Author Topic: Several questions: Antenna, range, schematic  (Read 700 times)

Sergegsx

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Several questions: Antenna, range, schematic
« on: July 03, 2017, 01:48:29 PM »
Hello,

I have an official moteino which although manages to send packages and RSSI reports -80dB, I sometimes loose packages.

Is there any way to slightly increase the range so that I dont have to relocated it? I am using this method for sending as per examples found on the web
Code: [Select]
sprintf(payload, "up:%ld,power:%u,Spower:%ld,temp:%u,bat:%ld", 
        millis()/1000,(int)PowerSend,SumPowerSend,temp,BATactual);
  byte sendSize = strlen(payload);

I have tried the 1/4 and 1/2 length but does not make a difference.

I have also bought and tried this antenna, no difference:
http://www.ebay.es/itm/171802354402


I have tried also several antennas I have found in my electronic boxes, some of them from nrf24l01 modules. I dont know if they are compatible but the RSSI report the same values.

Lastly, I have tried to solder a uFL connector just as the new moteinos, but same results.
BTW, is there any schematics of the last version of the moteino? Github reports no changes since 2016.

Thank you for your help.

Felix

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Re: Several questions: Antenna, range, schematic
« Reply #1 on: July 03, 2017, 02:17:29 PM »
The NRF modules are 2.4ghz, so those antennas are probably very mismatched to the sub-ghz radios on the Moteinos.
Using the Moteino radios without or with improper antennas can potentially damage the radios. This was discussed in the forum if you're interested to read more details.
It sounds like something is wrong in your setup. You're either not using the right settings for your radios, or they are already damaged.
There's now an RF best practices guide which might benefit you to better understand antennas and RF in general.

Sergegsx

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Re: Several questions: Antenna, range, schematic
« Reply #2 on: July 03, 2017, 03:56:07 PM »
The 2.4ghz antennas were tested for a few minutes, and that could explain one of the radios not working.

But on the other side, I did use the correct 1 wire antenna of 1/4 and 1/2 in length.

Regarding the ebay one (http://www.ebay.es/itm/171802354402) this one is the correct frequency, but I get the same results, I was expecting at least a little improvement.

I wanted to analyze how the uFL has been added to the moteino, and compare to how I have soldered it to an old official moteino. see if there could be any improvement in buying the new version. Are the schematics released?

thanks felix !!


I will read now the best practices, thanks for the link

captcha

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Re: Several questions: Antenna, range, schematic
« Reply #3 on: July 03, 2017, 06:29:13 PM »
With your eBay antenna, did you attach it on a metal ground plane? These antennas look all nice and well, but they do require a large enough metal base, either capacitively or electrically coupled.

Most sites selling these antennas won't tell you this, assuming you know that it's only one half of the antenna.

Sergegsx

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Re: Several questions: Antenna, range, schematic
« Reply #4 on: July 04, 2017, 12:37:07 PM »
interesting point captcha!

The actual upright antenna does seem to be connected to the center pin, however I have measured the ground of the connector and there is no continuity to the base of the antenna.
This means the ground plane of the antenna is just a 30mm diameter area inside the magnetic base.

I have opened the base of the antenna and connected the ground to a 20x20cm metal sheet and readings are -81dB, whereas if I hold the antenna in may hand its -91dB

However, this does not show an improvement over a single wire antenna of the moteino (good job felix) but I would like to be able to improve a bit.

btw, I am connecting this antenna to the gateway moteino, keeping the nodes with the original antenna, I should see improvement anyway right?

thanks

joelucid

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Re: Several questions: Antenna, range, schematic
« Reply #5 on: July 04, 2017, 05:08:03 PM »
Quote
I have an official moteino which although manages to send packages and RSSI reports -80dB, I sometimes loose packages.

The sensitivity of the RFM69 radios at the stock 55kbit bitrate is < -100 dBm. If you lose a significant amount of packets at -80 dBm you have a different problem. Typical is that either the sender sees so much noise that it never actually transmits the packet (check canSend() and the CSMA limit define). Or the receiver (likely the gw) is so noisy that even at -80 dBm your signal to noise ratio is insufficient.

If the problem is noise pickup from the gateway it can often be solved by using captcha's dipoles at a safe distance from the rest of the gateway.

Joe