7
S 2 3 2 = 0 ^M ^J S232=0..
S 2 5 2 = 0 0 0 0 ^M ^J S252=0000..
S 2 5 6 = 0 0 0 0 ^M ^J S256=0000..
Interpretation:
(Details of these settings are in the ARF53 User’s Guide)
S200 is the hopping table channel order, S220=2 sets the protocol to ‘hopping all
bands’ which includes all of the high and low band frequencies. S202=0 sets
10KHz narrow band. (Narrow band operation has longer range than wide band
operation, but limits the data transmission rate to 10,000 bits per second, which
is just what we need for 9,600 baud.)
S210=4 sets 9,600 baud, S211=8 sets 8-data bits, S212=1 sets no parity,
S213=1 sets 1 stop bit. S215 sets RS-232 interface (as opposed to RS-485).
S252 and S255 set the reception and transmission address. (Both these values
would need to be changed for repeater operation.)
Expected Range
My testing and RF characterizations lead me to believe that the ARF53
radios have a 1,400 foot urban non-line-of-sight range and a 7-20 mile RF Line-
of-Sight range.
In town with buildings and trees in the propagation path and the radios 6
feet off the ground, you won’t do much better than 1,400 feet. If you can set
your base on top of a very high hill, you could have coverage out to the fixing
range of a ProMark3.RTK system (about 6 miles). I have personally used
unmodified radios at distances exceeding 3 miles by placing the base
on a high hill.
You may have noticed that I claim a 7 mile range with RF line-of-sight.
This does not imply that radios will work with a visual line of sight. You need a
RF line of sight.
What is RF line-of-sight? French Physicist Augustin-Jean Fresnel, 1788-
1827 (http://en.wikipedia.org/wiki/Augustin-Jean_Fresnel
) figured all of this out for
us. Checkout this Wikipedia link for Fresnel Zone information:
http://en.wikipedia.org/wiki/Fresnel_zone (Even if you are using Pacific Crest high
power radios you should read about Fresnel Zones. They are the reason your radio range
is not what you want.)
To greatly simplify Fresnel Zone theory: the radio beam is not a narrow
laser-like beam that propagates from the transmitter to the receiver. The beam is
actually football shaped, narrow at the path ends and tall in the middle of the
path. At 1 mile range you need both antennas about 23 feet off the ground or
above the highest obstruction along the path to only loose 40% of the signal to
obstructions. (In other words, 60% of the radio energy is contained in a 46’
diameter circle at the midpoint of the path.) At 2 miles you need 33 feet of
antenna height!
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