What do RF-engineers do when they are in self-chosen isolation: They measure antennas!
These antennas I purchased for experiments and specific projects
868 MHz dipole
The antenna is good for 868 MHz with > 17 dB return loss.
868 MHz logper
I purchased this antenna to connect to a node that has poor coverage at the edge of the TTN coverage of our town. 19 Dollar is a good price for a logper. The downside is that I have to reduce power from the node to meet regulator constraints.
At 868 MHz a return loss is delivered of 20 dB (very good!) The two dips are caused by the different length of the elements of teh dipole.
This antenna is painted for cloaking purposes.
434 MHz antenna
This antenna I purchased for an experiment (Not LoRaWAN).
Although this advert is no langer available, equivalent types can be found.
Does anyone has design for 868MHz PCB antenna or know where to buy some that can be useful? Iām looking something that I can use inside of enclosure, possible some tracker. Thanks
Hi all,
Have quick question regarding Antennas,
Currently I have two 868 and 923 band Kerlink Wirnet Outdoor Gateways. Also we have Antennas for 868 band but not for 923. I know that technically Antennas are different from each other but i would like to know how does it impact if one is used for different band gateway ?
Thanks in advance.
Hi,
Thank you so much for very quick response.
Actually we wanted to do a test in field where the gateway is 500 meters away. Unfortunately we donāt have Antenna for 923 band in which we wanted to carry out the test. So just a thought what happens if I use 868 band antenna for 923!
Excuse me for questioning again, As I said above if i use other band antenna will the existing performance of the gateway reduces ? OR efficiency ?
First thing to worry about is legal implications. In most EU868 countries the frequencies used for 915 will not be freely available as they are used by mobile operators. Are you allowed to use 915 outside a rf shielded room?
If the antenna is tuned to 868 very well you performance will be greatly reduced, a significant amount of energy will be reflected back to the gateway which in extreme cases might even cause damage to the gateway.
Hi @kersing,
Thanks for the reply.
We have got legal permission for using 915/923 bands for R&D purposes So we are allowed to use them for limited period of time with in company premises.
As you said, we canāt use 868 band antenna for 915/923 gateway. I really appreciate your conclusion.
Excuse me for last query, we have field setup approximately 500 meters away from Kerlink Wirnet Gateway [ https://www.kerlink.com/product/wirnet-station/ ] in clear line of sight but with out Antenna. Question is, In this scenario Do we still need Antenna ? Will there be any packet loss ? Could you suggest me.
( Background : we have ordered Antennas but due to COVID it will take 30-40 days to deliver, so to avoid blocking us Iām stressing about antenna)
Thanks in advance.
I have no problem at all with DIY antennas, but the responsible constructor does need some way of measuring the actual real world gain so you can be sure that the operation of the antenna is legal for your location, and that is not so easy.
You can of course take the designers word for it and reduce the power output of the gateway to compensate (and thus stay legal) for the fitting of a gain antenna.
What is often forgotten is the fact that using an antenna outside its intended frequency-range can strongly influence the radiation-pattern. Measuring the feed-point of an antenna using a VNA is important to know how the antenna behaves in terms of impedance, VSWR ā¦ But what you dont know, how much of the power is radiated to your nodes.
e.g. if you use an 3/4 lambda antenna this antenna is resonant with a feed-point impedance of abt. 50 Ohm - very well matched. But most of the power is radiated with an elevation of abt. 25 degrees - good for planes but not for nodes being short over ground.
Indeed, such absolute laboratory standard measurements are unlikely to be easy or quick.
There is a tendancy by some to make antenna performance measurments āreasuringly complexā. No doubt there are a few people (antenna designers likley) who are intersted in all the pretty plots and graphs.
What the majority, say > 99%, of actual antenna users are interested in is how well the antennas perform in the real world, that is outdoors in real situations. Which of the available antennas will really provide the best real world signal performance ?
Such measurments are dead simple. Use a reference antenna, such as a 1/4 wave vertical with radials and compare the signal reception performance of the reference versus antenna A,B,C,D etc. This is quick and easy to do, you can compare the performance of 10 antennas in 10 minutes. So after 10 minutes you know the best antenna to use. Tell the World.
That is simple if one company/person does it. However different companies would not be able to reproduce this without being able to create identical circumstances for testing. (For instance use the same reference antenna to compare measurements to.) That is where the expensive test labs with their setups come into the picture.
Or we need a volunteer in the community to buy each of the antennas and do the measurements for us using the same reference setup for every antenna. Anyone?
If you check back you will see I commented on the article āTesting and Reviewing LoRa Antennasā
Now the person who did the comparisons, produced all the lab measurments plots etc of 12 or 13 different antennas.
My point was that whilst those type of measurements are of interest to some, the majority would have been really really interested in what the real world dB difference was between the various antennas and those tests are easy to do. But so few āengineersā think about doing them.
