R820T Dongle Upgrade

Has anyone tried R820T2 variants with TXCO & bias tee fuse link perhaps with a Nevis/Habamp ?
There is one in an aluminium case and sma connector now I noticed at rtl-sdr.com shop plus a lot of others now using TXCOs.

By default it looks as though the bias tee is disabled (there is a check/tick box on the front of the enclosure)

Looking at any users out there who have tried enabling the solder pads to the bias tee fuse to provide 5vdc squirting up the coax to the amp.

Thanks Guys.


+1 for me for information. I may add an amp in the near future.
I have 3 NooElec 2+s and and old RTL T2(2 by 978 and 1090 setups). I may order the RTL-SDR TCXO/T2 with the aluminium case and SMA connector to play with.

Hi John,
Yes it seems a tempting set of enhancements on the newer versions of the dongle and things have moved on considerably since I set my adsb station up around 2 years ago.
I am currently using R820T original (“vanilla”) version which came blister packed with remote control and small mag mount antenna.
The R820T cost me the princely sum of around $10 USD shipped to my door from China originally bought as a bit of fun to have a play with SDR but given I was both a radio and an aircraft enthusiast I was bitten by the ADSB bug.
It has served my remote Pi station well and gave no trouble but perhaps its time to try to make some improvements.

Now it seems additional features cost practically nothing given the amount of use and enjoyment we get from these little things.
Recently we have the sub £5GBP/ $5USD pi zero single board computer coming along it appears to be cheaper than ever to set up a station.

Hi Mike,
I just looked at your stats and you have skyrocketed over the last few days.
It looks like your A/C are up about 20-30% but your position reports have more than doubled(100-140k to 300k).
Position reports at 120-160NM have gone form nothing to 11,000.
Did you make some improvements?

This is what you can do with an RPI1(yes 1), FA antenna(original not the new 978/1090Mhz one) and a 40 foot tower.

I saw some complaints on Amazon about the older RTL-SDR with SMA connectors with the plastic case. They complained about the SMA connector not being soldered to both sides of the circuit board. This may have been fixed on the later models with the aluminium case. I just ordered one to see how it goes. I dislike using the crappy SMA-MCX pigtails(even bought a few RG195 pigtails to see if they were better. no noticeable difference for me) and would love to keep the number of connectors to a minimum.


Hi John,
Yes some improvements were made that I was putting off for a long time.
I changed antenna from a homebrew 1/4 wave spider to a co-linear similar to the FA model, also the biggest improvement was re-location from upstairs room to attic mount.
Love the location on a 40ft twr btw John, they are some kind of set of figures, very impressive indeed.
Maybe I will catch you on the 20m band cw mode some time !

I have 2 hobbies, all things radio and photography “with a twist”.

Heres what you can do with a DSLR camera,a telescope, and very steady hand plus a lot… and i mean a lot of practice !



Best Regards,

Although I have been a Ham for 25 years, US and Aus, I rarely get on the airwaves.
Originally it was a better range CB with a friend(pre-mobile phone days).
I do have an APRS capable Yaesu VX-8GR handheld and two old 2m/70cm mobiles still in their boxes(from the early 1990s).
Would like to add an APRS gateway. Receive only is dead easy(and use an RTL dongle) but transmit would be nice.
Also may do some weather fax and satellite stuff.
D-Star interests me but it is way too expensive if I only do it once or twice a year.
When my kids are older I will have them get their US licences(too easy as you can easily memorise the answers). Easy to do at around 8-10.

I am also interested in ACARS and AIS. The dongles can do both.

I have also gone back to complete a degree so between that work and kids, I don’t have a lot of free time.

learning CW is on my to do list. Hopefully when I finish my degrees(in 10 years)


I just upgraded to the RTL-SDR dongle shown here:

amazon.com/gp/product/B0129E … ge_o02_s00

I haven’t enabled the bias tee - my preamp has hardwired power - but this dongle does work without any additional configuration, and I’ve only been running it for 12 hours or so but the performance does seem to be markedly better than the standard NooElec dongle. SMA connector seems really solid, complaints on amazon might be from earlier revisions.

Hi Jon,
It is good that you seem to be getting a marked improvement over the noolec which is well respected brand.
Its early days for you but it would be interesting if you could report back in a week or so with your findings.

I take it that you now have the txco, you have removed any ppm adjustments you had enabled in your start script.

I must admit that I had concerns about the SMA on this one reading some of the reviews but you have found no faults with yours so thats good to know.
It does seem to have all the SDR fans “wish list” items addressed, direct sampling,bias tee, stable txco plus an added bonus of a metal enclosure.
All for sub $20usd which seems like crazy value in terms of the enjoyment factor we get from fiddling with these things.

I noticed and the add on aluminium enclosure for a noolec cost $12 alone so it looks like you got a bargain Jon.
Aside from adsb receiving, You can have hours of sdr fun with these .

The bias tee for this one is via jump wire detailed below

rtlsdrblog.rtlsdrblog.netdna-cdn … ctions.jpg

Yes, I removed PPM adjustment - well, actually shortly after I installed the dongle I changed cards to one with the Mutability/Multi-Feeder/Monitoring Charts images linked in this thread.


and when I configured it obviously didn’t add any PPM adjustments. The downside is I don’t have a straight A->B comparison between the NooElec and the RTL-SDR - but nonetheless I’ll share some graphs in a few days.

And yes, there is lots of fun to be had with SDR. The NooElec is now my experimentation dongle, with the RTL-SDR dedicated to the ADS-B.

In terms of the SMA connector - it feels stable, but I’d be worried about hanging the FA 1090mhz bandpass off of it. I have the bandpass and the dongle both mounted to a surface. It doesn’t matter the build quality - I wouldn’t want to have that filter hanging of a connector on any device.

The “issue” with the connector is that it’s not fixed to the case - just soldiered to the board. The hole in the housing is larger than the stalk of the connector, and there’s no locking nut and no provision to add one (the connector is threaded only halfway) A bulkhead mount style connector would be more solid, but likely could not be fixed directly to the PCB as it is in this design. The design sacrifices a little bit of connector strength for the benefit of no internal coax. A tradeoff I’m willing to make! It’s really not an issue - Just don’t treat the SMA like a mounting point.

It’s plenty stable for normal use but I wouldn’t press my luck.

Anyway - Charts to come.

So what does the bias-tee do exactly?

I am using the Nooelec dongle with the FA antenna. Just curious if this dongle would make an improvement? And if the added 5V would help the FA antenna?

The bias tee just puts 5v onto the coax. It’s used to power an amplifier mounted usually near the antenna, without having to have an external power connection. If you don’t have an amplifier connected then you don’t need it enabled.

Yeah that’s exactly right: it’s only needed for Amps.

Some people use amplifiers like these mounted right next to their remotely mounted antennas.

The thinking is to boost the signal AT the antenna so that it overcomes any loss from their long cable run. By sending the power over the coax, the need to also run power up to the antenna is eliminated. Activating the bias tee sends 5v over the coax so you don’t need to use an additional power injector.

Not something you want to turn on unless you’re sure you need it and you’re sure it’s okay for your antenna.

But in my experience this dongle is an improvement over the regular NooElec - although NooElec also makes a TXCO version. If you already have that one i’m not sure if you’ll see improvement. The TXCO version of the NooElec says “NESDR Mini 2+” whereas the standard dongle lacks the plus sign. It’s worth noting that the RTL-SDR TXCO dongle is cheaper and comes in a metal case.

The TV amps require double to triple the power available from the dongle. You can only use it with amps which can operate on 5 volts.
Like: http://ava.upuaut.net/store/index.php?route=product/product&product_id=85

I added a Bias-T to my 820T2 (amongst a couple of other mods) to give 5v on the coax feeder to power a lna4all amp.
First removed all the IR components, soldered in a 4.7 uH inductor connected to the USB 5v supply.
After this mod, you cannot directly connect an antenna that presents a direct DC short to the feeder.


Screening from thin brass ‘shimstock’



Hi Nigel,
Do you have a decent link for some of the mods?
I did a Google search but didn’t find anything I could use.

Any thoughts on using heatsinks on some of the dongle ICs?
I bought a bunch for the RPI and have plenty left for the dongle.

I have the FA filter on both of my setups. I have seen people say it helps them when they have cell towers a few hundred yards/meters away. I have a few on apartment blocks maybe 60 yards away. Plenty more within 300-500 yards/meters. How do I know if the filter is enough or if I need a better one? I have spare RPIs and dongles I can use to test.

My dump1090(Mut) log stats from the better RPI
Statistics: Wed Feb 24 23:33:57 2016 UTC - Thu Feb 25 00:33:57 2016 UTC
Local receiver:
8640004096 samples processed
0 samples dropped
0 Mode A/C messages received
57578987 Mode-S message preambles received
35485969 with bad message format or invalid CRC
21247585 with unrecognized ICAO address
805656 accepted with correct CRC
39777 accepted with 1-bit error repaired
-30.8 dBFS noise floor
-12.9 dBFS mean signal power
-0.8 dBFS peak signal power
19412 messages with signal power above -3dBFS
Messages from network clients:
0 Mode A/C messages received
59151 Mode S messages received
0 with bad message format or invalid CRC
0 with unrecognized ICAO address
59151 accepted with correct CRC
0 accepted with 1-bit error repaired
904584 total usable messages
22 surface position messages received
86033 airborne position messages received
83945 global CPR attempts with valid positions
0 global CPR attempts with bad data
0 global CPR attempts that failed the range check
0 global CPR attempts that failed the speed check
34 global CPR attempts with insufficient data
2057 local CPR attempts with valid positions
1770 aircraft-relative positions
287 receiver-relative positions
53 local CPR attempts that did not produce useful positions
27 local CPR attempts that failed the range check
5 local CPR attempts that failed the speed check
0 CPR messages that look like transponder failures filtered
285266 non-ES altitude messages from ES-equipped aircraft ignored
312 unique aircraft tracks
125 aircraft tracks where only one message was seen
0 HTTP requests
CPU load: 20.7%
488011 ms for demodulation
233834 ms for reading from USB
24178 ms for network input and background tasks


@ jonhawkes2030 The heat sinks look good 8), weather they make any significant difference is debatable. Probably good airflow around the dongles is more important.
Unfortunately your not the only one that had life get in the way of their ham radio stuff :slight_smile:

@Devonian Did the brass shield make any difference with the noise? I have some shim brass somewhere so might give it a try it if its worth the effort, it would be lot cheaper than getting aluminium cases here.

I picked and chose some of the mods from here (mostly the additional caps on the underside and on the top side inductor + brass screening - also on the underside of the mcx connector)

The 5v bias tee is from somewhere else that I can’t find right now, but there is enough info and the pics above to do it yourself if you need it.
Remember to remove the back to back diode at the feedpoint near the IR connections (for removal of anti-static build up).
It’s the little black rectangle component next to where Martin has added a 100pF cap here

It’s difficult to say which mod worked the best as I did them all at once and noticed a general improvement, but can’t put any actual figures to it.
Would I do it again - yes :slight_smile: