Return Channels for Cablemodems could be from 5 MHZ till 68 MHZ. The Problem ist the most HF (Verstärker und Dosen) are only from 5 MHZ till 30 MHZ for the back Channel.
When you have the american Standard you have 7 MHZ band with Euro Standard you have 8 MHZ.
----- Original Message ----- From: "Daniele Guazzoni" daniele.guazzoni@gcomm.ch To: swinog@swinog.ch Sent: Saturday, December 16, 2006 11:34 AM Subject: Re: C(c)able Problems was: [swinog] de-peering
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 porcus@porcus.ch To: swinog@swinog.ch Subject: Re: AW: WG: [swinog] de-peering Send reply to: swinog@swinog.ch
mailto:swinog-request@lists.swinog.ch?subject=unsubscribe mailto:swinog-request@lists.swinog.ch?subject=subscribe
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: swinog-bounces@lists.swinog.ch [mailto:swinog-bounces@lists.swinog.ch] 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
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[ Will van Gulik ] [ porcus@porcus.ch ] [ http://www.porcus.ch ]
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regards
Daniele Guazzoni Senior Network Engineer, CCNP, CCNA
Linux and AMD-x86_64 or do you still with Windows and Intel ?
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