I'm getting some odd results here with a PtP 5.8GHz link using MikroTik
that I setup to test with. Let me describe the setup...
The link is 7.9 miles with clear LoS and clear Frenel zone. Each end
has a 27db grid with a 3ft LMR-400 jumper to the MikroTik radio.
Using the link calculator at
http://www.zytrax.com/tech/wireless/calc.htm I get a predicted rx of
-60.8db at each end with CM9 radio cards (17db output). Using the SR5
cards, (400mW), I get a predicted rx of -51.8
On to the real world results.... (all reading taken from the MikroTik's
winbox. I am using version 2.9.11 on RouterBoard 230's)
With the CM9 cards, I get a measured rx of -62db, well within the margin
of error. An interesting note here is that I must set the CM9's output
power in the MikroTik at 30db to get these results.. I know that the
MikroTik must be doing something odd with this setting, as the CM9 can
not put out 30db. Reducing the setting drops the rx strenth by a like
amount. This link is stable and will pass 30Mb/sec in UDP and 22Mb/sec
in TCP mode
With the SR5 cards, I get a measured rx of -66db, well outside the
margin of error and 15db below the expected rx strength! An interesting
note here is that I must set the SR5's output power in the MikroTik at
30db to get these results. I know that the MikroTik must be doing
something odd with this setting, as the SR5 should not put out 30db.
Reducing the setting drops the rx strength by a like amount. This link
is stable and will pass 24Mb/sec in UDP and 16Mb/sec in TCP mode.
Nothing else is changed when I swap the SR5's for the CM9's or back
again. I use the same antennas, cables, boards and pigtails. The
antennas and cables are not moved between tests. (except for moving the
pigtail from one card to the other).
Can anyone tell me what I am doing wrong here? Or do I just have some
bad SR5 cards? Or is the tx power setting in the MikroTik flakey? Or
is the tx power setting relative db not absolute db?
BTW, I will be changing one end to a sector and wish to use the SR5
cards then. Otherwise I'd be happy with the -62 on the CM9's
Thanks in advance.
AOL IM Screen Name -- Theory240
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