17
t
848 Airport Road, Walla Walla, Washington 99362 U.S.A.
Tel: +1 509.525.7660 / Fax: +1 509.525.7907
twigwirelesscontrols.com
7.2 ThE ADvAnTAGE Of PROPER AnTEnnAS:
Strong radio power can give longer range but strong transmit power is only half the solution. Receiver power
on this same antenna is the other half of the answer. Receive signal is very much affected by the noise floor
present at the site (static). The source of noise in the environment ranges from all forms of digital products
and other radio communications. Antennas are everywhere so look around and try to minimize the noise
to the antennas for both the TWIG units and the TD200. Even weather conditions can limit communication
because increased moisture in the air weakens signals.
7.3 fACTS AbOUT RElIAblE RADIO RAnGE:
A frequently asked question is the distance that is good for signal range. For successful operation it is essential
to stay within the range of the TWIG signal. Don’t try to go out too far past the clear signal range. In order to
layout a good system use the range bar graphs in this section. And remember that the distances presented
in the guide are only achievable under optimum installation conditions. Radio signals have issues penetrating
water and soil. These are in abundance in the field. When radio waves hit an obstacle like the soil some of the
power is reflected and some of it is absorbed into the ground. In either case the signal is weakened. Normally
there is a lot of water in vegetable crops which will absorb the signal. Keep in mind that for farm crops such as
onions the crop changes as the season progresses. Initially the bare ground transforms into full onion tops filled
with water. Stay close enough to the controller or use a repeater so that it does not become a problem.
7.3.1 USEfUl TwIG SIGnAl RAnGE GRAPhS:
The range bar graphs are a simple way to look at wireless signal strength and spacing distance. These have
been prepared to show the range effect on the signal. A color gradient is used varying from good (green)
to poor (red). The red zone likely will have weak signal strength and poor reliability. The graphs in Figure
4.1 show the limits of spacing between the controller and TWIG units in the field. The bar graphs compare
several heights using 18 inches above the ground for the TWIG as a reference. To overcome this issue two
antennas are built within the TWIG box. Built-in signal strength logic continually seeks the antenna having
the strongest signal. Environmental conditions can reduce the range by as much as 60%. To factor in the
elevation of the TWIG radio antenna, the bar graphs have ADJUSTMENT FACTORS listed in the box. Pay
attention to the reduction percentages.
Basic rules to assure wireless success:
·
Do your homework up front just to make sure wireless is the best it
can be for the farm.
·
Be wary of background radio noise and do a site survey.
·
Remember transmit and receive for TWIGs are equally important.
·
Keep well within range to have a high degree of reliability.
·
Be cautious of leafy green vegetation, mounds of earth and even
mobile obstructions.
·
Know the distance between antennas. Don’t underestimate it.
·
Elevate the antenna where possible. Even a short distance up helps.
·
Separate two working antennas at least 2 ft. apart.
·
Remote mounting requires high quality cable. Be chintzy in the length
but not in cable quality.
TWIG
note
yOU MUST SElECT
An AnTEnnA lOCATIOn
ThAT IS GOOD fOR bOTh
TRAnSMIT AnD RECEIvE.
