# How Duty cycle affects transmission rate in RF module?

I planning to use RF module for communication of high precision GNSS module. So I am doing detail study on RF module. In one of the datasheets of RF module (part no: RFD868ux) mentioned that 'Duty cycle is percentage of time to allow transmit'.

I don't understand how the duty cycle of RF module effects transmission. Can someone please let me know how the transmission rate in the RF depends on the duty cycle?

• A link to the document where you read this would be helpful. Commented Jun 8, 2020 at 12:57
• Hello and welcome to ham.stackexchange.com! Commented Jun 8, 2020 at 14:49
• How and where do you plan on using this GNSS transmitter? Commented Jun 8, 2020 at 20:11
• @PhilFrost-W8II Added link to OQ. Commented Jun 8, 2020 at 20:19
• I saw that product page, but I don't see the words "Duty cycle is percentage of time to allow transmit" anywhere on it, or in the manual linked from there. Commented Jun 8, 2020 at 22:44

Under the heading of "Software features include," the landing page for the RFD868ux says, "Automatic duty cycle throttling based on radio temperature to avoid overheating". This means that transmit will not be allowed if the temperature of the radio is too high. In this case, the "duty cycle" is the average fraction of time that the radio may transmit, given the temperature limitation.

Duty cycle of a radio is the percentage of time it is putting out full power. You can calculate this by averaging off time with the duty cycle of the signal you are transmitting, weighted by the amount of time for each.

The duty cycle of the signal you are transmitting depends on the modulation method, and sometimes the information being modulated.

If it's FSK or PSK, it may be 100% duty cycle.

If it's on off keying, the duty cycle will possibly vary, and you'd have to do some statistics on the source data to figure out the duty cycle.

Similarly, if it's amplitude modulation of phone, the duty cycle will vary, but there's rules of thumb for, say, talking vs. music. Obiously, a slow speaker that leaves lots of gaps will have a lower duty cycle that someone who doesn't. :)

AM modulation of other media (i.e., video) is also possible.

FM modulation is probably constant duty cycle.