The permanent beacon is now on the air 24/7. I have tried several different antenna configurations and finally settled on a J-Pole as the permanent one.
I spent the better part of a day (10/14/07) working on the permanent beacon and got it on the air for a test. Here is a picture of the prototype. At the top, you can see the transmitter which is a modified pager transmitter and at the bottom is my home-brew Basic Stamp development board. The Basic Stamp is a complete computer system on a 24 pin chip. It is the brains behind the entire beacon. You program it in the Basic programming language.
This is what I built my beacon transmitter out of. I bought this new back in the mid 80's from Radio Shack and used it for several years before we got pager service in my town. After that, I boxed it up and stashed it away, thinking someday I might find a use for it. I think the use I found for it is even better than its original purpose!
It originally transmitted on 27.255 at 7 watts. All I did was a crystal change and added a trimmer cap to the circuit to fine tune the frequency. No re-tuning of the rf circuits was done and I got a perfect 5 watts out of it on 28.2215 mHz.
I have the beacon finished for the most part and mounted in a case. The metal enclosure is from an old audio amplifier.
An old computer power supply was used and I used a basic stamp for a keyer just because I had a bunch of them laying around from previous projects. At 50 bucks a pop, you probably wouldn't to use one unless you already had it on hand. Sometime in the future, I intend to add an LCD display and integrate a frequency counter, swr meter and power meter to the beacon.
In the 2nd photo, you can see the binding posts that I will use to eventually connect a backup battery to as well as the power supply, transmitter module and the keyer.
At the top right corner you can see the microprocessor cooling fan and heat sink I added to the final transistor. I transmitted a continuous carrier for 8 hours into a dummy load and at the end of the test, the transistor was ice cold.
Also note that the coax coming out is 75 ohm. I use the RG-6 for everything and it works great. I am in the satellite TV business and I buy RG-6 for 3.9 cents a foot and it works as well for HF as the high-dollar stuff all of my friends buy.
After much research and indecision, I finally built my permanent beacon antenna, a J-Pole. I wanted to use a J-Pole for several reasons (no radials, grounded feed, small amount of gain) but a j-pole for 10 meters is huge and can't easily be built the standard copper pipe way.
Staring out the window at my 50 foot telescopic pole in the back yard that had no antennas on it yet, it hit me. The pole itself could be the antenna! Thus was born my 10 meter j-pole. Plans are now posted in the projects section of this website.
Here are a couple of photos.
Last Updated ( May 15, 2011 at 09:35 AM )
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