The VHF station at N5XU

The VHF/UHF weak signal station at N5XU is designed with DXing and contesting in mind. Even though we have several radios, the equipment is arranged such that most everything that is important can be easily reached by a single operator. Amplifiers and power supplies, which generally do not require adjustment after they are turned on and plugged in, are all located to one side, out of the way. During VHF contests, there is still sufficient room for two operators to sit at the table, usually one to operate the six meter radio, and another to operate the other radios. We also have satellite antennas, and a modern, satellite-capable multiband transceiver.

The equipment is on a single table and shelf. On the top shelf, left to right: Tokyo HyPower HL-60U, Optimus PRO-50MX headset microphone, Kenwood SP-230 Speaker, Super CMOS Keyer III sitting on top of Yaesu FT-290R, and Realistic HTX-100/Downeast Microwave DEM28-222CK transverter combination. On the bottom shelf, left to right: Astron RS-35M power supply, Yaesu FT-726R, Bencher BY-1 paddles, Yaesu FT-847. The PC monitor, speaker, keyboard, and mouse are connected via long extension cables to a 90 MHz Pentium machine located out of the frame to the right. On the floor is a Henry 3CX800A7 50 MHz linear amplifier. On the right side of the table, you can see MFJ coax switches, used for our 50 MHz and 144 MHz antennas.

AM-6155 Amplifiers for 144 and 222 MHz

Our best equipped band is the six meter band. The Yaesu FT-847 is a modern radio, puts out 100 watts of power, and has built-in DSP receive filters. Our radio also has a 500 Hz CW filter in it, and the radio automatically does semi-break-in keying. The radio is compact, features dual VFOs, and can also be used with satellites on 145 MHz and 435 MHz. The six meter station at N5XU has been used to work hundreds of grid squares and several countries on multiple continents.

On two meters, the Yaesu FT-726R puts out 20 watts, which we can increase to 400 watts with a converted AM-6155 power amplifier. This amplifier belongs to a club member and is on extended loan. Like our AM-6155 on 222 MHz, it is mounted in the equipment rack beside the HF station. In the photo at left, the top amplifier is the 144 MHz amplifier, and amplifier below is for 222 MHz, and the oscilloscope at the bottom is used for HF RTTY operations. With only modest power and antenna system, the two meter station has been used to work over a dozen states. This station is adequate for all but consistent EME (moonbounce) propagation; contacts have been made on tropo scatter, tropo ducting, and meteor scatter. We have even made one EME contact on 144 MHz.

Realistic HTX-100 and DEM 222 MHz transverter

Our one and a quarter meter gear is an HF radio hooked up to a 222 MHz transverter. The transverter and HF radio configuration offers club members the opportunity to see up close a different way to build a VHF station. The HF radio is a Realistic HTX-100, a 10 meter mono-band mobile radio that became popular during the peak of the last solar cycle. It has been modified to put out a 25mW signal on transmit. The transverter is a Downeast Microwave DEM28-222CK, and was built from a kit by Ken WM5R. The amplifier is an FAA surplus AM-6155 using a single Eimac 8930 tube. It was converted for transceiver operation on 222 MHz by George K5TR and puts out over 400 watts key-down. For several years, we were the only fixed station in our grid square active on 222 MHz SSB/CW.

Our two meter radio is also our seventy centimeter radio. The radio only puts out 10 watts on 432 MHz. We have a modest solid state amplifier that puts out 60 watts of power. The Tokyo HyPower HL-60U is a fine amplifier, though, and is designed for 432 MHz SSB/CW, rather than the more typical 445 MHz FM. It also has a GaAsFET receive preamplifier. Seventy centimeters is the only band, so far, on which we have 1/2" hardline instead of flexible coaxial cable feedline. The hardline saves about 4dB of signal compared to the coax that it replaced, a bit over a 100% signal improvement.

Custom-built Super CMOS III memory keyer

The twenty-three centimeter band is N5XU's newest band acquisition. It is also our most complex and exotic equipment. The IF radio we are using is a Yaesu FT-290R, which puts out 2 watts in all modes on 144MHz. The rest of the equipment is mounted inside a rain-proof box at the top of the N5XU tower. The transverter is a UHF Units 3 watt model, a predecessor of the Parabolic AB of today. It is interfaced to the IF radio by a Down East Microwave PIN diode switch and a 10dB attenuator on the transmit side of the switch. A 35 watt amplifier made by Down East Microwave is switched in the transmit path. The external T/R switch is an Dowkey coaxial relay that is switched by the DEMI PIN device. 13.8VDC is brought into the box by two 80' runs of Romex 12/2 direct-burial type electrical cable. Voltage drop is 0.04V on receive and < 0.3V on transmit. The station outputs 35 watts on 1296.100 MHz transmit. 1.2GHz is the only band on which we are using a loop yagi antenna.

All four radios are capable of CW operation, and they are all hooked up to a custom-built electronic keyer. This keyer is a CMOS Super Keyer III; it has six memories, can handle auto-incrementing serial numbers, and is capable of 5 to 99 wpm speeds. The custom case includes four toggle switches; each switch turns on or off the keyer output to each of four radios. It also has a PTT line out associated with one of the radios, which comes from a circuit designed by Dale KG5U. The iambic paddles are a Bencher BY-1.

Ken KM5FA (now WM5R) operating in the ARRL September VHF QSO Party 1998

The computer at the VHF/UHF station is a 90 MHz Pentium running Windows98. It has a sound card and a big 17" monitor. It is mostly used to run TR Log contest logging software. It is also wired for use with the MS_DSP software for high speed CW meteor scatter work on 144 MHz. It is connected to the Internet through the shack gateway. The CPU case itself is actually located underneath a corner of the HF table, where there's more room; the monitor and keyboard are connected with long extension cords.

Check out UTARC VHF for more information on the club's VHF/UHF efforts in DXing, contests, and satellite operations.