What can you do to reduce multipath?
- Buy a good quality, well-designed antenna. A directional Yagi antenna is
best here. Select one with a narrow beamwidth or acceptance angle and a high
Front-to-Back Ratio. High gain is needed when your line of sight is completely
blocked by large obstacles, like a mountain ridge, or if you are trying to
pick up stations over long distances.
- Mount your antenna up high on a tall mast 15-20' above the rooflines of
surrounding houses. Usually the higher you get the antenna the better, but try
different heights to get the cleanest signal. Sometimes you will find that
some channels have different sweet spots in regard to height, so a compromise
may be needed.
- Try different X-Y locations on the roof, looking for the cleanest signal.
You can do this by taking a small TV on the roof, then mount your antenna to a
long lightweight pole and walk around on your roof.
- Yagi's with a tight beamwidth need to be aimed with accuracy in both the
vertical and horizontal plane. Normally a Yagi with a small horizontal
beamwidth has a even smaller vertical beamwidth, usually less than half the
horizontal width. Tilting the antenna up around 3 to15 degrees can improve
reception a lot in bad multipath areas. The exact angle must be found through
trial and error, or by using a remote controlled Vertical Tilter.
- Stack the antennas horizontally by placing two identical antennas on a
common boom. Out of all the experimenting I have done, horizontal stacking has
made the biggest improvement in multipath reduction. Stacking also requires
that you adjust the vertical and horizontal angle with even greater precision.
I have found vertical angle should be within one degree and horizontal angle
within two degrees for best results. The weaker the station the more critical
the adjusting becomes.
- Move to a different location. If you are moving, check with some locals
shops or neighbors about reception conditions. Use a elevation generating
computer mapping program, plot out a map of all possible moving locations.