Making a band-pass filter for 1090 MHz using Lumped LC Components
A filter in 1 GHz frequency range can be built using lumped LC elements, but a better filter could be built using micro-strip or a cavity.
I found this software (free of charge student edition) for LC filter design: http://tonnesoftware.com/elsie.html. Seems good during initial browsing.
The filter can be prototyped on a piece of PCB material, and tested and adjusted using a suitable signal generator and RF meter (not a DIY situation). It can be mounted in a screened enclosure with the input and output connectors, like a recycled TV splitter.
I’ve seen one commercial product mentioned on the forums, combining a LNA (PSA4-5043) and a SAW – pretty much the product I’d build if I was going to build one (well, I’d put a high-pass filter on the front end, but it’s close).
The SAW filters themselves appear on eBay for around $18 each from Europe; I’ve purchased a bunch that way. Yes, they’re surface mount parts, but you can do them dead-bug style on a scrap of pcb between two SMA connectors; I’ve done a bunch like that and they perform fine.
Because of the insertion loss of the SAW, it’s good to follow a LNA. In high RF environments you still have to worry about overloading the LNA. The approaches to that are to use an amplifier with a high IP3 (I use a Mini Circuits ZRL-2300 on one system, with a SHP-1000 high pass filter before the LNA), and/or filter the input to keep the LNA from overloading. For another system, I use a different LNA (Mini Circuits PSA4-5043) with the input blocking cap selected for operation at 1 GHz; that along with another SHP-1000 high pass filter knocks down the energy below 950 MHz or so.
Thanks. Price (US $22.15) is high compared to Satellite in line amplifier
Two years ago I purchased RCA D903 sat amp from local store for Canadian $3.99 = US $3.15. (Gain 13 to 18 dB, 950 to 2050 Mhz). Working great since then.
Anyway, I have adked the seller this question:
*"Can you offer a model with 1090 Mhz filter instead of 435 Mhz filter? There will be lot of buyer who will purchse this for use with ADS-B receiver.
Item #: 181695469072, 435Mhz Bandpass Low Noise Amplifier RF Receiver Amplifier High Gain 36 dBm"*
Got seller’s reply “hi friend,
of course, i can provide, but i need you paid more 4$ for it, are you OK?
I can let my supplier help you do it,
thank you!”
I’m new to this so please understand that I don’t know what I don’t know
Now, I have several VHF radio antenna’s that are off of a boat. These have a Coaxial cable coming out of them and I was wondering being that I have one (like 8’ long) can I put a cable end on the coaxial and then route it to my Pi for my ADS-B?
Also is there a way to be able to receive the radio frequencies from the airplanes? Such as 115.0 to 125.0 range?
Marine VHF is at around 150-160 MHz. Antennas designed for it are not optimised for ADS-B which is at 1090MHz. You are likely to just overload your dongle with off band noise from broadcast FM and pagers if you use one of those, and you won’t get very good performance for ADS-B at all.
You would be better off constructing your own antenna which is tuned to work at 1090MHz - the simple spider design based on a coax socket that appears in this thread is probably one of the easiest reliable antennas to build. Cost is minimal, and performance is quite good.
You could use your dongle to receive airband radio, but not simultaneously with ADS-B. Ideally you should use an antenna that is tuned for VHF airband, however you might find that one of your marine VHF antennas works well enough for this, as although they aren’t the exact frequency they are at least in the right area.
I’ve found that the dongle performance isn’t fantastic for receiving airband voice, since it is AM modulated and needs a good signal strength. I have a Yupiteru scanner that can receive airband transmissions that are perfectly readable, yet using the same antenna they are quite difficult to make out or even unreadable when using the dongle. That is admittedly with only an indoor portable antenna, so a discone or other external antenna might improve things.
Antenna question… I am currently using the telescopic chrome antenna that came with the dongle and I can see planes outside Reno from the SF Bay Area. Not a lot of planes, no Southwest Airlines planes, no… well that’s another topic.
I’ve seen where people put an AMP in line when they run coaxial cable, but I thought I read that one is suppose to keep the lead from the dongle to the antenna as short as possible so that made me think…
Why not put the dongle next to the antenna and then run a LONG USB cable back to the Pi instead of running a long coaxial cable back to the dongle?
Would this eliminate the need for an amp? Would it work?
You can get powered USB extenders like this one amazon.com/Plugable-Meter-Ac … B004AGX4YO - people have varying degrees of success with them with dongles - cost is probably similar to using an amplifier (but bear in mind the usb extender may not work with the dongle)
I have one ready to try out with the Nevis Filter & Preamp, but I’m waiting on a few dry days in a row. It will be connected to the input of the filter/preamp with a SMA-BNC adapter. Then down 5m of RG6 coax to the dongle.
…Tom
Edit: Actually, I believe abcd567 has experimented with a cantenna with the amp inserted as the bulkhead connector and a whip inserted into the amp. Maybe he’ll comment on it.
Another edit: I know you said spider, but this was handy and didn’t require soldering.
(not a DIY situation). It can be mounted in a screened enclosure with the input and output connectors, like a recycled TV splitter.
