144 MHz particulars
Antenna 1: 4 X 17 element yagis @136 ft. 20 dBd gain
Antenna 2: 16 X 5 element yagis stacked vertically, aimed at 230 degrees. 20 dBd gain
Antenna 3: 4 X 6 element yagis stacked vertically and aimed Northeast. 16.8 dBd gain. (2008)
Receivers: Ten Tec OMNI V with added INRAD filters. Elecraft K3
Transverter: DEMI 144-28 20 watt transverter with Teletek commercial solid state amplifier.
PA: Home brew Triode amplifier, W6PO design, 1200-1500 watts output
The 144 MHz LVA consists of 16 five element yagis all stacked vertically on one leg of the 130 ft Rohn 45 144 MHz tower. They are all aimed at about 230 degrees, and, with a -3 dB beam width of 57 degrees, provides good coverage over about 90 degrees of azimuth. The gain of the array is about 11 dBd at plus or minus 45 degrees of the boresight heading. ( 185 to 275 degrees!!) This covers a large portion of the activity centers in the Northeast including Boston, Providence, RI, Hartford, New York City, Philly, Albany, and even Toronto! The above picture shows the horizon facing southeast. Above the LVA is an array of 17 element yagis in a large H frame. The rotator is a Prosistel PST-61. It replaced a Hy Gain T2X rotor that was stripped out during high winds on the old 144 tower, which was a 90 ft Rohn 55 right next to the operating shack. The LVA provides about the same amount of gain as the high gain quad array on top of the tower. The top quad array is fully rotatable, and has a narrow beamwidth of about 11 or 12 degrees. The new 130 ft tower is about 235 feet away from the shack and off to the South. The main feedline is a 365 ft run of 1 5/8" coax. There is no preamp. Losses in the feedline are just under 1 dB. The tower base is located about 860 ft above sea level. The hill visible just to the left of the tower, and below the horizon, is about 750 ft asl. Garrison Hill in Dover, NH is visible beyond that. On a clear day, you can see the ocean about 27 or 28 miles away.
Another view of the 144 MHz LVA facing towards the south southwest. The small bright buildings visible to the right of the tower, are in Rochester, NH, about eight miles away. Boston's Hancock tower is just to the left of the tower and visible in 20 power binoculars on a clear day.
Telephoto view to the South from the 144 MHz tower, showing the Route 95 bridge at Kittery and Portsmouth, NH. The smoke to the right is from a power plant in Newington, NH. The tanks and structures just to the left of the 95 bridge are at the Kittery/Portsmouth Navy Yard. It is interesting to note, that while the Route 95 bridge over the Piscataqua River is a huge one, and 27 miles away, it is still below the horizon when viewed from the tower here. On a clearer day, the ocean and the horizon is visible just above the bridge.
This is the 144 MHz operating position. The operator is Pete, K9PW. The picture was taken just before the start of the September 2006 VHF Contest. Hopefully that will explain why Pete has four laptop computers there. I think he was programming SSB voice messages and setting up some needed files for Writelog, our logging program. Visible in the photo is the OMNI V exciter. Above the OMNI is an MFJ CW keyer and assorted rotor control boxes and some 2M FM gear. A WSJT computer is to the right of the FM gear. The 144 MHz receive line is heavily RF filtered, and one of several filters is visible on the left side of the operating table next to the 19" relay rack cabinet. The 144 MHz 8877 PA is just visible in the rack behind Pete's back. Filters are needed to keep fundamental overload problems down, while also taming strong out of band signals by shielding the frontend stage from the many FM and TV broadcast tranmitters that are LOS from our antenna. We can "see" Channels 6,8,11,13,21,25, 26,27, and 31. While channels 4, 5, 7, and 9 are only slightly obscured. This makes for some very strong out of band signals that can combine to kill most any preamp stage. In a multi op environment, the co located VHF kilowatt amplifiers on 50, 222, and 432 are also big problems. Without tyhose filters, we could not all operate at the same time.
K1NKR operating at the 144 chair in September 2005. N2EOC is visible straining to hear a new grid on 50 MHz in the background. Note the air hoses behind the equipment rack. These hoses bring cool air in from the outdoors, and exhaust hot air from the six and two meter amps back outside, in an effort to keep the room cool.
The operating positions are all networked together with a system of conduits and "CAT V" LAN cables. A large router is installed in a metal box housing for shielding. It distributes the network to each of four VHF bands, three microwave positions, two WSJT locations, and a server. Timing for the server is obtained from a GPS receiver on site, which is then routed to all of the laptops on the network. This ensures that our logging times are all the same, and our WSJT skeds are properly timed. The logging program is Writelog, and it seems to run fine in a network configuration. All the operating positions are plugged into the computer for frequency control. It is very nice to see what frequency everyone is on, while trying to pass QSOs between bands. We also use the gab line over the network to set up skeds on other bands as well. The timing issue was a critical thing, as there is no permanent AC power here, and no internet connection. The shack is a good half mile from the house and main road.
Lately, I have been trying out a new exciter on 144 MHz. The Elecraft K3 seems like a great IF radio for a serious contest effort on either six or two meters. Anytime you match up a "largeish" antenna on a band like 144, you can be greeted by extremely strong signals when aimed at the Golden Corridor between Boston and Washington DC. There are more VHF kilowatt amplifiers there than you can shake a stick at, and a crunchproof receiver is a requirement. So far, the ops who have used the K3 think it is a great addition. Mine has several roofing filters installed: 2.7 kHz, 1.8 kHz, and 400 Hz. Those, combined with the variable IF DSP filters, make for a very clean receiver setup. The noise blanker is quite adjustable between DSP and IF blanking, and does a great job on some very pesky power line rfi that can take out most receivers on a windy dry day. The combination of a very good transverter with a high dynamic range HF radio is required. Either the Ten Tec or the K3 can handle the strong signals encountered during contest conditions.
The antenna choices as of 2008 are quite flexible. For the September VHF Contest in 2008, we added a third antenna that is fixed to the northeast and VE1 land. We had the follolwing choices
1. Large fixed array that covers 185 through 275 degrees with 20 dBd gain at 230 degrees, and 11 dBd at 180 and 270 degrees with no nulls!
2. Rotatable quad yagi array at 136 ft with 20 dBd gain.
3. Fixed stack of four times six element yagis (18+ dBd gain) aimed at 50 degrees azimuth
An analysis of our operating practices showed that much time was being wasted while the big quad stack of 30 ft yagis was rotating toward the northwest and northeast. Activity was very spotty in those directions. Typically, when a VE2 would be worked to the NW, another station or two would be worked before the band was worked out in that direction. To the northeast it was worse. Typically, only one station would go into the log, even after repeated calls in that direction. Still, we had to check those directions often. Queries to the VE1 stations who we never worked until after the contest produced the same answers. "I listened off and on and made a few calls, but I never heard anyone". Clearly we needed more of a presence to the northeast. The "Northeast Array" is our effort to correct this problem. No more do we need to rotate the array. A simple switch closure and we are transmitting to the northeast. We can call directional CQs to the SW and NE without losing a good frequency. A suitable schedule might be three CQs to the SW followed by one CQ to the NE. At the same time, we can have the steerable array aimed up to the west or northwest ready to pick up a marginal signal, or a directional CQ to the north or northwest, all with a minimum of wasted time.