On 6/13/2013 1:38 PM, David Hannum wrote:
He strongly urged me not to even worry about balancing. He says run
everything wide open all the time - all SM's and all AP's. Now, I'm
not disputing you - I don't know enough too. I'm just relaying what
the Cambium engineer told me.
No worries (about difference in theology). I am not trying to change
anyone's mind, argue, or cause contention: just trying to help. Sorry if
anyone thinks otherwise: that is why I am more of a lurker than poster.
ALWAYS keep the AP at full power. Always, always, always. Well, I guess
if you are using it for a PTP not PTMP and you are causing interference
with other equipment then... anyway, if an AP is used as an AP, ALWAYS.
But the SM... no.
Through Cambium training, we were told differently: but I was not there
for that training. Quite honestly, it makes a lot of sense to turn down
a radio if the UPLINK strength at the AP is reading -30 to -55. Think
about it for a minute from an RF prespective. Your receiver is receiving
multiple transmissions. On some, it must increase the gain to make it
"sound right." On others, it must decrease the gain to make it "sound
right." These frequencies are preset to communicate (900 mhz band) and
fine tuned to pick up the quiet sounds. Will the much stronger RF
signal, over time, destroy the transceivers ability to hear the quiet
sounds? Yes. That is what RF does, and why the microwave oven is so
effective. There is an interesting study out there about the effects of
long term RF exposure on the structural integrity of buildings. These
units are not powerful and not going to damage buildings, but over time,
they will damage sensitive electronics.
Immediate problems, no. Long term, yes. Support for every other product
on the market tells you to turn down a transmitter if receive is better
than -50. A Canopy radio may be better than other radios, but we have
repeatedly seen that the receiver desenses over time (way before the
documented MTBF rate).
For the SM, it does not matter if the receive is hot. It will never need
to listen to the quiet sounds. The receiver can desense for that client
and you will not have an impact.
We test /every /radio before it is deployed/redeployed. This is due to
RF sensitivity, and ones that perform worse are marked for use in
locations with a strong signal only.
Really, you should turn down the SM if the AP receive is that hot. 9
months is fast for burning out an AP. As I said in the first email, I am
very suspicious that your problem is the power supply this time. But, I
have seen the receivers on the APs get more and more desensitized (16
months is fastest) to the point the truck was rolling all the time for
that AP, and a radio swap instantly fixed the numerous problems we were
seeing.
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