Greater performance from your RTL Dongle

[Tony7]

"Greater performance from your RTL Dongle"

This setup performs very very well in this order.

RTL Dongle
1090 High Pass Filter
ZX60-P162LN+ 20db Preamp
Coax LMR400
3 Element 5/8 Collinear.

Antenna details in the Antenna section of this forum.

Have provided the High pass filter details here...Cheap to build
using Brass and make sure its completely Solder shielded.

cheers. Tony7



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[Anmer]

"Greater performance from your RTL Dongle"

In what way is it greater?  What comparisons have you made and what were the results?

[Tony7]

Did a few quick comparisons to my PUCK.

The filter and I think the ability to set the gain to max (49.6 - No AGC) with the RTL dongle,Appears to give better results....
....Distance/Aircraft pickup ability with the RTL Dongle.

Just as a matter of interest

One filter reduces the FM band 88 to 108 Mhz signals from 9 to 20db down to
5db sig.strength.

Two filters in series wipes out completely the FM band and almost all other
interference. Without minor if any noticeable degradation to the 1090 mhz signal.

cheers Tony7.

[Anmer]

What were you comparing with the Puck?

There are many messages that are not usable for monitoring or plotting aircraft which more established decoders will discard.

[Tony7]

Comparison is between RTL Dongle/PUCK

RTL Dongle
ADSB# -- Virtual Radar Server (Aircraft Displayed + Distance)

Compare

PUCK
Basestation -- Virtual Radar Server (Aircraft Displayed + Distance)

The RTL setup appears to be better (More displayed aircraft + Greater Distance)

Thats assuming I have the PUCK setup correctly, I just change over the inputs from to the other for a comparison.

thanks Tony7

[Anmer]

Were you using the same antenna at the same time and if so, how were you splitting the signal?

Can you post the comparative results?

In my experience, the dongle performs reasonably well but the Puck has slightly more range and more aircraft plotting.

[Tony7]

I unscrewed the coax from the RTL and connected it to PUCK,
And from the PUCK back to the RTL. (Both still using the same Preamp/Antenna)

I would like to run them side by side, Though I haven't quite worked out how
to do that with the same Preamp/Antenna setup....
...Have ordered a Mini Circuits  Power Splitter/Combiner, Hopefully that will do the job?


Also ran some tests over a couple of days with both.

The dongle gets average results by itself.
The biggest difference is the filter/filters for the RTL.

These make a huge difference to the performance of the RTL.
And highly recommend building a filter or purchasing one for the RTL.

I will continue to experiment and do some screen captures and post the results.

cheers Tony7.

[Anmer]

Thanks.

Splitters are expensive.  I used the RF Systems SP3.

It would be good to see your comparative results.

[Tony7]

Mini Circuits  Power Splitter/Combiner $20 US off ebay.
... Mini Circuits ZX10-2-20-S+
Awaiting its arrival.
If it all works out we will post soon.

thanks Tony7

[Anmer]

Can I suggest you test the splitter carefully as cheap ones usually favour one connection over the other.

Swap the outputs around and check if you get the same results.

[Tony7]

Certainly will do.

Thanks again Tony7.

[Tony7]

*******Update*********

Built another 1090 mhz filter,This time using all 0603 type SMD`s.

Much better performance about 1 signal strength reduction in FM Band signal strength
than mixing 0805 and 0603`s.

This another 5 pole as pictured above.
Next project is a 7 pole filter for 1090 mhz.

Still testing the difference between the RTL and the PUCK...Not much in it.
Will post later on with pictures..Re: RTL/PUCK.

thanks Tony.

[9a4qv]

Thanks.

Splitters are expensive.  I used the RF Systems SP3.

It would be good to see your comparative results.

They should not be necessary expensive. Yes, fi you use the minicircuits one, but this is not required. The are expensive because they are wideband and this is what you don't need.
You need the narrow band splitter/combiner that can be made cheape and good.
One way to make it is to etch the splitter on the laminate and the other way is to use the short peaces of 75 ohms coaxial cables.

Just browse the web for the Wilkinson combiner and you will have the cheap result. I.L. only 3dB (lower then the Minicircuits one...)

Cheap wideband splitter can be done just using two SMD resistors. True, the losses a bit higher (4.5dB) and isolation not so good, but if you have the LNA infornt the splitter nobody cares for extra 1.5db loss.

So save your money and built one 

Adam

[Tony7]

*******************FILTER UPDATE**********************


A 900 mhz filter is better than the 1090 mhz filter.
The 1090 mhz filter attenuates the signal by 2 Signal points,
Thus reducing the aircraft pickup ability of the RTL dongle.

I thought this could be compensated by the preamps high gain.
This not the case.

The 900 mhz filter increased my range on average by 25nm.
And increased aircraft pick by a fair bit.

With the 900 mhz filter placed at the RTL input then Preamp then Antenna.
This will enable you to run the gain of the RTL at max 49.6
Plus no AGC settings enabled.


Signal levels as follows

RTL no Preamp, no filter, gain set to max  = S3 plus Noise.
RTL Preamp, 1090 mhz filter, gain set to max = S5 Clean.
RTL Preamp, 900 mhz filter, gain set to max = S7 Clean.





Butterworth Calculator link
http://www.calculatoredge.com/electronics/bw%20tee%20high%20pass.htm

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