FlightAware Discussions

40 percent increase in positions seen

I bought a LNA at K-mart for $10 that instantly increased my positions seen from 35000/day to 54000/day.

It’s a clearance item that now sells for $5. Get it while you can!

kmart.com/alphaline-trade-su … ckType=G47

That’s always great to hear. What kind of antenna do you use? Is this the only amp you’re using with it?

Having USB as a power source is convenient!

I have a homemade 1/4 wave vertical. Made out of an SO-239 panel mount fitting taken from an old CB. Soft aluminum wire radials are attached to the fitting with small nuts and bolts that held it in place in the CB. The vertical is a 6.8mm piece of #16 copper wire (house wiring) soldered to the center conductor of the fitting. It’s held in position on the window sill between the window and screen by putting the connecting coax thru a 1 1/2" piece of pvc about 12" tall. he radials had to be bent into more of a rectangular shape to fit the space but it does a much better job than the one that came from Nooelec with the dongle.
I live on the 5th floor of a seven floor apartment building facing ENE in downtown Syracuse, NY.

Sounds like a nice antenna. I haven’t thought of using aluminum wire and I have quite a bit of 12 or 10 gauge. Looks like you were lucky to get one of those amps. None available around here or online from Kmart.

Searching Google for “Alphaline SEA-100” will find plenty of results. Alphaline is nothing more than an in-house brand name for Sears / K-Mart… The same little amplifier is also marketed toward satellite television users and sold under several other brand names.

At this point, I’m most interested in finding out the actual frequency ranges this little thing is amplifying. Finding a manual online doesn’t appear to be easy, and pics of both sides of the box it comes in don’t seem to show anything about frequencies.

Even if it’s a low quality Sears/K-Mart knock-off, having an amplifier is always nice. On that note, a quality filter (such as the VBFZ-1065+ from Mini-Circuits) should pretty much be considered required equipment when using one that is amplifying more than just the frequencies we’re interested in. As we all know, an amp with such a wide range of affected frequencies is not only going to amplify 1090 MHz, but also every other noisy/interfering frequency it receives…and it’s going to blast them all right in to the SDR dongle if they’re not removed prior to that point.

I’m wondering how much feed line dibbyb has between this LNA and his SDR dongle? I haven’t found any proof yet, but there is plenty of discussion (speculation) around the web about over-driving an SDR dongle by having an amp installed too close to it. I ask because we know that the amp needs to go at the base of the antenna…but it doesn’t sound like he’d have much feed line involved with the antenna in the window of an apartment.


Call me picky, but…

The best place for an amplifier is at the base of the antenna. The worst place for an amplifier is disconnected in a drawer or on a shelf. An amplifier placed just before the receiver/sdr isn’t as good as an amplifier at the base of the antenna, but it’s better than no amplifier at all:

Left to right: RL Gore feedline from antenna to blue cylindrical Mini Circuits SHP-1000 high pass filter, LNA, SMA male-male adapter, 1090 MHz SAW filter, SMA right angle, SMA - MCX adapter, SDR (in blue enclosure), Raspberry Pi B+. The yellow and orange clip leads go to a bench power supply. This is a development system, and is working quite well. Eventually it will be repackaged and put in the attic within a few meters of an antenna.


Just to clarify my installation here, the antenna has a 2ft piece of RG-6 to bring it inside to the amp and then the amp is connected by a short pigtail adapter to the dongle. The 1/4 wave elements are 6.8 cm not mm.
I set dump1090 to use the AGC (–GAIN -10), when I take off the AGC the received message count seems to go way down, possibly from audio overload to dump1090.
The amp comes with an instruction sheet that just states the specs as:
Gain: 20dB (typical)
Noise figure: 1.0dB (typical)
Power supply: +5V at 130mA

I may get something with a bit more sophistication that’s targeted to the 1090 frequency but right now my total cost for what I have is about $30. Hard to justify spending more on a filter/amp than the whole setup costs.
Maybe FlightAware could make a big buy on some filters and offer them to members at cost.

I like this idea… :smiley:


Or a reasonable markup. After all, they are a for-profit business. :wink:

Just chiming in here, mine showed up today from Amazon (~$14, prime shipping). I connected it at the base of the antenna and I’ve seen a pretty significant increase over the last few hours (20-40%) in traffic. I live in a valley and the antenna is in the attic, so I didn’t expect much beyond what I was already getting, but for $14 it was worth an experiment. Once stats get compiled for a few days we’ll see if it’s actually the case, but so far it looks promising!

One thing to note was that the included AC adapter was DOA, but I have a ton of ~500mA USB AC adapters so I wasn’t stressed over it. YMMV.

This is an amplifier for boosting following TV bands:
VHF-Low or Band I (54 to 88 MHz)
VHF-High or Band III (174 to 216 MHz)
UHF (470 to 806 MHz).

The frequency range of this type of amplifiers is either from 47 to 850 Mhz or from 54 Mhz to 1000 Mhz.



Yeah, well it works for me.

Made a COCO antenna.

forum.planefinder.net/threads/ad … 23/page-18

The four element one at the end of the page.

Increased my “positions seen” by about 20 percent over my spider ground plane antenna. Not much increase in “planes seen”.

(1) What is the Velocity Factor of the Coax you used for making the CoCo. Element length (shown 114mm in planefinder design) depends on VF of Coax used.

(2) Try the 4-element one without the matching stub(two parallel wires) at the bottom , just normal CoCo

It’s RG-6, the .83 factor type. It’s from an old dish kit. I’ll be experimenting with the antenna but I’m pleased with the initial results.

Just added this to my setup this week (Cantenna, really roughly cut/drilled and probably needs to be rebuilt or changed to one of the spider/ground plane style ones), I’ve noticed around a 50% increase in positions seen(20k-30k), and ~20-30% more aircraft seen(~650/700-800). Now I’m curious what a proper ADS-B filter would do, or other changes to my setup. I currently run the current image for piaware. Any suggestions and what to add/change next? Dump1090mut? Change antenna? A proper filter

Where is your antenna now? Where would it like to be to have a better view of the sky? If your antenna doesn’t have a clear view of the sky, location is the first thing.

And don’t worry about a fancy antenna – the cantenna is a good start.

I think the next thing to try is one of the in-line amps, power source, and sat diplexer (the diplexer acts as a high-pass filter). Use a good grade of RG-6.

If your numbers go down when you move the antenna to a better location, or when you add an amp, then you need to figure out what the strong signal sources close to you are, and how to reduce the trouble they’re causing. That can be as simple as the sat diplexer, lowering the SDR gain, or may require more complex filtering. That filtering should be based on frequency scans so you know what you’re up against.

And remember – it’s just a hobby. This is supposed to be fun! Bonus points for experimenting and learning!

bob k6rtm

It’s in my attic, can’t get it any higher(other than attempting to move the clamp that’s holding to the rafter a few inches higher), or outside probably. I just added the LNA mentioned in this thread. I’ve seen a few different parts mentioned in various threads for filters/power/etc, just no clue what any of them are, and what’d be the best resulting combo to add, I’d prefer to just add a few more items to the setup(or spend ~$30/month on upgrades/changes to the setup max until I top out the stats in my area :wink: )

I have one of these amps, as well. Got it on eBay for $10. It definitely gives the signal a boost. RF chain = cantenna, sat amp, 50 ft of RG6, power inserter, Alphaline amp, receiver. Easily worth what I paid for it!

Definitely go with dump1090-mut if you haven’t already. Personally, I’ll stick with stock Piaware, but I install the deb on Raspbian Wheezy.

Well, I tried to follow the commands at github.com/mutability/dump1090 and they executed correctly, as far as I can tell… just now that it’s done that I can’t tell if it’s configured in PiAware correctly or running properly.