HackRF
simply using a second HackRF One, it made sense to keep the device small, portable, and low cost for everyone who
does not require full-duplex operation.
Question: How could the HackRF One design be changed to make it full-duplex?
Answer: The HackRF One hardware design is actually full-duplex (at lower sample rates) from the USB connection
through the ADC/DAC. The RF section is the only part of the design that cannot support full-duplex operation. The
easiest way to make HackRF One full-duplex would be to create an add-on board that duplicates the RF section and
also provides an external power input (from a wall wart, for example) for the additional power required. This would
also require software effort; the firmware, CPLD, libhackrf, and other host software would all need work to support
full-duplex operation.
If you were to try to redesign the RF section on HackRF One to support full-duplex, the main thing to focus on would
be the MAX2837 (intermediate frequency transceiver). This part is half-duplex, so you would either need two of them
or you would have to redesign the RF section to use something other than the MAX2837, likely resulting in a radically
different design. If you used two MAX2837s you might be able to use one RFFC5071 instead of two RFFC5072s.
7.10 What is the receive sensibility of HackRF?
Question: What is the minimum signal power level that can be detected by HackRF?
Answer: This isn’t a question that can be answered for a general purpose SDR platform such as HackRF. Any answer
would be very specific to a particular application. For example, an answerable question might be: What is the minimum
power level in dBm of modulation M at frequency F that can be detected by HackRF One with software S under
configuration C at a bit error rate of no more than E%? Changing any of those variables (M, F, S, C, or E) would
change the answer to the question. Even a seemingly minor software update might result in a significantly different
answer. To learn the exact answer for a specific application, you would have to measure it yourself.
HackRF’s concrete specifications include operating frequency range, maximum sample rate, and dynamic range in
bits. These specifications can be used to roughly determine the suitability of HackRF for a given application. Testing
is required to finely measure performance in an application. Performance can typically be enhanced significantly by
selecting an appropriate antenna, external amplifier, and/or external filter for the application.
7.11 Troubleshooting
Question: Why is a known signal at an incorrect frequency which changes at a surprising rate when changing the
center frequency?
Answer: You may have a version mismatch between the firmware and CPLD bitstream. [Update your firmware to the
latest release](Updating Firmware) to solve this problem.
28 Chapter 7. FAQ
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