I dont see any difference between the Wide Band (20 - 3000 Mhz) and Narrow Band (1090 Mhz) units on Ebay, except that in the 1090 Mhz unit, the coupling capactors between input-amp1 and amp1-amp2 have been replaced by SAW filter chips.
It seems the RF Amp 1 & 2 in both these units are same wide band chips (20-3000 Mhz), and narrow banding in 1090 Mhz version is achived simply by adding 2 SAW filter chips.
The 20 - 3000 Mhz 35 dB Amplifier
.
1090 Mhz 38 dB amplifier
You are correct, it amplifies before it filters.
It could be an optimum way of doing the task
as its 2 stages as you point out.
When I change the gain, I am not seeing much change in
the aircraft that I can see displayed. But that’s only an antenna 5
feet above the ground and the amplifier is at the computer, not the antenna
about 12 feet of coax a way.
You can assess the presence and degree of Cell phone signals at your location (particularly the GSM 850 Mhz band), by conducting RF Scan of signals received by your antenna.
If strong cell signal exists, then adding a filter between antenna and the ebay amplifier will substantially improve performance.
The method to conduct the RF scan is given in this thread. Do this scan without the Ebay RF amplifier.
hi ramjet555
a much better option is ModeSdeco [http://xdeco.org/?page_id=30#md2] for those
using Windoze, or RTL1090 by Malcolm Robb (without gui).
Hardware:
Flightaware 26 inch Antenna + Generic DVB-T (Black), plugged into Windows Computer. NO FILTER
Strong Cell phone signals detected.
And my spectrum, to show why I wanted those filters:
960MHz is Aeronautical Radionavigation - I am just a couple miles away from an airport.
I downloaded Modesco and it appears to work with airspy only?
I run it a administrator and a box flashes on my screen for a few miliseconds
and then disappears.
Has anyone seen signals on 1090 come alive AFTER installing a Filter?
950mhz is 90 mhz away, and I am wondering if signals that far away in the spectrum affect the sensitivity of a FlightAware Blue Stick with a built in filter?
YES, it does in many cases, depending on relative strengths of 1090 Mhz and 850/900 Mhz signals. Please see the Message Rate graph below. It clearly shows a substantial drop in message rate when EXTERNAL Filter was removed from Blue Pro Stick Plus.
Thanks for posting that image.
Just goes to show that the Pro Stick Plus Filter
does not do the job it suggests.
Is it better to use a purpose built filter followed by
USB receiver? If so, is any USB receiver better than
another for 1090 Mhz ADSB?
This diagram shows the differences well.
My understanding is a “H Q” Gasfet preamp is in itself a filter.
If it makes that much a difference, I’m planning on making one
with a full length inductor just a bit shorter so it can be tuned
with a screw from the other end.
Your conclusion is not accurate.
The above test applies only for his location, and only for a given time and date. You can’t generalize from it that “Just goes to show that the Pro Stick Plus Filter does not do the job it suggests.”
It actually does the job it is called for and it’s up to everyone to experiment/decide if they need an amplifier or not or if they need more filters than others. The RF conditions of each site are vastly different, you can’t generalize like that.
My plane numbers are very varied based on the day of the week and hour, even minutes, because we are talking about real-time air traffic.
@ramjet555
As @SoNic67 has already mentioned, you cannot generalize from my results.
The need for additional filter for ProStick Plus (blue) is NOT universal, and depends on strength of Cell Phone signals, which varies considerably with location.
A large number of users have reported satisfactory performance with the built-in filter of ProStick Plus.
Determining the presence and strength of Cell signals by RF Scan do give a clue if filter is needed or not. However benefit of adding a filter at a specific location/installation can only be confirmed by installing the filter. This is a trial and error process.
Does anyone manufacture a mast-mounted or antenna mounted LNA for 1090 MHz?
Might help increase coverage towards the horizon. I’m using a Flightaware prostick (yellow) with a 1090 flightaware filter in-line. It works ok but thinking there might be some increased coverage potential having a preamp at the antenna.
Found this one, any of you have any experience with using this model?
https://www.wimo.com/download/as-1090-deutsch.pdf
-G.
Did you adjust the gain and found out that you are maxed out and need more gain?
I have this;
https://www.amazon.com/gp/product/B01MQWOM65/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1
and with; https://www.amazon.com/gp/product/B010GBQXK8/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
for my second ADSB system. My Pi Aware used the flightaware pro stick plus.
I have increased and decreased the gain and found I get best plane counts around 12-18 (not sure if that is dB or s-units). The Flightaware dongle apparently has a preamp built-in, and I am using the Flightaware 1090 filter directly attached to the dongle RF input. I have some cell towers close by, and the filter improves reception considerably. (did some RF scans with and w/o). I think the LNA would require filtering as well to be helpful.
A wide-band preamp is just a waste of money, you already have the gain reduced from the max 50dB, so it’s not gain that you need.
I have the blue FA Pro stick (filter and preamp). I have added a supplementary preamp with filters, not a wide band one like above. This is to clean up the signal because I am near an airport with SSR operating at 1030MHz (2 miles / 3km away).
This is not an usual issue for most of people, a simple filter to cut off cell frequencies is usually sufficient.
My item was this one and I have to reduce the receiver gain to 8dB:
https://www.ebay.com/itm/NEW-1PC-ADS-B-1090MHz-RF-Low-Noise-Amplifier/122228184927
As you can see it does not have a box, I personally didn’t need one. It might be useless for many, because they don’t have to cut very strong, close-by 1030 MHz signals like me.
Raising the antenna just over the obstacles around you, to clear the line of sight to horizon, is much more efficient.
In my case, I have some big, very tall trees in the neighbor’s yard that I cannot clear by raising the antenna. The foliage effect is a reduction of range by 33%, visible on my range pattern:
Anything mounted up near the antenna would have to be well weatherproofed for 50’ up on the tower. “N” connectors are somewhat weather resistant if installed properly and would match the antenna I am using. The German unit I found is most suitable but the price is a bit of an issue.
Is that little preamp/filter board from E-Bay powered via feedline/bias-T, or do you have to use the VCC input on the board? Doesn’t look like it from the description. Board could be altered I suppose.
Hi, drop me a pm, ramjet555 at gulf maail d o t com
I don’t believe a pre-amp will help at all unless you are running a long coax length which is not necessary and the wrong solution.
The solution is to have the USB stick mounted directly at the antenna, feed that to the raspberry pi within a usb cable length.
I’ve got a preamp here, tried it and it only had a negative effect.
