Set Maximim Frequency

Sets the maximum frequency of a COMM, NAV or ADF instrument. For ADF, the 5th and 6th digits have no meaning. When the maximum frequency is reached by incrementing, the instrument automatically loops to the minimum frequency. Also, see the remarks.

See RNS Features in the beginning of this chapter for more detail.

Request

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ID	25	I	X	X	X	Y	Y	Y

Request Structure

Byte	Value	Size	Type	Description	COMM/NAV	ADF
0	ID	1	BIN	RNS address (ID)
1	25	1	BIN	Set Minimum Frequency instr. code
2	I	1	BIN	0-NAV, 1-Comm, 2-ADF
3	X	1	BIN	1st digit	1st integer	1st upper
4	X	1	BIN	2nd digit	2nd integer	2nd upper
5	X	1	BIN	3rd digit	3rd integer	1st lower
6	Y	1	BIN	4th digit	1st decimal	2nd lower
7	Y	1	BIN	5th digit	2nd decimal	-
8	Y	1	BIN	6th digit	3rd decimal	-

Response

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ID	25	V

Response Structure

Byte	Value	Size	Type	Description
0	ID	1	BIN	RNS address (ID)
1	25	1	BIN	Set Minimum Frequency instruction code
2	V	1	BIN	1 for successful, 0 otherwise

Factory Default Values

Instrument	Increment
NAV	117.950
COMM	136.975
ADF	9999

Remarks

Setting the maximum frequency of a COMM or NAV (but not for the ADF) should be done with care to ensure the expected behavior. The maximum frequencies are directly related to the minimum frequencies and the increments.

Looking at the factory default values, the NAV maximum frequency is set to 117.950, not 118.000. This is due to the relationship between the minimum frequency and the increments.

The maximum frequency can be calculated as follows:

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Calculation Example 1 (Decimal Increment):

Parameters:

• Minimum Frequency: 108.000
• Target Maximum Frequency: 118.000
• Decimal Increment: 50

Steps:

1. Delta = Maximum Frequency – Minimum Frequency Delta = 118000 - 108000 = 10000

2. Steps = (Delta / Increment) - 1 Steps = (10000 / 50) - 1 = 199

3. Range = Steps * Increment Range = 199 * 50 = 9950

4. Result = Minimum Frequency + Range Result = 108000 + 9950 = 117950

Result: The maximum frequency is 117.950.

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Calculation Example 2 (Integer Increment):

Parameters:

• Minimum Frequency: 108
• Target Maximum Frequency: 118
• Integer Increment: 1

Steps:

1. Delta = Maximum Frequency – Minimum Frequency Delta = 118 - 108 = 10

2. Steps = (Delta / Increment) - 1 Steps = (10 / 1) - 1 = 9

3. Range = Steps * Increment Range = 9 * 1 = 9

4. Result = Minimum Frequency + Range Result = 108 + 9 = 117

Result: The maximum frequency is 117.

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Tips:

1. For Consistency: These calculations can be automated by interfacing software.

2. Quick Calculation Shortcut: Knowing that increments and frequencies are multiples of each other, you can subtract one increment from the target maximum frequency to obtain the same result. Example: 118000 - 50 = 117950

   Ensure that both the minimum and maximum frequencies are multiples of the increment. For instance:

   • 108000 / 50 = 2160 (integer, no fraction)
   • 118000 / 50 = 2360 (integer, no fraction)

   This confirms both are valid multiples.

Examples

Set COMM Maximum Frequency to 129.975 ( target = 130.000, increment 25):

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ID	25	1	1	2	9	9	7	5

Set COMM Maximum Frequency to 125.475 ( target = 125.500, increment 25):

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ID	25	0	1	2	5	4	7	5

Set ADF Maximum Frequency to 500 :

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ID	25	2	0	5	0	0