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#1 2011-10-13 22:12:45

maxpowel
Member
Registered: 2008-10-19
Posts: 5

HF antenna weird behaviour

I have an antenna that get 9,5V (down to 6 when tag is near). I read that this is enough for read from a tag but when I try to read a tag, proxmark cannot find anything.
Other commands like detect reader works fine but "hf 14b read" always get "bad CRC". I also read that this problem is caused by insufficient voltaje but in the antennas in proxmark3.com gives 8-9V and because of that I'm confused.
My antenna was built according to roel's guide.

Anything that might shed some light would be grateful

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#2 2011-10-14 07:50:24

Cex
Contributor
Registered: 2009-12-14
Posts: 104

Re: HF antenna weird behaviour

I think you need around 12V for the antenna to work well.
If you built Roel's one (the one using an USB cable) try to make the loop a little bigger/smaller, or modify the shape. This way the inductance get modified and you could get better tuning (so higher voltage).

Hope this helps.

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#3 2011-10-14 20:21:06

maxpowel
Member
Registered: 2008-10-19
Posts: 5

Re: HF antenna weird behaviour

Thank you for your answer!
Other trouble while making the antenna is the C35 capacitor. The guide says that for a 100pF capacitor the length of the cable should be shorter but I dont know what proportion. In only found an equation that relates inductance, frecuency and the capacitor capacity but nothing about the cable length.

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