[Hackrf-dev] interested in lower minimum frequency (LF range)

[Dominic Spill]

On 18 November 2015 at 13:40, Frank Ch. Eigler <fche at elastic.org> wrote:
>
> I'm interested in receiving and low-power transmitting with the HackRF
> at LF-range frequencies below, the 1MHz floor.  What are the limiting
> factors in the hardware or firmware that would impede transmitting a
> 100kHz AM signal?

The HackRF One transmit path passes a stream of complex bytes to two
DACs, then combines these two analogue signals and finally mixes the
signal up to the desired transmit frequency (in fact, HackRF shifts
the signal twice, but that's not important for now).  The hardware
limitations will be filters at the baseband and at the mixing stage,
which will filter out your LF signal.

For this sort of operation I would normally recommend a ham-it-up
device[1], but even they only go down to HF/MF.  Perhaps other
upconverters are available, but I haven't seen any to recommend.

> As I understand it, receiving is probably OK via decimation in software.

Have you tried this with HackRF One?  I would assume that you will
find the same issue with filters.

Dominic

[1] https://www.nooelec.com/store/ham-it-up.html