Looks great, definitely one to try out . You posed a question:
How would you rate that? You used an analyzer that is able to produce quite fancy pictures, so probably it isnāt cheap?
Do you think we can get decent results with just the layout you described without using an analyzer?
I guess your PVC pipe passed the microwave test? (although 2450 Mhz is not 868 Mhz ;-)).
Expected gain is typically 2.2 DBi in the H(orizontal)-plane I understand? (assuming you put the antenna upright).
How about our 434 and 915 Mhz friends, I guess its just scaling the math?
How would you rate that? You used an analyzer that is able to produce quite fancy pictures, so probably it isnāt cheap?
Depends on what you call cheap.Compared to Rohde & Schwarz analyzers the Megiq VNA is cheap but for most of us around 4k EUR is a lot of money
I made way more measurements that the few posted. I played around with the feed point and the length of the legs of the antenna to see how much this influences the frequency and return loss. Looking at the fact that it was not that hard to tune the length and the position of the feed point within 1mm, I concluded that it is not that hard to create more antennas with equal performance.
I actually made the original antenna using the same calculator and number provided by Lex and that one was almost spot on. After placing the antenna in the PVC tube I calculated the new valocity factor and the new antenna was (again) spot on but could be improved by placing the feed point 1mm further.
I wrote something similar in my previous post but that got lost when WIndows 10 had the excellent idea of rebooting my PC before I could press the reply button
The next thing to do is to bend a few more welding rods and test then on the analyzer. The analyzer is something I can borrow from the office but itās being used right now by another colleague to test a product we sell so I donāt expect any new results before end of next week.
On Saturday the 5th of November we are organising a LoRa hackfest at the SODAQ HQ to exchange ideas, thoughts, designs etc. on LoRa antennaās and boards. You guys want to come?
We have some prizes for the best antenna design to be won!
Gateway: RasPi + RFM95 + J-Pole located indoors on my window board
Mobile station: homebrew 5/8 wavelength antenna with magnet-mount on my car + node with RFM95 module.
My antenna is made of 1.3mm solid copper wire:
251 mm (long leg)
83 mm (short leg)
7 mm spacing
feedpoint 9mm from bottom
no radome/pipe
you solved of the riddle ;-).
As 868MHz is travelling almost line-of-sight, a slightly elevated gateway will cover most part of our flat 25km meteorite crater.
The J-Pole performed quite well. There are 20km points that are not elevated and some points were even logged out of small towns where no LOS is possible.
No problem at all ā¦ but Rob65s design is much more what you like to see on photos.
My motto is: āRF current has no eyes - so antennas do not have to be prettyā
The ābig copperpartā has nothing to say, I just cut the wire too short while tuning and had to add something to get it longer. The capton tape is just for fixing the spacing between the wires and has nothing to do with the function.
Using a right-angeled SMA connector and 5mm cable, it is ready to use for indoor experiments without having to care about mounting.
Nice to find some fellow hams here
At the time I found about LoRa I was fascinated by bringing together two hobbies of mine, ham and IoT. Having played extensively with JT65 in QRP and worked US and Brazil with only 5W and a 1m diameter magloop antenna I immediately jumped to the conclusion that LoRa and magloops can be best friends. Only to realize shortly after that this isnāt going to happen because thereās no way for a rougly 6kHz magloop bandwidth to accomodate a LoRaWANās 125kHz channel. The 2.5kHz JT65 bandwidth fits just fine although tuning the antenna is a bitch
Iām currently looking to buy an outdoor antenna for my gateway but unfortunately the local market is pretty poor when it comes to 868MHz and most of them are unidrectional. Iād avoid purchasing one from abroad since Iām pretty worried that it may get damaged during transport. So I was wondering if I could use a 3/4Ī» antenna in 433MHz as a 1.5Ī» in 868MHz.
This is what I had in mind: http://www.sirioantenne.it/en/products/uhf/cx-70-cm
More precisely CX 425 which is supposed to cover the 425-440MHz range. I know a thing or two about antennae, but Iād like to know if there are other things to be considered.
Lex, did you build that cloverleaf antenna?
I am interested in circular polarization results as -unlike gateway antennas- nodes are often not positioned well for vertical polarization. Reinier (AI6CT, ex-PA3DJM)
The cloverleafs started life over in the RC forums, used mainly for video transmitters. Good for a transmitter antenna I thought, but not as a receiver ?
From what I read and hear is that the 3 lob has a better 50Ohm match and a more donut like radiation pattern like a ground plane. The 4 lob has better polarization characteristics (itās looking more up which is from good for a ground operator ). But that is second hand information for me. I havenāt build a 3 and a 4 lob one for LoRa and compared them.
I have simulated the 4 lob version and itās showing a nice apple shape pattern.