Intermod Explorer Documentation
Introduction
IntermodExplorer is an advanced, web-based software application designed for the wireless, professional audio industry.
Its computational engine rapidly generates frequency sets of intermodulation distortion-free (IMD-free) radio
frequencies -- applying user-defined stringencies, signal bandwidths and channel spacing. The resultant frequency sets
are used for frequency coordination -- that is, assigning the most reliable channels to your wireless transmitters.
IntermodExplorer offers two services in the form of a monthly subscription -- Basic and Advanced. The Basic service is free.
The Advanced service is $10 USD / month -- though is currently free. The monthly subscription can be cancelled and
restarted as often as you wish or as needed. The table below summarizes the differences between the two services.
| Features | Basic Service | Advanced Service |
|---|---|---|
| Basic Frequency Set | YES | YES |
| Smart Frequency Set | YES | |
| Dynamic Frequency Set | YES | |
| Manual Frequency Set | YES | |
| Import Spectrum Trace | YES | |
| Start / End Frequencies | YES | YES |
| Multiple Stringencies | YES | YES |
| Rank Frequencies | YES | |
| Shuffle Candidates | YES | YES |
| Channel Bands | YES | |
| Lockout Bands | YES | |
| Reserved Frequencies | YES | |
| Validate External Frequency Set | YES |
Settings
IntermodExplorer calculates the 3 types of intermodulation products closest to our fundamental frequencies:
What this means is that a frequency set created under 'Strict' conditions has a high probability of being free of intermodulation interference caused by 2Tx 3rd, 3Tx 3rd and 2Tx 5th intermodulation products. Similarly, a frequency set created under 'Moderate' conditions has a high probability of being free of intermodulation interference caused by 2Tx 3rd and 2Tx 5th intermodulation products. And so on...
Near Hit Settings:
Related to 'Stringency' is the concept of 'Near Hits'. This means that in order to qualify as a compatible frequency and be a member of a frequency set a candidate frequency must not match an intermod product nor be within a specified distance of an intermod product. A 'Near Hit' setting specifies the minimum distance a candidate frequency must be from an intermod product in order to qualify as a compatible frequency. If a candidate frequency is too close to an intermod product then it is disqualified. For example, by default, intermod-compatible frequencies must be at least 99 KHz from 2Tx 3rd-order products, 49 KHz from 3Tx 3rd-order products, and 89 KHz from 2Tx 5th-order products. As the 'Near Hit' distance is increased then the frequency set becomes more stringent, but that comes at a cost -- fewer candidate frequencies will qualify as members of the frequency set and, hence, the frequency set will be smaller. The Near Hit settings for IntermodExplorer are fixed at 99 KHz, 49 KHz and 89 KHz for 2Tx 3rd-order products, 3Tx 3rd-order products, and 2Tx 5th-order products, respectively, and can not be changed.
Step Size
Most audio transmitters are designed to operate on channel frequencies that fall on 25 KHz boundaries -- i.e. they are "tunable" in 25 KHz steps. Given a frequency range (e.g. 470 MHz to 500 MHz) and a step-size of 25 KHz, then only frequencies within that range and which are multiples of 25 KHz are potential candidates to be included in the frequency set that is generated (provided they also meet the stringency requirements described above). The Step Size for IntermodExplorer is fixed at 25 KHz and can not be changed.
Signal Bandwidth
This setting controls the minimal distance between adjacent frequencies in the resultant frequency set that is computed. From a practical standpoint the distance between adjacent channel assignments should be sufficient to ensure transmitters do not interfere with one another. The recommended, default value of 299 KHz is on the conservative side. It is important to note this value has a direct bearing on the final size of the frequency set. The larger the signal bandwidth, the less chance adjacent transmitters will interfere with one another -- but the smaller will be the frequency set. The smaller the signal bandwidth, the greater the chance adjacent transmitters will interfere with one another -- but the larger will be the frequency set. So, if you need more channels then experiment with decreasing the size of the signal bandwidth.
Interference Bandwidth
When a spectrum trace is imported and a threshold specified, then RF energy above the threshold line is treated as interference and IntermodExplorer excludes 200 KHz on either side of the interference peak. This setting is fixed and can not be changed.
- Two-transmitter products closest to 3rd-order components (2Tx 3rds)
- Three-transmitter products closest to 3rd-order components (3Tx 3rds)
- Two-transmitter products closest to 5th-order components (5Tx 5ths)
| Stringency | 2Tx 3rds | 3Tx 3rds | 2Tx 5ths |
|---|---|---|---|
| Strict | YES | YES | YES |
| Moderate | YES | YES | |
| Lenient | YES |
Near Hit Settings:
Related to 'Stringency' is the concept of 'Near Hits'. This means that in order to qualify as a compatible frequency and be a member of a frequency set a candidate frequency must not match an intermod product nor be within a specified distance of an intermod product. A 'Near Hit' setting specifies the minimum distance a candidate frequency must be from an intermod product in order to qualify as a compatible frequency. If a candidate frequency is too close to an intermod product then it is disqualified. For example, by default, intermod-compatible frequencies must be at least 99 KHz from 2Tx 3rd-order products, 49 KHz from 3Tx 3rd-order products, and 89 KHz from 2Tx 5th-order products. As the 'Near Hit' distance is increased then the frequency set becomes more stringent, but that comes at a cost -- fewer candidate frequencies will qualify as members of the frequency set and, hence, the frequency set will be smaller. The Near Hit settings for IntermodExplorer are fixed at 99 KHz, 49 KHz and 89 KHz for 2Tx 3rd-order products, 3Tx 3rd-order products, and 2Tx 5th-order products, respectively, and can not be changed.
Step Size
Most audio transmitters are designed to operate on channel frequencies that fall on 25 KHz boundaries -- i.e. they are "tunable" in 25 KHz steps. Given a frequency range (e.g. 470 MHz to 500 MHz) and a step-size of 25 KHz, then only frequencies within that range and which are multiples of 25 KHz are potential candidates to be included in the frequency set that is generated (provided they also meet the stringency requirements described above). The Step Size for IntermodExplorer is fixed at 25 KHz and can not be changed.
Signal Bandwidth
This setting controls the minimal distance between adjacent frequencies in the resultant frequency set that is computed. From a practical standpoint the distance between adjacent channel assignments should be sufficient to ensure transmitters do not interfere with one another. The recommended, default value of 299 KHz is on the conservative side. It is important to note this value has a direct bearing on the final size of the frequency set. The larger the signal bandwidth, the less chance adjacent transmitters will interfere with one another -- but the smaller will be the frequency set. The smaller the signal bandwidth, the greater the chance adjacent transmitters will interfere with one another -- but the larger will be the frequency set. So, if you need more channels then experiment with decreasing the size of the signal bandwidth.
Interference Bandwidth
When a spectrum trace is imported and a threshold specified, then RF energy above the threshold line is treated as interference and IntermodExplorer excludes 200 KHz on either side of the interference peak. This setting is fixed and can not be changed.
Frequency Sets
IntermodExplorer supports calculations for 4 types of frequency sets:
When the intermodulation calculation is completed the resultant frequency set is displayed and can be copied to your operating system's "clipboard" for subsequent pasting into a text file or document where it can then be saved.
The following considerations apply to all 4:
1. Regardless whether the frequency range is specified by entering Start / End frequency values or a spectrum trace is imported, the minimum and maximum spans are limited to 10 MHz and 150 MHz, respectively.
2. When *.csv files are imported for spectrum trace, Channel Bandwidth, Reserved Frequencies or Lockout Bands then the proper format must be followed otherwise the calculation will fail. Please refer below for examples of the correct format to use for each of these import types.
3. When a spectrum trace file is imported it is crucial that you consider its resolution bandwidth (RBW). The RBW of the spectrum trace can have a big affect on the resultant frequency set -- please read this article to understand why.
Basic Frequency Set
Simple, accurate and fast -- the Basic frequency set allows you to specify a stringency to control the size and reliability of the resultant frequency set.
Smart Frequency Set (patented)
Not all frequencies in a frequency set are equally reliable. The Smart frequency set ranks frequencies by reliability based on the density of neighboring intermod products. This allows you to prioritize channel assignments.
Dynamic Frequency Set
Automatically calculates frequency sets for strict, moderate and lenient stringencies -- adjusting the signal bandwidth setting to optimize the size of the resultant frequency set. You then choose the one that best satisfies your channel needs.
Manual Frequency Set
You have complete control over the available settings -- input Start / End frequency range or import spectrum trace, stringency, Channel Bands, Reserved Frequencies, Lockout Bands, signal bandwidth, ranking frequencies, and shuffling candidates.
- Basic Frequency Set
- Smart Frequency Set
- Dynamic Frequency Set
- Manual Frequency Set
When the intermodulation calculation is completed the resultant frequency set is displayed and can be copied to your operating system's "clipboard" for subsequent pasting into a text file or document where it can then be saved.
The following considerations apply to all 4:
1. Regardless whether the frequency range is specified by entering Start / End frequency values or a spectrum trace is imported, the minimum and maximum spans are limited to 10 MHz and 150 MHz, respectively.
2. When *.csv files are imported for spectrum trace, Channel Bandwidth, Reserved Frequencies or Lockout Bands then the proper format must be followed otherwise the calculation will fail. Please refer below for examples of the correct format to use for each of these import types.
3. When a spectrum trace file is imported it is crucial that you consider its resolution bandwidth (RBW). The RBW of the spectrum trace can have a big affect on the resultant frequency set -- please read this article to understand why.
Basic Frequency Set
Simple, accurate and fast -- the Basic frequency set allows you to specify a stringency to control the size and reliability of the resultant frequency set.
Smart Frequency Set (patented)
Not all frequencies in a frequency set are equally reliable. The Smart frequency set ranks frequencies by reliability based on the density of neighboring intermod products. This allows you to prioritize channel assignments.
Dynamic Frequency Set
Automatically calculates frequency sets for strict, moderate and lenient stringencies -- adjusting the signal bandwidth setting to optimize the size of the resultant frequency set. You then choose the one that best satisfies your channel needs.
Manual Frequency Set
You have complete control over the available settings -- input Start / End frequency range or import spectrum trace, stringency, Channel Bands, Reserved Frequencies, Lockout Bands, signal bandwidth, ranking frequencies, and shuffling candidates.
Validation
IntermodExplorer's Validation feature allows you to validate frequency sets created by other programs or scripts. The computations involved in generating an intermod-compatible frequency
are not complex, but because of the thousands of computations and permutations that must be taken into account, they are prone to error. The Validation feature provides a means
for you to ensure no conflicts exist and the frequency set truly conforms to the intermod stringency or compatibility level you expect. The frequency set to be validated is imported
as a *.csv file and its format is the same as Reserved Frequencies (see below).
Imported *.csv Files
IntermodExplorer supports the importing of 4 types of *.csv files: spectrum trace, Channel Bands, Reserved Frequencies and Lockout Bands. These are simple text files that are typically
created with a Text Editor program. Each line in the file is entered either as a frequency or band, in MHz. If the number has significant digits then it should be denoted with a decimal 'dot' (.)
and not with a comma (,). When a line begins with a semi-colon (;) it is treated as a comment and ignored. Below are examples for each type of import file:
Spectrum Trace
When you import a spectrum trace and threshold value then IntermodExplorer will generate a frequency set that takes into account interference from both interferring RF signals and intermodulation products.
Example:
524.446,-74
524.471,-71
524.496,-63
524.521,-41
524.546,-30
524.57,-54
524.595,-67
524.62,-62
524.645,-70
524.67,-73
524.695,-73
524.72,-78
524.745,-75
Channel Bands
Channel Bands allow you to organize the frequencies within a frequency set into different groups based on their frequency ranges. Channel Bands may overlap one another -- in which case certain frequencies may belong to more than one channel band. It is important to note that frequencies not included within a Channel Band will be locked-out of the intermodulation analysis.
Example:
512-541
572-590
Reserved Frequencies
A reserved frequency is one that will always be included in the frequency set. Reserved frequencies provides a means for you to enter one or more frequencies into the coordination when a particular device is considered mandatory. For example, facilities or events often have a pool of existing equipment to which channels will need to be added. Also guest systems using preconfigured channels may have to be integrated and coordinated with resident systems.
Example:
475.075
480.15
485.225
490.3
495.375
500.45
505.525
520.750
537.50
551.200
567
574.625
582
592.975
Frequency Set (for validation)
A frequency set includes a list of frequencies that have previously been determined to be free of interference from intermod products. IntermodExplorer allows you to validate a previously computed frequency set.
Example:
470
471.2
472.050
473.15
475.60
479.600
484.9
491.55
499.150
506.150
510.35
518.050
534.9
546.450
551.85
559.1
568.350
574.450
579.1
589.150
591.850
Lockout Bands
This feature allows you to lock out frequency ranges of your choosing and can be used to exclude DTV stations. Frequencies within the locked-out bands are removed from consideration as potential candidates for a frequency set.
Example:
;Ch 32
578-584
;Ch 31
572-578
;Ch 30
566-572
;Ch 29
560-566
;Ch 28
554-560
;Ch 27
548-554
;Ch 26
542-548
Spectrum Trace
When you import a spectrum trace and threshold value then IntermodExplorer will generate a frequency set that takes into account interference from both interferring RF signals and intermodulation products.
Example:
524.446,-74
524.471,-71
524.496,-63
524.521,-41
524.546,-30
524.57,-54
524.595,-67
524.62,-62
524.645,-70
524.67,-73
524.695,-73
524.72,-78
524.745,-75
Channel Bands
Channel Bands allow you to organize the frequencies within a frequency set into different groups based on their frequency ranges. Channel Bands may overlap one another -- in which case certain frequencies may belong to more than one channel band. It is important to note that frequencies not included within a Channel Band will be locked-out of the intermodulation analysis.
Example:
512-541
572-590
Reserved Frequencies
A reserved frequency is one that will always be included in the frequency set. Reserved frequencies provides a means for you to enter one or more frequencies into the coordination when a particular device is considered mandatory. For example, facilities or events often have a pool of existing equipment to which channels will need to be added. Also guest systems using preconfigured channels may have to be integrated and coordinated with resident systems.
Example:
475.075
480.15
485.225
490.3
495.375
500.45
505.525
520.750
537.50
551.200
567
574.625
582
592.975
Frequency Set (for validation)
A frequency set includes a list of frequencies that have previously been determined to be free of interference from intermod products. IntermodExplorer allows you to validate a previously computed frequency set.
Example:
470
471.2
472.050
473.15
475.60
479.600
484.9
491.55
499.150
506.150
510.35
518.050
534.9
546.450
551.85
559.1
568.350
574.450
579.1
589.150
591.850
Lockout Bands
This feature allows you to lock out frequency ranges of your choosing and can be used to exclude DTV stations. Frequencies within the locked-out bands are removed from consideration as potential candidates for a frequency set.
Example:
;Ch 32
578-584
;Ch 31
572-578
;Ch 30
566-572
;Ch 29
560-566
;Ch 28
554-560
;Ch 27
548-554
;Ch 26
542-548