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Author Topic: UNNT (OVB). International airport Tolmachevo, Novosibirsk, Russia.  (Read 8455 times)
Radiotrance
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« on: August 12, 2014, 12:19:58 PM »

[actual photos of the feed setup is down the thread]


Hello there.

Just wanted to let you know that here in Russia we're not only invading foreign countries, shooting down passenger airplanes and making other evil world-occupation stuff (all according to impeccable western media, of course), but has some sort of hobbies too. This is the handmade avia-antenna located 22km from airport Tolmachevo without actual radio visibility to it. Nevertheless, the quality of recieving is very good, exept for the planes on the ground. I'd like to raise the height of it, but unfortuanely this makes matters worse because of the intermods from FM Broadcast stations.

Will try discone antenna with the higher mast though. So far you can listen to the traffic here: http://mtl2.liveatc.net/unnt
« Last Edit: October 14, 2015, 03:48:50 PM by Radiotrance » Logged
colonel_Shults
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« Reply #1 on: August 17, 2014, 10:43:22 PM »

Hello and thank you! Now I can finally listen to the planes that flying above my home grin
And yes, quality is pretty good, at least, I can't tell the difference from other "mainstream" ATC.
« Last Edit: August 18, 2014, 12:09:55 AM by colonel_Shults » Logged
Radiotrance
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« Reply #2 on: September 24, 2015, 09:29:42 AM »

It's been more than a year and feed setup had changed many times in search of a clear audio.

Discone antenna turned out to be a no-go. That's the antenna now:

There is a NF-88118 notch filter and a lightning protection installed.

Airport Tolmachevo is weeell beyond those buildings. Distance is 22km (14 miles), there is a hill on the way and there is no line of sight whatsoever:

Despite that, all dispatchers do sound loud and clear now. But not the planes/cars on the ground, which are 50/50.

Backlight colors of the Uniden BCD996XT scanner are set accordingly to the Flightradar's 24 flight level coloring, from magenta to white:

For the listeners I'm streaming a metadata with channel names, so your media player should also show you who's talking right now.

Im planning on installing a higher mast and increasing antenna stack from 2 to 4 yagis.
There's a lot of international traffic in Novosibirsk Control zone, even some of the russian planes talk in english.
So, welcome to UNNT!
« Last Edit: September 24, 2015, 12:03:58 PM by Radiotrance » Logged
InterpreDemon
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« Reply #3 on: September 28, 2015, 06:00:03 PM »

Comrade,

Looks like a nice setup, and getting anything on the ground, let alone 50/50 at 22km and over a hill is pretty damn good. That being said, there may be a few things you might ponder as you experiment. Firstly, the theoretical gain of 3db by doubling the elements in your array is just that... theoretical, and to really HEAR a difference between 50/50 and say, 80/20 in the real world requires more like 5+db over whatever you are getting now. I also believe that your current mounting arrangement is not ideal for those two-element arrays since the reflectors are too close to the mast and you've got all kinds of interaction going on there. In fact, since your driven elements are simple dipoles, you'd probably be better off removing the reflector elements and spacing them (the driven elements) both in distance from the mast as well as distance from each other as if you were just making a vertical collinear. Of course it would be even better if you made some folded dipoles for the driven elements because it is much easier to make a phasing harness from 75 ohm cable and the bandwidth is wider, etc., but I really think that two more yagis and another ten feet ain't going to get you there with all the additional configuration parameters and losses.

If I were to do anything at all with your current, working array, I think I would instead try stacking your two yagis HORIZONTALLY, using a horizontal cross T at the top of your mast. Spacing say, six feet apart should be enough, but you can work with the spacing model on a computer (EZNEC, etc) to minimize and/or tailor the side lobes, which is the principle advantage to stacking vertically polarized yagis horizontally since a yagi in vertical polarization is not as tight in azimuth as it is in elevation, and you want to focus both. Stacking at the correct horizontal spacing can do that. For more information and/or pictures of what I am talking about, search "amateur EME arrays".

Anyway, it's good hearing from Novosibirsk, my favorite Russian town. It's the name of the Russian sub tender in that terrific cold war movie, "The Bedford Incident".

Good luck with your experiments in seeking perfection, obviously you have not been properly indoctrinated in the old Russian engineering axiom, "Better" is the enemy of "Good Enough".

Yours,

Capitalist Pig

Кстати, семья моей жены из России

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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
Radiotrance
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« Reply #4 on: October 10, 2015, 09:40:16 AM »

Thanks for your reply.
I've upgraded the set. This is how antenna looks like now.

Whole construction is 15 meters high. Improvement is noticeable but as you said, it is not huge.

Vertical spacing is 1.9 meters boom-to-boom (0.8 of the wavelenght) As far as I know this is how it should be done, not just 1/4 lambda between vibrators. Antennas and splitter are home-made but not by me. The seller provided them like that and I dont really get a reason to remove reflectors and therefore loose much of a gain. I like these yagis as they are - not very directional, but with noticeable gain over simple dipole.
Also, stacking antennas horizontally would narrow down the diagram in a horizontal plane instead of a vertical. I dont need that at all. So I cant see a reason why I would prefer horizontal stacking.

Если есть желание помочь исправить ошибки в конструкции, буду рад.
Аська 156984709, скайп radiotrance_54
« Last Edit: October 10, 2015, 09:58:58 AM by Radiotrance » Logged
InterpreDemon
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« Reply #5 on: October 10, 2015, 11:21:31 AM »

No, spacing the elements horizontally will narrow your azimuth beam (horizontal direction) IN ADDITION TO the elevation beam (aiming at the horizon). For ground antennas and vehicles at a distant airport you need BOTH. In any event, without the proper test equipment it is very difficult to get the maximum or proper performance from an array such as yours, the losses in spacing and phasing may offset much of the advantage of the multiple elements, but as I said before the additional two elements and a few more feet in height were probably not going to make much difference here, well tuned or otherwise, so you are not missing much.

The best thing to do now is use it for a while and look for common areas where the performance is below what is needed, then take your time and figure out if anything can realistically be done about it. For example, rarely can you go from a signal not being heard at all to solid copy, a jump of about 12db, which is sixteen times the signal strength, so even if your array is only running at half efficiency and you get it tuned perfectly you'd still need another eight times the signal strength to pull that walkie-talkie out of the mud.

The same goes for elevation, but it's even more depressing... each doubling of tower height gets you about 50% more range. Right now the radio horizon for your antenna is about 14km, so if you double the height to 30m that only gets you to about 20km, which is close to your requirement and should get base station antennas pretty solid, but still a bit less than needed for solid ground mobile traffic.

If it were me in your situation I would probably opt for elevation over complex array, a really good, wide band coaxial dipole antenna up as high as I can get it on a guyed mast extension and hardline (Heliax) transmission line.

The attached photo shows two arrays that between them are able to pick up all the ground and airborne traffic at an airport 14km distant, and the elevation of the arrays is just a few feet above yours, the 4-element beam being at about 16m and the coax dipole a few meters higher. The gain of the coax dipole over a normal ground plane is 2-3db and the gain of the beam is about 9db, both are very wide band and exhibit that gain across the aviation band. The other 2-element beam to the right is aimed at a different coverage area (out to sea).

So you see, for me to get the same performance from an airport 22km away I would need to raise those arrays to more than double their current height, like 40m, which would be pretty tough for all the antennas, but relatively easy for that omni on the top. By the way, there is little on the ground that the beam picks up that the omni cannot pick up as well, when we surveyed the location we did it with the omni only, but the beam was added to make solid copy of the planes at their gates, cars and hand-held radios on the ground. That's what an additional 6db will get you... things that are already heard being heard better.
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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
Radiotrance
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« Reply #6 on: October 11, 2015, 03:35:42 AM »

Thanks for clearing things up.

No, I dont want to narrow azimuth beam at all so I certanly wont stack anything horizontally. Im recieving more than one aerodrome and traffic from different directions and aint willilng to sacrifice that.

15-meters mast is installed on the roof of a like 30-meters building, so top antenna hight is 45 meters at least. Its the hill that dish it out.

Im interested in your set. What is the 9dB yagi beam made for? Is it for airband 118-136 or for ground airport communications (163-164MHz)? Have you made it yourself or we can buy one? And the most interesting part is how you combined the coax dipole at the top and this yagi into one cable (if you did)? Some kind of a splitter? If so, could you point me at one?
« Last Edit: October 11, 2015, 04:04:13 AM by Radiotrance » Logged
InterpreDemon
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« Reply #7 on: October 11, 2015, 05:43:36 PM »

All those antennas are custom made to requirements... by me. The coax dipole omni is wide band, from 117-137 with SWR below 1.5, and the 4-element beam has a match below 1.5 from 118 to 134, with a perfect match and best gain pattern at around 129, which is where most of the company ground communications between aircraft, vehicles and ramps/gates takes place at the target airport. All three antennas have their own dedicated 1/2" Andrew Heliax (hard line) that terminate at an enclosure at the base of the mast which contains three 20db VHF preamplifiers, lightning protection and various tuned stub filters that notch out certain offending signals or their components. From there three plenum rated rg-58 lines run via conduit 80 feet down into the building to a climate controlled data center where about 20 receivers monitor about 28 frequencies. The purpose of the preamplifiers is merely to offset the losses in the distribution and splitter system, NOT to try to pull "more" signal. The arrangement of splitters, antenna gain and coverage patterns tailored to get the required minimum signal levels from the various targets, as well as to minimize interference from a cluster of broadcast stations. Some of the remote airport terminals have better paths than others, and airborne traffic is also intercepted. The two element beam is aimed out to sea and tuned specifically for reception of ARINC on 129.9 and 129.4. The attached pictures show the head-end distribution scheme and receiver layout.

As to splitters and combiners there are all kinds, including the cheap and easy Wilkinson splitter/combiner you can make yourself with some 75 ohm coax and a 100 ohm resistor (learn about them here: http://www.i1wqrlinkradio.com/antype/ch79/chiave8.htm ). However I generally do NOT recommend trying to combine two antennas of different reception patterns or pass bands into one feedline when working a broad band solution such as the aircraft band... that type of combining is very difficult and best done when working discrete frequencies and/or extremely directional arrays where you can use high-Q duplexers, circulators and such to minimize or eradicate any unwanted interactions. In other words, it is far easier to get two receivers with dedicated antennas to talk into one audio stream than to get two different antennas to talk into one receiver RF input.
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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
Radiotrance
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« Reply #8 on: October 14, 2015, 02:07:06 AM »

Is this thing will do the trick?
http://www.ebay.com.my/itm/ELISRA-2-WAY-Power-Divider-10-1000-MHz-MW-12910-S-TESTED-/271216630646

Im kind of confised about it widebandity and interested of what's inside.
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InterpreDemon
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« Reply #9 on: October 20, 2015, 01:30:07 AM »

I wouldn't get that one, it has SMA connectors. The choice depends upon budget and type of coax you are using. A good quality line for professional work that is reasonably priced is MiniCircuits, and you can see a couple of 3 and 8 port units in that photo of the radio tray. They make them in all different port configurations, impedance and connector types. Doubtless there are Russian equivalents as well. But unless you are also going to be looking outside the air band or just don't want to experiment, I still say a Wilkinson combiner will work fine if you are just going with two ports and they can be made for almost nothing. They are not a broadband device as the two legs are tuned quarter wave sections of coax, but I have actually found that to be an advantage in high density RF environments as it adds some band pass selectivity with no additional loss. I have also found that I can tweak them slightly (unbalance them) to to "split" the air band into "lower" and "higher" when wider bandwidth is required, but if you use relatively cheap coax (RG-59 solid core instead of foam) the performance is good over +/- 5 mHz from the center frequency. All you need to do is get a BNC "T", get a six foot or so RG-59 video cable with BNC connectors on it, cut it in half, then attach the two ends to the "T". Then, you trim the two halves to a quarter wave  for the desired center frequency ( divide 7500 by the frequency in mHz to get 1/4 wave in cm, then multiply by velocity factor of the cable to get the stub length. Example: 7500 / 127.000 = 59cm, x .66 = 39cm ), making sure the length is measured from the center of the "T" to the end of the shield.

I have even made them just using two 6ft BNC video cables tee'd together as above, then simply removing an inch or two of the jacket at the appropriate location on each cable, bending the cables back on themselves, pulling two loops of the center conductor through the shields, soldering the 100 ohm resistor between them, then binding all the shields together with some wire and soldering them... input at the tee, two outputs on the two cable ends. It's not rocket science, you can make them from just about anything.

Here's one I made using RG-179 miniature cable, three BNC bulkhead connectors and a small plastic box.
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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
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