Can you get an infrared remote's signal modulation with an Arduino?
You can't do it with a common IR receiver like TSOP4840 or CHQ0038 because those already have a demodulator built in (see the block diagram in the datasheet).

You need an AC coupled sensor like the TSMP58000.

The IRLib2 Arduino infrared library has an example sketch that determines the modulation frequency. The procedure is described in more detail in the manual.



By the way, in my opinion it's more likely that you have some timing, decoding or range problem than that the TV uses something other than 38 kHz. Do you have an oscilloscope/logic analyzer and a second IR receiver?