Farm alarms and rural signal: what to check when one network falls short
Water, slurry, shed and cold-store alarms can sit in outbuildings where one network reaches and another does not. This guide covers why a single-network SIM can fall short, how to test and place the antenna, and how the 2G and 3G closures affect older GSM diallers.
One network is not the whole picture
When the government announced the proposed Shared Rural Network (SRN) deal in October 2019, it described a partial not-spot as an area with coverage from at least one operator but not all of them, and a total not-spot as an area with no coverage from any operator [2]. For a fixed alarm unit the partial case is the awkward one: the signal exists, but only on some networks.
The SRN site says geographic outdoor 4G coverage now extends to over 96% of the UK, and that coverage from all four operators has risen to 84%, up from 66% before the programme [3]. It takes its current figures from Ofcom's Connected Nations report published in November 2025. By nation, SRN gives these 4G figures [3]:
| Nation | 4G coverage from all four operators | Before the programme |
|---|---|---|
| England | Minimum of 90% (forecast) | 81% |
| Northern Ireland | 85% (work completed) | 75% |
| Scotland | Minimum of 70% (forecast) | 41% |
| Wales | Minimum of 78% (forecast) | 57% |
For England, Scotland and Wales the figures are the minimums SRN forecasts by the end of the programme, and SRN marks Northern Ireland's work as completed. SRN says improvements depend on suitable sites, power, backhaul and planning permissions [3]. Its headline figure is geographic outdoor 4G coverage, so it says nothing about the inside of a steel cabinet.
Why a single-network SIM can fall short
A single-network SIM has nowhere to go when its network is weak at the unit. The 2010 Cooper dialler guide and the GJD manual both list a better antenna or unit position, or another provider's SIM, as the remedies [6][7]. SimFalcon's alarm page says that for rural sites, plant rooms, basements and weak-signal areas, managed multi-network connectivity is standard and can improve resilience [9].
A SIM can fail quietly too. A farm alarm may send nothing for months, and both manuals warn that some pay-as-you-go accounts are closed or disabled after a period without activity [6][7]. The GJD manual adds that some providers now require a voice call or message rather than data only to keep a PAYG SIM active [7]. SimFalcon says it supplies managed IoT SIM options rather than consumer PAYG products, which avoids relying on manual top-ups [9]. Its UK plans are priced per SIM per month and billed annually [11].
Testing before you move anything
At the antenna position
A phone in the open yard, or on a different network from the alarm's SIM, says little about an antenna inside a cabinet. The Cooper guide suggests holding a phone on the same network as the SIM at the exact spot where the antenna will go and looking for at least three bars. It then says to fix the antenna within 20 mm of that spot, because moving 80 mm can change signal strength markedly [6].
On the unit's own meter
The GJD dialler shows signal on a 0 to 7 scale and says to install only where it reads 2 or more [7]. If a router or modem reports dBm, Teltonika's wiki, which covers the modules in its own devices, treats a 4G RSRP weaker than -100 dBm as poor [8]. Register the SIM first: the Cooper unit reports the strongest network signal until then, which may be an emergency network, because in the UK all networks must give any mobile phone access for emergency calls [6].
End to end
Trigger the real alarm, whether a float switch, thermostat or door contact, and confirm the message reaches your phone. Both manuals describe sending a scheduled test call or message [6][7]. For text alerts, see the SMS problems guide.
Where the unit sits decides the fix
- Steel cabinet or other metal enclosure. The GJD manual says a unit mounted in or on metal acts as a shield, and suggests swapping the antenna for a remote one on a cable [7].
- Pump house or below-ground chamber. SimFalcon lists basements and plant rooms among difficult coverage areas [9], and a below-ground chamber is similar. Test at the antenna position and move the antenna out if the reading is poor.
- Outbuilding at the far end of the holding. Test at the planned spot and at one or two alternatives nearby. The GJD manual says to move the unit to a different location if its meter reads low [7].
- Boosters. Ofcom's 2018 regulations exempt certain static mobile repeaters from licensing only if they are used indoors, meet Ofcom's published interface requirement and cause no undue interference. “Indoors” means premises with a ceiling or roof, wholly enclosed apart from doors, windows and passageways [4], which an open-sided barn is not. That is the 2018 text as originally made, so check Ofcom's current rules before buying.
- Power. On the GJD unit a power-fail text goes out only if a backup battery is fitted, and the manual advises replacing it at least yearly [7]. Cable and antenna basics are in the weak or no network guide.
2G and 3G: where each network stands
Mobile UK says all the mobile providers have confirmed to the UK Government that they do not plan to offer 2G and 3G beyond 2033 [1]. Several networks give more detail in their own statements:
- EE says it switched off 3G in January and February 2024 and will begin closing 2G from May 2029 [12].
- Three says its 3G network was completely switched off across the UK in November 2025, and that it has no 2G network [13].
- Virgin Media O2 said on 23 June 2026 that it completed its 3G switch-off in late 2025 and will start switching off 2G in summer 2029. It adds that organisations using its network for IoT devices will need to act before then [14].
- Vodafone Group said in September 2025 that VodafoneThree will switch off the Vodafone UK 2G network during 2030 [15]. For Vodafone's 3G, use Vodafone's own notice.
Mobile UK says virtual operators such as giffgaff, Tesco Mobile and Smarty follow the schedule of the network they run on [1]. A “GSM” label does not settle whether the unit also has a 3G radio. The data sheet does.
| Radio in the unit | Where it stands | What to do |
|---|---|---|
| 3G only | EE, Three and Virgin Media O2 each say in their own statements that 3G is already switched off [12][13][14]. Check Vodafone's notice if the SIM is on Vodafone. | Ask the supplier for a 4G version. A new SIM cannot add a radio. |
| 2G only | Needs a network that still runs 2G. Three has none [13]; the other closing dates are listed above. | Put it on a replacement plan, oldest and most critical first. |
| 2G and 3G | Where 3G has gone it can only use 2G, which has the end dates above. | Check the manual to see whether alerts go by SMS, voice or data. |
| 4G | Does not depend on 2G or 3G. | Confirm 4G support on the data sheet. If the unit dials out by voice, also check it supports 4G Calling (VoLTE): EE says a 4G device without it will lose service once 2G closes, and Three says calls need it [12][13]. |
The step-by-step check is in the 2G and 3G switch-off guide.
Slurry stores: an alarm is not protection
HSE's slurry information sheet says incidents on farms in Great Britain include people being overcome by toxic gases, drowning after a fall into slurry or liquid stores, and being injured when structures containing slurry collapse [5]. A level or temperature alarm does a different job. It does not make a store safe to approach.
What the SIM can and cannot do
SimFalcon says a device on its multi-network SIM can register on supported partner networks rather than depending on one operator, subject to coverage, hardware capability and service configuration [10]. It is not a signal booster and does not guarantee the strongest network [10]. It cannot add a 4G radio to the unit, and it does not change what a metal box does to the antenna. SimFalcon says device installation, wiring, programming and similar work are not included unless agreed separately [10], and it asks for the panel model and deployment area when advising on an alarm SIM [9]. See the alarm SIM page, the CCTV SIM page for yard cameras, pricing, or contact SimFalcon.
Sources
- [1] Mobile UK: 2G/3G switch off. Checked 3 October 2026.
- [2] GOV.UK: Shared Rural Network deal announcement. Checked 3 October 2026.
- [3] Shared Rural Network: Forecast coverage improvements. Checked 3 October 2026.
- [4] legislation.gov.uk: Wireless Telegraphy (Mobile Repeater) (Exemption) Regulations 2018, as made. Checked 3 October 2026.
- [5] HSE: Managing slurry on farms (AIS9). Checked 3 October 2026.
- [6] Cooper Security: SD-GSM Speech Dialler guide (PDF, dated 16 June 2010). Checked 3 October 2026.
- [7] GJD: GSM Communicator GJD710 manual (PDF). Checked 3 October 2026.
- [8] Teltonika Networks Wiki: Mobile Signal Strength Recommendations. Checked 3 October 2026.
- [9] SimFalcon UK: Alarm SIM cards. Checked 3 October 2026.
- [10] SimFalcon UK: Multi-network IoT SIM. Checked 3 October 2026.
- [11] SimFalcon UK: Pricing. Checked 3 October 2026.
- [12] EE: 2G and 3G switch-off. Checked 3 October 2026.
- [13] Three: Our 3G switch off. Checked 3 October 2026.
- [14] Virgin Media O2: to start switching off its 2G network in 2029 (23 June 2026). Checked 3 October 2026.
- [15] Vodafone Group: Vodafone to boost network performance for customers by phasing out 2G (22 September 2025). Checked 3 October 2026.
Frequently asked questions
Why does my phone get signal in the yard when the farm alarm does not?
A phone is usually used in the open and may be on a different network from the alarm's SIM, while the alarm unit may sit in a metal box with its antenna inside. Test at the antenna position with a phone on the same network as the SIM. If the reading is poor, move the antenna out of the metal first.
What is a partial not-spot?
In its October 2019 announcement of the proposed Shared Rural Network deal, the government described partial not-spots as areas with coverage from at least one operator but not all. A SIM tied to one network may sit on the wrong side of that gap.
Do I need to replace a 2G-only GSM dialler now?
Not because of the 3G closures, but 2G has end dates too. EE says it will begin closing 2G from May 2029, Virgin Media O2 from summer 2029, and VodafoneThree has announced that Vodafone UK's 2G will go during 2030, while Three has never had 2G. Put 2G-only units on a replacement plan, oldest and most critical first.
Can I use a pay-as-you-go SIM in a farm alarm?
It carries a risk. Dialler manuals warn that some PAYG accounts are closed or disabled after a period without activity, and an alarm may send nothing for months. SimFalcon says it supplies managed IoT SIM options rather than consumer PAYG products.
Questions about connectivity for your equipment? Talk to SimFalcon or ask Engineer Support.