100KHz - 1.7GHz RTL Based SDR Kit

[silverspring]

A friend of mine bought this very kit 5 weeks ago. He says there were no build instructions. I haven't really taken a good look at it, but what I remember seeing was a PCB with component values printed on the silkscreen so the majority of the kit should be self-explanatory. Not sure about that broadband transformer though - that could be tricky, although like I said I haven't had a chance to look at it properly. I do remember a dongle (R820T based) was supplied with the kit that you would crack open out of it's plastic case and transplant it onto the PCB supplied - a cutout is present so it's just a case of connecting the inputs/outputs. The rest of the PCB looks to be a LPF and a tap off the transformer - looks to be a crude method to be honest.

It's a cheap SDR however performance will no doubt be crap. My mate has told me I can have it but it's probably not worth the hassle.

[kr0ne]

Yep, you're right silverspring - it's not exactly what I was expecting and I'd say at £22 it is a little overpriced for what it is, although I'm looking at it as somebody who already had most of what came in the box in stock...

The biggest surprise concerned the RTL2832 and R820. Don't worry SMT-phobes, you don't need to solder these. You do need to unsolder the USB plug and TV antenna jack though, as these are actually supplied in the form of a tiny (and complete) dongle. It appears that the constructor is expected to remove the board from it's plastic casing and de-solder the connectors before soldering the PCB into a perfectly sized hole that has been cut out of the main PCB!

I did a double take when I first saw this but now I'm beginning to think that this is actually a really good idea that helps bring these kits to market at a very reasonable cost indeed.

As mentioned, no instructions - although the screen print tells you everything you need to know... EXCEPT how to wind the coils and transformer. (You should see the size of the toroid btw )

The transformer is really the only bit that I still have questions about but I haven't had a chance to look into it properly yet.

Will try to get some photos up tomorrow. I took a couple on my phone but they are crap, so will need to break out the good camera and get you all some nice close ups.

[Admiral]

I'm more interested in the performance, as there's no way I can fanny about with components I can't see.

If it performs well then I may get the fully assembled version.

[Cowthief]

Hello.

Old commercial radios, like the Motorola Micor, make excellent foundations for such a project.
You can BUY the kit, with instructions, to convert a Micor, but it is $300 US, and support is $30 hr.
24.5 MHz to 2.4 GHz.
But, assembled is only $350.
You need a quality computer and 12 volts at 20 amps to make it work.
But, no soldering, it is all assembled!

[Andy]

I'm more interested in the performance, as there's no way I can fanny about with components I can't see.

If it performs well then I may get the fully assembled version.

It's based around an RTL 8-bit DVB dongle, so it's never going to perform 'well'. On VHF it's OK as generally the bands are quiet and un-crowded, but on HF (with an up-converter) it will be very dirty and cluttered with noise. As an intro to SDR and as something to mess with these things are OK, but as a station receiver, no way.

[Cowthief]

Hello.

For VHF/UHF, again, old analog cable boxes and a cheap scanner work wonders.
TV tuners and satellite tuners also work.
TV sets can normally tune from about 45 to around 900 MHz.
Satellite receivers do from around 950 to 2100 MHz with some going as high as 2400 MHz.
http://en.wikipedia.org/wiki/Television ... requencies
Remember that we are talking a used analog cable box or old TV tuner and an old scanner.
There are plenty of examples on the web.

[crusty]

Anyone know what the max viewable (reasonably linear) bandwidth on the HF up-converters is?

[kr0ne]

As an intro to SDR and as something to mess with these things are OK, but as a station receiver, no way.

I would agree with this completely.

For me anyway, these devices are building blocks for larger projects. The technology is very impressive and has many, many uses but I always chuckle to myself when I see the threads asking for advice about which is the best SDR to get and then read on only to discover that the options under consideration are three or four RTL dongles from various sources...

If I remember I will take some photos of this kit later on and put them up (still haven't done anything with it as have been too busy of late).

[cjay]

I like the one I have but it's not a good receiver. Fun gadget to play about with though.