Hi folks, first post. I’m no expert on RF so I’ve been doing some reading to try to get my head around stuff.
Is there a difference between the maximum allowable transmission power for an emitter in the UK versus the max transmission power allowed in the US?
Looking at the tech-specs for the default TTN gateway linked to from this site, I noticed that the 868 Mhz variant (EUR) has a maximum TX power of 14 dBm or 25 mW and the 902-928 Mhz variant (US) has a maximum TX power of 27 dBm or 501 mW. That’s some jump in power output!
If I am correct, does this have a significant effect on signal penetration in urban areas in the UK vs when used in the US?
Yep that’s about right
You also need to be cognisant of differences such as duty cycle (varies by sub band typically 1% but there is a 'quiet band at 0.1% and the ack/downstream responce in LoRaWAN RX2 slot is in a 10% band. Also the +14dbm allows for assumed use of a +2db gain from the antenna (effective EIRP +16dbm), so what you do wrt ant and any feeder cable, matching components, TxRx switch path losses/mis-match etc will also have impact on your permitted source TX level that is allowed within ETSI regs. Also another difference if I recall is US vs EU measurement method - conducted vs radiated measurements etc.
Note also where we are restricted by duty cycle our US cousins have to consider on air dwell time - limits time on a given channel - impacting e.g. use of higher SF/longer payloads, so its a bit swings & roundabouts
Disclaimer - I’m no radio expert so best u do lots of reading (this forum a good source/start if not a little fragmented on the topic!), ask others if in doubt and check 1st before doing anything potentially illegal or ‘anti-social’! If not done so yet join your local TTN community - a potential good source of guidance…if non in your area initiate your own and solicit expertise to join…
I think Mr Robinson - originally from Oldham if I recall old biz meetings - and contributor to several TTN North communities already has Hull up and running (its reach ‘official’ status) I believe https://www.thethingsnetwork.org/community/hull/
As I read the EU spec there’s a small sliver of frequency (869.4 - 869.65 MHz) that is allowed to go up to 500 mW (27 dBm). What are the drawbacks of using that band, is it too thin for channel hopping, etc?
I believe the key point of that band isnt just the TX pwr option but the fact that it allows for 10% duty cycle and is therefore useful for the GW’s (which clearly have to serve a greater number of nodes) to use for ACK’s and DL/Confirm/Join Ack msgs - RX2 window (RX1 follows the Node TX characteristics). Note also that if nodes close to GW and lowering TX power an option then ‘Q’ has interesting possibilities wrt duty cycle/message on air time (SF) and payload length…just whisper it vs shouting over people
I don’t know whether it’s of any interest but Ofcom have said that:
“Non-specific Short Range Devices (SRDs) and SRD Data Networks in 870 to 874.4 MHz band: we are making 4.4 MHz of continuous spectrum available by aligning the technical parameters and authorisation regime across the 870 to 874.4 MHz band. These changes will make the band more suitable for applications including smart metering and Machine-to-Machine communications that wish to use wider bandwidth technologies.”
