SRDs operate in four distinct sub-GHz frequency ranges: 315MHz, 433MHz, 868MHz, and 915MHz, and it depends primarily on your geographic location which frequency you may legally use:
| Region | ISM Band | Frequency Range | Bandwidth | Channels | Max Power | Regulatory Remarks | Typical ASK/EV1527 Frequency |
|---|---|---|---|---|---|---|---|
| US | 315 MHz | 314.92 – 315.08 MHz | 160 kHz | 1 | ≤ 25 mW ERP | FCC Part 15.231 (remote control, non-continuous only) | 315.00 MHz |
| Europe, Asia | 433 MHz | 433.05 – 434.79 MHz | 1.74 MHz | ~20 | ≤ 10 mW (EU) | EU: License-free ISM band, ETSI EN 300 220 | 433.92 MHz |
| US | 433 MHz | 433.05 – 434.79 MHz | 1.74 MHz | ~20 | ≤ 10 mW ERP | FCC Part 15.231 (only for alarms, remote controls, etc.) | 433.92 MHz (limited use) |
| Europe | 868 MHz | 868.0 – 868.6 MHz | 600 kHz | ~6 | ≤ 25 mW (low duty) | EU SRD band, ETSI EN 300 220, limited duty cycle | 868.35 MHz |
| US, Australia | 915 MHz | 902 – 928 MHz | 26 MHz | ~50 | ≤ 1 W (US) | FCC Part 15 ISM band, widely used for general data | 915.00 MHz |
| Worldwide | 2.4 GHz | 2.400 – 2.4835 GHz | 83.5 MHz | 79 | ≤ 100 mW (EU) | Global ISM band, used for Wi-Fi, Bluetooth, Zigbee | Not typically used for ASK |
| Worldwide | 5.8 GHz | 5.725 – 5.875 GHz | 150 MHz | ~25 | ≤ 1 W (US) | Global ISM band, used for Wi-Fi, radar, industrial use | Not typically used for ASK |
Sub-GHz ISM bands (license-free bands) are strictly regulated with significant differences between geographic location. More modern ISM bands above 1 GHz are globally regulated and free to use (within the thresholds) almost anywhere on the world.
Crystals
Breakout boards for receiving or transmitting in the sub-GHz region are typically made for one specific ISM band only and cannot be changed later.
Even though the transmitter chip used on a board may support multiple ISM bands or wider frequency ranges, and even though a vendor may claim 315/433/868/915MHz supported, this is not true.
There are distinct external components such as crystal, capacitors and coils (that form filters), which determine the frequency the board is optimized for. The antenna length, too, must match the desired frequency. You cannot use the same antenna for multiple ISM bands (without significantly hitting transmission performance).
So when you purchase a SRD receiver or transmitter, you must make sure it is desiged to use the frequency you want to use (and that is legal to use for you in your region).
The crystal can be a good indicator to reveal the frequency range your devices is designed to work on. The operating frequency is typically a multiple of the crystal frequency. There can be different factors used by your device, so there are a number of commonly used crystal frequencies per ISM band.
The table below can help you identify the frequency range your device was made for: compare the crystal frequency on your device with this table:
| ASK/EV1527 Frequency | Region | Crystal Frequencies & Factors |
|---|---|---|
| 315.00 MHz | US | 13.560 MHz × 23.25, 21.000 MHz × 15 |
| 330.00 MHz | Some regions | 13.200 MHz × 25 |
| 390.00 MHz | US | 13.000 MHz × 30 |
| 418.00 MHz | UK (legacy use) | 13.933 MHz × 30 |
| 433.92 MHz | Europe, Asia | 13.52127 MHz x 33, 13.560 MHz × 32, 6.7458 MHz × 64, 21.600 MHz × 20, 6.000 MHz × 72, 7.000 MHz × 62, 8.000 MHz × 54.4, 12.000 MHz × 36 |
| 868.35 MHz | Europe | 13.560 MHz × 64, 21.708 MHz × 40 |
| 915.00 MHz | US, Australia | 13.107 MHz × 69.8, 26.214 MHz × 35 |
It’s not uncommon for the bandwidth to span over a small range of frequencies around the nominal frequency, i.e. 433.92 MHz (typically within ±100 kHz), especially with basic OOK modulation and lower-cost receivers.On 433MHz, the signal may be anywhere in the range of 433.8-434.0MHz.
Slow Website?
This website is very fast, and pages should appear instantly. If this site is slow for you, then your routing may be messed up, and this issue does not only affect done.land, but potentially a few other websites and downloads as well. Here are simple steps to speed up your Internet experience and fix issues with slow websites and downloads..
Comments
Please do leave comments below. I am using utteran.ce, an open-source and ad-free light-weight commenting system.
Here is how your comments are stored
Whenever you leave a comment, a new github issue is created on your behalf.
-
All comments become trackable issues in the Github Issues section, and I (and you) can follow up on them.
-
There is no third-party provider, no disrupting ads, and everything remains transparent inside github.
Github Users Yes, Spammers No
To keep spammers out and comments attributable, all you do is log in using your (free) github account and grant utteranc.es the permission to submit issues on your behalf.
If you don’t have a github account yet, go get yourself one - it’s free and simple.
If for any reason you do not feel comfortable with letting the commenting system submit issues for you, then visit Github Issues directly, i.e. by clicking the red button Submit Issue at the bottom of each page, and submit your issue manually. You control everything.
Discussions
For chit-chat and quick questions, feel free to visit and participate in Discussions. They work much like classic forums or bulletin boards. Just keep in mind: your valued input isn’t equally well trackable there.
(content created Mar 10, 2025 - last updated Mar 15, 2025)