Don't forget that most of the cable installation in apartment buildings
has been done quite some time ago and they are not really
"state-of-the-art", especially regarding ground-loops, HF-grounding and
cable segments acting as antenna.
And anyone who has a Ham-Radio station (like me) in the neighborhood has
anyway to expect interferences on CATV in the ranges:
1.8 - 2.0 MHz
3.5 - 3.8 MHz
7.0 - 7.4 MHz
10 MHz
14.0 - 14.4 MHz
18.0 - 18.2 MHz
21.0 - 21.5 MHz
24.8 - 25.0 MHz
28.0 - 29.7 MHz
50.0 - 52.0 MHz (limited to 25 W EIRP)
144 - 146 MHz
All frequency range above are allowed with a maximum EIRP of 1 kW !
Note also that all the above ranges beside the 7MHz band are exclusive
assigned frequency.
Therefore the cable provider has to ensure that there are no leakage
from CATV to air and vice versa.
The return frequency band is 6 to 29MHz so wherever the return channel
will be it always overlap with one of the Ham bands.
Daniele
Roger Schmid wrote:
so then in english ..
i measured the backward channel ingress on an 10 appartment house in
zurich, this was after CC had upgraded the whole cabling.
i got levels up to 70dbuv arround 15-16 mhz during early nighttimes,
20mhz was arround 50dbuv, 27mhz nearly nothing, but the HF condition on
this frequency'y are not good actually as we are on the sunflare
minimum, lets see what happens to the backchannel in 5-6 years when we
are on the sunflare maximum where you can reach australia with 1watt
power on 20 mhz ;-)
The ingress dropped 20db when i was pulling a 4mm2 wire from the cable
ground to the power ground. (sideffect, there was a 2,5A current flow
thru that earthwire connection)
btw: there was a 100hz TV and a PC with videocard connected to the CC
net, if switched on they produced additional 10DB wideband noise between
10 and 45 mhz
this leads me to the idea, what when a CC angry user with HF experience
inject a jamming signal into his wall socket ? ;-)
That is one big disadvantage of that technology. how about the legal
issue then ?
Roger
Am 16 Dec 2006 um 0:30 hat Will van Gulik geschrieben:
Date sent: Sat, 16 Dec 2006 00:30:43 +0100
From: Will van Gulik <[EMAIL PROTECTED]>
To: swinog@swinog.ch
Subject: Re: AW: WG: [swinog] de-peering
Send reply to: swinog@swinog.ch
<mailto:[EMAIL PROTECTED]>
<mailto:[EMAIL PROTECTED]>
This sounds really interessting, but what about an English version, or
worse, a french one ?
Please, well all know that communicating is not as simple as we'd liked
it to be, (read : packet loss, version problems, flapping, [use any
silly/true reason here]), but *trying* to make it readable to anyone
else is quite a nice bonus.
Did we won that one ? ;)
Xaver Aerni wrote:
> Hallo Peter,
>
> Die meisten CC Modems ist das Webinterface gesperrt.
>
> Deshalb ist es nicht möglich.
> Laut den Spezifikationen war der Upstream auf 27 MHZ. Bei unseren
Messungen
> sind die auf 23 MHZ gewesen.
> Die Frage ist nur wieso... Man sagt ja das von 15 - 20 MHZ die Störungen
> sehr gross sind (auf den Kabelnetz) und wenn die Mittelfrequenz bei
23 MHZ
> ist (8 MHZ Bandbreite) kommen die recht in diesen bereich runter.
>
> Gruss Xaver
>
>> -----Ursprüngliche Nachricht-----
>> Von: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] Im Auftrag von Peter Baumann
>> Gesendet: Freitag, 15. Dezember 2006 17:24
>> An: swinog@swinog.ch
>> Betreff: Re: WG: [swinog] de-peering
>>
>> Xaver Aerni schrieb:
>>> Hab mal eine ernste Frage betreffend Cablecom und ihren dauernden
>>> Störungen…
>>>
>>> Ist es möglich dass die CC ihre Upsteamfrequenz von 27 MHZ
>> auf 23 MHZ
>>> gewechselt hat? Das würde die Störungen dauernden Störungen
>> erklären.
>>> Gruss Xaver
>>>
>> Hi Xaver
>>
>> Meistens kann man auf dem Cablemodem Webinterface die
>> Up-/Downstream Frequenzen und HF-Pegel anschauen.
>> Versuch mal mit dem Browser auf http://192.168.100.1 zu
>> connecten, dort gibts ev. je nach Modell eine Diag-Seite.
>>
>> Ev. hilft auch das folgende Tool um die Abfrage via SNMP zu machen:
>> http://homepage.ntlworld.com/robin.d.h.walker/docsdiag/
>>
>> Gruss
>>
>> Peter
>> _______________________________________________
>> swinog mailing list
>> swinog@lists.swinog.ch
>> http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog
>>
>>
>
> _______________________________________________
> swinog mailing list
> swinog@lists.swinog.ch
> http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog
>
--
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[ Will van Gulik ]
[ [EMAIL PROTECTED] ]
[ http://www.porcus.ch ]
graphic
csdata brasil Ltda.
Roger Schmid
Rua Arquiteto Luiz Nunes 186
Imbiribeira
CEP: 51170-430
Recife / PE
BR +55 81 3422 1714
US: +1 360 515 33 80
CH: +41 32 5110858
UK: +44 8444845331
VOIP: [EMAIL PROTECTED]
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Daniele Guazzoni
Senior Network Engineer, CCNP, CCNA
Linux and AMD-x86_64 or do you still with Windows and Intel ?
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