FlightAware Discussions

LNA or no LNA

Hello everyone.

Have a Pro FA receiver connected directly to the Pi3B. Between the receiver and the antenna there is about 18M of good quality cellfoil cable (RG58).

1.Should I add a LNA to the arrangement?

2.Should I install it close to the receiver or the antenna?

Thanks in advance

YOLDOG

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Normally RG58 sounds bad, but your coverage seems to say otherwise:
https://flightaware.com/adsb/stats/user/vk5mw

If you go with an LNA, it’s better near the antenna to compensate coax losses.
With very low loss cable that isn’t as important.

Not sure you can get much improvement with an LNA, your reception looks pretty impressive already!

If you get a filtered LNA, then you might see an improvement, if you have local cell towers or other sources of noise.
Otherwise, 18 meters of cheap cable and mismatched impedance (75 ohm VS 50 ohm) is not that bad… sure, not great either.
I would replace it with RG6 first, it’s easy and cheap.

PS: Maaan, you really are in the middle of nowhere!
https://binged.it/32Cr7FS

With that reception the cable really can’t be bad at all.
I’d wonder what the datasheet for the product he’s using says.

Indeed the variation in quality is very wide on those RG58 cables…

Olympic Dam Mine

“the largest known single deposit of uranium in the world.”

https://www.rfiwireless.com.au/cellfoil-9006-low-loss-rg58-coaxial-cable-5mm-50-ohm.html#tab_desc

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Hi all. Thanks so much for the great positive feedback.

I used the 50ohm cable simply because it was there. What better reason right? Oh and it fit the cheap and nasty connectors i bought on Ali Express. Went with SMA as they fit the receiver.

Future plans will probably look at a better 75ohm cable of sorts and will also be reducing the cable length. Have ordered an enclosure to mount the Pi and Receiver on the base of the mast. This will drop the cable length to about 5 meters. Will claw back about 3 or 4 db perhaps.

Considering the overall result and getting the above done. I think i will hold off with the LNA and monitor the results. As for the range achieved so far it is mostly due to the terrain. Well the lack of it mostly! Quite flat out here and don’t need to go much above roof line to get a good 360 line of sight. Makes ADSB fairly easy. Im motivated to get the extra little bit of reach as i’m competing against a work mate. He has the first receiver in town and using distance he WAS in front at 239nm. Overnight I think I have him at 242nm.

Im so having fun with radio again!

9 dB per 30 m at 900 MHz is actually quite ok.
That’s roughly 5.4 dB for 18m, 200 MHz more probably 6.5 dB of attenuation.
Not terrible as one can see from your reception.

I’m not sure how hot it gets where you are, but consider a fan inside the enclosure, so the temperature of the electronics is closer to the air temperature inside.
Using a separate shade also makes sense. (probably sufficient)
There are some threads around here on enclosures.

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Well done.

Just to be clear do you have the orange FA receiver or the blue Pro Plus?

What antenna are you using and how high is it mounted? I suspect if you are looking for more range in your circumstances you should first look at more antenna height and an antenna with more horizontal gain.

I went for a drive around your place three months ago ; Port Augusta, woomera, Coober Pedy, Painted Desert, oodnadatta and home via Halligan Bay to see the water in Lake Eyre. No water.

From Olympic Dam you would have seen the approximately 30 planes flying tourist all day from William Creek.

S

I’m pretty sure an rtl-sdr LNA mounted directly at the antenna would be the cheapest and easiest option to improve range.
High gain antennas are expensive, and extending the mast is likely quite expensive too.
Not sure a higher mast is gonna make any difference where he is.

Just to be clear, before i was mostly saying that your range is already good. If you ask me what you should upgrade next, an LNA would absolutely be the first thing.
Get the rtl-sdr LNA and a bias-t.
Feed the bias-t 4 v or just the 5V off the RPi.
That way you don’t even need to move your Pi to the enclosure, difference in coax attenuation doesn’t matter much if you have an LNA boosting the signal by 28 dB or so.

^ That is absolutely right.
With that you can add longer cable, and keep the receiver and the Pi in cooler space. The receivers hate the heat, it increases the reception noise level.

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I have the Prostick Plus (Blue One) and that was the reason of my original question about using an LNA. Just a little concerned about overdriving the receiver and making the noise level rise. Im now also a little concerned about the heat. It gets very hot here at times. We are about to enter the hotter part of the year. As for the antenna its a vertical with a claimed gain of about 4.5dB bought on line. I cant really get it any higher off the ground than it is.

Not an issue with the 18 m of coax you have :wink:
If you are concerned you can get the v3 dongle as well which doesn’t have an internal LNA.
But in your case the ProStickPlus should work fine with the LNA.
(It does in most cases even with less cable)

So the LNA is the better part to stick outside compared to anything else.
Drive it with 3.5 V and it shouldn’t get too hot.
A watertight enclosure plus a little sun shield are still the way to go.

https://www.rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/
They have an ebay bias-t linked on that page as well which you need for feeding the voltage into the coax.

If you don’t want to mount it all the way at the top of the mast, putting the LNA in an enclosure 2m up the the mast is also an option of course.

The nearest major airport is ADL which is nearly 600km away and most of the aircraft he sees will be traversing to airports at least 1000km away.

Without seeing the piaware map it is not possible to see what he is already seeing. It may be that he is already seeing all the aircraft traversing that part of Australia.

He is already seeing to the horizon in all directions and most of the aircraft he sees will be between 30,000 and 40,000 feet.

Raising the antenna and using an antenna with more horizontal gain may possibly pickup another few NM of range over the horizon.

S.

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Yeah, that’s pretty much all you can have there! Anything over 200nm is great. Very seldom I am seeing planes over 200nm.

This is the traffic there now, you need more range to the east if any:

And this is me, about 200nm max range.

As expected, everything in view is over 30,000 feet and heading to or coming from a long way away.

Is it a generic antenna that they claim 4.5dB on any frequency or is it from a reputable seller where the gain might be correct?

S

Pretty much everything to the east already comes into range unless the range is increased to get the north south tracks out of Melbourne and that would need an increase of 300 NM.

I’d be really really pleased if i could get that range from Melbourne.

S

https://www.everythingrf.com/rf-calculators/line-of-sight-calculator

For planes at around 35000 ft, the max radio range is around 425km or 230 nautical miles.