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Author Topic: TBPB - Barbados Setup  (Read 4291 times)
FlightTracker2
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« on: March 14, 2012, 11:29:44 AM »

Happy to say that after waiting three months to receive the Uniden BC355C Receiver, I was finally able to see what the home built 1/4 Wave Ground Plane antenna was able to do.

The hardest part really was finding 1/4" aluminum tubing for the vertical element. After much running around I  found two 3' pieces that cost me US$20.00. The other components were readily available at the hardware store. Each antenna cost around $30 to build.

I built two, one cut at 118.7 MHz and the other at 129.35. The testing was done using a Coby CX-CB91 9 Band Short Wave Transistor Radio which was adjusted to receive the Aircraft Band.  The good thing about this radio is that it has a digital readout, and the frequency tuning was quite accurate.  The bad news is that I couldn't listen to any aircraft transmissions within 15 miles as the signals were too strong. All I got was bleed distortion. The radio has no built-in AGC.

After much reading-up on which coax cable to use, 50 or 75 ohm, I went with the 75. The length is 82' from antenna to receiver.  The difference in reception between the two antennas was quite marginal. The Coby was able to receive transmissions some 85 miles from the South, a clear view to the sea.  However from the North was a different story, reason being that my location is below a ridge, and there are houses next door. My biggest challenge was getting the antennas as high as possible. They ended up being 39'. Got scared trying to go for more seeing that the wind is a major factor. To reduce the weight of the mast, I used 12' of 1" aluminum tubing at the top.  The antennas are still about 15' below the roofs of the obstructing houses, no clear line of sight to the North.  

Reception from the West - North was limited to about 12 miles and about 80 from the North - East. Reception from the Tower/Ground/Radar at the Aerodrome which is 7 miles away was good, but only if using a signal booster. After seeing that things weren't going to get any better I adjusted  the 129.35 MHz antenna to 124.00 MHz and called it a day.

When I finally connected the Uniden, I was very happy with the outcome. Being below a ridge proved not to be that major of a problem after all, although there is still a noticeable difference in reception range between the North and South, 145 compared to 300 nautical miles. Transmissions from Aircraft crossing the Trinidad/Guyana Boundary which is roughly 250 miles South-East of Barbados are received around S3. After reporting at that point, quite a few miles elapse before flights again make contact with Georgetown ATC, by which time they are certainly out of range, so at this point I have no true idea of the range to the South.  



http://flighttracker.homestead.com/Techinfo.html

Update 25 May, 2012

Most of the above has gone out the window.  Have added Radar since and made some other changes. The above link will bring you up to speed.

Just one note - Listening to Barbados ATC can be a bit annoying. Like all stations they have primary and back-up transceivers. When the primary radios are in use, no problem, loud and clear. When the Controllers switch to the back-up radios, you can hardly hear anything, sometimes nothing at all. Unfortunately, they seem to switch quite regularly throughout the day. Can only wonder why.

I was at the Airport recently filming some landings and I had the Uniden with me hooked-up in the car. Must have been a quarter of a mile from the Terminal. I could hear the flights twenty-five minutes out, but couldn't hear the Controller in the Radar room.  Maybe they are using some kind of Technology I know nothing of. Sometimes I feel like calling them up and asking WTF they are doing.

Don't they know people are out here trying to listen to a decent two way conversation?  angry  I guess not.
« Last Edit: February 19, 2014, 09:49:05 AM by FlightTracker2 » Logged
dave
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« Reply #1 on: March 14, 2012, 11:39:00 AM »

Great picture!  And thanks for posting about your experiences with the antennas and the new receiver.

The main issue I see with those antennas is that they are very close to each other, and since they are cut for the same frequency band, they will interact with each other.  This means the radiation/reception patterns for each antenna will be distorted somewhat.  Hard to say exactly how because it depends on the exact spacing and lengths of the vertical elements, and any other resonant antennas or structures in the close vicinity.

The good thing is that they are both at the top of the mast - if you separate them vertically (to avoid them interacting with each other) the mast would likely interact with the lower antenna.

My suggestion would be to separate them as much as possible - consistent with your receiving goals, of course.

Happy to help with any other specific suggestions depending on what you want to do.
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