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3889 posts

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  # 671208 11-Aug-2012 22:06
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Ok, so the end point is hiding 5m down from the site line, behind a hill... with the other end 700m away.

Not liking the sound of this plan so far.

Where are you based? Seems to me like you really need a local provider who has a couple of radios you can have a play with to prove your concept.

D




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  # 671212 11-Aug-2012 22:07
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DonGould: Ok, so the end point is hiding 5m down from the site line, behind a hill... with the other end 700m away.

Not liking the sound of this plan so far.

Where are you based? Seems to me like you really need a local provider who has a couple of radios you can have a play with to prove your concept.

D



Oh dear :( - Located in the Gulf Harbour area, Auckland(ish haha)

BTW: from the calculations done on google maps, it says about 500-550m, which would be about right.





 
 
 
 


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  # 671215 11-Aug-2012 22:16
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Do you have a TV antenna poll up there on the roof?

You could mount the unit on that. You'll need a ubnt mounting arm as well so you can angle the unit in the right direction. These things don't like being off direction by more than 15 degrees.

D




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  # 671216 11-Aug-2012 22:22
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DonGould: Do you have a TV antenna poll up there on the roof?

You could mount the unit on that. You'll need a ubnt mounting arm as well so you can angle the unit in the right direction. These things don't like being off direction by more than 15 degrees.

D


Not entirely sure tbh. Being three storey's high, it's not the easiest roof to look up on top of. Because its an apartment complex, I think they may have a shared antenna, not sure where it is though. 

 

now you've definitely got me worried by saying that (about the angle!)





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  # 671223 11-Aug-2012 22:33
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ya, what you're saying is that the units do not have LOS at all. LOS means LOS, not NLOS - near LOS.

I wouldn't expect more than 20mbit, layer 2, between the units given what you've described.

D




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  # 671230 11-Aug-2012 22:52
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DonGould: ya, what you're saying is that the units do not have LOS at all. LOS means LOS, not NLOS - near LOS.

I wouldn't expect more than 20mbit, layer 2, between the units given what you've described.

D


Still faster than what I get currently by 20 times lol. but yeah, not ideally what I was hoping for... Damn.





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  # 671232 11-Aug-2012 23:12
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Aaroona: Still faster than what I get currently by 20 times lol. but yeah, not ideally what I was hoping for... Damn.


ya, sorry to rain on the parade here.  What you're trying to do is why everyone wants 700mhz space from the analogue TV space.

5x space is way more directional and won't punch though much, not at .5w anyway.






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  # 671233 11-Aug-2012 23:13
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DonGould:
Aaroona: Still faster than what I get currently by 20 times lol. but yeah, not ideally what I was hoping for... Damn.


ya, sorry to rain on the parade here.  What you're trying to do is why everyone wants 700mhz space from the analogue TV space.

5x space is way more directional and won't punch though much, not at .5w anyway.





What about at 1watt? probably not much better... Might just keep looking around for other options.. though I dont think there are any!





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  # 671234 11-Aug-2012 23:17
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Aaroona:  What about at 1watt? probably not much better... Might just keep looking around for other options.. though I dont think there are any!


Na, the loco's are the right product over that range, you just need to get LOS on them.

D




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  # 671273 12-Aug-2012 07:39
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sbiddle: Why are you bothering with shielded cable? It's not going to give any benefit unless you're in a high thunderstorm area.

It is not about thunderstorms as such, anything that gets hit by lightning will die, it is about the difference in earth (GND) potential as a lightning strike propagates through the ground.  You have 2 items far apart with an earth wire between them so for a brief moment the earth at one unit will be at a higher voltage than the earth at the other unit yet they are electrically connected.

There is a compliance test for this, any data/signal cable over 3m outdoors (10m indoors?) must pass this test.  From memory it is a 1kV common mode surge with 8us rise time and 40us fall time, for power ports it is 2kV differential mode.  The characteristic impedance of the surge tester is 42 Ohm so you have a potential peak current of 24A and 48A.  Very few products pass this test first time.

Use shielded cable and connect the shield at both ends with shielded connectors.




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  # 671558 12-Aug-2012 20:04
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Niel:
sbiddle: Why are you bothering with shielded cable? It's not going to give any benefit unless you're in a high thunderstorm area.

...
You have 2 items far apart with an earth wire between them so for a brief moment the earth at one unit will be at a higher voltage than the earth at the other unit yet they are electrically connected.
...
Use shielded cable and connect the shield at both ends with shielded connectors.

Isn't this the very reason they say not to ground the cable shield at both ends?

With audio circuits, you commonly get ground loops, resulting in hum injection into microphone circuits when the shield is grounded at both ends.  With the Airspan 2.3GHz equipment I have just replaced, they explicitly said NOT to ground the shield at the antenna end, only at the end inside the building.

Maybe I'm barking up the wrong tree here, but it seems to me that the last thing you want to do is have an electrical connection between two separate ground points under lightning strike conditions.  Having just one end grounded, with a MOV spike catcher from each data line to the shield would seem to be a better idea.





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