in the upper left hand corner of the screen.  To clear the error just type in a valid number to be converted.

See the Glossary for definitions terms used here.


Mismatch Error Limits
Mismatch Error Limits Calculator

Calculates Maximum SWR, Phase Error and Mismatch Error given two mismatches that will be connected together.  Suppose you have two circuits that you are going to connect together that you have measured their return loss with respect to the characteristic impedance of your circuit e.g. 50 ohms.  You can calculate the possible range of mismatch loss error and maximum standing wave ratio.  When you are connecting two circuits that have mismatches the actual mismatch loss realized depends on just what the complex impedance is.  For instance if both circuits are mismatched relative to 50 ohms the same amount but their complex impedances are actually the same there will be no mismatch between the two.  If on the other hand the phase of two complex impedances have opposite phases the mismatch loss will be twice the mismatch loss of that relative to 50 ohms.  If the both circuits are not mismatched the same amount the error limits will be somewhere in between.  This is where the Mismatch Error Limits Calculator comes in.

Practical Example:

You are trying building an 20 dB amplifier which consists of two identical 10 dB amplifier stages.  The output of each amplifier stage is measured to have a return loss of 9.5 dB measured in a 50 ohm system.  The input of the each amplifier stage is measured to have a return loss of 14 dB measured in a 50 ohm system.  Using the Return Loss Calculator to convert the return losses into mismatch losses we could calculate the following results:

Total Gain = Gain Stage 1 - Stage 1 Input Mismatch loss - Stage 1 Output Mismatch Loss + Gain Stage 2 - Stage 2 Input Mismatch loss - Stage 2 Output Mismatch Loss.

Total Gain = 10 dB - 0.517 dB - 0.176 dB + 10 dB - 0.517 dB - 0.176 dB = 18.614 dB.

This is lower than the 20 dB you originally wanted but when you connected the two stages together you measured something different that calculated.  We will use the Mismatch Error Limits Calculator to calculate the effects of having two mismatches connected together.  In the Mismatch Error Limits Calculator enter in the return loss of the output of stage 1 (10 dB) and the input of stage 2 (14 dB) which are connected together.  The Mismatch Error Limits Calculator shows the following results:

Max. Standing Wave Ratio  = 2.885 : 1

Max. Phase Error                = +/- 3.618 degrees

Max. Mismatch Loss Error Limits = -0.566 dB and + 0.531 dB

This means that your total gain could be different by as much as -0.566 dB to + 0.531 dB due to these two stages being connected together.  The maximum standing wave ratio where these two stages are connected together is 2.885 : 1.  We can now calculate the expected range of Total Gain of our completed amplifier:

Lower Limit Total Gain = Total Gain Nominal + Lower Limit Error

Lower Limit Total Gain = 18.614 dB - 0.566 dB = 18.048 dB.

Upper Limit Total Gain = Total Gain Nominal + Upper Limit Error

Upper Limit Total Gain = 18.614 dB + 0.531 dB = 19.145 dB.

See the Glossary for definitions terms used here.


Log <=> Linear

Converts between Log, Linear, Power Ratio, and Voltage Ratio.  Enter the number to be converted into the box at the upper right.  Then select which type of parameter it is.  The results are show below the input number.  The Log <=> Linear Converted assumes that input and output impedances are equal for dB, Power Ratio, and Voltage Ratio conversion.  This is typically the case.

The units of the output numbers change according to the type of input parameter is selected.  There are three sets of parameters that are converted between each other.  Entering one of the parameters in the group will show you the rest of the parameters in the group.  The three groups are as follows:

dB, Power Ratio, and Voltage Ratio

dBm, dBuV, Milliwatts, and Mircovolts

dBW, dBV, Watts, and Volts

A couple of handy relationships to keep in mind are shown below.

1000 mW = 1 W

30 dBm = 0 dBW

To go from mW to W slide the decimal place 3 places to the left on the number in mW.

To go from dBm to dBW subtract 30 from the number in dBm.

Practical Example:

Continuing from the example under the Return Loss Calculator .  If we know we have 40 dBm of power coming out of our transmitter and want to know what that corresponds to in watts.  We simple enter 40 into the input number box and select dBm as the type of parameter.  We see that 40 dBm corresponds to10000 mW or 10 W.

If our mismatch loss between the transmitter and the feedline to the antenna is 0.661 dB and the loss in our coax known to be 3 dB, how much of our 10 W from the transmitter is going to the antenna itself?

We first calculate the number in dBm that is actually going into the feedline:

Power at Antenna = Power transmitted - Mismatch loss

40 dBm - 0.661 dB = 39.339 dBm

Entering this into the Log <=> Linear Converted and selecting dBm we see that only 8588 mW or 8.588 W is going in to the feed line.

To see how much power is going into the antenna we subtract the loss of the coax:

Power into Antenna = Power into Coax - Loss in Coax

39.339 dBm - 2.0 dB = 37.339 dBm

Entering this into the Log <=> Linear Converted and selecting dBm we see that only 5419 mW or 5.419 W is going in to the antenna.

In this example we can see that just a little more than half of the power is getting to the antenna.  And that about 1.5 W are loss in the mismatch itself.  This shows the importance of having a low loss feedline and a good match between it and your transmitter.  A transmacth device can be used to minimize the mismatch loss if it is excessive.

See the Glossary for definitions terms used here.


Constants
Fundamental Constants

Fundamental Constants - Shows physical and numerical constants commonly used in electrical engineering.  This can be very helpful when you know a formula but are not sure what the exact number is.  For example:

Wavelength = c/F

If you what to find the wavelength at 145 MHz, you would lookup the velocity of light, c, and find 2.9979250 e8 m/s.  Then calculate:  2.9979250 e8 m/s  /  145e6 Hz.  = 2.067 meters.

See the Glossary for definitions terms used here.


Options Menu

The Options menu has the following menu items:

Decimal Places

Brings up a dialog box that lets you select how many decimal places should be displayed on calculations.  Type in a new number or click on the up or down arrow to change the number accordingly.

Help Hints

Selecting Help Hints menu item toggles the check mark in front of the menu item, which indicates whether this feature is on or off.  When the check mark is showing, hint boxes will appear to help explain what input to type.  To see the hint boxes appear, hold the mouse cursor over an input field for about 2 seconds.

These settings are stored in the HAMHELP.INI file located in your windows directory.  When you change your options HamHelp saves the new setting automatically.  When you start up HamHelp again your previous setting will be restored.


Help Menu

The Help Menu has the following menu items:

Help

Displays this help system.

How To Register

This menu item only appears in the shareware version.  Displays details on how to Register this product.

About

Shows the program name, version number and copyright notice.


General Entry
General Entry:

When you move the cursor to the next field, if the field becomes highlighted, typing in data will replace what was already there.  If you want to keep what was there position the mouse cursor at the point you want to change then click the mouse button.

Moving Through Controls And Fields:

Mouse	Click on the desired field.
Tab	Will move cursor to next field.
Shift + Tab	Will move cursor to previous field.
Up and Down Arrows	Will move cursor within field.
Editing Entries:

To edit entries, you can position the cursor, which appears as a flashing line, anywhere in the field with the mouse or keyboard.  To position the cursor with the mouse, just point and click.  When you move to a field and it is highlighted, typing will replace the highlighted text.  Pressing Home or End will unselect text and position the cursor accordingly so you can add text instead of replacing text.

To use the keyboard use the keys shown in the following table.

Cursor Movement keys

Key	Action
Right Arrow	Moves cursor one character to the right.
Left Arrow	Moves cursor one character to the left.
Home	Moves cursor to beginning of current line.
End	Moves cursor to end of current line.
Ctrl + Right Arrow	Moves cursor one word to the right.
Ctrl + Left Arrow	Moves cursor one word to the left.
Ctrl + Home	Moves cursor to beginning of text.
Ctrl + End	Moves cursor to end of text.
Selecting Text with Keyboard

Shift + Arrow  (Right / Left)	Selects one character at a time.
Shift + Arrow (Up / Down)	Selects one character at a time
Shift + Ctrl + Left Arrow	Select from cursor to beginning of word.
Shift + Ctrl + Right Arrow	Selects from cursor to end of word.
Selecting Text With Mouse

Double click on word	Selects a word.
Shift + click	Select a segment of text between beginning and ending cursor positions.
Cutting and Pasting Text

Ctrl + x	Cuts selected text and places on clipboard.
Ctrl + c	Copies selected text and places on clipboard.

To deselect a selection place the mouse pointer in the field and clicking.


Glossary

Here is a list of terms and their definitions.

dB - decibels - see dB Tutorial for full description.

dBW - dB referenced to 1 Watt.

dBmW - dB referenced to 1 milliWatt.

dBV - dB referenced to 1 Volt.

dBuV - dB referenced to 1 microVolt.

Mismatch Loss - The transmission loss due to an impedance mismatch.

Reflection Coefficient - Is the relationship of the source or load impedance to the characteristic impedance of the circuit.  Reflection Coefficient = (Z - Zo)/(Z+Zo).  Where Z is the source or load impedance and Zo is the characteristic impedance (e.g. 50 ohms).

Return Loss - Return loss is a measure of the ratio between the transmitted and reflected signals due to impedance mismatch.

SWR - Standing Wave Ratio - A measure of the impedance match between two devices.


Registration Information

HamHelp Version 1.0 For Windows

This program is shareware.  It is not free software.  You are hereby licensed to use this software for evaluation purposes without charge for a period of 30 days.  If you use this software after the 30 day evaluation period a registration fee of $10 is required.  Payments must be in US dollars drawn on a US bank, and should be sent to:

ValuSoft, P.O. Box 95573, Hoffman Estates, IL  60195.

Quantity discounts are available, as described on the Order Form.  When payment is received you will be sent a copy of the latest registered version of HamHelp.  The registered version of HamHelp does not have an About screen that appears when the program starts.  Unregistered use of HamHelp after the 30-day evaluation period is in violation of U.S. and international copyright laws.

Click here => Order Form to display the order form.  Then select Print Topic in the File menu of this Help system.

ValuSoft can also be reached by E-mail at 74017.1374@Compuserve.com.

ValuSoft is a registered trademark of ValuSoft.

See License Agreement for more information.


Order Form

MAIL TO:

ValuSoft

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        Please make remittance payable to ValuSoft. Prices and terms

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License Agreement

HamHelp version 1.0

Copyright (C) 1995 ValuSoft

All Rights Reserved

For ordering information, see "Registration Information" and "Order Form" in the on-line help.  Or see the file ORDER.TXT

License Agreement

You should carefully read the following terms and conditions before using this software.  Unless you have a different license agreement signed by ValuSoft, your use of this software indicates your acceptance of this license agreement and warranty.

Shareware Version

Evaluation and Registration

This program is shareware.  It is not free software.  You are hereby licensed to use this software for evaluation purposes without charge for a period of 30 days.  If you use this software after the 30 day evaluation period a registration fee of $10 is required.  Payments must be in US dollars drawn on a US bank, and should be sent to:

ValuSoft P.O. Box 95573, Hoffman Estates, IL  60195.

Quantity discounts are available, as described in the file ORDER.TXT or in the help topic Order Form.  When payment is received you will be sent a copy of the latest registered version of HamHelp.  The registered version of HamHelp does not have the about screen appear when the program starts.  Unregistered use of HamHelp after the 30-day evaluation period is in violation of U.S. and international copyright laws.

Distribution

Provided that you verify that you are distributing the Shareware Version (select About from the HamHelp Help menu to check) you are hereby licensed to make as many copies of the Shareware version of this software and documentation as you wish; give exact copies of the original Shareware version to anyone; and distribute the Shareware version of the software and documentation in its unmodified form via electronic means.  There is no charge for any of the above.

You are specifically prohibited from charging, or requesting donations, for any such copies, however made; and from distributing the software and/or documentation with other products (commercial or otherwise) without prior written permission, with one exception:  Disk Vendors approved by the Association of Shareware Professionals are permitted to redistribute HamHelp, subject to the conditions in this license, without specific written permission.

Registered Version

One registered copy of HamHelp may either be used by a single person who uses the software personally on one or more computers, or installed on a single workstation used nonsimultaneously by multiple people, but not both.  You may access the registered version of HamHelp through a network, provided that you have obtained individual licenses for the software covering all workstations that will access the software through the network.

Governing Law

This agreement shall be governed by the laws of the State of Illinois.

Disclaimer of Warranty

THIS SOFTWARE AND THE ACCOMPANYING FILES ARE SOLD "AS IS" AND WITHOUT WARRANTIES AS TO PERFORMANCE OF MERCHANTABILITY OR ANY OTHER WARRANTIES WHETHER EXPRESSED OR IMPLIED.  Because of the various hardware and software environments into which HamHelp may be put, NO WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE IS OFFERED. The user must assume the entire risk of using the program.  ANY LIABILITY OF THE SELLER WILL BE LIMITED EXCLUSIVELY TO PRODUCT REPLACEMENT OR REFUND OF PURCHASE PRICE.