What is the best antenna for a Helium Hotspot?
If you are part of the Helium Hotspot revolution, welcome. We are happy to join you as miners ourselves. Since launching our Rokland 915MHz 8 dBi outdoor antenna for LoRa/HaLow & Helium & 5.8 dBi model in the spring of 2021, we have received some excellent feedback, and have also had a number of common questions asked.
Is 8 dBi the highest gain available or should I go higher?
For most environments we recommend 5.8 or 8 dbi as they provides a good tradeoff between signal gain and vertical beamwidth. As the gain of an antenna increases, its vertical path gets more narrow (this is the angle at which it can transmit and receive). Very high gain antennas will have a very low vertical path, aka beamwidth- think of a beam of light, you can concentrate light into a very narrow angle but then it does not offer as much visibility above and below its path. If the vertical path of your antenna is too low, you may over or undershoot the transmitter you are trying to connect to.
In city environments, you can consider both our indoor and outdoor 4 dBi gain setups, the former which ships with the official RAK magnet base.
Because signals bounce off obstacles, we only recommend very high gain antennas like our 10 dBi for very open environments with full line of sight.
We develop our antennas with basic terrain in mind. You can opt for a very high gain if you have a complete line of sight to other helium hotspots but for most of us that's not the case. If you are in heavy terrain- areas with heavy tree coverage for example, higher gain won't permeate obstacles better, and you may not be able to use a hotspot in such terrain without getting the antenna above the tree line. Contact us directly for custom cable options if that could be necessary.
*a gain of 8 dbi may work much better in environments with some trees and homes vs. a very high gain antenna. Conversely, environments with many trees are not optimal for hotspots regardless of gain unless you can get the antenna above the treeline with a cable.
Would a directional antenna be better?
With other types of data transmission where your primary goal is to receive a signal, a directional antenna can be useful because it concentrates its reception and transmission in a directional path both horizontally and vertically. This focused directional path eliminates interference coming from other directions. For Helium hotspots, we advise against directional antennas in most cases. The goal of Helium Hotspots is to expand the reach of the network, and to expand the reach of the network, hotspots should be able to send and receive in all directions. While a directional antenna could increase your signal to another hotspot, it will decrease your ability to transmit to other hotspots in different directions.
The exception would be if you have a mountain or ocean behind you, where another miner could not be setup. Then a directional antenna could be of benefit. The ALFA AYA-9012 is a great choice for a Helium compatible directional antenna.
*directional antennas can go further in one direction, but render your Helium hotspot a weak link when it comes to transmitting to other hotspots. This is not ideal if you have hotspots all around.
What about coax cable?
Cables come with different shielding. While adding a cable between your miner and your antenna causes some signal gain loss, the loss can be kept minimal with 400 grade low loss shielding. For example, a low-cost RG-58 shielded cable has a gain loss of over 3 dB at 20 feet for the 915 MHz band, whereas our RFC-400 grade shielded cables have just 0.8 dB loss at the same length. We do offer RFC-600 and LMR-600 solutions from Times Microwave for very long cable runs. Contact us for your cable needs or see compatible links below.
Recommended cables for your RAK2, Bobcat 300, or Nebra Indoor miner & our 8 dbi outdoor miner antenna:
3 feet - RFC-195 (LMR-195 equivalent) RP-SMA male to N-male cable
10 feet - CFD-240 (LMR-240 equivalent) RP-SMA male to N-male cable
16 feet - CFD-400 (LMR-400 equivalent) RP-SMA male to N-male cable
20 feet - CFD240 (LMR-240 equivalent) RP-SMA male to N-male cable
29.5 feet - CFD-400 (LMR-400 equivalent) RP-SMA male to N-male cable
45 feet - RFC-400 (LMR-400 equivalent) RP-SMA male to N-male cable
Have a different miner or antenna? See our new cable page here for full selection.