Date: Tue, 16 Mar 93 04:30:07 PST
From: Advanced Amateur Radio Networking Group <tcp-group@ucsd.edu>
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Subject: TCP-Group Digest V93 #72
To: tcp-group-digest


TCP-Group Digest            Tue, 16 Mar 93       Volume 93 : Issue   72

Today's Topics:
                  A practical 1-10meg microwave link

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Date: 15 Mar 1993 23:01:08 -0500 (Mon)
From: Steve_Wright@kcbbs.gen.nz (Steve Wright)
Subject: A practical 1-10meg microwave link
To: tcp-group@ucsd.edu

>  
>>>From: jackb@mdd.comm.mot.com (Jack Brindle)  
>>>Subject: hidden transmitter routing  
>>  
>>Message-Id: <9303092305.AA06616@kcbbs.gen.nz>  
>>Date: 9 Mar 93 23:05:40 EST (Tue)  
>>  
>>  
>>Great! but how to do this in the 70cm band without wiping out many, many  
>>frequencies. This is the only band that 9600 baud gear is commercially  
>>available, unless you're advocating 1200 baud (shudder.)  
>  
>As a now-misplaced GRAPES person active with 56K, I advocate neither 1200 or 
>9600 baud. 56K is the minimum! A full duplex setup with 56K modems uses 150 K
>of bandwidth. This could be within a single band or split between two bands. 
  
If each user occupies two frequencies, we'll still run out of space real  
quick. The only ways I can see is microwave gunnplexors (at close range) or  
SS/CDMA.  Spread Spectrum is not really available to the masses yet (we need  
at least a kitset,) but the gunnplexor units need only a RX demodulator (TX is
direct FSK.)  These units are about US$50 here (new) so the only expensive bit
you need is then the SYNC DMA card to drive it. At the switch end you already 
have a high speed switching unit so you just need the RF bits. Sure, 3 users  
wipes out one pTen switch at $800 each, but I suspect there are those amonst  
us who will pay this amount for this type of connection. (simplex, 1200 baud  
users pse ignore last statement.)  8-)  
  
I haven't had any experience with the above gear, so lets hear from someone  
who has ....  
  
>  
>This, of course, assumes no trees or other blockages around. Microwave is  
>notorious for these problems. That would be the right place to do high-speed 
>spread-spectrum, though, since ss requires LOTS of bandwidth for reasnable  
  
On 10GHz, you don't need SS because of its' point to point nature. Just the  
10Ghz link itself.  How will the hilltop site get on with lots of uWave  
signals all pointing at a small cluster of parabolic reflector/antennas ? This
may create problems for the IF reciever/demodulator in each link unit.  
  
>  
>However... I really believe the microwave approach is worth experimenting wit
>and would encourage someone who knows what they are doing to persue it. That 
>is, after all, what this "hobby" is all about, experimentation!  
  
me too !! So who do we have who knows more about this as I'm just speculating.
  
>  
>>over to you.  
>  
>Tag, you're "it."   :-) :-) :-)  
>  
>Jack Brindle  
  
Thanks Jack!  
  
Steve Wright  
  
   

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End of TCP-Group Digest V93 #72
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