[USRP-users] Amplifiers for USRP Transmission

Evan Chavis echavis at umich.edu
Mon Jul 6 15:32:55 EDT 2015


Hello USRP users,

I've been working with a USRP1 to transmit an amplitude modulated signal to
a very basic improvised receiver, basically just a wire of length
corresponding to the frequency I'm transmitting at attached to a microphone
such that the microphone is picking up the signals on the wire as it would
audible noises.  I'm using an SBX daughterboard (which can produce 100 mW)
and a log periodic antenna (with 5-6 dbi gain).  I can get a decent
transmission at a range of up to about 25 cm, although it is best at a
distance of just a few cm.  I've got the gain set with GnuRadio as high as
possible without causing distortion, and I'm looking to improve the range
of possible transmission.

My questions are, what do I need to consider when looking for an amplifier
to use with a USRP, are there any special problems a beginner would be
likely to miss when trying to use those 2 things together?  Also, if an
amplifier's gain is listed at 20 dB, would that be 20 dB on top of the 31.5
the daughterboard is capable of outputting, or would the amplifier be
useless in that it is capable of providing less power than the
daughterboard itself?  And third, how is a device such as this one:
http://www.minicircuits.com/pdfs/ZX60-V63+.pdf powered?  The data-sheet
gives the numbers 5 V and 69 mA but I don't see an obvious way to power it
aside from just soldering wires onto the marked bumps that say +5 and
ground, is that the actual intended way to do it?

Many thanks for any input and have a great day
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