shield needs to be grounded
Please cover the side flanks:
For shielding AND cooling (EMI foam):
was also considering using flat brass sheet, with only the skirt printed. or make it even simpler. the skirt could be hotglue, except for a few wire risers soldered between the shield and the gnd pads. anything to take less tooling, not that i don’t have access to all the relevant tools, just refuse to build a die fixture for a oneoff
I’m afraid that the information provided to you by the seller is the closest to reality. It is a problem with the power amplifiers.
Join me in these investigations:
This is a picture of the 2.4GHz RF part of an AX router. The main chip (MediaTek MT7976GN) is visible and the four RF Front-End Module (FEM), i.e. the dedicated power amplifier chips (KCT8239SD), are also clearly visualized:
Now, the RF part at 5GHz, with dedicated MediaTek MT7976AN chip and its four dedicated FEM/power amplifier chips (KCT8539HE FEM):
If we take a look at the picture of the BE14 board:
Both front and back, no FEM is displayed, so these chips appear to carry eFEM and as many have already found, the performance of this module can exhibit highly variable range. That is, they work this way by design, as the vendor indicates.
The question that should be asked is:
Is there a possibility that, through drivers or EEPROM firmware, they will improve the management of the eFEM (embedded Front-End Module, also known as integrated power amplifiers) of the BE14 board?
If not, do we know if SinoVoIP will release an improved revision of the eFEM chips or will they make a dedicated FEM design instead?
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You haven’t actually investigated anything, this is all well known from beforehand the issue isn’t in the range it’s rather the noise (excluding boards with 7dbm limit bug)
IMO the BE14 “as-is” is a lost cause. It’s become crystal clear, as your post shows, that the real issue is the hardware itself.
I have no idea if it was done on purpose or not, but it’s just not designed to the same standards that an off the shelf router would be. That’s why everyone’s attempts at shielding, including my own, have made no difference at all.
If we want anything useable from the BE14, the real and slightly crazy question should be;
Is it possible to design a separate PCB to add the proper FEMs?
It’s actually really funny I logged in and saw your comment because I have been thinking;
- What would be needed to add FEMs with as little modification as possible?
- Could the boards could be made for a reasonable price?
- It absolutely must be done without the need of custom drivers or software.
This led me to doing some research into filter and amplifier circuits, though I should mention I am definitely not an expert in this area!
But ultimately this led me to a resounding…maybe.
Since the issue is both noise from the BE14’s poor design and weak amplifiers, this led down a pretty interesting rabbit hole. And anyone who knows more about this please feel free to chime in.
The idea is a small custom PCB, the R4 even has additional mounting posts on the bottom that are unused.
- The PCB would attach to the existing u.FL connectors on the BE14. Keeping the cables as short as possible.
- First in line would be a filter specific to the band in use. For example the Qorvo QPQ5600TR13 to help clean up the signal provided by the BE14. (Might be overkill)
- That then feeds to a FEM such as the Qorvo QPF4659TR13. This contains an additional BPF along with the amplifier circuit and other logic.
- (Again not an expert) From my understanding the FEM needs to know if it needs to be in RX or TX mode since WiFi is Half-Duplex. The solutions from Qorvo contain a SPDT switch to handle the actual switching part of this.
- The RX/TX switching needs to be controlled by something. This is where the Qorvo chips help again with a built in coupler, and constant slope voltage logarithmic power detector which will provide a signal to tell us what the radio on the BE14 is trying to do (RX or TX).
- The signal provided by the power detector can be fed into a small MCU that can be programmed to handle telling the FEMS which mode they need to be in. Maybe something like a STM32L0 would be fast enough?
- The entire circuit can be fed by the 5V pins provided by the R4 itself near the main power input, and fed through a simple regulator and filtering circuit.
- Beyond that I believe the rest of the circuit would be made up of passive components.
My example included only components for 6GHz. The same would need to be done for the 2.4/5Ghz connectors as well. Each antenna would have its own circuit. (Just like what’s shown in your pictures above).
The idea may be totally asinine for all I know, and I cannot stress enough that dealing with RF and PCB design are not areas I’m an expert in. All I can say is theoretically the idea seems sound, and all of the components can be bought on Mouser for under $5…
Or, maybe Sinovoip will release the BE19, and it could have these issues fixed? Then it could be packetized with the needed extra antennas and cables as an upgrade for the BE14 kit.
Very interesting…
It reminded me of these gadgets:
Anyway, these are gadgets that require external power for each antenna. Killing flies with cannons, totally exaggerated. I do not know to what extent they do or do not improve the signal.
Your approach of something more integrated is more interesting.
That would definitely be the preferred option. Or even just a new revision of the BE14 with the issues fixed.