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--- filters [2024/10/03 23:28] – river
+++ filters [2024/10/04 01:57] (current) – river
@@ Line 15: / Line 15: @@
 I found, after a bit more searching, some LC filters with fairly good looking specs.
-===== Aliexpresss 868MHz bandpass =====
+===== Aliexpress 868MHz bandpass =====
 [[https://www.aliexpress.com/item/1005007539598090.html]]
@@ Line 55: / Line 55: @@
 I believe I was testing at +5dBm. Device power was set to "-4dB" on low frequency transmitter, and "+5dB" on high frequency one, which a forum, but not the manual, says changes over at 140 MHz. I would like to try on higher power when I get an amplifier.
+Chip marked Gr 2J, or Qr 2J?
+Ohmeter shows open circuit on input, output, and between them.
+The ports are marked in and out. I tried testing the board backwards, and the results were almost the same, but I think there is a small difference in RL.
+Testing one board, at 870 MHz, RL forwards was -17.41dB, backwards -17.04dB. S21 forwards -1.69dB, backwards -1.67dB. I think it probably doesn't matter which way it is connected.
+I noticed the return loss numbers are significantly different from earalier measurements, which as seen in picture above are around -30dB, not -17dB. I don't think I changed anything. Maybe because the LiteVNA was left to warm up? That is a huge difference though. I tried recalibrating and then got numbers around -25dB, closer to what we had before.