1090 Mhz Preamp


#1

I’m about to try out a 30db preamplifier and was wondering
if anyone has tried this and could tell me what their experience was
and the results obtained?

Just built a new antenna that should give 15dbi.
This given me other ideas for
which I’ve purchased the materials and will post later.

Thanks

Ramjet


#2

What type of Preamp you want to use?

I have used a low cost 18 dB amplifier for Satellite L-band (950 - 2050 Mhz), about 4 years ago when I started this hobby. Please see following thread for details


#3

The amp I obtained is 38dB Gain and 0.8dB Noise Figure
that is at 1090, your amplifier is a line amplifier which is very broad
and a much higher noise factor which means yours is great for
amplifying at the antenna to send down a long length of coax.

Mine is going to detect very weak signals at the antenna , a high gain antenna,
and then boost up a hell of a lot to send it down the coax.

What I’ve noticed is that if an ADSB signal does not have sufficient signal strength
it will not display a position and will miss the gps position. IF its got enough signal
strength, the GPS gets displayed. A poor antenna will show less gps positions and
more non adsb transponder signals.
(correct me if I’m wrong on this)

You want the “lowest noise factor”, to amplify the signals at the extreme bottom of the noise level
that can barely be detected. When I listen to digital signals, it never ceases to amaze me
how the machine can detect the data when a human cannot even detect that a signal exists.

Its a bit like listening for Voyager 1.

My latest antenna is a 8 stage J-pole co-linear. Next version will be more elements and made of
solid copper pipe that enables more accurate measurements.

So far, without an amp, and using a old oil can, its getting occasionally over 200 nm in 3 areas of the compass. NW N and ESE, I’m aiming at adding some significant distance to it.


#4

@ramjet555

May be these two meet your requirements. I have not used these. If someone has used it, please post your opinion about it.

  1. https://store.uputronics.com/index.php?route=product/product&product_id=50

  2. https://v3.airspy.us/product/upu-fp1090s/


#5

I’d be interested in looking at your build and where you get the dimensions for the J-pole

Have you already bought the preamp or just looking for one to buy?


#6

I use the Uptronics 1090MHz ADS-B Ceramic Filtered Preamp in combination with the RTL-SDR BLOG V3 R820T2 RTL2832U 1PPM TCXO SMA SDR. https://www.rtl-sdr.com/product/rtl-sdr-blog-v3-r820t2-rtl2832u-1ppm-tcxo-sma-software-defined-radio-dongle-only/

I’ve been very pleased with the results.


#7

Since a couple of weeks I use the Uptronics 1090MHz ADS-B Ceramic Filtered Preamp in combination with the FA ProStick (orange) and I receive approx. 50% more a/c as before and the range increased too.
I checked it also with a RTL-SDR BLOG V3 R820T2 RTL2832, but results are slightly less.
Antenna: 5/8 (via ebay by Stanilav Palo/SVK).

So I can recommend the UPUTRONICS filtered PreAmp.
Or you will use the FA ProStickPlus (blue) only, that’s nearly the same … compare the cost …


#8

Depends of your location. If most of your planes are seen at a big distance, then yes a preamp would help. If you have lots of planes close-by, the preamp might overload the input in your receiver and actually make it loose samples.
I have tried a simple wideband preamp and, in my place, it just made things worse. Even without the preamp I have adjusted the receiver gain at 38dB to maximize the samples.
Now I have bought a preamp with two ceramic filters (1090MHz) and it seems to have improved my rates - but only if I power it at 5V and set my own receiver gain as low as 4dB!



#9

The RTL-SDR Blog recently released a preamp and filter combo.


#10

Are you sure these are Ceramic Filters? At $19, it is unlikely to be ceramic. Most likely these are low cost SAW filters.

In photo at Ebay, these resemble SAW filters. If you see the chips closely and read their markings, you may find if these are SAW or Ceramic.

TAI SAW FILTER CHIP

TAI SAW Filter 1090 Mhz

38 dB Amp with 1090 two stage filters.

1090MHz RF Low Noise Amplifier-Description Added


#11

You’re right, they are SAW, 30MHz bandwidth:

In front of this I also have installed the FA filter.


#12

This is NOT a low noise amplifier, which is narrow band.
This one is a broad band and suitable only for boosting a signal
down a long line, not boost signals


#13

Here is a cheap Bias Tee, for feeding 5V over the coax.


#14

The regular grey sdr-rtl(excluding the FA versions) dongles can feed Bias-t.
V1 and 2 require a solder connection.

V3 can do it in software.

I have a few powering uptronics amps.

Wideband is probably not a good idea for our use, unless you use a cavity or other filter beforehand.
It will probably amplify too much noise and overload the receiver. This depends on the noise at the receiver’s location.

Redo the gain optimisation after you add an amp. You may need to lower the setting considerably.


#15

Please post make & model, photo and link to seller’s site for your above noted amplifier. Thanks.


#16

Warning. I just tried out the 35db gain low noise pre-amp from Ebay
NEW 1PC ADS-B 1090MHz RF Low Noise Amplifier

and
it did not pass any signals what so ever, I ran a test with an antenna 5 feet above the ground
to keep the signal strength as low as possible, using RTL1090 I had very signal strengths showing and none of these would show up on RTL1090 until I removed the amp from the line.

Has anyone else had a similar experience?
image


#17

Mine works fine. Did you measure the actual DC voltage at the GND and VCC (positive lead here)?
Mine wasn’t initially 5V because… the power supply fell out of the socket, so it was 0V.
Check that the antenna in at RF in.
On mine I have a FA filter in front, but it was working even without one, just less decoded signals. Of course this depends of location and what RF pollution you have there.
Also, you absolutely have to reduce the receiver’s gain, like I said above. This adds 35dB of gain, you need to reduce it with approx that amount!
If that’s all right (3.3-5.0V) look at the soldering with a magnifying lens, the shipping and packaging of those can be/is really bad.


#18

@ramjet555
It seems due to TV+FM+Cell signals overloading and making deaf the RF Amp #1 chip, as there is no filter between it and antenna. Please see photo below.

1090MHz%20RF%20Low%20Noise%20Amplifier-Description%20Added

.

Has anyone else had a similar experience?

Yes, I have twice faced same situation, but not with this one. It was with these two:

  1. First case was with a Satellite+TV in-line amplifier (47 Mhz to 2500 Mhz) without filter. It proved to be deaf. I solved the problem by using another amplifier (RCA D903) which was designed for Satellite L-band only (950 - 2050 Mhz). As a result, TV VHF/UHF FM and Cell signals were all rejected, being outside its pass band (950-2050 Mhz), and this amplifier performed amazingly good.

  2. The second case was Pro Stick Plus (blue). It has a 1090 mhz filter, but it is not located between antenna and rf amplifier chip (the filter is located between rf amp and tuner). As a result TV+FM+Cell signals overloaded RF amp, deafning it. Adding FA external filter between antenna and Pro Stic Plus overcame this problem.


#19

Thanks for the reply however your amp and my amp are not the same, yours is broad band,
mine is narrow band and in a way a bit like a filter as it only amplifies the 1090 segment.

Amplifiers need to be narrow band and if you use a BROAD band amp, YES, you will need
to put a filter in front of it, that is not as necessary if you have a Narrow Band or “hi Q” LNA


#20

Just noticed that my AMP seems to be working
I’m using RTL1090 and it has the following controls at the top.
Tuner AGC on or off. ( a slider | ) [ db indicator ] ? Test
RTL AGC on or off. Send UDP on or off
Mode S or Mode AC . Config on or off . SISEX ON or OFF

I’m unable to make any changes that seem to affect the number of transmissions or the signal strength in RTL1090

Is there or are there options in Flight Aware to be able to control gain for optimum
performance with an amplifier?