SDR Radio 'UK Upgraded'

[WaveyDipole]

I was thinking about getting one of these cheap R820T+8232 SDR radios from eBay either in kit form or ready made, but there appears to be two variants: one is about 25-30GBP, the other more expensive at 45-50GBPish tagged as 'UK upgraded'. They have the same tuning frequency range and look identical except for the decor, so does anyone know what the difference is? What does 'UK Upgraded' mean?

[CJay]

I think they might just mean the 'upgrade' was done in the UK, if not then I fail to see what they could mean, ask the seller perhaps?

Some of the RTL devices are sold with a mixer to enable them to receive lower frequencies (generally 100KHz to 1.7GHz), some have a TCXO to help stop them drifting, some have extra shielding, there's all sorts of mods and upgrades to be done but there's only so much improvement you can make before it becomes less expensive to have just bought something better to begin with

(that's not to say the RTL dongles aren't excellent value for the money and lots of fun to tinker with, but they do have some rather unpleasant shortcomings).

[cdev]

More expensive it sounds like   

From what I can tell the "rtlsdr blog" units version 3  appear to have done several useful mods (an OCXO, built in bias tee, upgrade of antenna connection to an SMA, metal case, added filtration, bringing the unused Q input to pins for direct sampling, etc.)

If thats the case, it is likely a good deal at $25. Not more. I would never pay more than that for a RTLSDR, nomatter what had been done to/for it.

Maybe you mean the UK company "cosy cave" sells SDR stuff, which sometimeshave seemed like a good deal.

RTLSDRs are great for traveling, because they are small. They are fun for VHF/UHF. (but not as sensitive or selective as other SDRs, especially at the higher frequencies-

The sdr dongles are not at all good for HF DX. With a good upconverter and a above average long wire antenna, they can function around as well as a decent tabletop consumer shortwave radio. Not better. Not up to the level of any real communications receiver.

They are fun, cheap, very small size.. and convenient, easy to pack in a night bag.. But if your goal is HF DX - get something else.. There is a whole world of stuff on HF that I have never heard with an rtlsdr. The weaker signals just aren't there.

Ebay, banggood, and all the other vendors that sell far eastern electronics stuff have them. Price varies but typically they sell for around $10-11 with free shipping.  $7 is the least I have seen.


People might want a bit more but there are limits to what can be done with them. $25 for the rtlsdr blog version 3 (with the bias-tee, OCXO, metal case, direct sampling input,  and so on..) sounds like a good deal. That sounds to me to be about as good as it gets for the RTLs.  If you want a better SDR you likely have to spend several times more and get an airspy or if you want better HF I would not get an upconverter, I would get an SDR that could do HF natively.

[WaveyDipole]

Thanks for the comments. I have asked the seller and am still waiting for a response. Interesting notes about HF and 'unpleasant shortcommings'. I don't expect it to perform like a HF rig though. I did have a Realistic DX394 HF radio a while back which wasn't bad after mods.

I haven't seen them for as low as $7 though? Any pointers as to where from?

[CJay]

This one? Not a recommendation of the seller but it's the first cheap RTL-SDR dongle I found on eBay.

http://www.ebay.co.uk/itm/RTL2832U-R820T-DVB-T-RTL-SDR-DAB-FM-Digital-TV-Tuner-USB-2-0-Stick-Receiver-New-/192049703963?hash=item2cb70dec1b:g:4L8AAOSw44BYS8ro

Think I paid about that for mine.

Would recommend adding a more useful antenna connector or buying an adapter. A decent fillet of solder around the barrel of the original makes them a lot more robust.

I added some shielding to mine, didn't do an awful lot, earthing the body of the crystal made a little bit of a difference.

Knowing how to configure the software and what the options (specifically AGC) do makes a big difference.

Despite the shortcomings they're great value for money, they won't beat a 'proper' scanner or HF receiver but they work surprisingly well for the price.

[Codebird]

I was confused by this too, but I do have a theory: There's an extra switch on the 'uk upgraded' ones. I think it lets you select between het and direct modes without having to swap a cable over. Possibly.

[CJay]

I suspect it's even simpler than that, I think it's just UK held stock of upgraded RTL-SDRs.

[WaveyDipole]

This is the response I got to my query about what the difference is with the upgraded version: 

Hi there,

Thanks for you message.

This is the upgraded version. Hope you like it.

Regards,
Shirley

I have replied asking what is new/upgraded...

[CJay]

This is the response I got to my query about what the difference is with the upgraded version: 

Hi there,

Thanks for you message.

This is the upgraded version. Hope you like it.

Regards,
Shirley

I have replied asking what is new/upgraded...

English isn't their first language, obviously, so you have to be very specific in simple terms, the fact that they replied pre-sale is a good sign though they may not know the answer to your question as they are probably just a box shifting operation.

I'd have a go at one of the really cheap dongles first and see what you think, once you're happy or unhappy with that you can make the decision as to buying one of the 'upgraded' ones.

There's a nice little article in the GQRP mag about extending these too...

[tronde]

You don't happen to have a link to the upgraded unit?

[cdev]

Maybe they mean R820T (versus e4000) or R820T2 vs R820T

[cdev]

Quote from: CJay on 2017-06-01, 04:02:03>I think they might just mean the 'upgrade' was done in the UK, if not then I fail to see what they could mean, ask the seller perhaps?

>Some of the RTL devices are sold with a mixer to enable them to receive lower frequencies (generally 100KHz to 1.7GHz),

Kn0ck has a dongle he sells that has a tiny upconverter built into its case..  Is that what you mean? I think its $70.

It doesnt seem to be so well known. Ive never tried one, Maybe some new mod has come out. Doesnt sound like it though.

Do you mean the simple tap into pins 4 and 5? - basically two unused pins on the RTL chip, that still needs a lot (ESD protection, band pass filtration and impedance matching to the differential pins)  to turn it into a usable antenna input for HF.

>some have a TCXO to help stop them drifting, some have extra shielding, there's all sorts of mods and upgrades to be done but there's only so much improvement you can make before it becomes less expensive to have just bought something better to begin with.

The $25 rtl-sdr blog v3 dongle looks like the one to get if you are just starting out with SDR..  And thats as good as it gets for RTLSDR.

>(that's not to say the RTL dongles aren't excellent value for the money and lots of fun to tinker with, but they do have some rather unpleasant shortcomings).

Selectivity is horrible on HF. Basically on HF you don't hear any of the weaker signals. Its as if they arent there. VHF/UHF its better up to maybe 1400 MHz.. then they start having issues.

Those shortcomings would be major for me if I paid $40 for one but for $10 I can live with them.  For $23 I expect the most fixable ones to be fixed.. which it seems rtlsdr blog has. So they deserve support.

Its not worth spending a lot of money on add ons to the RTLSDR, that money is far better spent on a better SDR.

[WaveyDipole]

Here is one of the 'upgraded' devices:
http://www.ebay.co.uk/itm/400909628678?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Here is one of the cheaper ones:
http://www.ebay.co.uk/itm/121928055076?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

There is one subtle difference. The 'upgraded' version has a switch on the front panel which the non-upgraded version does not. Other than that, both cover 100kHz to 1.7GHz.

[tronde]

The upgraded version seems to have an upconverter. The text mention an offset of 40MHz, and an image search sends me to banggood with a better description. The text also says 100MHz local oscillator.

https://www.banggood.com/100KHz-1_7GHz-VHF-UHF-Full-Band-RTL_SDRUpConverter-SDR-USB-Tuner-Receiver-NFM-FM-DSB-LSB-CW-p-1070964.html

I guess the other version is similar to the direct sampling SDR made by BA5SBA.

http://www.rtl-sdr.com/assembling-chinese-rtl-sdr-direct-sampling-kit/

or a clone
https://www.banggood.com/100KHz-1_7GHz-Full-Band-Software-Radio-HF-FM-AM-RTL-SDR-Receiver-Radio-Frequency-Modulation-Kit-p-1120249.html?rmmds=search

[cdev]

I built that. (the non upgraded one)

It needs a decent antenna and ground to work well. Its a pretty good design. After the modifications its a better unit. It uses a midsized R820T dongle that comes with the kit.

There is also a lot of space and breadboard areas in the case to add several additional devices. You could for example, put an LNA in there very easily. It comes with a bias-tee but to turn the bias tee on you have to open the unit and change a jumper. So it really needs a switch for the bias tee..

As a kit, most of it was easy but soldering the two tiny wires to the RTL chip was a major PITA. I would say maybe a hour and a half construction time. You also need some double sided tape to affix the toroid to the board. Foam tape has low RF loss.

[WaveyDipole]

So, the switch is there to enable the upconverter, i.e. switch in a diode ring mixer. I just noticed that there is a newer version of the dongle based on a new version of the R820T, namely R820T2 which is supposed to be more sensitive. Not many kits using this yet it would seem. Maybe worth biding ones time?

[tronde]

From what I have seen it seems like the blue R820T2 dongle like this type

http://www.ebay.com/itm/USB-2-0-Digital-DVB-T-SDR-DAB-FM-HDTV-TV-Tuner-Receiver-Stick-RTL2832U-R820T2-HE-/111731066549

have got exposed pads for pin 4 and 5 on the RTL2832U so it's much easier to use the direct sampling mod.

[WaveyDipole]

Ah that is interesting. Maybe I should get this kit:

http://www.ebay.co.uk/itm/281979737300?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

And the updated dongle:

http://www.ebay.co.uk/itm/371780691616?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Maybe that way best of both worlds?

[cdev]

I don't think connections for pins 4 & 5 are standard in any of the dongles. Some companies likely get them custom made to include them, one would likely be disappointed otherwise.


Also, leaving those pins connected to pads likely introduces noise unless something is done to prevent it.

[tronde]

I started to modify the type1 dongle, and collected some links about direct sampling.

I have not finished the project yet, but spend some time on the links. Some of them will benefit from google translate.

http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/

http://www.g8jnj.net/softwaredefinedradio.htm

https://bbs.kechuang.org/t/62913

http://www.rtl-sdr.com/tag/direct-sampling-mod/

http://www.radioamatoripeligni.it/i6ibe/rtl2832hf/dongle.htm

https://www.reddit.com/r/RTLSDR/comments/30rv9j/upsychopat666s_photo_shows_possible_new_dongle/



Description of the banggood clone:
http://img.banggood.com/file/products/20170109215514SKU472022.pdf

Description of the original Chinese kit: (2nd link is to the pdf)
http://www.rtl-sdr.com/ba5sba-direct-sampling-kit-english-build-instructions/rtl-sdr-diy-kits-installation-instructions/





Picture of dongle with pads for 4 and 5 here:
And here



I understand that the T2-dongle in blue have those two pads, but it is Chinese, so...

A dongle with pads makes the direct sampling mod easy. You will need a steady hand and a very fine tip to solder wires directly to the chip. I used single strands from a tinned wire, and fixed them with a droplet of epoxy.

[tronde]

Seems like BA5SBA has discovered the T2-dongle with pads for pin 4 and 5.

http://blog.radiospy.ru/dorabotki/aktivnyj-direct-sampling-mode-ba5sba-pksato.html

http://ur8lv.com/index.php?id=1489825510

http://anyram.net/blog_ru/?p=814

[charliedelta]

You  might want to watch the SM5BSZ videos on Youtube,  before you start buying cheap SDR dongles.

[WaveyDipole]

Thanks for all those links and reference to SM5BSZ videos. I'm not sure how the author of the Mifare sniffer picked up that radio for $4 as I can't find it for any less than 36GBP! I have noted the problem with lack of gain control and overload. With regards to the SM5BSZ videos, it seems he uses Linrad in conjunction with much more expensive SDR hardware (e.g. Perseus) so I'm not sure what the relevance is to the cheap RTL-SDR clones? Obviously you get what you paid for and I thought it might be fun to get one of these cheap dongles to see what can be done with it, but I'm not interested on spending 699.95GBP on a Perseus just yet! For that price I would more likely be looking to buy a proper communications receiver covering the bands I am interested in.

[cdev]

Wavy,
Look on eBay under rtl 2832 and sort by price. I am in the US and they range down to $7. For that you get a basic dongle no bias tees etc.
Quality is consistently good. No need to spend more.

Also, if you want to avoid wasting lots of money, for HF RD take my advice.

For HF avoid dongles and get a real SDR.
There is a whole world of signals you will never hear with a dongle. Compare it to trying to do astronomy in Times Square with all the light pollution.

[Codebird]

"For HF avoid dongles and get a real SDR."

They have their place at the low end. They are perfect for listening to commercial radio, or evesdropping on amateurs in the VHF and UHF bands, or listening to air traffic control if you really have no life at all. If you want a 'real' SDR, it'll be far superior in every way, yes - it'll also cost ten times as much.

[CJay]

If you want a challenge, Teensy SDR is looking *really* interesting and it's accessible.

*waits patiently for Teensy to arrive*