Hello,
I have an install where cameras are being modulated onto the cable system and a channel plus low pass filter is being used to clear out the injected channel range before the modulated signal is applied and everything works just fine.

However, I have one room where they want cable modem service, regular cable, and to also be able to see the modulated cameras on the regular cable service.
The room has only one cable to it and I have found that if I use the low pass filter to clear out the channel range (LPF-470) so the modulated cameras can
work properly, it does not allow the cable modems to function, I can remove the Channel Plus filter and the cable modems work just fine.

Has anyone else had this issue before? I need the filter on the incoming cable to make the camera modulators work but it kills the cable modem service and vice versa if I install it, the cameras look nice and clean but the modem service stops.

Any ideas of how I can have my cake and eat it too!
I did not expect the filter to affect the modem service but it sure does.

Thanks for any ideas you all may have
Jeff

Yup, this is just such a classic problem! I have used that filter to solve a couple such problems.

I see your difficulty with the cable modem and the single cable. I am guessing that adding another cable is out of the question.

All I can think of is to see if there is some way the cable modem can be elsewhere with a different type of wire connection to the computer in that room.
What is the output wire of the modem? CAT5? Can you run a CAT5?
Are there two spare pairs of CAT3 or whatever is in the walls now that you could use to feed the data signal from the cable modem to that room? If there is CAT3, but the run is not too long, the signal might not be noticeably slowed down.
There are also methods of getting camera signals over twisted pairs, i.e. phone lines. Your local CCTV guru should know about this.

I checked the specs of that filter... It passes
only 40MHz-xxxMHz. Cablemodems use 5Mhz - 42MHz
for their upstream. So, I think you have an
unsolvable problem if you want to use this
filter in any way that lets it be inserted
between your cablefeed and your cablemodem.

Channel Vision makes filters that can eliminate i.e. 70-76 allowing you to do want you want 714-424-6502

It's a little deceiving because on the filter itself, it says "Passband 0-470Mhz" which looked to me as though there would be no problem. Oh well, I'll check out the channel vision filters.

Thanks for the input.
Jeff

Just a quick note of caution on cable modems. Check with your local cable company to see where they have placed their up and down links before working with filters and modulators..... Cable One uses channel 28-30 space for uplink and channel 78 for downlink.... not all systems use the space below channel 2 only.

For clarity, refering to Cable Ones system where I live. Don't know what they use in other cities.

Oh, yeah, another thing about these filters --

They don't carry every channel up to the named channel, then totally cut off everything above there. The cutoff is gradual. The spec means that they do not cut off signal at the frequencies specified, only frequencies above that. But if the filter goes to, say, 550 mHz, then cuts off at 18 dB/octave (pretty good filter!), it will only be down about three or four dB at 600 mHz!

I installed a two way splitter before my 3x8 onQ amp. Then I install the splitter on the incomming cable from the pole, then I run one of the wires direct to the amp and i run a coupling to the coax wire going to the modem.

Works for me, B