Hi again,
I've managed to build a few nodes using Mega2560, level converter, AM1117 LDO, using pretty long breadboard cables and lousy RF wiring, antenna measured by eye, all working good and stable. Excellent RSSI. (Maybe from the perfume chip box
)
Then I've crammed all up on some piece of perfboard, keeping all wires short, neaty, tidy.
And problems start to arise:
-only big packets going through, no ACK gets across
-replacing chip roles (send/receive) the same happens
-it only works when "cuddling" the chip, touching GND or the antenna
-the antennas were exactly 86mm long, as calculated for 868Mhz, tried trimming them to 85...84...83..., nothing
-added decoupling caps 10nF, 100nF, 10uF, 100uF, nothing
What i tried:
CUT the antenna in half and it started working but with really low rssi, like -70 at a few centimeters apart, but I get ACKs.
REPLACED antennas with 12cm antenna, works but still low rssi
CURLED 12cm antenna as in the picture, the signal is -93 at 5 meters through a door, direct sight, radio set at full power.
I've read somebody else having the same "chip needs cuddling" problem and it was due to some missmarked chips. So I did try the 433Mhz setting with the 86mm antennas but only got worse rssi and working seldomly when touching the antenna. Felix maybe you can shed some light on how to identify the correct freq of the RFM69HW.
And maybe somebody can explain how come the chip refuses to work when using the right antenna length but starts working when using a much shorter or longer antenna.
Thank you.