Re: Inexpensive USB-only SDR
- Re the Funcube Dongle.
It may be "not cheap" bo comparison to the simple softrock kits. But it
does come with a built in 96k sampling sound codec chip, and lots of
tweakable (via freely available software) filter and gain settings, post
mixer, pre digitising.
A portion of your money also goes to Amsat, to help fund the Funcube
It's not a kit, as the codec chip (among other things, I think including
the DTTV front end chip) was not condusive to DIY assembly, without a
reflow oven. Also, if you think some of the SMD parts used in the
SoftRock kits, at tiddly, "you aint seen nothing yet." Most of the parts
in the FCD are truly tiny. Realy tiny! Not the sort of thing you can
easily assemble yourself, although that's how the first few "production"
dongles were built by it's designer. Even he said it was not for the
feint of heart, or those with less than 20:20 close up vision.
He also says, that some 50% of the parts, are EMC/EMI/ESD related, to
keep the digital stuff out of the analogue channels, and for the
antistatic safety of the dongle active parts themselves.
When plugged into a windows PC, it "just appears" as another available
sound interface, and has to be said, it works *VERY* well indeed!
The controls (LO frequency selection etc) are accessed via the HID class
device it also "appears as". The freely available software, and firmware
updates are of good quality too. There is also a custom ExtIO.DLL for
it, for some of the popular SDR application software.
The only downside AFICT, is the need for an upconverter for signals below
(about) 70MHz. It also (due to it's top sample rate of 96k) has some
dificulty with FM broadcast signals distorting. But that's not it's
intended purpose, though it does work quite well for that, with a "paper
clip" antenna, just to listen to the news!
For VHF/UHF use, up to low GHz, it's suprisingly sensitive, and very
usable. It is also even able to power (up the coax) any LNA's you might
need via a built in bias tee. All that in a single USB dongle form
You do get a lot for your money with the FCD, but it will not suit
everyone, and it's RX only of course..
The current converter kits (I have one too, yet to assemble it due to
time constraints) put the IF at about 106MHz. Some have concerns about
local FM broadcast breakthrough, but others who have used it expecting
trouble, in fact say it's not a problem. You could change the LO
oscilator part anyway for a quieter IF frequency if you needed to.
I think there are also murmerings of a mk2 upconverter design to address
some people's comments. The developer of that, is in no way connected to
the Funcube project AFIK.