Helium Hotspot Antenna Upgrade Guide – 8dbi vs 5.8dbi vs 3dbi – Which cables & connectors to choose to reduce signal loss?

I have previously written a post on upgrading my Helium Hotspot with the MikroTik LoRa 6.5dBi Omni Antenna.

When it comes to Helium antennas, a 5.8dBi variant can be an interesting option to explore. Generally speaking, the ‘dBi’ rating indicates the antenna’s gain—essentially, how well the antenna can focus energy in a particular direction. A higher dBi rating means that the antenna can send the signal further in that focused direction. However, it’s crucial to remember that gain doesn’t mean ‘more power.’ Instead, it’s more about concentrating the available power in a particular direction.

Let’s delve into some technical specifics to understand the potential range of a 5.8dBi and other gains for Helium antenna.

8dbi vs 5.8dbi vs 3dbi Antenna – Different antenna gains have different degrees of coverage

Omnidirectional antennas are not quite as omnidirectional as you think when you increase the antenna gain. So you can’t just buy a Taoglas Barracuda 12dBi antenna and think it will cover a huge distance with 360-degree coverage – trust me, I tried, and it is a super expensive antenna.

The gain of an antenna needs to be evaluated in the context of its environment. Higher dBi antennas tend to focus their energy in narrower lobes. While this makes them excellent for long-range communication in relatively flat terrains, they might not be ideal for hilly or multi-storey environments where a more isotropic radiation pattern might be beneficial.

Now, how does this translate to range? In perfect, free-space conditions without interference, a higher dBi would mean a greater range. However, in real-world scenarios—think urban landscapes with buildings, trees, and other obstacles—the effective range could be considerably less. Obstacles can cause attenuation, reflection, or diffraction of the signal, limiting how far it can effectively travel.

If you’re eyeing up a 5.8dBi antenna for your Helium Hotspot, you’ll want to think about your specific situation. If you’re in an area with a relatively flat topology and few obstacles, the higher gain could indeed extend your hotspot’s coverage area, perhaps even by a few kilometres compared to a lower dBi antenna. However, it’s not as simple as “5.8dBi will give me X kilometres of range” because so many variables can influence the effective range.

Moreover, placement of the antenna can also influence its performance. Higher elevations can mitigate some of the environmental challenges and help you achieve closer to the ‘ideal’ range that the antenna’s specifications might suggest.

A lot of people choose to use something around 5dbi or 6dbi because this will offer a good balance of range and being able to connect to nearby antennas at different heights as yours.

The lower the gain, the better the coverage, at 2dbi, you get 360° coverage, but at 5dbi, it drops down to 40° then 7dbi is 30°.

So in a city with a lot of hotspots around, you might be best off with a lower gain antenna.

Also, remember, you will need an antenna that is compatible with your specific region. Some antennas cover multiple frequencies, which is fine, as long as it covers your frequency.

• For the UK this is 868Mhz
• For the US this is 915Mhz

Optimal dBi for Helium Antennas For Different Environments

Flat and Open Terrain

Characteristics

In flat and open terrain, you’ll have fewer obstructions like hills, buildings, or trees to interfere with the signal. This setting usually allows antennas with higher gain to perform at their best.

Optimal dBi

In these conditions, you may want to opt for an antenna with a higher gain—say between 5.8 to 8dBi. These antennas focus the signal in a more narrow beam, making them ideal for long-range communication over flat surfaces.

Caveats

Although you’re likely to achieve longer range in these conditions, be mindful that higher-gain antennas are often more susceptible to noise from other RF sources, so some additional fine-tuning might be necessary.

Urban Environments

Characteristics

Urban environments present a unique challenge due to the presence of multiple obstacles like buildings, cars, and even people. These obstacles can reflect or absorb RF signals, making it difficult for the antenna to perform optimally.

Optimal dBi

In these scenarios, a lower-gain antenna between 2 to 4dBi usually fares better. The signal from lower-gain antennas tends to spread more isotropically, increasing the likelihood of the signal navigating around obstructions.

Caveats

While a lower-gain antenna will generally be more effective in urban settings, each individual location might have its unique considerations. Site surveys and RF spectrum analyses can be invaluable in these situations.

Hilly or Mountainous Terrain

Characteristics

These terrains are characterised by significant elevation changes, making it difficult for signals to travel great distances without interruption.

Optimal dBi

Lower-gain antennas in the 2 to 4dBi range are often more effective in these settings as well. The broader radiation pattern allows for more flexibility when the terrain is uneven.

Caveats

Higher elevations usually favour antenna placement. Even a lower-gain antenna might achieve improved performance when placed at a higher elevation to ‘see over’ some of the terrain features.

Indoor or Multi-Storey Buildings

Characteristics

Multiple floors and walls can significantly degrade RF signals. Material like concrete and metal can especially interfere with signal quality.

Optimal dBi

In indoor settings, an even lower gain antenna, possibly around 2dBi, might be the most effective. These antennas offer a more spherical radiation pattern, which could be advantageous when dealing with multiple floors.

Caveats

Placement becomes exceedingly crucial in indoor environments. Antennas should ideally be placed away from large metal objects and electronic equipment that could introduce noise into the RF spectrum.

Helium Hotspot Antennas for the UK 868Mhz models of the Helium Hotspot

Be warned, the Taoglas 12dbi option is not likely the best choice unless there are not many hotspots near you.

I wouldn’t personally buy from Nebra anymore, the way they have dealt with the Helium Hotspots is poor. But the below antennas are still worth considering. I personally use the Paradar 8.5dBi which I reviewed here and is available on Amazon.

• Glass Fiber LoRa Antenna Peak Gain (5.8dbi) by Nebra for £40
• Glass Fiber LoRa Antenna (3dBm) by Nebra for £35.99
• Various antenna options on CalChip (just make sure it is a 868Mhz antenna)

Helium Hotspot Antennas for the US 915Mhz models of the Helium Hotspot

• Signalplus Helium 10dbi Antenna
• LoRa Gateway Antenna 3dbi Gain Antenna – On Amazon with stock available on the 18th for $39.99
• 5.8dbi RAK Fiber Glass Antenna Kit for Helium Hotspot – $40
• Various antenna options on CalChip (just make sure it is a 915Mhz antenna)

Signal loss through the cable

You also need to consider how the signal degrades on the way back from the antenna to your hotspot. The longer the cable, the bigger the signal loss. Again, in hindsight, I messed up here buying cheap cables on Amazon.  Similarly, if you use the SMA adaptors you buy on Amazon, you can potentially introduce further signal loss.

You can get low-loss cable, Amazon has lots of these listings, but a decent low-loss cable is LMR-400 which is harder to find and much more expensive.

Just be warned, the LMR-400 is very thick, I had an old hole coming through into my office for a TV antenna, and I only just managed to squeeze it through. I had previously run cables through a small window, leaving a small gap with the window partially closed, but this cable would have left a huge gap.

Custom cable and which connectors to use on your antenna  

You can get cable made up to custom lengths, this will be your ideal option allowing you to select the minimum length required to reach your hotspot.

To avoid using adaptors, you will need to work out which cable end you need. For the MikroTik LoRa 6.5dBi Omni Antenna I use, it has an SMA female end while the Helium Hotspot has an RP-SMA Female .

So for the MikroTik, I needed the opposite connectors, which are RP SMA MALE (Helium hotspot side) to an SMA Male (Antenna side)

I ended up buying off  McGill Microwave Systems on eBay. I think it was this cable but then I messaged them asking for the RP SMA MALE & SMA Male cable ends.

Some antennas use the larger N-Type Male connection, this includes the RAK 5.8dbi Fiber Glass Antenna Kit, so this would require a N-type female 

If you get a cable made up I would suggest confirming with the company the exact ends required, I get easily confused with all the connector types and it is easy to get mixed up. A professional will know best.

Some of the options on Amazon are available below, but you may need to buy the adaptors to fit things properly.

Last update on 2023-12-07 / Affiliate links / Images from Amazon Product Advertising API