[CQ] Cheap SDRs?

[Josh Myer]

First off, thank you to everyone who replied, there was lots of
useful/valuable input in here!

I spent a lot of time poking around, trying to feel out the
possibilities at the same time as exploring the options of what kinds
of things I want to do.

Here's the single most valuable link I found in the process:

http://f4dan.free.fr/sdr_eng.html

>From there, you can do your own research, but here's what I found for
myself: There isn't an SDR for under $1000 that isn't only useful for
HF, and none for under $100 that are generally useful.  Basically,
with any device you can get for under $150, you're getting into the
"QRP of the SDR world," where everything is crappy, but part of the
fun is rolling with the crap.

The Soft66AD gaspo linked to is surprisingly great, but it only really
goes to 70MHz (6m band and longer), and comes in a little over $100.
(http://zao.jp/radio/soft66ad)

The SoftRock looks good if you're keen on tapping into your radio, and
is incredibly cheap.  I'm a little nervous about both of these.

Related to what Dr J posted, here's someone using a bit-twiddled
BrookTree BT8xx to dump raw signal, which is awesome:
http://www.domenech.org/homebrew-sdr/receiver-1.htm  Amusingly, he's
just recording signal with the monitor off, and decoding it offline
(this probably made a lot more sense in the Spain of 2004, though I'd
have thought GHz class machines were common by then).

As usual, TAPR looks promising but mostly just makes me want to die (I
spent a lot of time with their wonderful documentation for the
wonderful AX.25 protocol when hacking together ArdPRS).  In
particular: their SDR stuff sounds interesting, but most of it's out
of stock, and, in any case, you have to buy a eurocard backplane and a
half-dozen daughterboards to do anything.  Admittedly, this makes
things nice and modular, but I think it comes out more expensive than
a USRP+daughterboards (assuming you could actually, y'know, buy the
TAPR kits).  If you want more info on the TAPR stuff, go to
http://www.tapr.org/kits_atlas.html is the backplane, try to go
through the list at the bottom in alphabetical order, lest you get
irrationally angry at the TAPR guys and write a really long, annoyed
sounding paragraph about them in an SDR roundup.

Other than that, there's the USRP.  Ettus has a really solid product
which is a little rough as a ham radio, but is great for doing
research.  The only real "failing" is that it's OMFG expensive.  The
lowest base unit is priced near at the low end of the mid-range units.
 But then you have to spend another $75 to get a basic HF receiver,
and another $100 to get up above 50MHz.  And then another $75 to
transmit in HF, and ...  On the positive side, the USRP only has 4
slots to fill with expensive expansion cards, so you can't go too
crazy with it.

The newer USRPs look really great, but they're even more expensive.
I'm sure they're reasonably good deals for what they are, but,
starting at $1700 for the latest unit, plus all of the same
daughterboard pricing, it's serious change.

For my purposes, it seems like the USRP is a fantastic unit, and I can
probably get by with the lowest end one and a few expensive
daughterboards.

Thanks again to everyone for their great input, and I hope this
round-up is helpful to anyone else looking to do SDR now or in the
future!
--
/jbm


On Sat, Nov 13, 2010 at 9:31 PM, Josh Myer <josh at joshisanerd.com> wrote:
> Does anyone have experience with a cheap-ish SDRs?
>
> In particular, I'm looking for something that will let me tune in to
> ATSC or FM radio bands, and which has enough bandwidth to pass back
> the signal.  For FM, this is pretty simple (~50kHz bandwidth, so need
> ~100kHz samples, at 16b/S it's only 200kBps), but ATSC is a bit
> trickier (6MHz bandwidth).
>
> GPS would also be of interest, but 1.5GHz seems like it's just asking
> for trouble.
>
> Thanks!
> --
> Josh Myer 650.248.3796
>  josh at joshisanerd.com
>



-- 
Josh Myer 650.248.3796
 josh at joshisanerd.com