Wednesday, November 11, 2015

TinyLNA housing selection

I figure the next step is to make new antennas to improve my reception.  However, I have a problem in that I'd would like to characterize the antennas so I know that I've made them correctly.  I have no equipment to do this, so I am planning on making my own using guidance from one specific post on the RTL-SDR webpage.  I need a white noise source.  I would also like to have an LNA to boost the signal from the antennas I make.  I think I can kill two birds with one stone.

Most white noise sources I've seen are a rather simple source with one or two LNA stages.  So making my own LNA could go right into the white noise source.  So step one is to get an LNA.  I've reviewed a couple and it seems the LNA4ALL is very popular.  It's a good solution for $20.  However, it really needs to have the case which adds a significant cost ($60).  So I've decided to design my own customized LNA based on the LNA4ALL.

I've found a housing that I believe will work well.  It's about $8 which is way lower than $60.  However, this would mean I would have to feed DC power up the line.  But the RTL-SDR has a provision for that with a build-in bias-T.  I can solder a jumper to the RTL-SDR to get ~4.5V DC up the wire.

I believe I can fit a circuit board inside this housing with an LNA on it.  For sure it will be a tight fit to get a PCB in there with everything I need but I believe it can be done.  The shield will slide over the top of it providing a good ground and EMI/ESD protection.  Next step is to figure out how much space I actually have to cram circuits in there.

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