The idea for this post came to me from seeing all the nice enclosures people are 3D-printing for their Emlid M2&#;s, using the drone helical antenna for keeping the size of the setup down.
I have seen numerous people claiming that the drone-antenna is just as good as a classic patch antenna for classic surveying on the ground. Looking at data-sheets and radiation plots it simply couldn&#;t be true.
So, what to do about that? Experiment of course!
For this experiment I have selected 2 antennas:
They were chosen as they both are around 200 USD. The GPS500 antenna has the further advantage of being NGS calibrated.
I set up the antenna on a well-known and well-defined point at my home. The point that has low to medium multipath potential, with a roof to the east blocking the view up to 20 degrees. I have not elevated the antenna very much, again to make it a little tougher on the antennas for test-purposes.
Here the helical antenna mounted, rubber-band-style!
Let&#;s start with how the 2 antennas are different:
Tallysman HC871
This antennas is a helical design, which makes it quite compact. Doesn&#;t require a groundplane either (although it can benefit from one, but that will be a project for another day), which makes it super compact and lightweight, ideal for a drone.
On top of these advantages, it also allows for signals to enter from below 0 degrees, which is ideal on a drone that pitches and banks while in the air. Up high in the air, multipath issues are more or less non-existent anyway.
However, when used on the ground these advantages quickly becomes disadvantages. The disability to block signals from below becomes a problem. The lower gain of the antenna (~1.6 db) (partly from a missing groundplane) also becomes a problem, especially under less-than-ideal scenarios.
Datasheet: https://www.tallysman.com/app/uploads//03/Tallysman®-HC871-Datasheet.pdf
Harxon/Swiftnav GPS500
So now to our second contender. The antenna is a patch design, a design used for GNSS since the very beginning. It consists of the antenna itself, on top of groundplane, usually 10-15 cm in diameter (but can be up to 40 cm on large choke ring geodetic antenna designs).
This antenna weighs in at almost 400 grams, making it 10 times as heavy as the helical.
However, the patch design makes it quite effective at stopping signals from below 0 degrees. It also feature much higher gain that the helical, at 5.5 db, further contributing to a better signal.
Many other parameters are also better, like the axial ratio (the ability to dampen signals with unwanted polarity).
Datasheet: https://www.swiftnav.com/resource-files/GNSS%20Antenna/v1.2/Specification/SwiftNav%20Mini%20Survey%20Antenna%20GPS500%20Specifications%20v1.2.pdf
So with that introduction, let us look at some hard data. For the 2 antennas I have collected raw-data for 5 consecutive days for each to make sure to have a good average.
Data was logged in UBX on the Emlid M2 and converted to Rinex 3.04 in RTKconv demo5_b34d using a 30 second interval, resulting in epochs each. Represented in RTKplot with a 15 deg mask (the grey area in the plots below).
Let&#;s look at the L1 band first (~-~ mhz) for all logged constellations, left HC871, right GPS500:
Almost identical! So if you where using the M+ you would notice little difference. The signal-to-noise ratio seems to drop off a little faster as we go from 90 deg to 0, as indicated by less green, going towards yellow.
Let&#;s focus on the L1 band but GPS only and another view:
We are here seeing 1-2 dbhz (Signal-to-Noise Ratio) less for max signal, and roughly similar multipath value. Insignificant difference in most regards.
So let&#;s do the same on the L2 band, (~ mhz - ~ mhz), left HC871, right GPS500:
Oh boy, what a difference! Much lower SNR!
Let&#;s try the alternative view from before to see more detail, but for L2 GPS, left HC871, right GPS500.
Around 5 dbhz of difference to the advantage of the GPS500 antenna, and significantly more multipath.
Let&#;s see what Beidou on L2 has to say, left HC871, right GPS500:
Here the difference in multipath is through the roof!
Finally, let&#;s look at Glonass at L2:
9 dbhz difference and also a significant difference in multipath.
Conclusion:
As with so many other tasks, it is all about choosing the right tool for the right job. Here it is clear to see that for ground-tasks, there are better alternatives to the helical. However, for drone RTK/PPK, the patch antenna design simply isn&#;t feasible due to size and weight.
27 Sep
A helical antenna is an antenna that is designed with the help of a conducting wire. It has a helix shape and is widely used in high-frequency operations. The polarization properties of a helical antenna depend on various factors such as diameter, number of turns, excitation, space between helical loops, pitch, and wavelength.
If you want to learn more, please visit our website mide.
This blog highlights everything about a helical antenna its features, uses, benefits, and other factors. We will also discuss the working process of a helical antenna.
Before we discuss everything related to a helical antenna, let us first understand the meaning of this antenna. A helical antenna is also known as a helix antenna. In this antenna, the conducting wire is connected to the ground plate with the help of a feeder line.
This is one of the simplest antennas to use in high-frequency operations. It offers circularly polarized waves and is used mainly for communication in satellite relays and other devices. It works with UHF and VHF ranges.
A conductive wire in a High Gain Helical Antenna is excited with the help of a coaxial cable or two-tore transmission line. This pattern then causes a current flow via a conducting wire. It also further causes emission and generation of field lines and radiations.
The typical helical antenna can radiate in several ways but the most popular modes of the antenna are:
Another name for normal mode is a perpendicular mode of operation. In this normal mode, the radiation is emitted in the plane&#;s direction perpendicular to the antenna axis. It causes circularly polarized waves.
This mode is achieved when the antenna dimensions are smaller than the wavelength. A small dimensional antenna gives low radiation efficiency. The radiation pattern of a helical antenna depends on turn spacing and diameter values.
Another name for axial mode is the end-fire mode of operation. In this mode, the maximum radiations are emitted along the helix axis. The radiation pattern in axial mode is circular. The main difference between the normal mode and axial mode is the radiation pattern.
In normal mode, maximum radiations come along the perpendicular direction of the axis. On the other hand, the maximum radiation comes along the axis in axial mode.
After knowing the Helical Antenna Working and radiation pattern, we will discuss its benefits.
An Advantage of a Helical Antenna is that it has a simple design. It has simple helical loops made of a thick conductor that looks like a screw thread. This antenna is connected to a ground plane made with a conductor. A ground plane contains a sheet or screen of concentric conductors.
Helical antennas come with a compact structure. This compact structure makes it easy to use on several devices that work on VHF and UHF bands. High directivity and simple design of a helical design are the main reasons to use space communication.
One of the major Helical Antenna Benefits is that it includes a circularly polarized pattern. This pattern makes it easy to use a helical antenna to use with other types of antennas with vertical and horizontal patterns. Moreover, this antenna can be used in television and weather satellites.
A helical antenna is mainly used for communication. It can be used in ground stations and satellites. Many weather satellites and data relays also depend on a helical antenna for showing correct data.
Additionally, this antenna is used in space applications because of its simple design and circular polarization. It is also used for radio astronomy and space telemetry. Moreover, the antenna is useful for transmitting and receiving VHF waves for ionospheric propagation.
One of the major benefits of a helical antenna is that it offers a highly directional behavior. It also has a wide bandwidth that gives a good signal. You will get clear communication by installing a helical antenna.
Helical antennas do not rust or corrode easily. They are made of durable materials and can withstand even the strongest windstorms and ice storms. It is easy to use a helical antenna for satellites and radio stations in any type of weather. They give the best performance because of their radiation pattern and high directivity.
We discussed all the advantages of a helical antenna and its patterns. Now, let us discuss the Disadvantages of the Helical Antenna in the below section:
Helical antennas are large in the size. They are larger than other types of antennas. Because of their bulky size, these antennas consume a lot of space in radio stations and satellites. It is also difficult to maintain bulky antennae in day-to-day life. Cleaning this type of antenna is also a difficult task because of its large size.
We discussed the efficiency of a helical antenna depends on several factors. These factors include the number of turns, diameter, space between the helical loops, excitation, pitch, and wavelength. Due to several factors, the efficiency of the antenna is often reduced. Due to a decrease in efficiency, it is difficult to communicate over a long distance.
Helical antennas are more expensive than other kinds of antennas. They are used mainly in large radio stations and satellites.
As a helical antenna is connected with a ground plane, you will need a powerful ground plane to use it. A good ground plane will improve the performance of a helical antenna. It also gives poor signals sometimes due to the narrowband.
It is easy to find the best High Gain Helical Antenna Manufacturer online. You can visit the official site of these manufacturers and look at the list of their products and get the best quotes.
27 Sep
The company is the world’s best gnss helix antenna supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.