The system is working for some months, and noticed that the lowest level I see in the received messages (I log the RSSI for each received message) was -94dBm. Also noticed that when the average receive level goes down to about -85dBm I start to lose some messages, even using retries. For the standard config shouldn't be expected to receive messages down to -110dBm? This is the receiver sensitivity and the configured receiver threshold, so I was expecting to see messages received with an RSSI level near -110dBm, but it seems to be limiting the reception at about -94dBm. Am I missing some point here?
As an alternative to solve this sensitivity problem, one solution could be to reduce the bandwidth and bitrate. I have already discussed this in this forum a few months ago, I have made some tests in the past and with your help I have obtained better sensitivity results but had the need to calibrate the nodes to minimize the frequency error and to compensate the frequency for temperature variation - between day and night we could have a change of more than 20ºC in the outdoor node and almost no variation in the indoor node.
Another way could be to get a better antenna, perhaps a simple dipole for a test, at least it is not so dependent of the ground plane as the 1/4 wave antenna.
Do you have any other suggestions?
RegTestLna (0x58)
SensitivityBoost
High sensitivity or normal sensitivity mode:
0x1B Normal mode
0x2D High sensitivity mode
I think that to raise the antenna could avoid the cars in the middle of the RF link between the two nodes, reducing this problem, don't you think?
I've found the most common cause for these issues to be noise at the receiver.
Dec 21 11:59:03 esp_817a48.lx [38] [RX_RSSI:-102]
Dec 21 11:59:03 esp_817a48.lx thol1 -> nd:38,nr:80,pw:-17,ph:1,vc:298,t:226,h:410,mv:267,fp:7
Dec 21 11:59:06 esp_817a48.lx [38] [RX_RSSI:-107]
Dec 21 11:59:06 esp_817a48.lx thol1 -> nd:38,nr:81,pw:-17,ph:1,vc:295,t:226,h:411,mv:282,fp:7
Dec 21 11:59:09 esp_817a48.lx [38] [RX_RSSI:-105]
Dec 21 11:59:09 esp_817a48.lx thol1 -> nd:38,nr:82,pw:-17,ph:1,vc:296,t:226,h:412,mv:282,fp:7
Dec 21 11:59:12 esp_817a48.lx [38] [RX_RSSI:-101]
Dec 21 11:59:12 esp_817a48.lx thol1 -> nd:38,nr:83,pw:-17,ph:1,vc:298,t:226,h:413,mv:281,fp:7
Dec 21 11:59:14 esp_817a48.lx [38] [RX_RSSI:-104]
Dec 21 11:59:14 esp_817a48.lx thol1 -> nd:38,nr:84,pw:-17,ph:1,vc:296,t:226,h:416,mv:281,fp:7
Dec 21 11:59:17 esp_817a48.lx [38] [RX_RSSI:-104]
Dec 21 11:59:17 esp_817a48.lx thol1 -> nd:38,nr:85,pw:-17,ph:1,vc:298,t:226,h:418,mv:281,fp:7
Dec 21 11:59:20 esp_817a48.lx [38] [RX_RSSI:-104]
Dec 21 11:59:20 esp_817a48.lx thol1 -> nd:38,nr:86,pw:-17,ph:1,vc:299,t:226,h:420,mv:282,fp:7
This power supply decoupling you have done was only to the power of the RFM69HW right? I'm assuming that you have separated the power supply lines for the ESP and for the RFM69, and introduced this decoupling on the RFM69 side, can you confirm?
I recall that originally (https://lowpowerlab.com/forum/projects/(update)-rfm69-library-for-esp8266-moteino-compatible!/msg13730/#msg13730), with a more rough and ready dipole setup, you thought you were getting a 16dBm improvement.
I was thinking if it wouldn't be better to have two separate filters to supply the RFM69 and the ESP8266?
BTW, I was able to send someone to check the gateway antenna placement, he found out that he had placed the antenna very close to a metallic window frame, he just re-positioning the antenna some 10cm away and that gave a signal about 10dBm better :-)
Or better yet three filters - one to filter any noise entering through the power line and then one radio and the MCU. I have the pi filter on the power supply and then 500pF and 0.1uF at the radio and the MCU and I chose the 500pF especially to filter in the 430 mhz area.
Do you know the reason for this behavior? I'm not finding it! Could it be only "wrong statistics", that I didn't take a log enough observation to have meaning? I just let it receive about 10 messages (the node transmits only one message per minute) for each test...
Then I changed the LNA impedance for 200 ohm ( radio.writeReg(0x18, 0x88);). I started to receive messages without failures, with an RSSI level of -95dB (I got messages between -92 and -97dB without failures).
hen I activated the LNA sensitivity boost, and it started again to receive messages, now at about -102dB, between -101 and -105, without failures.
FWIW attached is my current design which works pretty well. I have about 10 dBm less noise on this one than without filters. Good thing about a ESP8266 based gateway is that you only have power coming in (other than doing debug on the FTDI header). So fix that and things should be fine.
I think I'll play around with adding the choke again. If the issue was really the two grounds may this could help even more.
BTW, now that this one doesn't have much conducted noise I notice the radiated noise much more. Fairly significant: switching my LCD displays on or having the router near a 433mhz AC plug increases noise levels by more than 10 dBm!
And here is the gateway together with 3 small loop th-motes and captcha's dipole. Th-motes have a 32.7k clock crystal and - drum-roll, this is my first mote with one - an on/off switch. :) An air trimmer is mounted on the underside of the board.
(http://i.imgur.com/rv9QJYY.jpg?1)
Joe
I just now ordered your board from osh park, as well as captcha's PCB antenna. Would you mind showing closeups of how you made the cable connections on the two pieces?