ADS-B antenna question

freema22

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I am currently running a small "spider" antenna in a window for my ADS-B feeder. It has worked well for many years, but because of its location, is very directional. I am planning on putting a new wideband discone antenna, like a Diamond D130J or Tram 1410, on my roof to feed my scanner. Both advertise coverage up to 1300mHz, but has anyone ever used these types of antenna to feed their ADS-B receiver?

Thanks!
 

eorange

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Cleveland, OH
I have a D130J, but never really considered using it for ads-b. I built a colinear dipole, and also use the little telescopic dipole that came with my RTL SDR. Both have lengths that are resonant on 1.09 GHz. I also use a 1.09 GHz filter/preamp and I get really good results. Both antennas are indoors.
 

Thunderknight

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If the antenna is on the roof and your receiver is a significant cable distance inside somewhere, you need to be thinking about a preamp or some really loss loss ($) feedline. The feedline losses at 1GHz can be high. A dedicated 1090 antenna, with a filter and then a preamp at the antenna would, IMHO, be the way to go. If you skip the preamp, then make sure you are using good low loss feedline. Some people put the antenna on the roof, and then a short feed into their attic where they have their receiver. That way the feedline loss are kept low.
And I would use an antenna with N or SMA connectors, not PL-259, for 1 GHz.
 

iMONITOR

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vagrant

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First off, for permanent use the Diamond is better than the Tram. I have that exact Tram, but I only use it for temporary/weekend projects. If you can afford it use LMR-400 coaxial cable. Alternatively, RG6 may work well enough for the area you want to monitor.

A discone on the roof will help, but it's not that great as it is not specifically tuned for 1090 MHz. Also, if you use a simple T splitter the signal strength will be lower for the scanner and ADS-B receiver. You would want to use an amplified splitter to make up the losses, or one that is able to split the signal, but gives 0 dB gain out so you suffer no loss from the split.

I use an ADS-B outdoor antenna from dpdproductions. It is about 30' above ground and I use 50' of shielded RG6 coaxial cable. I also use an ADS-B filter/amplifier on the coax. Depending on the altitude of the aircraft, 200-250 nautical miles is not a problem as long as terrain (a mountain range) is not in the way. Still, I am more interested in MLAT and share my data with others to plot aircraft. I could use 1/2" Heliax which would keep it at 50 Ohms as well as reduce my signal loss. This would help me a little further out and with distant lower altitude aircraft, but I am not sure I care about monitoring some aircraft at 10k feet 150 miles away. If someone is interested in that area, they should help with a receiver of their own and share the data.

Here's the thing, if you want to just cover the general area where you live, a discone will work well enough if it is above your roofline. Use some LMR-400 coax if you can as it has lower signal loss. What you may not get is coverage of aircraft when they are on the ground if an airport is nearby. Ultimately, I presume the discone is primarily for your scanner. Go ahead and try it on your ADS-B receiver by connecting it directly and not use a splitter. Do this during midday when the air traffic will be busy. If you get the coverage you're looking for, fantastic. You can then purchase a proper splitter and enjoy the discone with both.

Also, have you tried adsbexchange.com? You may not need to worry about it if you're already covered. If you live south of Saginaw that area is covered. If you live north of Saginaw, it needs help.
 

mtindor

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Carroll Co OH / EN90LN
I am currently running a small "spider" antenna in a window for my ADS-B feeder. It has worked well for many years, but because of its location, is very directional. I am planning on putting a new wideband discone antenna, like a Diamond D130J or Tram 1410, on my roof to feed my scanner. Both advertise coverage up to 1300mHz, but has anyone ever used these types of antenna to feed their ADS-B receiver?

Thanks!
They are garbage for ADSB. If you want useful results for ADSB, you really need to use an ADSB-specific antenna with some gain. @iMONITOR posted a link to one. Flightaware sells some too. I have the big one from DPDProductions and it's better than any ADSB antenna I've ever used. I use an preamp (at the antenna) and a run of about 50 ft of LMR-400 coax. If you are serious about ADSB, you don't want to skimp on antenna or coax -- and depending upon your situation, a preamp at the antenna is a good idea.
 

nmelfi

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I use the flight aware 1090 antenna, about 20 feet Of solid copper quad shield RG6, and the purple flight aware stick with the amp and filter build in. I can reach 250 miles with no problem, except for SW. Those pesky mountains, do block lower altitude aircraft heading to Atlanta.
 

mtindor

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I use the flight aware 1090 antenna, about 20 feet Of solid copper quad shield RG6, and the purple flight aware stick with the amp and filter build in. I can reach 250 miles with no problem, except for SW. Those pesky mountains, do block lower altitude aircraft heading to Atlanta.
Yeah LMR-400 can be overkill if one has a preamp inline. In my case, I didn't add a preamp to make up for the little bit of loss in the coax run but rather because I'm in a rural area, not near any major airport, and really wanted to make sure I had as much signal available to work with as possible. I don't doubt that the built-in amps on the sticks do well and make a difference. But I needed it at the antenna to ensure I was amplifying what signal there is, rather than amplifying the noisier signal from the receiver end.
 

belvdr

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I simply put an SMA antenna on my RSPdx and can get 250-300 miles from my desk. Don't know if I'm receiving them all, but the map in VirtualRadar is full.
 

nmelfi

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Yeah LMR-400 can be overkill if one has a preamp inline. In my case, I didn't add a preamp to make up for the little bit of loss in the coax run but rather because I'm in a rural area, not near any major airport, and really wanted to make sure I had as much signal available to work with as possible. I don't doubt that the built-in amps on the sticks do well and make a difference. But I needed it at the antenna to ensure I was amplifying what signal there is, rather than amplifying the noisier signal from the receiver end.
Not much loss on 15 feet of 3gig swept cable, or noise for that matter.
 

nmelfi

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I just modded my Pi4 to 2 gigs and have it running off a M2 Nvme drive. Only have cubic SDR on it now, but installing flight aware this evening. 2 gig CPU speed, it is a 8 gig Pi. Will be interesting to see if it changes from the original as far as flight aware . Don't think so, but maybe faster will process stuf faster and show me more.
 

Ubbe

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@mtindor I believe I have your same preamp. It's on the front end of my ads-b scanner and I think it nearly doubled the throughput.
A 1090MHz filter and a preamp directly at my SDR dongle pretty much doubled my range. A homebuilt coax coliniar antenna with 8 sections worked ok, I tilted and angled the antenna to see if the directivity where pointing up in the sky but no improvement, but a $25 vertical GP at 1/3 the size from Ebay worked just as good.

/Ubbe
 
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