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| -rw-r--r-- | 4.-Antenna-Array-Setup.md | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/4.-Antenna-Array-Setup.md b/4.-Antenna-Array-Setup.md index 3c7bae2..2b40197 100644 --- a/4.-Antenna-Array-Setup.md +++ b/4.-Antenna-Array-Setup.md @@ -73,18 +73,21 @@ I_e=sλ # Antenna and Coax Precision The KrakenSDR will not compensate for phase distortion in the external antenna system. -Therefore, you must use identical antennas, and lay out your antenna array as precisely as possible. You can use one of our layout templates on krakenrf.com to help with placement. A tip is to measure the interelement spacing between elements after placement and confirm that all measurements are identical. +Therefore, you must use identical antennas, and lay out your antenna array as precisely as possible, so we recommend using our templates. A tip is to measure the interelement spacing between elements after placement and confirm that all measurements are identical. All the coax cables connecting the antennas to KrakenSDR must be identical lengths to a tolerance within a centimeter or less. If cables have different lengths, then direction finding will not be possible. The higher your frequency of interest, the more precise you need to be with your antenna position layout and coax length tolerances. -For example, at 800 MHz a 1 cm difference between coax cable lengths in the array could result in a phase distortion between elements of up to 14 degrees. At 400 MHz the same 1 cm difference results in 7 degrees distortion. Note that this distortion is between elements and does not translate directly to a bearing distortion which is often less. Nevertheless, be aware cable length precision is an important consideration. +For example, at 800 MHz a 1 cm difference between coax cable lengths in the array could result in a phase distortion between elements of up to 14 degrees. At 400 MHz the same 1 cm difference results in 7 degrees distortion. + +Note that this distortion is between elements and does not translate directly to a bearing distortion which is often less. Nevertheless, be aware cable length precision is an important consideration. # Antenna Array Positioning On a vehicle you will want to have the antennas on the roof of the car. Ideally objects that could block the antennas like roof racks will be removed too. For a fixed site, you want the array to be placed up as high as possible, away from obstructions. Nearby obstructions like other antennas, poles, roofing can cause multipath and other refractive type effects that can distort the angle that the signal arrives at, resulting in poor results. + In both cases, ensure that the coax cables are neat, and ideally all run in the same direction, and are bundled together with cable ties. Being neat like this ensures that any phase distortions caused by bends in the cable happen identically to all cables. Note that some fixed site antenna arrays like the array produced by the company Arrow Antennas may have holes drilled for elements that can be placed at different radii. It’s important to note that you can only use ONE set of elements at a time. If other unused elements are placed on the same array at the same time, those elements will block, reflect and refract the incoming signal causing massive distortion to the angle if the signal arrive direction that the system detects. @@ -109,7 +112,7 @@ If you ordered our 5x KrakenSDR antenna set, you will need to assemble them. Thi You will then want to adjust the telescopic whip for the length that is best covered by your frequency of interest. Under normal circumstances, you will want the length to be a quarter of the wavelength of the frequency of interest for best reception. -Obviously if you are running the antennas on a vehicle, you do not want the antennas to be extended too long for safety. Using shorter than optimal antenna lengths will generally be acceptable in most cases. +Obviously if you are running the antennas on a vehicle, you do not want the antennas to be extended too long for safety. Using shorter than optimal antenna lengths will be acceptable in most cases. # Theory of Resolving Resolution |