Subject: [NEXTEL-1] RE:Propagation through a busy tunnel

From: Marcel <[email-masked]>
Date: Tue, 29 Oct 2002 19:35:40 -0500

-------- Original Message --------
From: Davor Virkes <[email-masked]>
Subject: PROP-L:Propagation through a busy tunnel

>It will be a better solution to use cross-polarized antenna. Because
>this antenna is having element with 45 degree inclined.

Ideally yes, but there are some limitations I forgot to put earlier:
- there is no diversity at the repeater side
- antenna profile must remain slim

Trouble with x-pols is their size. They tend to come in panels, and these 
are quite big.
Helixes are cute slim solution, and there are some solutions built 
especially for tunnels and mines. Again, my problem is justifying this move 
prior to installation.

Thank you for every input

Davor

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From: Marcel <[email-masked]>
Date: Tue, 29 Oct 2002 19:33:44 -0500

------- Original Message --------
From: [email-masked]
Subject: RE:Propagation through a busy tunnel

I have seen this when I worked for Nextel which uses Iden technology,
similar TDMA` technology to GSM.  I saw it in areas without a prime server,
or area's that needed more RSSI to overcome the fading.  I agree that you
have a difficult situation here.

Circular polorization can give you a 20 db cross-pol loss.  

A thought would be to make your own cross pole yagi.  RFS (Cellwave) makes a
stacked 800 mHz (I assume they have it for 900 Mhz) that consists of two
yagi's connected together to make a higher gain array.  You could mount on
yagi at say +45 degrees and one at -45 degrees using that same matching
network.

What the exact pattern would look like I am not sure but it will still have
gain.

I know its sounds a bit crazy but I would say that it will help.  

The only other thought is to go omni but your power budget may not work.

Just some thoughts

Dave

__________________________________________________
David Donaldson
Senior RF Engineer
Verizon Wireless

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