UPDATE on Seeking Ideas for RoadTesting Antennas

Hi Randall,

That sounds interesting! I think if it was paired with a couple of development boards it would be great, e.g. microcontroller+wireless dev-boards. That way the boards can be used to send and receive data.

For ISM bands if such antennas are to be part of the roadtest, there is a slight difference between some regions, e.g. Europe uses the 868MHz band, but USA uses 915MHz. The 433MHz band is used by both.

It would be great for such a roadtest to offer (say) three of the same antennas for each antenna model that would be roadtested, so that consistency

between them could be tested too, since sometimes there is some variance.

Some of the antennas (like that SMD antenna) will need some PCB design work, but most people will have their favourite software to use for that.

A few connectors may be required too, but they could vary.

Anyone with a VNA or spectrum analyzer will be able to test for how good the antenna match is, which helps determine how efficiently power is being used, but the range test with the couple of development boards is good too, for anyone who doesn't have access to the VNA or spectrum analyzer.

Well, the key parameters of an antenna are the gain and radiation pattern.

As shabaz said, some specialist gear - and the experience to use it - are required to do a full quantitative analysis.

But I'm sure that there are plenty of people who are not antenna specialists, but familiar with working with radio systems - which, of course, always require antennas!

I think I would come in that category.

I'm sure such people could do some useful qualitative investigations into coverage/range when using the different antenna types...

Having spent time in a previous life doing RF work for the NZ Post Office (later Telecom) I've seen a vaste array of antennas, and antenna designs.

Each has a specific purpose, and some are designed for the environment, so they have special charateristics or materials.

As awneil said the radiation pattern and gain are the key differences between antenna.

The examples above are all omni-directional, (but for different bands) so the gain is the final figure as to how well it will perform.

Therefore the 2.7-6GHz version should have a longer range with the same power.

To test these you need a transmitter with adjustable gain, and a receiver that can provide the RSSI (Received signal strength).

They need to be tested in an open environment, clear from reflections.

While this provides the optimal conditions, in reality they are used in an urban environment, placed to suit the box or mounting.

This means the real world result is varied and not able to be duplicated easily.

What I think might be useful is to see if the testers can increase the range of the middle example by directing it, to provide a cheap link between two points.

I've aluded to some antenna theory here BT_Sentry : Zero Emission Detection

I have to build something that will allow my modifications to be tested, which is likely to involve a servo and stand in the middle of a paddock.

Cheers

Mark

Hi Mark,

While the gain is indeed a measure of how well the antenna performs, to calculate the range you need to take into account also the frequency of the signal (assuming all the other parameters are identical).

The Omni-directional SMD Antenna and the OMNI ANTENNA, 2.7-6GHZ, 5DBI, ADHESIVE both work on similar frequency bands, so looking at their datasheets, we can already infer the OMNI antenna performs better (higher gain).

To establish which has a better range between the OMNI ANTENNA, 2.7-6GHZ, 5DBI, ADHESIVE and the OMNI ANTENNA, LINEAR, 433MHZ, 0.7DBI, we can use the Friis Equation - (aka Friis Transmission Formula). The distance R can be calculated as:

R=√(Pt·Gt·Gr)·c√Pr·4πƒ

where:

   c is the speed of light

   f is the frequency of the signal transmitted

   Pt is the power transmitted

   Pr is the power received

   Gt is the gain of the transmitting antenna

   Gr is the gain of the receiveing antenna

To simplify,  lets assume the power transmitted, the power received and the receiving antenna's gain are the same for both antennas. Lets call R1 the range for the 5dBi antenna, and R2 the range for the 0.7dBi. If we calculate the ratio R1/R2, we get:

R1R2 =√Gt1Gt2 ·ƒ 2ƒ 1

where:

    Gt1 = 5dBi = 3.16 ,    f1=2.7GHz  (lets use the lower end of the band)

    Gt2 = 0.7dBi = 1.17 , f2=0.433GHz

Calculating, we get:

R1R2 ≈0.26   

Therefore, under the assumptions above, the 0.7dBi antenna should give a range about 4 times longer than the 5dBi one.

Fabio

to calculate the range you need to take into account also the frequency of the signal

of course ... and yes you're quite right that the losses increase with frequency.

I mistaken assummed that the testing would be on antennas in the same band

Mark

To establish which has a better range

It may be interesting to some ... we had much better signal to noise ratios not by increasing the power, but reducing the bandwidth of the receivers.

Many of our receivers were capable of being used across the band they were designed for, but in reality they stayed on a fixed frequency, for varying reasons.

Careful tuning reduced that to a narrow frequency, and thereby reducing the noise floor.

Many of these receivers have no filtering on the front end, and therefore wide bandwidth antennas can provide higher background noise.

Trying to extract the signal you're after in amongst the noise, can be a struggle, but is dependant on the hardware and techniques used.

Mark

mcb1  wrote:

 

To test these you need a transmitter with adjustable gain, and a receiver that can provide the RSSI (Received signal strength).

They need to be tested in an open environment, clear from reflections.

Yes, to do quantitative measurements.

But I think a Road Test could also benefit from more "qualitative" results - experience in real-life situations; eg,

in reality they are used in an urban environment, placed to suit the box or mounting.

This means the real world result is varied and not able to be duplicated easily.

 

What I think might be useful is to see if the testers can increase the range of the middle example by directing it, to provide a cheap link between two points.

Interesting question as to whether the Road Test should provide "reference" receivers & transmitters (eg, Dev Kits): this would certainly help to provide more consistent, comparable results - but I suspect that many testers would rather see how the antennas perform in their own systems.

There's also the question of the learning curve with devkits - which takes the focus off the antennas, and onto the devkits & associated stuff.

To do comparative tests of antennas really needs the antennas to be in the same band.

This is going to be difficult to roadtest.

Normally, when you design a product, and it's the first time you evaluate antennas for it, you select a couple of antennas that fit the specifications and try them all.

In this case, you only have the one antenna, so there's nothing to compare it to. Also, it's impossible to choose other antennas to compare them to, because there are no specifications to be met, so on what criteria would the other antennas be chosen?

Obviously, someone who is an expert in antennas (has dealt extensively with most of them, knows all the strengths and weaknesses of each type of antenna, knows their intended use cases, etc), could write a pertinent review, but that person is going to be very difficult to find. The fact that the community has become centered around hobbyists, not engineers, won't help.

Not sure if I would put too much value on a review that merely characterizes an antenna or sends some data using it.

When it comes to components, and this holds for any sort of specialized gear too, you want to read what an expert has to say, not someone who might not be aware of the various pitfalls (and there are many in RF design), who may or may not be able to test the DUT properly.

In my opinion, the first step should be to figure out how many such candidates are available in the active user base and then find a way to incentivize them (maybe offer the components as part of some bigger roadtest). Alternatively, you could offer a big selection of antennas, because the odds that they're interested in a particular PN is very slim, so either go with "pick any 5 you want to test" or "here's 30 models from which you can evaluate any of them".

I may be missing something here, so I'm looking forward to see what comes out of this.

Razvan

I worked on many RF projects, including building an integrated test facility for testing all antennas on aircraft in a huge anechoic facility, so I am not sure what you would have anyone do with just the antennae.

I could see people set up the antenna and then use it to broadcast information to a receiver that you then take around an area to measure reception/detection to do rough antenna pattern information.

You could do distance measurements, weather effects, and in some instances atmospheric and EM effects.

If you want to do detailed measurements then you are talking about some serious RF gear to make the proper measurements.

DAB

I have to agree, I too have worked both in design and service of RF Systems. Even the project I am working on requires 2 antennas at 150MHz and 2.4GHz. For review though it is difficult to judge the best way to review. In my case till April 2019, I have access to some specialize gear and chambers to characterize antennas but for the majority most people can only provide a review based on project implementation. If that is enough then it is quite possible be the best route. The only problem though with this method is that the reviewer could find the project implementation more often than not fail depending on what there expectations are and could lead to a negative review.

Very few people will have access to EMC chamber. Although in saying that more people will have access to signal generators and spectrum analyzers to carry out reasonably precise measurements while the rest would have to provide subjective review based on there reception capabilities.

Malcolm