Author Topic: TBPB - Barbados Setup  (Read 13350 times)

Offline FlightTracker2

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TBPB - Barbados Setup
« 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.

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.

Another Update - August 2014  Out of total boredom I decided to reposition the VHF antenna and go with 50 Ohm RG58 cable.  The Antenna is now 26' off the ground instead of 42' and the coax cable is 34' instead of 82' of RG6 75 Ohm. I know the move sounds kinda stupid, but you won't believe that the long range reception strength has remained the same, but the S strength from aircraft on the  tarmac has gone up from a 2 to 5.  Boredom is sometimes a good thing  :lol:
« Last Edit: November 20, 2014, 06:12:43 PM by FlightTracker2 »

Offline dave

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Re: TBPB - Barbados Set Up
« 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.