Hi vk4ffab. Thanks for your reply. But I think you overread something:
Without this I get -65dbm and with about -40dbm
This means the Backend outputs around -65dbm and the first stage -40dbm. I mean, if I would have +5dbm why would I bother amplifying anything? I have no way to directly measure this however. It is possible, that my phone is not really the best. But the manufacturer claims at most 100mW of output power (consisting of 4 channels). Originally I measure however -20db. Okay lets do some simple math:
The 20dbm in total for a single channel are 14dbm for the original circuit. My phone measures -20dbm (a lot of loss, but very repeatable measurements with multiple devices). Okay, I measure -40dbm with a single of the replacement Frontend IC's. That is 20db lower, so +14dbm-20db = -6dbm. This is well within range of what the input of these ICs can handle according to the spec.
Okay, this clearly shows that the -65dbm at the beginning are incorrect, but it backs up that I have 1 order of magnitude of safety left. That also means, that if it works, the output power basically lands right in the perfect spot of +20dbm. That would actually be absolutely amazing.
My question is just, if you look at the circuit: Can you chain 2 of these ICs in series, or do you need some passives in between? Remember, I do not look for perfect performance at all. It just needs to work reasonable for a low effort. I would think, that the Output is basically at DC level, just like the input - so I would think it should be fine. All circuits use 3.3V as input, so I expect the voltages to be at equally fine levels.
TLDR:
- Input power is definitely within safe range
- Question: Do I absolutely need some passives or could a direct ANT Out to RXTX work with a direct connection? (ignore impedance and parasitics for now)
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