Opinion on low cost wideband LNAs?


#1

In short - are these worth the hassle for increasing ADS-B reception?

ebay.com/itm/LNA-0-1-4000MHz … 1699774008


#2

I just added the one listed on Flight Aware https://store.uputronics.com/index.php?route=product/product&path=59&product_id=50 today. By looking at the map, I cannot see a lot of difference, but it is very early… I personally think a higher outdoor antenna is the best option out there with a Higher Gain antenna. My next step is to get my antenna up about 20 feet. From being experienced in Avionics and Amateur Radio Natural Height is a much larger gain than an amp especially at this frequency (1090 Mhz).

Reasons for Higher Antenna:

1.) Line of site. The higher you are up even looking in different directions you have a better view and less blockage.

2.) and for the same reason as 1, Curvature of the Earth. The higher up you are, the farther you can see in a distance.

Bottom line, No amplifier is going to help you with line of sight, but by the same token, if you have a weak signal that your receiver just can’t get a good signal on then you will find that the amp will help in that situation.

Sparkie


#3

If you can keep the coax short or afford good coax then antenna height will be the most beneficial.
My antenna is less than 100ft AMSL yet I can receive aircraft 215NM/400KM away on a daily basis with the FA Pro-stick.

Some receivers, like the airspy, do require a preamp and filter to work well.

20 feet made a huge difference to my setup.
I have apartments and a ridge shielding me to the SW and S.


#4

This amplifier is so wide-band (0.1 - 4000 Mhz), it will amplify everything from AM, FM, TV, all VHF & UHF communication, and all cellular & wi-fi signals. It sure is going to overload the front end of the receiver to make it useless, unless a good 1090 mhz filter is used with it.

Noise Figure (S/N ratio in dB) is not specified, instead Noise Floor has been specified as 20 dBm. To get noise figure, a formula should be used:

Noise Floor (dBm)=10Log(K x T0 x 1E3) + Noise Figure(dB) + 10Log(BW)

Where:
K = Boltzmann’s constant = 1.38e-23 Joules per Kelvin
T0 = Temprature of amplifier in Kelvin = 50 deg C + 273 = 323 deg Kelvin.
BW = Bandwidth of amplifier in hertz = 4000 Mhz x 10 e 6


#5

Wideband amps (LNA) are very useful, particularly IF they are low noise AND used properly.

I like the Mini Circuits amps, such as the ZRL-2300. This is a low noise (2.5 fB) amplifier with reasonable gain (21dB) and a high IP3 (+42 dBm). I ran one for over a year and a half feeding my ADS-B receivers, with the ZRL-2300 feeding a SAW filter. Oh, these amps are $120 new.

You can get wideband LNAs on eBay for $20 or so, low noise and reasonable gain. Don’t trust anything over 30 dB. It’s that IP3 figure, which is an indication of the ability to handle strong signals, that’s lacking in most of the inexpensive amps.

For use with a SDR, you MUST have some kind of filter, either before, after, or both before and after the LNA. If you don’t, you are going to overload your LNA, and your SDR as well.

At a minimum, you need a filter such as the FlightAware filter before the LNA. That greatly reduces or eliminates strong signals from cell services, digital TV, and a whole lot of other crap that’s a whole lot stronger than the ADS-B signals you want to receive.

When the new FlightAware SDRs and filters came out, I ditched my old SDRs, the SAW amp, and the Mini-Circuits LNA and just use the FightAware SDRs + filters. Works great, and I can use my ZRL-2300 for something else once more.

cheers–

bob k6rtm


#6

Just an update… After watching for several hours with the PreAmp I am seeing a pretty good difference. I am seeing a/c that were on the edge intermittently much stronger and regular now in addition to probably getting an additional 25 to 30 more miles out of it.

I am currently using the Raspberry 3 Model B, USB Prostick receiver, 090MHz ADS-B Outdoor Antenna, and 1090Mhz ADS-B Filtered Preamp. Once the weather cools down I plan to raise my antenna height by about 15 to 30 feet

I think that the unit that you are looking at on EBAY may not be as good of a deal, but check out: store.uputronics.com/index.php? … duct_id=50 which is already filtered and amplified and does not overload the front end of the receiver which is never a good idea. This unit came out of the UK and arrived in good order in 6 days and depending on your shipping options less than 50 US dollars. It requires a mini usb power adapter, but current is not a big problem, it only requires 56, so any usb power supply will work and have plenty of overhead to support the unit. The Amp is rate for 14 DB.

Sparkie


#7

So in short I’m hearing garbage-in-garbage-out.

Get/build a good, tuned antenna. Put it outside, up high. Then filter. Then amplify. Fair assessment?


#8

KISS. If you can keep it simple then it should be reliable.

This is my current setup (It will change soon)
flightaware.com/adsb/stats/user/ … tats-20037
RPI3(an RPI2 has enough grunt) FA pro-stick (Gain set to 38.6), Cavity filter(however the FA filter should work just as well), 35ft/12M LMR400UF and a DPD antenna less than 100ft/30M AMSL(FA antennas should would just as well).

This is another setup (RPI2, 2nd floor, inside FA Antenna, FA Dongle, Cavity filter)
flightaware.com/adsb/stats/user/ … tats-17065

Amps are great at overcoming long coax lengths, especially at 1Ghz frequencies.


#9

Not sure about that particular amp. I use a 15dB LNA powered from the RPi GPIO. It was $10.50 on eBay.

ebay.com/itm/172248610203

Here’s the map showing the difference. The plots marked “GP 30’ , outside, and GP 30’,outside, 15dB amp” are the ones to compare.


#10

Just curious? what did you use to get the mapping overlay?


#11

Paint.net :smiley: The contours are from VRS plots, just stacked up on the same map.