As a minimum, 1/4 wavelength should be provided outboard of the array. Do not try to make an antenna with the four elements located in the corners of a square ground plane. It will not work properly.
Assuming that proper processing is done, the accuracy is determined by the number of antenna elements. A four element array has a one sigma or typical accuracy of about 2.5 degrees and an eight element array has a one sigma or typical accuracy of about 1 degree. For mobile operation, Read more…
We measure sensitivity by driving the inputs to the RF summer through a signal splitting device that simulates the antenna. The input signal level is adjusted until the standard deviation of the bearing is approximately 5 degrees. This input level, after compensating for the loss in the signal splitter, then Read more…
We measure accuracy under very controlled conditions that are designed to eliminate multipath reflections. The DF antenna is rotated on an index head and the bearing angles are recorded at 1 degree intervals. The error at each angle is then calculated and the mean and standard deviation computed. This process Read more…
Earlier simulated Doppler direction finders switched between adjacent antenna elements. Our RF summers combine the antenna inputs on a continuous basis. The method provides improved sensitivity because hard switching generates RF noise at the front end of the receiver, and it also produces sidebands which have the effect of causing Read more…
At frequencies up to 500 MHz, try to cut the feed lines within 6 mm (1/4 in.). If the feed line is relatively short, say 3.5 m (12 ft), this is not difficult. It is much harder to match longer feed lines or to match at higher frequencies.
On a mobile installation, drive to an area clear of reflections with a good line of sight to a known transmitter, such as a NOAA weather station, radio repeater site, etc. Point the car at the transmitter and calibrate the bearing angle to zero degrees. Drive the car slowly in Read more…
The preamps used are rated at 100 milliwatts maximum input and in our series 7000 direction finders we provide additional protection that increases the rating to about 1/2 watt. Transmitting 10 or more watts from a mobile antenna a few feet away in the same band will probably damage the Read more…
No, unless the emitter being tracked is located close to other transmitters which would overload the RF summer. The RF summer design is broad band and has a high dynamic range, but it is possible to overload it when the direction finder is close to high power broadcast stations. It Read more…
Any narrow band FM receiver with an external speaker connections can be used. However, software control of the receiver from TargetTrack, Signal Track, or the MPT User Interface requires one of the following receivers: ICOM R1500 ICOM R2500 ICOM R8500 ICOM R8600 ICOM R9500 ICOM R30 AOR SR2200 AOR AR5000 Read more…