FlightAware Discussions

Antenna Question From A Flightaware Newbie

I just signed up and have been doing a lot of reading in the forum. For those more experienced people I have a few questions:

  1. Is 13m (42 foot) of coax going to impact my signal ? eg: The pi wont find as many aircraft.
  2. Should I mount the antenna on top of my TV mast on the roof ?
  3. Is there any issue like interference with using the same mast, or should I use a stand off ?

By way of background, I’ve got the:

  • PI
  • FlightAware 5dBi 66cm/26 inch 1090MHz Antenna
  • Flightaware Prostick Plus (Blue).
  • I didn’t get the band-pass round filter as the blue seems to include it ??

With cable, I couldn’t find any cable locally and ended up buying “13 metre RG223, RF Coaxial Cable assembly Male N to Male SMA RG223, Telegartner”.

Having read through many posts I’m now concerned about loss, using that length of cable.

I’ve put the antenna in the window and confirm that everything is working. The range isn’t very good. It’s about 11km or 7 miles.

I’m in a double story house and have an existing TV antenna on a mast on the roof. So I was thinking of mounting the flightaware antenna on the top of the TV mast. To do this, I was thinking about using something like this:

the other option I thought of was to use a stand off like this: https://www.telcoantennas.com.au/telco-galvanised-clamp-stand-off-mount-50mm~81587 but I dont know if its worth the extra $$$ and if it matters that the flightaware antenna is mounted the TV mast or not.

The other thing I’m concerned about is running a long line of cable. I don’t have power up there and can’t get into the roof space, so its a big deal. I might be able to run cable under the roof and grab it via a light switch and run it down a wall and into a plug. That’s how I was thinking of dealing with it. The other option was to run that full 13m coax and then connect up the blue prostick and then run a long USB into the PI.

I’d really appreciate thoughts of more experienced people on the forum. Thank you.

That’s quite a lot of loss, RG223 won’t be great for longer cable runs like this; you’re probably looking at 6dB loss there.

This is an extremely low range unless you are being limited by terrain. Do you have another antenna (even just a little quarter-wave magmount or something) that you can try in the same location for comparison?

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Ok. What sort of cable would you recommend?

I don’t but I might be able to source a small cable and connect up the pi and see what happens.

As @obj has already pointed out, this is extremely low and most likely due to long RG223 (6dB loss).

Try a straightened paper clip inserted directly into the dongle’s input connector as antenna. Please see photo below.

Thanks for the suggestion. I’ll do that and post an update. So that I can understand what’s going on, I’ve ordered:

SMA Male to N Male Adaptor (which will allow me to plug flightaware usb straight into the antenna.

and

5dBi Magnetic Base Mobile Antenna with SMA Male connector (which will allow me to test the range)

Those two items will take a few days to come back to me. In the meantime I’ll go find a paperclip and see what the difference is.

That’s really quite a high quality Coax, but best suited to short patch leads.
For 9m run, I use LL195 which is very similar to LMR200. A better (but thicker) cable suitable for long runs include LMR400.

Be that as it may, you have a good receiver and a good antenna. 6dB cable loss will (may) limit your range, but given your location, you should still be getting 100~150Nm.

Great place to mount your antenna. This style of clamp may suit you better


(cheaper elsewhere though)
image

It’s worth trying, but don’t believe the specs.

Have a close look at your SMA plug on the cable. Make sure the plug has a center pin. Many people get caught with an RP-SMA intended for WiFi systems.

Thanks. I’ll take a look.

Yes thank you. I wasn’t sure about fitting that cheaper one. The stainless one looks pretty solid. I’ll have a look into it further. I just dont want to drill into my roof. Might have to take it under the eaves or work out how to get power up there.

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As already stated the COAX you are using is no good. 6dB loss means only around a quarter of the signal received by your antenna is being received by your dongle. Look at replacing this with something low loss, like Ultraflex 10 or Hyperflex 13.

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This one uses zero length, zero loss coax to connect antenna to dongle :wink:

I’d say ‘inappropriate’ rather than ‘no good’. RG223 is very good cable, just not intended for this purpose.

The maths is correct, but you are comparing 13m of cable with no cable at all. Even the impressive Hyperflex 13 will give you 1.5dB loss before you put connectors on it. The difference is 4.5dB (not 6dB).
But have you priced it? That’s a 100euro cable you’ve spec’d there


As for the Ultraflex 10, where do you get connectors for 10mm (0.4") cable?

Just because you can, doesn’t mean you should.
Jamming a random piece of wire into a socket risks destroying the socket. Either you’ll permanently deform the contacts or at the least, destroy the contact plating.
The center pin of an SMA plug has a smooth tapered point to gently spread the mating contacts.
The guillotined ends of a paperclip will brutalize an SMA socket
Note the SMA Pin diameter has a tolerance of 0.0015"

This extended the range about 10 miles. Thanks, it gave me some perspective on how to treat this.

I’ve ordered a LL-195 Coax Cable, Length 25cm (about 9 inches). I also bought a straight N to SMA gold adapter which I thought I’d try temporarily just to see what would happen if I directly connected it (without a cable) to the flightaware antenna.

Today I received a magnetic base 5dBi Antenna and tried that out. Immediately I picked up a plane that was over 20 miles away. That’s never happened before. So clearly the problem was the cable. The unit was in the same spot.

I wasn’t comparing with anything. I simply stated that with 6dB cable loss, the signal received at the Dongle will be a quarter of what is received by the antenna.

I use these…

SMA Compression Plugs

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Before, I didn’t understand - now I’m confused.

Hyperflex 13 is described as 0.500" cable
Ultraflex 10 is described as 0.400" cable


Ok, but it only tells half the story.

I’m confused about what you’re confused about?

LMR600 is good too.

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(Random characters added due to not being bothered to add blank spaces) .

I highly recommend the LMR400. But it’s pricey…

The connectors you linked above claim to be suitable for 0.400" cables as well as RG8 & RG213 - both commonly referred to (apparently incorrectly) as 1/2" coax.
I can’t find SMA connectors for the 0.500" cable.

Regardless, it’s still a 100euro cable (120usd) and the sellers in Australia who list it, don’t seem to have stocked it. Add international postage to an order and you may as well be using an LDF or FSJ cable

You asked where I got connectors for 0.4" cable, I posted a link to them. Now, I’m the one who’s confused :stuck_out_tongue:

I should have asked where you get 0.500" connectors. I can only find Type-N and PL259, but they certainly aren’t common.

I wouldn’t know, never used them. My Install uses WF103 cable as I hadn’t heard of Ultraflex at the time. WF103 is still pretty good though.