432MHz

432 is an interesting band. This is the first band where you really have to be positioned in a good location with no tree foliage to insure good results. This was all made clear to me in 1982, when I first started contesting from the present hilltop location here in Maine. My regular 432 station at the house, was 200 ft lower on the side of the same hill and was blocked to the North and Northwest. For my first contest effort at the new hilltop spot, I used a single 15 dB gain yagi, RG-8, a push up mast, and a 30 watt brick. After the contest, VE2DFO asked me what did I do differently on 432 because I was so much louder than normal. My home station ran 1300 watts and eight modified NBS yagis at 78 ft! Further testing with both stations transmitting at the same time over paths of 75 miles or more indicated that the hill and foliage was blocking me by over 30 dB to the Northwest. Even in the clear directions, the added height and clearance above tree foliage helped me by 12-15 dB. This was a shock to say the least. It was also the reason that I lost interest in operating from the house, and poured my efforts into moving the shack up to the hilltop!!

The present 432 setup consists of an eight yagi array of DSFO432-25s (25 element yagi) on a 100 ft Rohn 25 tower. The PA is a homebrew Eimac 8938 triode that runs at about 1200-1300 watts output. Feedline is a run of 1 5/8" Heliax, with a tower mounted preamp. The receiver is a DEM transverter and Ten Tec OMNI V combo.

The antenna system was assembled with a four high configuration to maximize the horizontal beamwidth for contesting. It does make for some serious strain on the vertical mast during high winds. That 24 ft mast was chosen very carefully, with very high tensile strength ratings. It was also very heavy and hard to haul up the tower. It took two men and a block and tackle to raise it into place. Note the star guying at the 90 ft level. Originally, that was the highest set of guys, but after watching the tower flex at that point during high winds, we added an extra set of guys at the top to stiffen things up. This array is rather big for Rohn 25. As can be seen in the photo, there is not much that breaks up the wind before it hits the tower! The nearest thing to block the Northwest winds is about 12 miles away. Note the "step" midway between the two four bay sections. It allowed some poor fool to climb up, and push the upper H frame into position and lock it down. That was a job not for the faint of heart.

A closeup of the H frame showing the tower mounted preamp in it's little box. The box is actually very big and includes two coax relays plus the preamp. As mentioned before, the TX feedline is 1 5/8" while the receive line is made of 7/8" Heliax. The phasing lines are all Times LMR-400, with a 4 port divider at each bay of four yagis. The two way divider at the array midpoint is just visible at the top of the picture.

The shack is rather cramped. It is a re cycled CATV head end building from before the days of satellite TV. Dave K1WHS is sitting at the 222 position checking things out. The 432 operating position is between the two relay racks. The 432 KW amp is visible in the middle rack. It has the large handles and two square meters. The microwave positions are in the foreground. Four laptops are visible. They are set for 222, 432, lower microwave position, and upper microwave position. They are all networked with the lower VHF stations, the WSJT machines, and a server. There are eight computers networked during a contest.

Here is a better shot of the 432 operating position. You can see the OMNI V clearly along with assorted keyers, paddles etc. The interesting thing is that the operator is none other than N1LBI, our illustrious cook, "Chef Monte". It is rare to catch him actually operating a radio. Our favorite "Monte Moment" was when he was calling CQ on 222 MHz impersonating Monty Python characters. We suspect his coffee cup had more than coffee in it. We let him continue with the impersonations as the SSB radio was tuned to 222.475!! The Q rate dropped on 222, but we all had some pretty good entertainment listening to all the Monte Python sketches!

The antenna system used on 432 is a great antenna for DXing. The performance is truly outstanding, with an estimated 24 dBd of forward gain. This gain comes at a price however. The half power beamwidth is a mere 11 degrees horizontally, and a little over 5 degrees vertically. I have tried a few horizon EME attempts and have had great success, but only for about 25 minutes or so!! For contesting, the beamwidth is a bit tight, even with stacking the antennas four high. This previous September contest, (2006) WZ1V tried his hand at the controls and was convinced that the antenna was not working as he missed several contacts that he figured were possible. I could find nothing wrong with it afterward, and even tried an EME QSO to test it out. I received a 579 on CW from DL9KR, so I would say that it was working. Eleven degrees is awful narrow for contesting unless you know the headings really well, and are aware of any aiming error, you can miss much!

It would be hard to make a very wide beamwidth LVA type array that approached the 24 dBd of this array, so we are planning a less capable system, and hoping for about 20 dBd with a wide 60 degree main lobe. I am hoping to have something like that running for the 2007 summer season. It should improve the contact totals on 432 for sure.