RFM69 antennas comparison
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I wanted to share my finding following my RFM69 signal scanner I previously built. I used 2 types of antennas:
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Hand made like the one mentioned by @sundberg84 in [his project](https://www.openhardware.io/view/389/EasyNewbie-PCB-RFM69-HWW-edition-for-MySensors
I let them run several hours reporting TX power since the new rfm69 driver adjusts power output to the default target RSSI of -80db
The test was done on the same spot (my desk) and the gw about 5 meters away (1 floor difference, and a couple of walls in between; gw running the coil spring antenna).
I am currently testing the SMA antennas and results are better than the hand made antenna with a TX power of 35/40% instead of 55/60%. My guess is the hand made antenna had to be squeezed inside the box getting a wrong orientation, while the SMA one is outside and it can stay perfectly vertical.
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@Yveaux Excellent summary, yet well worth reading through.
What I found fascinating elsewhere was where 2.4GHz compressed PCB antennae such as the zig-zag pattern underperformed compared to their U or J type countertparts, despite identical claims as to gain, which is bidirectional.
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It is more or less related, but just this evening I had the garden sensor going out of range for 2 hours (from 6 to 8 pm). It happened a few time in the past but for shorter periods. Looking at the TX power it seems there is something affecting the communication from time to time. It would be nice to know the source since I live in the countryside and I have only another house near mine... I have to make other outdoor sensors to see if I get the same pattern
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It is more or less related, but just this evening I had the garden sensor going out of range for 2 hours (from 6 to 8 pm). It happened a few time in the past but for shorter periods. Looking at the TX power it seems there is something affecting the communication from time to time. It would be nice to know the source since I live in the countryside and I have only another house near mine... I have to make other outdoor sensors to see if I get the same pattern
@gohan
Hi. i know that its 3 months + old discussion .but i only read now :)
i have the same problem,probably same time that hapens to you. my nrf24 modules between front gate and gateway stops comunicating at end of day.
My bet it that signal its already on limit ,(at 50m between gate and home), and at the end of day ,air humidity increase and signal just don't arrive. I already change antennas but signal strengh it's on limit and some days are worst than others.Now i will change all my nrf24 for rfm69's (they arrive today) and try again at 868mhz and simple wire antenna(dipole).
Just for confirm; are the grownd plane from rfm69hw good enought? or i need something more than a piece of wire on ANA pin ?i'm a arduino fan .Even sometimes don't undestanding how to use it :P
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@gohan
Hi. i know that its 3 months + old discussion .but i only read now :)
i have the same problem,probably same time that hapens to you. my nrf24 modules between front gate and gateway stops comunicating at end of day.
My bet it that signal its already on limit ,(at 50m between gate and home), and at the end of day ,air humidity increase and signal just don't arrive. I already change antennas but signal strengh it's on limit and some days are worst than others.Now i will change all my nrf24 for rfm69's (they arrive today) and try again at 868mhz and simple wire antenna(dipole).
Just for confirm; are the grownd plane from rfm69hw good enought? or i need something more than a piece of wire on ANA pin ?@tmaster Pending @gohan's response, I suggest you try a simple 1/4 plain wire whip initially.
You are using not simply different devices with differing characteristics but different frequencies, penetration of 2.4GHz and 868MHz wavelengths are not the same, lower frequencies have better penetration.
Should you require additional gain either to reduce transmission power input, or to increase effective radiated power it is easy enough to add a mirror 1/4 later to make it a dipole should you desire... -
You could also use a PA LNA radio on the gateway and maybe on node. Also trying different antennae on the radio, as previously suggested, is an option. RFM69 have a good advantage of reportig signal strength (I published a small signal scanner for RFM69 in the My Project section) that gets handy in detecting blind spots.
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@gohan
Hi. i know that its 3 months + old discussion .but i only read now :)
i have the same problem,probably same time that hapens to you. my nrf24 modules between front gate and gateway stops comunicating at end of day.
My bet it that signal its already on limit ,(at 50m between gate and home), and at the end of day ,air humidity increase and signal just don't arrive. I already change antennas but signal strengh it's on limit and some days are worst than others.Now i will change all my nrf24 for rfm69's (they arrive today) and try again at 868mhz and simple wire antenna(dipole).
Just for confirm; are the grownd plane from rfm69hw good enought? or i need something more than a piece of wire on ANA pin ?@tmaster I had similar problems with nrf24 and also decided to switch to rfm69. I used nrf2rfm69 board to replace nrf24 modules. As an antenna I use a simple 1/4 wavelength flexible wire with isolation. And it works far more better than nrf24 even at 0dBm tx power. The modules are only twice the cost of nrf24 and perform much better. I guess the frequency (I use 868MHz) is the key factor here.
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You could also use a PA LNA radio on the gateway and maybe on node. Also trying different antennae on the radio, as previously suggested, is an option. RFM69 have a good advantage of reportig signal strength (I published a small signal scanner for RFM69 in the My Project section) that gets handy in detecting blind spots.
@gohan I meant to ask about that scanner project... Is this now fully realisable under v 2.2 ?
