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Author Topic: KMEM / KACY Feeds  (Read 5201 times)
bugalou
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« on: November 28, 2014, 06:47:00 PM »

Hello everyone.  I provide the feds for KMEM (Memphis International Airport) and KACY (Atlantic City International Airport and the 177th ANG fighter wing).  Below are some basic pictures of the feed.   KMEM is hosted at my parent's house just outside of Memphis, and I host KACY at my house in south Jersey.  Both feeds are very simple consisting of a few scanners and a Raspberry Pi providing the stream.  Thanks to Dave for all the help getting these up, and thanks to all my frequent listeners.  Please follow me on Twitter @hgbugalou for the latest on all the feeds I provide.



KACY:







KMEM





« Last Edit: November 28, 2014, 06:55:06 PM by bugalou » Logged
verbatim
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« Reply #1 on: December 01, 2014, 12:16:10 AM »

awesome, it's possible an antenna close-up picture? is the antenna homebrew??
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bugalou
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« Reply #2 on: December 06, 2014, 08:06:06 PM »

awesome, it's possible an antenna close-up picture? is the antenna homebrew??

I can try when the weather clears out here.

It is a custom made Arrow antenna (http://www.arrowantennas.com/).  I have the same model for the KMEM feed in my parent's attic.  I did an outdoor setup here to try and pickup an NY center feed I am right on the fringe off.  KACY is less than 2 miles from my house and I could probably pick it up with a cloths hanger  cheesy .
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viista
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« Reply #3 on: December 15, 2014, 08:08:58 PM »

Great setup! What kind of USB audio converter(blue box) used on KACY feed? Mind sharing with some technical info?

Thanks

Jeff
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dave
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« Reply #4 on: December 20, 2014, 06:31:03 AM »

Great setup! What kind of USB audio converter(blue box) used on KACY feed? Mind sharing with some technical info?

Thanks

Jeff
WMKB



Jeff-

We generally use one of the two audio interfaces on feeds that LiveATC helps with:

http://www.amazon.com/gp/product/B009NVS6KS/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

We also use the Griffin iMic - available from various sources.

One reason is that these cards have a proper Line In interface which presents the proper impedance to a scanner's audio output.  The other reason is that these cards have tested out pretty well in audio quality tests.

The cheap $1USD audio interfaces that exist can be made to work - you just have to either very tightly control the scanner volume so as not to overdrive them or provide your own impedance matching network so as not to overdrive the mic level input of those cards.

Dave
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InterpreDemon
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« Reply #5 on: December 20, 2014, 01:42:41 PM »

My only suggestion, FWIW, would be to rotate that antenna to horizontal or end-mount it from the handle if you want to stay with vertical polarization. Having the driven element right next to the mast is killing the gain and pattern, not to mention making any setting of that gamma match moot once mounted to the mast. Ideally you would pull that rubber handle off, add a foot or two of tubing and mount vertically with the reflector element at least a foot away from the mast. The coax from the driven element would then be strapped to the antenna boom, fed straight back to the mast and then down. Here's an example of the ideal mounting for vertical arrays:
« Last Edit: December 20, 2014, 01:45:08 PM by InterpreDemon » Logged

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
bugalou
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« Reply #6 on: December 21, 2014, 03:53:40 PM »

Good to know.  I will adjust it the next nice day we get.
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bugalou
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« Reply #7 on: December 22, 2014, 01:44:29 PM »

My only suggestion, FWIW, would be to rotate that antenna to horizontal or end-mount it from the handle if you want to stay with vertical polarization. Having the driven element right next to the mast is killing the gain and pattern, not to mention making any setting of that gamma match moot once mounted to the mast. Ideally you would pull that rubber handle off, add a foot or two of tubing and mount vertically with the reflector element at least a foot away from the mast. The coax from the driven element would then be strapped to the antenna boom, fed straight back to the mast and then down. Here's an example of the ideal mounting for vertical arrays:

On my computer so I can be a little more verbose now.  Would you recommend doing the horizontal option, or just mounting it at the end vertically with a rubber insulating grommet? Is there a name for the bracket needed I could search for to purchase or will it just be something I will have to engineer?  Thanks for the input!  I am still learning when it comes to some of the radio side of this despite hosting feeds for a few years. Smiley
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InterpreDemon
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« Reply #8 on: December 22, 2014, 07:23:44 PM »

Well, the quickest thing you could try without modifying anything would be to simply loosen the clamp and rotate the array horizontal. You lose 3db (half power) picking up vertically polarized signals, but that is more critical with any marginal ground based stations you are getting verses the airborne, which tend to get scrambled around a bit anyway and are much stronger. The point is that the elements need to be perpendicular to the antenna mast if that mast passes through or near them. Alternatively you could use non-metallic mast, however your coax would then act as a mast unless you fed it first back along the boom past the handle a foot or two and then swept it around and down to the mast below... difficult to do and ugly.

On the other hand, if the vertical mast is BEHIND your reflector element (the longest one in the back and next to the handle) it has far less effect, especially if over a foot behind and preferably two feet or more. All you have to do is find some tubing that will fit inside or outside the diameter of the antenna boom tubing, slide it in/over in place of the handle right up to and against the reflector element, drill a hole through both and install a bolt, or split whichever is the outside tube with a couple hacksaw slots and clamp them tight with a hose clamp, then clamp the back of that new extension tube into your right-angle mast clamp as before.

Finally, you run the coax straight back from the feed point right along the boom (that would be the "side" of the boom, "under" the center of the reflector element) to the mast and then down, holding it with zip-ties. With this mounting your array will preserve the pattern and gain it was designed to deliver, which could be as much as 8db if properly tuned, otherwise six or so, which is about four times what you get with an ordinary ground plane antenna. Right now, I suspect a good ground plane would probably have equal gain in the direction your antenna is "pointed" (in quotes because as mounted it is impossible to know where your gain nodes, if any, are) and superior performance around the rest of the horizon. By rotating your antenna to horizontal you lose about half your gain for vertically polarized signals, but you would still be 3-5db stronger (roughly double) than a ground plane in the direction you would now KNOW that you were pointing. Unexpected bonus... if there is a VOR out in that direction with ATIS information you will pick it up better than otherwise possible because VOR's are horizontally polarized.

I actually built an array with both horizontal and vertical elements, two antennas together with two different driven elements, to pick up the horizontally polarized KHPN ATIS signal coming from the CMK VOR about ten miles north of me, as well as the vertically polarized Liberty East departure transmissions coming from that same site, which is actually on the other side of a hill from my location. You can see them in the foreground below, a three-element vertical beam like yours and a two element horizontal, both on the same boom and neither interfere with each other.
« Last Edit: December 22, 2014, 07:51:56 PM by InterpreDemon » Logged

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
bugalou
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« Reply #9 on: February 26, 2015, 10:20:23 AM »

Still planing on making the antennae adjustment if it ever warms up here on the east coast! I will be sure to update this thread then.
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