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▲ 3 r/meshtastic_meshcore+1 crossposts

Can the cheap 20dB saw filters from AliExpress survive at 22dB

Hi,

I bought some of the Seeed Xiao nrf + wio board combos and in the data sheet it says 22dBm max power.

I live close to cell towers and need to use filters, as far as my experience shows so far with heltec devices. For the heltecs I bought expensive saw filters from a shop in Germany which support up to 28dB and have low loss.

But the Seeed nrf chips I bought for cheap optimized repeaters placed in the countryside. So no large investment wanted. I discovered cheap saw filters on AliExpress and bought some. They say max 20dB. Do any of you have experience with them? I'm sure some of you have already tested them.

Do I need to limit the repeater tx to 20 to not fry them? I know 22 is a lot more energy in mW than 20, but maybe they can manage that? I don't want to put my repeaters in hard to reach places and have them break down after 6 weeks.

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u/Type-21 — 10 hours ago
▲ 14 r/meshtastic_meshcore+1 crossposts

Solar Panel vs RAK4601

Hey everyone,
I built my first MeshCore repeater, designed to run autonomously powered by a solar panel and batteries (RAK4601 + 5V panel + 21700 battery).

So far so good, everything seems to work, except for one thing: the solar panel doesn't seem to be charging properly. Right after (re)plugging it in, charging starts immediately: the charge LED lights up bright red, voltage rises (per telemetry).

Once it gets dark, the voltage naturally stops rising — but the next day, charging doesn't start again either. Despite the 4.1V threshold mentioned by RAK (https://forum.rakwireless.com/t/rak-repeater-mini-not-charging/14716).

During the day the LED only glows very faintly; at night in darkness it was off.

Before I deploy the repeater, I'd like to get this sorted. Could the charge controller be defective? Or would it not charge at all in that case? Or is the threshold significantly lower before it kicks in again? And why did it kick in when I first plugged it in?

One more thing worth mentioning: the repeater ran incorrectly connected for about a day — I connected the solar panel FIRST and the battery SECOND, which is contrary to the manual. Could this potentially have damaged something?

Fact check: the panel is correctly oriented, has no shade during sun hours (approx. 6am–4pm), open-circuit output is 5.3V.

Claude mentioned a possible explanation related to the TP4054 charge controller (which appears to be used in the RAK19003). According to its datasheet, a new charge cycle only starts when:

  1. The VCC input voltage rises above the UVLO threshold (i.e. panel newly connected or voltage freshly applied)
  2. A battery is newly connected
  3. The battery voltage drops below ~2.9V (trickle charge mode)

This would explain why charging starts immediately after re-plugging the panel (condition 1), but doesn't restart automatically the next morning: if the panel voltage rises too slowly at sunrise (gradual dawn light), the UVLO threshold may not be crossed cleanly enough to trigger a new charge cycle?

Has anyone experienced similar behavior, and does this diagnosis sound right? I am not THAT familiar in electronics and cannot verify if this explanation makes sense.

Thank you for your time reading this, I hope I can make clear what's the problem.

u/sinanmuslu — 3 days ago