FlightAware Discussions

ProStick + , external amp + filter combination?

Did you properly reduce the gain set in dump1090? Without that the reduction in messages is expected.

The gain seems very high compared to the competition. There is no mention of the semiconductor used.

But the biggest question mark of all is the noise figure. At these frequencies, it’s a very important spec to be left out.

I would say, go for it. One for the team. I’ll be right behind you, if it’s good. :wink:

That’s like the one that I am using now.

The “caption” of the 1090MHz signal (active part of the antenna) is happening with the actual external shield, not with the internal core.
Only the delay links in between are using the cable as is intended to be used (1090MHz signal running inside the cable core), so those should be calculated with VF.
As a side note, I don’t think that installing whole assembly inside a PVC tube any calculations, because there is air again in between the tube and actual antenna. So the VF goes Air-PVC-Air.


Look at the eBay listing below. It includes a diagram. Not the same circuit, just one SAW filter, but it may give an indication of the semiconductor used.

The price is reasonable for what you get: antenna, amp, bias t adaptor.

Go for it. I have the Pro Stick Plus as well and a clean spectrum nearby. Despite this I bought the Uputronics SAW preamp for the extra gain and installed it at the receiver end for convenience. It gave a big increase in messages, aircraft and range. I’m very pleased with it.

After installing I saw the benefits straight away. But after some experimentation I got a slight improvement again by changing the gain in PiAware, from the default -10 (max/AGC) to 49.6 (the next one down). This is because the preamp introduced a bit of in-band noise which was drowning out some of the weaker signals, and dropping the gain a touch sorted it out.

As you can see from the photo I’m powering the preamp from a USB port on the RPi. It works no problems. I’m using the official 2.5A RPi PSU.

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I’m really confused by people running double amplifiers with max gain on the dongle. Oh well.

Gotta still ask: Have you tried for example 34 as a gain?

Max gain is the default setting, chances are some people will install a preamp and leave the settings alone. But in any case the preamp still more than compensated for any loss due to the gain being too high, here at least.

With the preamp in place I found that 49.6 gave the best result. -10 (default) was too high with distant aircraft being drowned out and 48.0 lost some range and aircraft, with lower values losing even more.

Specially when using an FA antenna outdoors, up high. I’m puzzled as well. But hey, if it works, it works!

I guess so. Should stop questioning it. I guess the flatter the gain pattern of an antenna the better you can set high gain when you don’t have low flying aircraft nearby. Still…

I think they either have all the planes far away or… a bad antenna, installed indoors that cuts down all the signals. Maybe a bad connection between elements on the cable?

I literally have the gain at 8dB after adding a preamp in front of my FA ProStick Plus with FA antenna installed outside. But I have lots of planes flying in 50-100 miles radius.
At 30dB I see the number of planes reduced at 1/4. At 50dB I see none.

One possible explanation is that some of the installations must have huge losses that are compensated by the extra high gain.

Indoor antennas, as you mentioned, but also poor connections, excessive number of adapters, long cable runs, poor quality cable, etc.

Looks like the noise figure is around 2 dB.

The RTL-SDR Blog LNA is less than 1 dB.

This is the generic LNA I purchased some time ago. I’ll solder the barrel connector to the board, and feed it with 12 VDC. I’ll also use the spare FA filter in series with the LNA. Curious to see if the location, before or after the LNA, will make a lot of difference.

Just ordered this Bias T board. Different than the one I purchased in the past, and currently use, but cheaper.

I don’t trust wide band amps. At the minimum I would put the filter in front, to cut-out any other signals. Heck, that thing can overload even from AM radio! Or your computer PS, or TV (switched mode) radiating electrical noise.

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That’s what I said. See quote below:

Very true, fully agree.

In 2013 the 1090 Mhz LNAs were very costly, 100 euro plus. I decided to use a cheap satellite amplifier and purchased a Satellite+TV in line amp, 18 dB, 47 ~ 2400 Mhz. Instead of improving performance, it reduced it. I thought it is defective, so purchased another make from another supplier also 47 ~ 2500 Mhz. That also reduced performance. Finally I purchased a Satellite narrow band amplifier 950 ~ 2050 Mhz (Satellite L-band), and it greately enhanced performance.

Some of the eBay ADS-B LNAs appear to be generic amps, but with SAW filter/s added.

And for the few dollars difference, there is no reason not to go with other LNAs designed specifically for ADS-B.

I have other possible uses for the generic amp, but will try it on ADS-B just for for fun. The extra FA filter will be used as well.

Installed the generic eBay wideband amplifier board and the spare FA filter. After a quick gain adjustment, from 49.6 to 38.6, I’m happy to report that early results are satisfactory.

The reference station is composed of: FA antenna, RTL_SDR Blog triple filtered LNA unit, and an RTL-SDR Blog v2 dongle.

The test station is now composed of: Homebrew QuickSpider antenna, FA filter, generic eBay wideband amplifier, generic no-name dongle.

The two stations are installed in the garage, including antennas, 1 foot apart.

Before the changes, the test setup was always between 45-50% worse than the reference station, for both planes seen and messages. Now, there are times the test station is only 5-10% worse than the reference station in the number of planes seen, and better than the reference station in the number of messages.

Again, very early results, not enough observation time. More gain tweaking likely possible, but for a $8 amplifier board that was in the junk box waiting for some use, the results are encouraging.

Stick with the good stuff, but if you have one of these generic amps in the junk box, give it a try.

As always YMMV.

Update: Settled on 43.9 for gain on the test station. Incidentally, the total gain of both stations is practically the same now. The reference station is 48+27=75. The test station is 43.9+30= 73.9. The 1.1 difference plus 5 dB of the FA antenna, used by the reference station, likely accounts for the variation between the two stations. Very pleased with the results so far. Once again YMMV.

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