FlightAware Discussions

45 m (150 ft) from antenna to FlightAware Pro Stick Plus

I am looking to moving the antenna to a higher location which will mean 45 m (150 ft) from the antenna to the FlightAware Pro Stick Plus which plugs in to a Raspberry Pi running PiAware. The first 30 m (100 ft) will be on the outside of the building.

I currently have the following antenna and cable which I understand will not scale to 45 m:

I have tried to read and understand other forum discussions on the subject, but I am bound to fail if I try to compose a solution myself. I understand that RG-6 cables are suggested for long stretches, and I may need an amplifier, but I need more concrete help.

I hope to re-use at least the antenna, but I am open to any suggestions which can give a good and stable result.

Thank you for any help.

145ft of RG-6 will give you over 15dB loss which is roughly 93% of the signal and that’s not taking into account the impedance mismatch. There’s little point in putting an amplifier at the bottom end of that length of cable because the signal to noise ratio will be awful.

LMR-400 will be a better option but you’ll still be losing over 75% of the signal.

Is there any way you can mount the receiver and the Pi closer to the aerial, run a length of network cable to it and power it using PoE?

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One shouldn’t switch from dB to percent for dramatic effect …

You’re not even gonna mention an amplifier before the lossy cable run? :slight_smile:

Also a good quality LNA after 30m of LMR400 will still give good results i’d expect.

RG6 has attenuation of 6.2 dB / 100 ft.
150 ft of RG6 will have attenuation of 9.3 dB.
Any good LNA installed near the antenna (powered by DC fed over coax), can easily compensate the loss, as LNA’s generally have again of 15 dB to 30 dB.

I have used 50 ft RG6 with a 18 dB satellite LNA immediately after a dipole, and could easily get planes 250 ~ 300 nm.

NOTE: Initially I used two LNA, one at antenna other near the dongle. Later I found that removing the LNA near the dongle improved reception… 2 LNA were too much gain and were overloading the Dongle.

File Photo: Sept 2013

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Thank you very much for your replies and suggestions. This is far from my comfort zone, so I appreciate your help.

I understand that better cables will not be enough. I need to amplify the signal, and when amplified the cable type will not really make much difference as the signal is very strong - i.e. RG6 will be perfectly fine.

@wiedehopf, I think you suggest to have a good cable (LMR400) for the first 30 m/100 ft which are outdoors, then have an LNA, and then e.g. RG6 for the remaining 15 m/50 ft. It would certainly be nice to have the LNA indoors. In my understanding this will give ~4dB/60% loss of signal - which may be good enough, but may also disappoint.

@abcd567, In your solution the LNA is installed outdoors, near the antenna, and RG6 can carry the amplified signal for all the 45 m/150 ft. I like the thought of a LNA powered over coax, but I will discuss the idea with an electrician for any concerns about safety of the installation when it will be outdoors. In my understanding this will give nearly zero relevant loss of signal - or at least all air tracks wil reach the receiver as if there were a very short cable.

For the best result I will initially fo for the @abcd567 solution - with a fallback to the @wiedehopf solution if there are any concerns from an electrician.

On a separate note, the mention of LMR400 made me look at our AIS-installation. We will also be moving an AIS antenna next to the ADS-B antenna. The AIS installation uses an RG213 cable which in my understanding has similar qualities as LMR400.
Knowing very little about radio signals, I expect that AIS installation will also benefit from some amplification. Then I wonder if the same cable/LNA can be used for both with some combiner/splitter to carry the two signals to their respective receivers.

Do you have some insight into the idea of combining AIS and ADS-B in this way?

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I wrote putting the LNA after the LMR400 to keep it inside as he stated it goes inside after 30m.
This would be an acceptable solution if maintenance at roof level is very expensive and one doesn’t want active electronics there.

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Yeah that was what i was suggesting.
4 dB is an acceptable loss considering the LMR400 has good shielding and you’re gonna place an LNA there that has a low intrinsic noise floor.

There are 2 relevant LNAs with a good price:
adsb receiver shopping list · wiedehopf/adsb-wiki Wiki · GitHub

Just in case you weren’t up to date on that.

I wouldn’t recommend it, combining and splitting the signals with the appropriate hardware would be possible but much more expensive than an extra coax run.

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It probably won’t make much difference unless you have the antenna mounted very high. AIS signals are at or close to sea level so are much more constrained by the curvature of the earth than ADS-B signals are. Class A transmitters used on ships use 12.5W power and have antenna heights anywhere from around 20-50m above sea level depending on the size of the vessel. That will give a radio horizon somewhere around 35 miles.

It may improve reception of class B and B+ transmitters used on leisure craft somewhat, which have transmitter powers of 2W and 5W respectively, but again they tend to use lower mast heights and subsequently have lower range.

In my experience you can reliably receive class A out to the radio horizon with no problems with a decent unamplified antenna and good quality coax. Occasionally tropo ducting allows very long range reception - I’ve seen 150-200nm occasionally, again without amplification.

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I’d look into moving the Pi closer to the antenna, and using PoE over “outdoor grade” (meaning, UV-protected) Cat5e cable to power it. You can buy PoE injectors, etc., fairly inexpensively.

(But that’s because I’m a “digital guy”, and the idea of running analog signals over long distances seems non-ideal to me.)

Those sat amps are definitely not LNA - they add typically ~5dB noise.
Whether this matters will depend on the rest of the site.

Yes it can be done, but a pair of diplexors (needed to combine and then separate the two signals) will cost more than two runs of LMR400

I am running successfully, for a few years now, 150 ft of RG6 cable, with F-SMA adapters, and this LNA:

https://www.rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/

There is nothing to gain, compared to the LNA followed by long coax, by moving the Pi outdoors. You just add noise close to the antenna, possibly overheat the Pi… for no real gains.

Yes you are right about noise figure of most of satellite in-line amplifiers.

That said, please note that this photo is from 2013, when ProStick did not exist, and 1090 MHz LNA were a specialty item, costing over €100, while I purchased this satellite amplifier from a local Electronics shop for Canadian $4.

With this huge difference in price, I just did not bother for noise figure. I did not even know how much noise figure it had, as it’s specs did not tell anything, but being from a very reputable USA manufacturer RCA, I am pretty sure it was not as high as 5 dB.

In any case, irrespective of its noise figure, it gave me a fantastic improvement at a very little cost of Canadian $4.

 

I wasn’t suggesting you shouldn’t use it, I was saying it’s not an LNA (it’s just an amp)

Can you justify that belief or do you just want it to be some other figure?

  1. The jump in performance by using RCA Sat Amp was very good.
  2. When I tried Sat Amp of another make, which had same gain and frequency band, the performance improvement was much less.

Above observation lead me to belief that RCA one had lower noise figure. There seems to be no other reason for this difference in performance, as gain, frequency bands, and dc voltage ratings were same for both. As both did not specify noise figure, I cannot prove it, can only say “I believe”.

Those amps were the “LNA” at that time, not so much by today standards :slight_smile:
Technology advances… I still remember times when BFY90 / BFX89 were the state of the art in RF amplification: transition frequency of 1.4 /1.2 GHz, NF 2.5 / 3.3 dB (at 500MHz) or 5.5 / 7 db (at 800 MHz). “Very Low Noise”, amazing good stuff in 1989!
There were articles about the promising new Ga-As technology that would replace Si at some point… That was stuff from military, Cray computers, and space probes.
In 2000-2003, the new cell phone technology required mass production of GaAs transistors and LNB’s…

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Compared to what?

That not quit accurate. The “claimed” gain of your RCA amp is 13-18dB (950-2150MHz)
while your first amp made no claims at all
and your third amp claimed 20dB (950-2150MHz). That’s about 5dB up on the RCA amp

You could start a religion with that, but not much good evaluating amps.

A typical sat amp

You have quoted a post where I mentioned two amplifier which proved dead. There I did not mention another amplifier which worked, but with reduced performance as it was out of context.

I think we have agreed not to agree on anything. For quiet some time I am noting that you are trying to prove that whatever I say is wrong. Thank you.

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If what you mean is that I am not shy pointing out the errors in what you say, then so be it.

Just because you say something, doesn’t make it true.

If and when I point out an error, I back it up with evidence, not:

Your scripts are quite impressive, but your knowledge of RF theory and hardware is poor to say the least.

If you don’t want people to point out your errors, please be a little more careful what you state as fact.

As an example: when you call a noisy sat amp, “an LNA”, it devalues the term and clouds the benefits of using a “real LNA”.
(For sat installations, it doesn’t matter if the IF amp is noisy as the high gain/low noise stage is in the feed horn).

If you keep making outrageous statements, I will keep pointing out what is wrong with them.

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