Society of Ether Explorers San Francisco

PROJECT 33

Of all the VHF and UHF amateur bands, the 33 cm (902-927 MHz) allocation is generally the least used, because: There are NO off-the-shelf 33cm radios on the amateur market, most likely due to the lack of international allocations for this band. This band is shared with a plethora of industrial, medical, and other license-free wireless services such as video links, internet providers, remote sensing and control, and other OEM applications. With a few exceptions (namely Motorola Maxtracs and Spectras), surplus commercial gear for 33cm is difficult, if not impossible to modify for the adjacent ham band. Increased multipath propagation makes mobile and portable operation in urban and mountainous areas more difficult.

Of all the HF amateur bands, the 10M (28-29.7 MHz) allocation is generally the least used, because: Decreased solar activity over the past few years means that the Maximum Usable Frequency almost never reaches this high. This band is very dependent on constantly fluxuating solar activity, making regular nets or schedules on this band frustrating at best. Much of the local activity on this band (especially during the low end of the sunspot cycle) is on FM, yet many older HF rigs do not provide this mode. Commercial low-band (30-50 MHz) equipment that can be converted to this band is difficult to find and often expensive, since the most frequently used channels are in the top end of the allocation.

System Overview

Which is why, in keeping with our mission of exploring uncommon and underutilized frequencies, we are working on a project to link these two bands together! Project 33 will link a 33cm split-site FM repeater to a 10M all-mode simplex tranceiver. So what can we do with such an oddball system?

• As we move into the peak of the sunspot cycle (maximum solar activity is projected for the year 2002), we will be able to work world-wide DX from our portable and mobile UHF radios.
• We will gain the experience of developing customized circuitry to control the 10M radio.
• We will be able to experiment with methods of minimizing 33cm multipath, such as
  • circular polarization
  • Dual diversity antennas
  • Multiple receiver sites
• Because the 33cm repeater will be split-site, we will be able to place the RF equipment at the antenna to eliminate feedline and duplexer losses, and thus increase overall system performance.
• The system will be available during disasters and other communications emergencies as a backup area-wide communications path, in addition to existing ARES and OES systems. In this vein, we will experiment with NVIS (Near Incident Vertical Skywave) to ensure reliable 10M regional coverage.

Because of the shortage of portable 33cm radios, we have decided to make this a split-site system so that we can use our current dual-band HTs. Many HTs will receive 33cm, but will not transmit in this band. Therefore, we can transmit on the 70cm link frequency to "cheat" our way into the system.

33cm Receiver Site

• Located at QTH of KQ6DY, about 100ft ASL
• Frequency - 902.??? MHz
• Micor 800MHz repeater receiver strip - mod to 33cm ham band
• NHRC-2 Repeater/Link Controller -- built and ready for smoke test
• Micor 460MHz repeater transmitter strip, 15W output - mod to 70cm ham band
• 33cm circularly-polarized Antenna -- homebrew
• 70cm vertically-polarized Link Antenna
  
  

33cm Transmitter Site

• Located at QTH of KK6XF, about 250ft ASL
• Frequency - 927.???
• Micor 460MHz repeater receiver strip - mod to 70cm ham band
• NHRC-2 Repeater/Link Controller with digital voice ID and additional 10M link controller circuitry -- hack
• Micor 800MHz repeater transmitter strip, 15W output - mod to 33cm ham band
• ???? 33cm Power Amplifier -- kit
• 33cm vertically-polarized Antenna
• 70cm vertically-polarized Yagi Link Antenna -- homebrew
  
  

10M Link

• Modified Ranger RCI-2950 10M All-mode Tranceiver -- hack, schematic in hand, still looking for Tech Manual
• 10M horizontal Dipole Antenna -- homebrew

The initial phase of the 10M link controller will use the Ranger's 10 programmable memories. Future expansion will provide direct frequency entry and scanning control.

Project Schedule

Construction has started! Status of subsystem is shown in bold italic. We hope to have a 33cm beacon on the air by the end of 1997, with the complete 33cm repeater system active by Spring, 1998, and the whole enchilada (including the 10M link) working by Summer, 1998 -- just in time for the predicted upward trend in solar activity!

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last updated 12.31.97 by KK6XF