BEACON
7 days a weekID String used on the KD4MZM beacon
V V V DE KD4MZM/B EL87RG
A beacon on a budget project.
Hello and Welcome. This page contains the information for the KD4MZM beacon. Here at the shack I run a 10 meter radio beacon. The beacon is a homebrew design. Most of the system is a converted CB Radio system. The radio is a Cobra 148 GTL 40 channel AM/SSB unit. The radio has been modifed to the 10 meter band. This is a real easy task with this unit. A quick retune of the output and the VCO and it will perform well. After moving it up in frequency, I reduced the power output on SSB to about 1.5 watts total output. This is done so as the radio can transmit 24/7 without a problem. To confirm that this radio could and would perform 24/7, I placed a jumper on it so as to make it transmit 24/7 on AM into a dummy load for thirty (30) days solid. After this simple test, I then placed a 1000hz tone into the mic circut and ran the test again for thirty days. I did this so that if I decide to relocate the beacon to a remote site I wouldn't have to worry about it quitting. To help maintain a cooler heatsink and radio I removed the 4" speaker and installed a 4" muffen fan. I then removed the front meter movement. This allowed a forced air type cooling system. I can say that the radio doesn't even get warm to the touch doing this.
The next part was the CW id'er. This was pretty much an easy task. With all the new digital voice holding projects out there a simple run to Radio Shack and that was done. I came about this system while looking around the local R/S store. The project comes with all the parts and paperwork to get it running. Now as hams we just have to make it work for our needs. The voice circuit is R/S part 276-1326, and sell for about $20.00 bucks. Now unless you want to run it on batterys, and I didn't, a simple 7805 voltage regalator will fix that. The next thing to do was to program the ID string into it. With only 20 seconds of record time I had to come up with a beacon string. I worked on a few and finally came up with the current one I use now. It takes 15 seconds to send at 20 WPM. The project device has 2 push button switchs on it to make it work. After recording the ID, you only need to push one to start the program string. I was able to use a shareware CW program from the computer to make the ID string with. After doing this I then took the output from the sound card and feed it into the voice project bypassing the project mic. I had to use a dropping resistor so as not to over drive the unit. You may have to try this many times before getting the right tone, loudness etc,. I know I did. After you feel you have that done you can then move on to the next step.
So far eveything going together as planned. hihi
The next thing I needed was a simple timer to set the beacon cycle with. I was going to use a 555 timer, but again Radio Shack pulls thru on this one. While reading the catalog making a parts list, I found that they sell a 555 timer circuit with relay, board and all the parts, plus it has adjustments for the timing. After compairing a parts list to that, the kit was the way to go. It is R/S part #RSU 12127114 and sell for $9.99. The timer runs on 12 volts DC. This is just right as now the radio, ID'er all run on 12 volts too. The next thing to do was hook the radio to the timer circuit and test the keying cycle. This takes a few tries before you get it going. I needed at least 15 seconds of key time so that the ID'er beacon could send it's message. After getting that, I then set the unkey time. Once that is done you are then ready to hookup the ID'er. Using the same relay contacts for the keying of the radio you hookup the ID'er. Now what happens is that when the timer cycle starts it will key the radio and start the ID'er sending it's message. If eveything is right you are good to go on the air with it. But we all know that don't always happen. Back to reprogramming the ID'er, what was happening was the ID'er was wanting to start as soon as the 555 timer said start. Well the radio was just a touch behind. So I reprogrammed the voice project starting with about 1/2 second blank spot. Now when the 555 timer starts it gives the relay and radio about a 1/2 second to balance out before it starts sending. Now to get the CW to go out on the air I feed the audio from the digital voice board into the mic jack as normal. Then by putting the radio into USB mode it sends it as modulated CW. The real freq is moved up by zero-beating effect. As for my 10 meter beacon, the radio transmits on 28.275, but zero-beats at 28.277.
This whole setup was then placed into a controlled on-the-air cycle. I ran a working beacon for another 30 days into the dummy load again. Along the way I would check power output, heat build up, and the frequency output. After the 30 days passed I felt the beacon was ready for the air waves. The beacon went live on April 1st., 2000. It has now been over 1 full year and I've had a zero down time with it. The system is still producing the 1.5 watts it started with and stays rock solid. I have gotten reports via QSL cards, emails, and voice QSO's about it. The beacon has been heard in all parts of the USA and world. This just shows that if the band is open a QRP station can work the world.
This beacon project was a result of a close friend having the Cobra 148 GTL radio that went bad. The radio's recieve was out and damaged further than what he wanted to invest to repair it. After see'ing and hearing about the freebanders using this same type of radio to invade 10 meters with I got the idea to use it for something good, as the transmitter still worked fine. The moving of the frequency output can be found almost any where on the internet. I then got a 3 amp power supply to run the radio, timer and digital voice project with. I was then given a Antron A-99 antenna. I then had about 75 feet of RG-8x coax that I used to feed the antenna with. The antenna is up about 15 feet to the base.
If you are planning or would like to put a 10 meter CW beacon on the air, I would say that this would have to be the best cost saving way. I'm willing to help you get one running also. If you don't want to build the system yourself, lets talk. I may be willing to build you one that would be a plug and run system, all complete with your call and information. You would of course have to find a clear spot on 10 meters that you could place your beacon. This may take some time. I spent many months listening up and down the 10 meter beacon area. I also checked the beacon lists of who was active, who was running part time etc,,. Although it's quite today it may be active tomorrow. The radio can produce up to about 15 watts, but I don't recommend this as it will be hard on this radio in a 24/7 setup. By using the 1.5 watts out I do think it would run for a long time as it's not over taxing the transmitter.
Eric...KD4MZM...