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 last month, 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?
Though you can go higher, we recommend 8 dbi as it 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 very low vertical paths- 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. Because signals bounce off obstacles, we only recommend very high gain antennas for very open environments with full line of sight.
We developed our 8 dBi antennas with basic terrain in mind (see full antenna spec sheet here). 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. 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, a directional antenna will decrease your ability to transmit to other hotspots in different directions. We have not confirmed this officially, but word online is you can receive a mining penalty for using a directional antenna. Hence, we advise against directional antennas. However do do carry 915 MHz directional antennas. If you know what you are doing, and know that it is OK with the community, these directional antennas can work on the Helium frequency, but again we recommend our 8 dBi omni 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.
What about coax cable?
For the RAK Miner 2 and the Nebra indoor, you need an RP-SMA connector to go to your miner, and an N-male connector to go to our antenna. For the Nebra outdoor, you would need an N-male to N-male barrel connector.
Cables comes with different shielding. You may have read that adding a cable between your miner and your antenna causes some signal gain loss. This is true, but the loss can be kept minimal with the low loss shielding. We recommend 195 grade or higher. For example, a low-cost RG-58 shielded cable sourced cheaply online has a gain loss of over 3 dBi at 20 feet for the 915 MHz band, whereas our CFD-200 grade shielded cables have just 2 dBi at the same length (or 1 dBi at 10 ft length. So RG-58 cables essentially have 50% more loss. If you need to minimize your loss even further, our CFD-400 16 foot cable has a loss of just 0.62 at it's 16 foot length. 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-200 (LMR-200 equivalent) RP-SMA male to N-male cable
16 feet - CFD-400 (LMR-400 equivalent) RP-SMA male to N-male cable
20 feet - CFD195 (LMR-195 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
Barrel converter to use our 8 dBi miner antenna with Nebra Outdoor:
N-male to N-male barrel connector
Recommended extension cables for your Nebra Outdoor miner and our 8 dBi miner antenna:
See compatible cables