WSPR Messages Explained
The Weak Signal Propagation Reporter (WSPR) protocol allows you to send a number of different message types. These have different performance and impact on the overall WSPR network. Choosing the correct message type is essential to being a good WSPR user.
Type 1 Messages
The normal WSPR message "Type 1" consists of a simple callsign (e.g. G3CWI), a four character locator (e.g. IO83) and a power level expressed in dBm (e.g. 23). This message is the most efficient and the most likely to be received. The callsign can consist of up to six characters.
The constraints on what can go in each position are as follows:
1 - can be a letter or number or left blank
2 - can be a letter or number
3 - can only be a number
4 - can only be a letter or left blank
5 - can only be a letter or left blank
6 - can only be a letter or left blank
You should always use a Type 1 message if possible. It is the most efficient and works best - especially when making measurements.
Type 2 and Type 3 Messages
Type 2 and Type 3 messages extend the WSPR protocol to allow the transmission of compound callsigns (e.g. F/G3CWI or G3CWI/1) and a six character locator (e.g. IO83wg).
- Type 2: PJ4/K1ABC 37
- Compound callsign, power
- Type 3: <PJ4/K1ABC> FK52UD 37
- Callsign hash, 6 char locator, power
The main part of the callsign must consist of 1 or 2 letters/digits, then a digit, then up to 3 letters (this part is the same as the simple callsign in normal WSPR messages).
A prefix or suffix can then be added, which can be either:
- xxx/callsign - 'xxx' is a prefix of up to 3 characters. Each 'x' can be any digit or letter or a space.
- callsign/x - where 'x' is any single digit or letter.
- callsign/dd - where 'dd' is a two digit number from 10 to 99.
The WSPRlite firmware will select which types of message to alternate between transmitting based on the WSPR settings:
- If a compound callsign is being used, type 2 and 3.
- If a simple callsign is being used, the locator is at least 6 chars long, and the "always tx 6 char locator" option is on, type 1 and 3.
- Otherwise, type 1 only (preferred).
Reasons not to use Type 2 and Type 3 Messages
Type 2 and Type 3 messages may well look attractive for general use, however they should be avoided wherever possible because:
- They require two transmissions to be transmitted and received instead of just one.
- They make less efficient use of the available bandwidth increasing the chances of interference to and from other users.
- There are only 32k callsign hashes available which can cause misreporting.
- You will get many fewer spots - our measurements show significantly less than half the number of spots (closer to 25%).
- Gathering enough data for robust measurements results will take longer.
- The likelihood of occasional DX spots will be much reduced.
- If doing antenna comparisons there are usually better ways to identify different transmitters (i.e. by using callsign aliasing on WSPR together with a CW ident).
- You do not need to use extended WSPR all the time for WSPRnet to report your six character locator. WSPRnet remembers your six character locator from previous spots, so you could enable extended WSPR until a spot with your 6 char locator has been reported, then switch back to normal WSPR, and WSPRnet will continue showing the 6 char locator. You can also make WSPRnet report your six character locator without actually transmitting it over the air, by manually submitting spots to WSPRnet.