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High location sector antennas talking to other high site sector antennas

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VE7TOP
High location sector antennas talking to other high site sector antennas
We are starting to plan a deployment on the east side of Vancouver Island and we have two tentative sites which are about 6 miles apart.   One is very high on a mountain at 955 m and the other is lower at 255 m in elevation.   There is a completely clear signal path between the two.  

My question is whether it would be viable for these two sites to be linked with only the 19 db sector antennas mounted at each site.  We are limited as to how many antennas we can mount at each site but adding a link dish could be an option if required.  Generally any users accessing either site would be pointing at only one location and would not likely overlap.

cheers
Chris
ve7top
w6bi
w6bi's picture
Linking sites

Chris, you can certainly do what you want, and get away with it because you'll be a low-traffic area.  However, you will end up with the classic "hidden terminal' issue that packet radio deals with, since all emitters are on the same channel.

A more optimum solution as you suggested, would be to use dish antennas to link the two sites together on a separate channel (and then, even better you could put the two sector antennas on different channels, thus eliminating the majority of possible hidden terminal issues.)

If funds are an issue, maybe plan on adding the link nodes as a later phase.

73
Orv W6BI
 

K6AH
K6AH's picture
Link antennas
6 miles isn't very far and you don't need a lot of gain to make that trip.  NanoStations will probably do just fine.,
nc8q
nc8q's picture
starting to plan a deployment

Hi Chris:

We are starting to plan a deployment on the east side of Vancouver Island and we have two tentative sites which are about 6 miles apart. One is very high on a mountain at 955 m and the other is lower at 255 m in elevation. There is a completely clear signal path between the two.

This sounds very nice.

My question is whether it would be viable for these two sites to be linked with only the 19 db sector antennas mounted at each site.

I don't know how much dBm you have at either end, but I have a 6.2 mile link between 36 meters elevation and 30 meters elevation with clear line of site.
The devices are Mikrotik LHG-5HP (edited 24.5 dBi+28 dBm) and SXTsq-5nD (16 dBi and 25 dBm).
The SXT displays 35 dB SNR and the LHG displays 32 dB SNR.
The sum of my RX gain is 43 dBi.
The sum of your RX gain is 38 dBi.
Use the difference of your dBm and mine to determine your approximate SNR.

We are limited as to how many antennas we can mount at each site but adding a link dish could be an option if required.
I do not know what a 'link' dish is, but the dBi is important.
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Generally any users accessing either site would be pointing at only one location and would not likely overlap.

Whoa, hold on here.
You didn't mention any 'users' until now!
Now 'hidden transmitters' and 'exposed nodes' enter into the equation.
Please further explain your use of 'overlap'.
How would or would not users 'overlap' ?

cheers
Chuck
nc8q

VE7TOP
Thanks for the good advice
I very much appreciate your advice on this deployment question.    I can see the issue associated with hidden transmitters and exposed nodes.   We will look at using a separate dish antenna to link the two sites and ensure that the specific sector antennas are operating on different channels.

cheers
Chris
ve7top

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