Ive looked through all the posts on the subject of external antennas mods but found them closed to further posts.
I was just about to start planning position of holes etc and got to taking pics before I start.
I noticed that the internal foil antenna for Zwave has a ground plane and an obvious longer trace than the Zigbee one - an Ohms check shows open between ground and feed, which I expected,
But the Ground plane and feed on the Zigbee antenna foil is one continuous track and reads as a short?
Im not an RF expert but know from CB days that Rf antennas have a ground plane of some sort. eg. the car is the ground plane of a mag mount antenna.
I checked many pics of internal foil antennas and have not come across one where the ground plane and feed are linked/shorted together. Close together parallel to give correct impedance maybe.
Surely this is an error and not good for the Tx output and very poor range? Has this been identified previously
I just added a pic to show blue trace from the screen/ground and the live/feed to the centre conductor.
Although it wont matter to me now, i wonder if poor range is caused by this for other users with non modded HE C7s
This may have been closed as part of a clean-up but it's definitely not old news.
Many of us did this mod in 2021/2022 and @lewis.heidrick has been a great help.
I think you maybe onto something. I for one, know the tremendous improvement with adding a Zigbee external antenna. I think everyone who did the mod went for 50 ohm impedance to stay compatible. I know we have at least a few engineers around here. Let's seek their input @JohnRob and @lewis.heidrick what do you guys think about the above discovery?
@dnickel There is no bridge between the 2 solder points, that is the clear centre conductor insulation. looked with high power magnifier as that is what it looked like to me at first.
measuring the trace length from the L shape tip down to the centre conductor and back up to the next bend is around 37mm, very close to the 1/4 wavelength of 2.4Ghz.
To me , from the trace at the top of the blue marked track between the parallel legs , 5.5mm down from the right side blue marked trace should be cut through to give a length of 31.5mm antenna length ( or 31.23mm to be exact)
Got the EXT.antenna fitted for Zigbee in about 30 mins or so from measuring (exactly) , drilling, removing the shorted foil antenna, soldering the U.fl connector to the board...after spending about 30mins looking for the dammed thing which popped out of the surface mount tape it was held in while trying to peel back the film, 2m away it flew... .
I started this project because the garage door switch kept eating batteries every couple of weeks and I put it down to it having a hard time transmitting / acknowledging at a distance of 10m through a glass door and brick wall. I even tried adding a 1/4 wave external dipole antenna to the Zigbee sonoff door contact which helped turn the light on quicker.
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