In a message dated 06/01/2008, ian@........... writes:

Looking  back I can see that there are a few traces (not many) which=20
flipped  between channel gains +/-0.1V and +/-1.0V.  So the feature is=20
giving  me more gain to look into the weaker signals without being=20
clobbered with  saturation on the stronger traces - both the high and low=20
pass filters  apply a 20db gain to compensate for the attenuation of the =20
filters.
Hi Ian,
=20
    I would expect that all your out of range signals  will be due to the=20
surface waves?=20

I asked  about your 12 Km gap as I was wondering if there was a way to=20
plug it with  equipment running at broadband rates.  I'm in one of the=20
BT(our  telco)  "black spots", condemned to never have broadband and I =20
eventually had to put together our own community wireless broadband =20
(http://www.gmccbroadband.org/ ).  This partly involves filling  "gaps"=20
across the countryside.  Our biggest gap is only 5 Km so the  stuff we=20
use might not help.=20
    The delay that I quoted was due to the speed  of light over the distance=
,=20
but the phase velocity in the wires will be lower. I  have not measured it.=20
    I only require four or five channels, not  eight.
=20
    One standard fix is to send the data  as packets, so greatly reducing th=
e=20
number of delays..=20

We use  Tranzeo 5Ghz point-to-point access points, these require line of=20
sight between  the two locations.  They might cover 12 Km but I'm not sure.=20=
 =20
Equipment is about =A3450 and you'll need to pay someone to install it on th=
e  roof.
    This is quite expensive. Even if I did install an  aerial on my roof,=20
there is still a hill in the way. Nor does it  solve the  problem of the two=
 way=20
signal delays.
=20
//    At the RF level, the system also reduces latency  and improves=20
throughput by allowing the user to adjust the RF ACK time, changing  the amo=
unt of=20
time the system will wait for an RF ACK to be returned. Radio  waves take a=20
finite amount of time to reach a destination, namely the speed of  light. Ev=
ery=20
packet sent via an
RF link needs to be acknowledged, in order to  ensure that the packet was=20
received intact.
//

The  other method is to rent a "private circuit" or EPS line from BT - a=20
private  wire between two premises sharing the same exchange -  over which y=
ou can=20
 connect a pair of sdsl modems.  These may not work over the distance,  agai=
n=20
I'm not sure.  Costs about =A345/month.  Maybe that's=20
what  you are already doing.


I have not tried to explore this recently. When I  last enquired, BT were no=
t=20
prepared to lay an additional 12 km of phone line.  And they didn't have a=20
spare line on their local cable. There is a relationship  between the distan=
ce=20
to the phone exchange and the maximum speed. There was  also a maximum=20
distance. From memory this was about 5 km when I  enquired.
=20
    Regards,
=20
    Chris Chapman



  =20





In a message dated 06/01/2008, ian@........... writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Looking=20
  back I can see that there are a few traces (not many) which 
flipped=20
  between channel gains +/-0.1V and +/-1.0V.  So the feature is 
giv=
ing=20
  me more gain to look into the weaker signals without being 
clobbered w=
ith=20
  saturation on the stronger traces - both the high and low 
pass filters=
=20
  apply a 20db gain to compensate for the attenuation of the=20

filters.
Hi Ian,
 
    I would expect that all your out of range signa=
ls=20
will be due to the surface waves? 
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>I asked=20
  about your 12 Km gap as I was wondering if there was a way to 
plug it=20=
with=20
  equipment running at broadband rates.  I'm in one of the 
BT(our=20
  telco)  "black spots", condemned to never have broadband and I=20
  
eventually had to put together our own community wireless broadband=20
  
(http://www.gmccbroadband.org/ ).  This partly involves filling=20
  "gaps" 
across the countryside.  Our biggest gap is only 5 Km so t=
he=20
  stuff we 
use might not help. 
    The delay that I quoted was due to the spe=
ed=20
of light over the distance, but the phase velocity in the wires will be lowe=
r. I=20
have not measured it. 
    I only require four or five channels, not=20
eight.
 
    One standard fix is to send the data=20
as packets, so greatly reducing the number of delays.. 
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>We use=20
  Tranzeo 5Ghz point-to-point access points, these require line of sight bet=
ween=20
  the two locations.  They might cover 12 Km but I'm not sure. =20
  Equipment is about =A3450 and you'll need to pay someone to install it on=20=
the=20
  roof.
    This is quite expensive. Even if I did install=20=
an=20
aerial on my roof, there is still a hill in the way. Nor does it  solve=
 the=20
problem of the two way signal delays.
 
//    At the RF level, the system also reduces late=
ncy=20
and improves throughput by allowing the user to adjust the RF ACK time, chan=
ging=20
the amount of time the system will wait for an RF ACK to be returned. Radio=20
waves take a finite amount of time to reach a destination, namely the speed=20=
of=20
light. Every packet sent via an
RF link needs to be acknowledged, in orde=
r to=20
ensure that the packet was received intact.
//
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>The=20
  other method is to rent a "private circuit" or EPS line from BT - a privat=
e=20
  wire between two premises sharing the same exchange -  over which you=
 can=20
  connect a pair of sdsl modems.  These may not work over the distance,=
=20
  again I'm not sure.  Costs about =A345/month.  Maybe that's 
=
what=20
  you are already doing.


    I have not tried to explore this recently. When=
 I=20
last enquired, BT were not prepared to lay an additional 12 km of phone line=
..=20
And they didn't have a spare line on their local cable. There is a relations=
hip=20
between the distance to the phone exchange and the maximum speed. There=
 was=20
also a maximum distance. From memory this was about 5 km when I=20
enquired.
 
    Regards,
 
    Chris Chapman