Coax cable loss calculator: LMR-400, LMR-200 and LMR-100A at 915 MHz
Work out how much signal your antenna cable loses before you buy. Pick the cable type and length to see the loss in dB, how much power arrives at the other end, and the in-stock cables that cover your run. Figures use Times Microwave datasheet values at 900 MHz, which covers Helium and LoRaWAN hotspots on 868–928 MHz.
Planning a full install? The Helium hotspot antenna setup planner picks the antenna, cable, arrestor and mount for your site.
Choosing between cable types? Read understanding cable loss and EIRP in Helium hotspots.
Coax cable loss FAQ
How much signal does LMR-400 lose per metre?
At 900 MHz, Times Microwave rates LMR-400 at 12.8 dB per 100 m, which is 0.128 dB per metre. Over 10 m that's about 1.3 dB, so roughly 74% of the power arrives.
LMR-200 or LMR-400: which should I use?
LMR-200 loses 32.6 dB per 100 m at 900 MHz, about 2.5 times as much as LMR-400 (12.8 dB). LMR-200 is thinner and easier to route, which suits runs of a few metres. For anything longer, LMR-400 keeps much more of the signal. Our 200-series cables are LMR-200 class, so this calculator uses the LMR-200 datasheet figure for them.
Does it matter whether my hotspot uses 868 MHz or 915 MHz?
Only slightly. Coax loss rises roughly with the square root of frequency, so across the 868–928 MHz LoRaWAN bands the loss changes by less than 2% from the 900 MHz figure this calculator uses.
How much cable loss is too much?
Every 3 dB of loss halves the power reaching the antenna, and incoming signals lose the same amount on the way back. Keep the run as short as you practically can and use LMR-400 for longer runs. If the run is long, consider putting the hotspot outside in a weatherproof enclosure beside the antenna.
Do connectors and adaptors add loss?
Yes, a little at each mated connection. This calculator adds an allowance of 0.1 dB per connection, the same figure our Setup Planner uses. It's an allowance, not a measurement, and a good connector is usually close to it.
How we calculate. Loss = the cable's attenuation per metre × length + 0.1 dB per connection. Attenuation is the typical value at 900 MHz and 25 °C from Times Microwave datasheets: LMR-400 12.8 dB/100 m, LMR-200 32.6 dB/100 m, LMR-100A 74.9 dB/100 m. Power arriving = 10^(−loss ÷ 10).
Important. These are typical datasheet figures. Real loss varies with temperature, cable age, bending and connector quality. This page is general information only, not professional installation or engineering advice, and it makes no promise of coverage or performance. To the extent permitted by law, Mapping Network accepts no liability for any loss or damage arising from its use.