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Problems with modulation?

post #1 of 11
Thread Starter 
Hoping someone can help me out...recently, I've noticed when I installed the new comcast digital converter boxes on my tv's, my modulation channels are not working? I have a channel vision modulator with an lpf-600 filter and usually use channels 100, 102, 104, and 106 as my four output channels.

FYI, I know it most likely has something to do with installing these new digital boxes because I can go to a tv that does not have one of these boxes installed and the modulation still works. This tells me nothing is wrong with my modulator or filter I assume.

Any ideas?

Thanks for any assistance you can provide,
Michael
post #2 of 11
Quote:


I've noticed when I installed the new comcast digital converter boxes

Assuming the digital converter box converts an ATSC or QAM signal to analog, what does it do with incoming analog signals, such as the ones from your modulators?
post #3 of 11
Thread Starter 
Quote:
Originally Posted by SAM64 View Post

Assuming the digital converter box converts an ATSC or QAM signal to analog, what does it do with incoming analog signals, such as the ones from your modulators?

Sorry about that, I guess I should have explained what it does when the boxes are hooked up. Basically on the tv's where I have installed the digital converters (which like you said convert the digital signal to analog) it basically just shows whatever is on that channel that is being broadcasted by the converter box. So for instance, when I turn it to channel 100 to see one of my camera's, it just shows a reg cable channel and not the modulated channel.

It's almost like they have continued the channel lineup to now go up into the 100's or something since I have the new digital boxes...or something like that?
post #4 of 11
Yeah, those boxes are very likely not going to tune to the IRC/HRC (IIRC ) analog cable bands where you've placed your modulated channels. If the cableco has turned off much of their analog tier, you might try a UHF channel (<63) as a new home for your modulated channels - and see if the digital converter will pick it up...


Jeff
post #5 of 11
Thread Starter 
Quote:
Originally Posted by jautor View Post

Yeah, those boxes are very likely not going to tune to the IRC/HRC (IIRC ) analog cable bands where you've placed your modulated channels. If the cableco has turned off much of their analog tier, you might try a UHF channel (<63) as a new home for your modulated channels - and see if the digital converter will pick it up...


Jeff

jautor-

Thanks for your help. So what would be some other UHF channels besides 63? Reason being is because I have 4 modulated channels I would like to cut in.

Dang it Comcrap! Messing up my perfect little system....LOL

Thanks,
Michael
post #6 of 11
Quote:
Originally Posted by M1chael View Post

Thanks for your help. So what would be some other UHF channels besides 63? Reason being is because I have 4 modulated channels I would like to cut in.

Any place they don't have a signal... 14-83. Something above 63 might have better luck since those UHF stations were moved after the digital transmission, but I found the modulators to work better on UHF at lower frequencies (~14-30).

Use an analog TV to look for open frequencies. Trial and error, I'm afraid.

Jeff
post #7 of 11
Thread Starter 
Quote:
Originally Posted by jautor View Post

Any place they don't have a signal... 14-83. Something above 63 might have better luck since those UHF stations were moved after the digital transmission, but I found the modulators to work better on UHF at lower frequencies (~14-30).

Use an analog TV to look for open frequencies. Trial and error, I'm afraid.

Jeff

Jeff-

Thanks for your help, I guess I have some work to do tonight. I will start with 63 and move up from there (65, 67, etc) and see how that goes. If that does not work, I will then try something between 14-30.

If anyone else has a similar configuration and is in the comcast area, feel free to comment on where your modulated channels are set up.

Thanks,
Michael
post #8 of 11
Thread Starter 
Well, just wanted to report back and see if I can get some addt'l assistance. I tried numerous channels last night and nothing is working (DTA will not pass modulated channel). I tried high channels ranging from 65 to 90 and low channels ranging from 14 to 30.

Contacted channel vision to see if I could get some addt'l support and they suggested their "Affinity modulation over digital cable" kit. He also said I could try and "rig" until I decided on whether or not to try the Affinity kit. He advised me to take 2 splitters and attempt to bypass the DTA with one of the legs. I had 2 splitters on hand and tried it but it did not work. The DTA would not accept you splitting the signal I guess.

Anyone have other suggestions that I can try with my existing equipment before I consider purchasing "extra" equipment like the Affinity kit? Can I use any other equipment (ex. vcr) to get my security cams to be viewable on the tv's in the house? Just brainstorming......

Thanks,
Michael
post #9 of 11
You're feeding an analog signal into a Digital to Analog converter box. If this box does not have an analog tuner, it will not be able to demodulate the analog signals you're feeding to it.
post #10 of 11
Thread Starter 
Quote:
Originally Posted by SAM64 View Post

You're feeding an analog signal into a Digital to Analog converter box. If this box does not have an analog tuner, it will not be able to demodulate the analog signals you're feeding to it.

So in layman's terms, I assume I am screwed...LOL

So does anyone else have any suggestions on how I can keep my current configuration (modulating over cable) in order to view my cams? If not, I guess I will need to eventually upgrade to IP cams and be done with ancient analog.

Thanks,
Michael
post #11 of 11
Quote:
Originally Posted by M1chael View Post

He advised me to take 2 splitters and attempt to bypass the DTA with one of the legs. I had 2 splitters on hand and tried it but it did not work. The DTA would not accept you splitting the signal I guess.

Anyone have other suggestions that I can try with my existing equipment before I consider purchasing "extra" equipment like the Affinity kit? Can I use any other equipment (ex. vcr) to get my security cams to be viewable on the tv's in the house? Just brainstorming......

Thanks,
Michael

Splitting the coax before it goes into the DTA should not be a problem but in addition to a single splitter at each TV, you'll also need an A/B switch. So, what you'll have is your original coax cable feeding a splitter, one leg of the splitter goes to the DTA, the output of the DTA feeds the A side of the A/B switch, the other leg of the splitter feeds the B side of the A/B switch and the output of the A/B switch feeds the RF input on your TV.

I'm not saying this is the most elegant fix since you'll have to manually flip the A/B switch in order to use your TV's tuner to tune in your modulated channels but it will work. Remote controlled A/B switches (http://www.radioshack.com/product/in...ductId=2049643) would address that issue but depending on how many TVs you have you may find that approach to be cost prohibitive.
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