[Hackrf-dev] foldover

[McDonald, J Douglas]

I got my HAckRF yesterday and am playing
with it. This is using SDR# on Windows.

It seems to work somewhat OK if you get the various gains set
so there is no problem caused by it, apparently,
having no dithering before the ADC.But except
for the wide bandwidth the performance is far inferior
to the heap DVB-T dongles.

In particular in "wraparound" of the FFTs is abysmal. It renders it
virtually useless for SW reception. It seems to work equally
well or badly with or without one of those 125
M Hz upconvertors; however I am feeding it from a fairly good
antenna and  a very good source follower 50 Ohm out preamp
at the antenna end of about 50 feet of coax.

Using the cheapie dongles, though they have only 2.8 MHz bandwidth,
the foldover is pretty well down 800 kHz from the foldover pint.
On the HackRF,  its still visible 10 MHz on the wrong side!

Am I doing something wrong to cause this to happen? Its not just at
shortwave, the same thing happens in the UHF TV band. I had
expected a device as expensive as this to have a really good say 16 to
19 MHz wide filter before the digitizer.

My ultimate goal was to try to implement my ATSC DTV patent
in a real receiver; the foldover won't bother this
due to our local TV allocations.

Doug McDonald
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