Evaluate the performance of LoRa antennas - Page 1
Forum section: electronics / rf-microwave

author: Nikos A.
author_rank: Regular Contributor
timestamp: March 04, 2022, 12:54:03 pm
content: Hi guys,I have three LoRa antennas, and I want to evaluate their performance. I have ordered the antennas to operate in LoRa EU bank that is 867-870MHz. I have the NanoVNA SAA-2N V2.2 as a mesurement tool.https://www.amazon.de/Converter-50KHz-3GHz-Measuring-Parameters-Standwave/dp/B099S5NNMN/ref=sr_1_1_sspa?keywords=nanovna+saa-2n+v2%2C2&qid=1646395901&sprefix=nano+vna+s%2Caps%2C160&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExT1RHNUU1V0FTUVlPJmVuY3J5cHRlZElkPUEwNjU0Nzg4MU9GTjRQNFg4VTlHTiZlbmNyeXB0ZWRBZElkPUEwNTg3ODMwM0lFQ0pCNFdQTFRHOSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=I do not expect the best accuracy with this VNA but an indication about the antennas' performance. Before measuring the antennas, I performed a SOL calibration, and I took into account the port extension (N-type cable to connect the antenna) to establish the reference plane at the end of the N-type RF cable.These are the antenna I measured:1.Brand New- Kerlink 6dBi, frequency range 865MHz ±5MHz2.Used- Kerlink 6dBi, frequency range 865MHz ±5MHzThis is the datasheet.https://cdn.shopify.com/s/files/1/0447/5633/6807/files/Datasheet-6dbi-ACCIOT-KAN01-ACCIOT-KAN02-v1-0tmzmxMR5JTmBJ.pdf?v=16155694193. Brand new - RAK 5.8dBiThis is the manufacturer's webpage and the datasheethttps://store.rakwireless.com/products/5-8dbi-fiber-glass-antenna?variant=41525017510086https://docs.rakwireless.com/Product-Categories/Accessories/RAKARG13/Datasheet/#featuresMeasurementsThis is my setup:- the same setup applies for both Kerlink and RAKKerlink brand new antenna:Kerlink used antenna:RAK brand new antenna:Comments1. In return loss and VSWR graphs, I have indicated with light gray strips the EU (867-870MHz) and USA LoRa bands (902-928MHz)2. The RAK antenna seems to be dual-band even though I ordered for the EU band. Also, it works better in the USA band (see marker 3, VSWR=1.115), but the second dip (see marker 2) is quite off. The VSWR at the center of the EU band (see marker 1) is 2.05It doesn't make sense that I ordered an EU antenna, but it resonates in the USA band. For VSWR=2.05, the antenna's efficiency is around 89%. Is this acceptable?https://www.skyworksinc.com/-/media/SkyWorks/Documents/Products/201-300/VSWRreturn.pdf2. On the other hand, the brand new Kerlink antenna seems to operate really well. The VSWR at 870MHz is 1.203; that is, the efficiency is around 99%3. The used antenna, however, resonates at 854MHz (the EU band is 867-870MHz), and at the EU band's center frequency, the VSWR is 1.821 (91.5% efficiency)What is your point of view regarding the measurements? Should I use the antennas I should claim to the manufacturers?What is the acceptable return loss for this type of application (antennas for helium miners)?

author: El Rubio
author_rank: Regular Contributor
timestamp: March 05, 2022, 11:38:25 pm
content: One thing I see that could be an issue is the antenna is to close to the wall and also pretty close to your test equipment.

author: tautech
author_rank: Super Contributor
timestamp: March 09, 2022, 12:08:59 am
content: Quote from: Nikos A. on March 04, 2022, 12:54:03 pmAs El Rubio points out you cannot judge antenna performance inside buildings due to proximity effects.We can get some idea of performance from connecting directly to the antenna however for a more accurate result the coax feedline to be used should also be part of the picture a VNA sees.My experiments with a # of antennas hoarded over the years:https://www.eevblog.com/forum/rf-microwave/what-really-is-this-antenna/Another thread you might get a few tips from:https://www.eevblog.com/forum/rf-microwave/antenna-project-log/