#garfield Logs

Nov 04 2022

01:08 AM rue_mohr: drat, I wanted to make a copper oxide diode today
07:47 AM aandrew: boo. I need to build a simple (key word) 20m (14.67MHz) receiver. I want to feed the audio into a uc to decode the CHU time signal
07:47 AM aandrew: I think I found one, gotta see if I can still build like this
07:50 AM aandrew: I need to find my torroid bucket
07:51 AM polprog: 14.67M sounds low enough for a passive receiver
07:51 AM polprog: antenna matched to some narrowband filter and a simple diode detector
07:51 AM polprog: perhaps you can even get a SAW filter like pagers used, their receivers were simple to save power
07:51 AM aandrew: yep that's the idea actaully
07:51 AM polprog: :D
07:51 AM aandrew: not the SAW filter but the diode
07:52 AM aandrew: https://miscdotgeek.com/building-a-direct-conversion-receiver-part-3/
07:52 AM aandrew: the same station is on 3.33MHz, 7.85MHz and 14.67MHz but the latter should be best for me
07:53 AM polprog: i was reading about ULF radios
07:53 AM polprog: ultra low frequency
07:53 AM polprog: gotta run to the grocery shop tho
07:53 AM polprog: have fun with the radio
07:54 AM polprog: i cant wait to finish the thesis, i have this many projects in the backlog
07:57 AM aandrew: yeah ULF is weird
07:57 AM aandrew: I gotta take some chicken out of the freezer or my kids will not have dinner
07:58 AM aandrew: and I should probably make a coffee
08:03 AM aandrew: maybe I should just try to do it all in software. direct conversion, 1 bit adc, just need a good tuned filter and LNA
08:18 AM rue_mohr: 14.67?
08:18 AM rue_mohr: modify an RC car reciever
10:24 AM aandrew: yeah that might be a pretty slick way to do it, next question is do I have any cheap RC cars that aren't 27 or 49MHz
10:24 AM aandrew: SAW filters don't seem to go down that low
10:26 AM rue_mohr: 14.958 ?
10:26 AM rue_mohr: is that what I remember some being?
10:36 AM aandrew: yeah some of these numbers "stick" in my head
10:36 AM aandrew: so I don't know if they're actually useful or just my stupid brain
02:45 PM polprog: ive scripted my smartcard reader
02:46 PM polprog: i need some way in python to download the traces from the scope
03:17 PM aandrew: I played with smartcards a bit waaaaaay back in the satellite hacking days
05:22 PM aandrew: so if I want to design a bandpass filter that hangs directly off of a 1/4 wave or "wire" antenna, should I be using 377 ohms as the impedance of the "input" side of the antenna?
05:22 PM aandrew: er filter
05:50 PM rue_shop1: http://www.sparkbangbuzz.com/els/zincosc-el.htm
05:53 PM Tom_L: new uses for tin bolts & lead sinkers
05:55 PM rue_mohr: well
05:55 PM rue_mohr: almost got something working
10:17 PM rue_shop3: trying to make a neative resistor
10:17 PM rue_shop3: I think I got one thats holding