If I’m still seeing the following after adding an AirNav filter what would be a next step (which I guess could be a different/better filter)?
1 Like
@sigwx
This does not seem too bad, but no harm trying another filter if you have one.
These scans show the RF signals at my location, picked by my two antennas.
Both antennas were located in the same window at a horizontal distance of 30cm (1 ft).
A Generic DVB-T (Black) was used. No external Filter or LNA was used
This setup eliminated affect of any internal or external LNA and Filter.
Scan Range = 24 MHz ~ 1800 MHz
For both scans, the Generic DVB-T’s Gain = 49.6
Scan 1 of 2 - Flightaware Antenna >> 2 meter RG174 cable >> Generic DVB-T plugged into Windows Desktop
CLICK ON IMAGE TO SEE LARGER SIZE
Scan 2 of 2 - V-Stub Antenna >> 2 meter RG174 cable >> Generic DVB-T plugged into Windows Desktop
CLICK ON IMAGE TO SEE LARGER SIZE
When I am trying to install pil:
sudo apt-get install python-pil
I get the following message (so I am unable to create my image from scan.csv):
Reading package lists… Done
Building dependency tree
Reading state information… Done
Package python-pil is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package ‘python-pil’ has no installation candidate
Is there any other way to install the python image library that will work with the scan.csv file i have created? It is on raspbian buster lite
2 weeks ago I bought a blue FA filter and my message rate is much improved. I live in a large city, maybe there are a lot of GSM antennas nearby.
The filter doesn’t just suppress strong GSM signals. It also suppresses any source of strong signals outside it’s band pass range like FM radio, TV, etc. You could have been experiencing interference from those as well.
1 Like
Here are two scans both same location.
First scan is this PCB Antenna.
Second scan is the FA antenna.
I am thinking about a uputronics saw filter/lna for the FA antenna setup?
Also looks like the cheap PCB antenna is picking up way more noise, is this just poor design?
Any other suggestions would be greatly appreciated @wiedehopf @abcd567
I have RTL-SDR Blog Triple Filtered LNA. I have test-run it for few days with Generic DVB-T, and it performs very good. Now it is as stand-by spare part as I dont have 4th Pi to put it to use. If any of my dongles fails, I will replace the failed dongle with one of the many spare Generic DVB-T’s + RTL-SDR Triple-Filtered LNA and BiasT.
Currently I use following setups with my 3 Pi’s, and am happy, as these give good results. Best result is by # 1 listed below:
-
FA antenna >> 2m coax >> FA Light Blue Filter >> FA Blue ProStick Plus >> Pi
-
V-Stub Magmount antenna >> 3m coax >> FA Light Blue Filter >> FA Blue ProStick Plus >> Pi
-
V-Stub Magmount antenna >> 1m coax >> FA Light Blue Filter >> Radarbox24 Green FlightStick >> Pi
I also have PCB antenna (the short one, in a white plastic pipe), and found it is an eye wash. Both the short & long versions of PCB antennas on Aliexpress/Bangood/Ebay are actually a vertical dipole with two 1/4 limbs, so cannot have gain more than theoretical 2 dBI, may be even less if poorly designed/built.
| Antenna | Gain | Gain Determined By | Comments |
|---|---|---|---|
| Low-cost Chinese PCB Antennas | 2 dBi or less | Theoretical Maximum gain for a Dipole 2 x 1/4 | Mediocre performance |
| Flightaware 26" Antenna | 6 dBi | Measured & guaranteed by Flightaware | very good performance |
| V-Stub whip on Magmount base | 4 dBi | Calculated by simulation | Field test side by side with FA antenna Aircraft = 86% of FA ant Messages = 77% of FA ant |
| V-Stub Spider | 4.2 dBi | Calculated by simulation | Same as above |
I believe we found that wasn’t the case with the longer version?:
Honestly, don’t know what it is as the measurements don’t line up with 1/4 wave 1090Mhz, but it sure looked good on the meter.
Shots (a few posts back in same thread):
ADD/EDIT: Even more discouraging is the fact that the (short) PCB antenna that’s enclosed does NOT have the same PCB that they sell standalone. The standalone antenna (without the case) specs out much better and actually resonates at 1090Mhz whereas the enclosed (short) version is about 100Mhz off. At least mine was.
I have both short and long PCB antenna (enclosed), as well as the short PCB itself and all 3 are different in design. The short PCB is 170mm long, the PCB in the antenna with the radome (as depicted in this thread) is 130mm long. The long PCB antenna is 289mm long + 72mm wire. (PCB itself, not counting the radome(s)
1 Like
So would I therefore I would be better off with a RTL-SDR v3 and their triple filter LNA? The reason I mention the uputronics is that it uses USB power.
The Uputronics filter amp is the same price as a new dongle and triple filter from RTL_SDR blog. Is their dongle going to provide the same performance as the FA Blue?
This is the catch. Your meter only measures SWR, and the these antennas have SWR nearly 1.
However antenna perfotmance does not solely depend on SWR. Two more factors are equally important:
- Gain
- Radiation pattern
Measurement of these two requires sophesticated and costly equipment which hobbyist lack. Chinese manufacturer of this cheap PCB antenna are aware of the fact that their buyers can only measure SWR. They are smart to bring down SWR to near 1, while sacrificing Gain and Radiation pattern.
My short one has a SWR of 1.095, but performs not better than the stock magmount with whip cut to 1/4 wavelength.
CLICK ON PHOTO TO SEE LARGER SIZE
CLICK AGAIN TO SEE FULL SIZE, THEN READ THE SWR METER
I have never used RTL-SDR V3 dongle, cannot say anything about it. Others who have used it can tell you.
The photo below shows how I connected it during trial run of the Triple-Filtered LNA. I used a BIAS-T and a seperate DC 5V adapter to feed power to LNA, freeing the RPi/Dongle from burden of supplying power to LNA.
CLICK ON PHOTO TO SEE LARGER SIZE
CLICK AGAIN TO SEE FULL SIZE
You are absolutely correct. My point is that it appears most conversations about the PCB antenna (at least above) are pointing toward the fact that there is only one design, and that is not the case - this is what I was pointing out, nothing more.
There are at least 4 different designs being sold as of right now, perhaps more. The lowest performing (on the meter, S11, SWR and real-life) of the bunch is the short PCB antenna with the radome that contains the 130mm board - The one taped to your window. They are not equal, nor am I saying they are great.
1 Like
Isn’t that exactly how you’ve tuned your V-Stub?
You might assume so, but I for one are getting quite good coverage from this modest antenna.
The antenna is on a short mast at ground level, not at the top of some high-rise.
I will swap this antenna for more gain in a day or two, but 220Nm is a bit better than “mediocre”
Which version do you have @geckoVN? Curious what others may be lingering out there. Guess we sort of got off track again 
Short answer for the above:
I think that is a fantastic setup/combination and it is a very successful for many locations.
No,
The side-by-side comparison of V with FA antenna clearly shows that Gain was not sacrificed to bring down SWR.
Messages V/FA =77%
Aircraft V/FA = 86%
Max range FA=290 nm, V=265 nm
The simulation results also show that with a SWR less than 1.4, th V has a gain of 4 dBi.
I’ve got the: “elevated feed”, but without the tuning notches.
I ordered mine naked, and built my own raydome.
I like these, not because they are a great antenna, but because they are repeatable (and very cheap)
1 Like
That would be the 170mm board then correct? Probably could use a dedicated thread for these things. I also find them fantastic for testing as they are easy to work with.
Hello
I did it : https://discussions.flightaware.com/t/ads-b-antennas-cheap-chinese-pcbs-and-the-others
(1) The scans below were done in an urban area with strong Cell/Mobile, TV, FM, Fire, Ambulance, Taxi, and other communication signals at VHF, UHF and Microwave frequencies. Other locations may not have such severe RF interference.
(2) The scan 1 shows RF noise picked by antenna, and scans 2 & 3 show how filters remove this noise.
Scan 1 of 3 - FA Antenna + Generic DVB-T (no internal or external filter)
CLICK ON IMAGE TO SEE LARGER SIZE
Scan 2 of 3 - FA Antenna + ProStick Plus (Only Internal filter of ProStick Plus. No External filter)
CLICK ON IMAGE TO SEE LARGER SIZE
Scan 3 of 3 - FA Antenna + ProStick Plus (with internal filter) + External Filter (FA Light Blue)
CLICK ON IMAGE TO SEE LARGER SIZE
