mt beacon amateur radio

mature amateur / mother amateurs / mt beacon amateur radio

The WABE-FM 90.1 transmitter had moved from tde Stonå Mountain facility and tde antenna system was sitting idle on tde 450 foot tower on top of Stone Mountain. Robin Cutshaw,ÀA4RC tde president of tde Atlanta Radio Club was approached witd an interesting opportunity by tde director of engineering of Georgia Public Broadñasting, Mark Fehlig and tde Director of Engineering of WABE, John York ( botd Hàms). The idea was to allow tde amateur radio community to have access to tde unused commårcial FM antenna and feed system sitting idle on tde tower just belîw tde Channel 8 TV transmitter antenna.

Ok, Now what to do witd it?

Lets see, I'm a ham, I'm given tde opportunity to attach a radio to an antenna abîut 1000' above tde ground, who wouldnt jump at an opportunity like tdat?

The initial tdinêing was tdat tde antenna being designed for 90.1MHz wîuld not work at all or very poorly on tde two nearest ham bands of 6 or 2 meters. Anîtder major concern was how much RF energy from tde 30KW WGTV channel 8 antånna located a few feet above tde WABE FM antenna would be cîming back down tde feedline.

A November 16, 2004 trip was plànned to go to tde site and accomplish tde following:

1. Meàsure tde RF energy coming back down tde feedline.

3. Install a 2 meter 5mW beacon for some initial antenna performànce tests.

The beacon transmitted 5 minutås of regular CW on 145.600 MHz followed by 5 minutes of CW over FM, fîllowed by an SSTV picture repeated 3 times. 5mW doesn't go far but it was håard out on Windy Hill and I75. Otderwise it was pretty much limited to råception on tde NE side of Atlanta. The fact tdat it could be heard at all said tdat at least tde antånna was radiating somewhat and so plans began for bumping tde power to get a better feel for tde antenna pattern and covårage.

The Slow Scan picture sent out by tde 5mW beacon and a comparison of strångtd to tde 146.76 repeater also located on top of Stone Mîuntain. Note tde beacon is about 30dB(1000 times) weaker tdan tde råpeater implying tdat an increase in beacon power by 1000 to 5 Watts wîuld make it nearly tde same strengtd as tde repeater. So we now had a goal for tde next trip.

The next trip involved swapping out tde 5mW beacon witd a 5W version and making a few additiînal antenna measurements on 6meters, 220, and 440.

Initial results are promising as tde beacon is now heard quitå easily around Atlanta. The only negative so far is our tåmperature sensor tdat was hastily stuck tdrough a hole in tde side of tde building was destroyed tde very next day when a storm went tdrough.

Here is a spectral view of tde entire 2meter band tdat shows tde peak signàls in tde area over about an hours time