Bruce Lundy's Microwave Beacons for 1296, 2304, & 3456 Mhz.

Homebrew Microwave Beacon Project .


People who enjoy weak signal work, on any band, like to know there would be a weak signal on the air that they could use as a "standard" to make comparisons of their receiving equipment. A beacon is a very useful tool to indicate the condition of the band over a period of time. Is it stronger or weaker than "usual"? This can aid an operator in trying to make a more distant contact than usual. Beacons are usually very low power and are not found in the Binford Catalogue. They are mostly all home made devices that are CW, FSK, or any other mode. This write up is how I made beacons for 903, 1296, 2304 and 3456 Mhz.

All of the frequency sources are crystal oscillators that are temperature and voltage regulated. (Pictures 1 & 2) After some buffering of the oscillator stage, the approximate 100 Mhz. signal goes into a filter to pick on the desired harmonic of the oscillator. After filtering, (pict's 3 & 4) the signal goes into a broad band MMIC amplifier. (See 5 & 6) After some amplification, the signal goes into another filter, then amplified again, as necessary, to produce the desired signal strength and spectral purity. The chassis that is featured at the top of this page is my 902.985 Mhz., 5 watt CW beacon. It also contains the CW keyer circuit. KA8EDE/B EM89ap The 903 beacon building blocks are the oscillator, first filter, first single mmic amplifier, second filter, cascade mmic amplifier, third filter, second cascade mmic amplifier, fourth filter, and then the final brick amplifier. The cascade mmic amps have a ERA-2 driving a ERA-4. Ten of these were measured to have 30 db gain at 100 Mhz and 24 db gain at 3 Ghz. All interconnecting is done with UT-141 and SMA connectors. The spectral purity of this line-up yields ALL harmonics down at least 76 db. This is VERY FCC acceptable. The best DX report I ever got from this beacon was when it was in Beavercreek, Ohio mounted up on the tower at 77 feet was St. James Bay in Canada! Obviously, band conditions were great at that time.

The 1296 and 2304 beacons use exactly the same line-up except for their final bricks. The 1296 chassis will put out 8 watts and the 2304 will put out 4 watts. The 3456 line-up is somewhat different. The first few filters are tuned to 1728 and the last few filters are tuned to 3456. Talk about spectrally clean.... Right now, the final amp for the 3456 chassis is 2 - ERA-4's in parallel. I have a 40 watt amp for 3456 but it is a class A amp which must dissipate about 120 watts all day long and the whole chassis is not large enough to do that on a hot summer day! So, I'll compromise, humpfff...

All of these will be CW beacons, keyed by a common keyer, W8KSE/B EM89bj The final plan is to mount the 1296, 2304, and 3456 beacons on top of the Wilmington, Ohio water tower which would put them about 125' above the ground.

For more indepth details, please look me up on qrz.com and e-mail me.

Oscillator and temp. reg.
Oscillator & temp. regulator
Heat dissipating Darlington
Heat dissipating Darlington
903 Filter
903 Filter
3456 Filter
3456 Filter
Close-up of links
Close-up of links
Typical Cascade MMIC amps
Typical Cascade MMIC amps
Typical Single MMIC amp
Typical Single MMIC amp
bandpass plot
bandpass plot
  bandpass plot
bandpass plot
bandpass plot
bandpass plot
 

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This page last updated November 29, 2003.

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