Geomagnetic activity is monitored by devices known as magnetometers. Small variations in the Earth's geomagnetic field are detected by the magnetometers and scaled to two measures - the A and K indices.

The K index provides an indication of magnetic activity during the previous 3 hours on a finite scale of 0 to 9.

Very quiet conditions are reported 0 or 1 and storm levels begin at 4.

A rising K index foretells worsening propagation conditions.

The a index (note the lower-case "a") is a 3-hourly "equivalent amplitude " index. The a index is related to the 3-hourly K index according to the following scale:

Finally, the A index (now we are talking about the upper-case "A") is a daily index of geomagnetic activity derived as the average of eight 3-hourly a indices. So, the A index reflects geomagnetic conditions summarized over a 24-hour period.

In the USA, stations WWV and WWVH broadcast the latest solar flux numbers, the average planetary A indices and the latest Boulder, Colorado K indices at 18 minutes after every hour, and can be heard on 2.5, 5, 10, 15 and 20 MHz.

Keep in mind that the A index information you will hear on any given day is a summary of what happened during the previous day.

What are Grid Squares?

Grid Squares are the intermediate level of definition in the geographic coordinate-based system known as WW QTH (or QRA) Locator.

They identify squares 2 degrees longitude wide and 1 degree latitude high. They are defined by two letters (FIELD) and two numbers (SQUARE).

How you go about finding your latitude and longitude depends to some extent on whether you want to know your 4-digit grid square or your 6-digit grid square.

Finding a 6-digit grid square requires considerably more precision in latitude and longitude.

The 4-digit grid squares covers a pretty big area, while the 6-digit grid square is fairly small. The actual size of a grid square depends on the particular location, as the 1° of longitude represents different distances at different latitudes; longitude lines are closer together at the Earth's poles than at the equator.

What is the World Wide QTH Locater?

Also called "QRA Locator system", it is a coordinate-based system originally introduced by the UHF-VHF enthusiasts to quickly exchange information about location, so to be able to calculate distances.

The locator has the format of two letters, two numbers and two letters. Ex.: IM58KS. The system is set up as follows. The globe is divided in 18 * 18 = 324 fields, each 20 degrees longitude wide and 10 degrees latitude high. Each of these fields is divided in 10 * 10 = 100 squares, each 2 degrees longitude wide and 1 degree latitude high.

Finally, each of the squares is divided in 24 * 24 = 576 sub-squares, each 5 minutes longitude wide and 2.5 minutes latitude wide.

What is the S-unit?

The S-unit is defined to be a 6 dB change in the signal strength, S-9 is typically defined to be 50 microvolts at the antenna input. If you are using 100 Watts and decrease the power to 50 Watts, then you have a reduction of 3 dB, decreasing again from 50 to 25 Watts you have another reduction of 3 dB in the signal strength = 6 dB or 1 S-Unit.

What is the Q Code?

Q codes are groups of, as a rule, three letters, always beginning with Q character, used to speed up message transmission, mainly in telegraphy. They are used often by amateurs, even in phone modes, because their meaning is standard and common to all languages.

Each code has two different meanings (although usually related) when used alone (affirmative meaning) or followed by a question mark (interrogative meaning).

The name of my station is...

The approximate distance between our stations is...

nautical miles, or kilometers.

I am bound for...from...

Your exact frequency (or that of...) is kHz (or MHz).

Your frequency varies.

The tone of your transmission is

1. Good

2. Variable

3. Bad

The readability of your signals (or those of...)is...

1. Unreadable.

2. Readable now and then.

3. Readable, but with difficulty.

4. Readable.

5. Perfectly readable.

I am busy (or I am busy with...).

Please do not interfere.

I am being interfered with.

I am troubled by static.

Increase power.

Decrease power.

Send faster (...words per minute).

I am ready for automatic operation.

Send at...words per minute.

Send more slowly (...words per minute).

Stop sending.

I have nothing for you.

I am ready.

Please inform ...that I am calling him on...kHz (or MHz).

I will call you again at...hours [on...kHz (or MHz)].

Your turn is Number...(relates to communication.)

You are being called by...[on... kHz (or MHz)].

The strength of your signals (or those of...) is

1. Scarcely perceptible.

2. Weak.

3. Fairly good.

4. Good.

5. Very Good.

Your signals are fading.

You keying is defective.

Send...telegrams at a time.

including your internal telegraph charge?

The charge to be collected per word to...

including my internal telegraph charge is...(euro).

I am acknowledging receipt.

Repeat the last telegram which you sent me [or telegram(s) number(s)...].

I did hear you [or...(call sign)]on...kHz (or MHz)?

I can communicate with...direct (or by relay through...).

I will relay to...free of charge.

I have a doctor on board [or (name of person) is on board].

Send or reply on this frequency [or on...kHz (or MHz)] with emissions of class...).

Send a series of V's on this frequency [or...kHz (or MHz)].

I am going to send on this frequency [or on...kHz (or MHz)](with emissions of class...).

I am listening to [call sign(s)] on...kHz (or MHz).

Change to transmission on another frequency (or on...kHz (or MHz).

Send each word or group twice (or...times)

Cancel telegram number...as if it had not been sent.

I do not agree with your counting of words.

I will repeat the first letter or digit of each word or group.

I have...telegrams for you (or for...).

Your TRUE bearing from me is... degrees (at...hours).

What is my TRUE bearing from... call sign)?

Your TRUE bearing from...(call sign) was...degrees (at...hours).

What is the TRUE bearing of... (call sign) from...(call sign)?

The TRUE bearing of...(call sign)from (call sign) was... degrees (at...hours).

call sign (repeated...times) [on...kHz (or MHz)]?

I am going to send two dashes of ten seconds each followed

by my call sign (repeated...times) [on...kHz (or MHz)].

Will you request...to send two dashes of ten seconds followed by

I have requested...to send two dashes of then seconds followed by

his call sign (repeated...times) [on...kHz (or MHz)].

My position is...latitude...longitude (or according to any other indication).

My TRUE track is...degrees.

My speed is...knots (or kilometers per hour).

My TRUE heading is...degrees.

I departed from...(place) at... hours.

I have left dock (or port).

Are you airborne?

I am airborne.

I am going to enter dock (or port).

Are you going to alight (or land)?

I am going to alight (or land).

I am going to communicate with your station by means of the International Code of Signals.

The correct time is...hours.

[on ...kHz (or MHz)] so that your frequency may be measured?

I will send my call sign for minute(s) now (or at...hours)

[on ...kHz (or MHz)] so that my frequency may be measured.

My station is open from...to...hours.

Stand guard for me on the frequency of...kHz (or MHz) (from...to...hours).

with me until further notice (or until... hours)?

I will keep my station open for further communication with you

until further notice (or until...hours).

Here is news of...(call sign).

height of clouds, direction and velocity of ground wind at...(place of observation)?

Here is the information requested...

you received from me [or from...(call sign)]?

The number (or other indication) of the last message I received from

you [or from...(call sign)] is...

I have received the urgency signal sent by...(call sign of mobile station) at...hours.

I have received the distress signal sent by...(call sign of mobile station) at...hours.

I am forced to alight (or land) immediately.

I shall be forced to alight (or land) at...(position or place).

The present barometric pressure at sea level is...(units).