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ChannelPlus/Channel Vision Modulation Problem

post #1 of 19
2/26/09 at 7:49pm
Thread Starter 
Installed a ChannelPlus DA-550BID and Channel Vision E4200. The Amp works great as an Amp, but can't get a good modulated picture from the CV E4200. Seems like I'm getting an over-processed signal through the DA-550, herringbone/tearing picture. Thought it was an impedance problem and put a 75ohm filter on, tried modulating on various available channels (123, 125, 130) with and without a notch (low pass) filter. Also tried to adjust the Video Level Adjustment on the 4200. FYI, just to make sure there isn't anything wrong with the 4200, I bypassed the DA-550 and output directly to a TV...worked perfect.

I called ChannelPlus (Linear) and they were of very little help since I was using a "non" ChannelPlus modulator.

I'm not terribly technical when it comes to Home Theater, nor do I have a scope or db tester, but I can perform basic trouble shooting. Any advice and suggestions is greatly appreciated.
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post #2 of 19
2/27/09 at 5:20am
Some Channel Vision modulators have very high output gain, it may be above the input signal threshold of your amplifier.

jcmitch
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post #3 of 19
2/27/09 at 5:44am
Thread Starter 
Quote:
Originally Posted by jcm View Post

Some Channel Vision modulators have very high output gain, it may be above the input signal threshold of your amplifier.

jcmitch

OK. On the CV if I adjust the Video Level Adjustment all the way down, I start to see a picture and audio is almost recognizable. So what you're saying may be the case. If so, how is it solved? Besides changing to a Channel Plus Modulator.
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post #4 of 19
2/27/09 at 8:13am
Calling RobertMee...
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post #5 of 19
2/27/09 at 1:52pm
Quote:
Thought it was an impedance problem and put a 75ohm filter on

...to filter out the ohms?
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post #6 of 19
2/27/09 at 3:59pm
Thread Starter 
Quote:
Originally Posted by duvetyne View Post

...to filter out the ohms?

...to follow the troubleshooting suggestion in the manuals.
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post #7 of 19
2/27/09 at 4:00pm
What is a "75 Ohm filter"?
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post #8 of 19
2/27/09 at 4:17pm
Thread Starter 
Quote:
Originally Posted by duvetyne View Post

What is a "75 Ohm filter"?

http://cgi.ebay.com/75-Ohm-Coax-Inli...206166004r3278
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post #9 of 19
2/27/09 at 4:20pm
It doesn't say what the corner frequency is.
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post #10 of 19
2/27/09 at 6:21pm
If the Channel Vision outputs a usable amount of signal alone, why do you need the amplifier?

jcmitch
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post #11 of 19
2/27/09 at 8:15pm
Thread Starter 
Yikes...you guys aren't getting it.

The 550 is a distribution "amp". The modulator must go to the 550 in order for the signal to be combined and "distributed" to the other TVs.

Looks like I know much more about this stuff than I thought....or at least more than some others here.

Quote:
Originally Posted by jcm View Post

If the Channel Vision outputs a usable amount of signal alone, why do you need the amplifier?

jcmitch
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post #12 of 19
2/27/09 at 10:59pm
Quote:
Originally Posted by JLondon999 View Post

Yikes...you guys aren't getting it.

The 550 is a distribution "amp". The modulator must go to the 550 in order for the signal to be combined and "distributed" to the other TVs.

Looks like I know much more about this stuff than I thought....or at least more than some others here.

No need to be rude. Seems to me like jcmitch is trying to understand it himself.
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post #13 of 19
2/28/09 at 5:37am
In that case, you use a combiner and a low pass filter, you don't need to run the modulated signal through the amp. An Rf meter will help you get the amp and modulator gain (cut) settings in balance. Channel Vision will help you design the solution if you can't do it yourself.

jcmitch

http://www.channelplus.com/product_d...p?productId=19
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post #14 of 19
2/28/09 at 6:32am
Thread Starter 
Quote:
Originally Posted by Neurorad View Post

No need to be rude. Seems to me like jcmitch is trying to understand it himself.

So sorry...just frustrated. This just seems to be such a simple setup that's not working properly.
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post #15 of 19
2/28/09 at 6:36am
Thread Starter 
Quote:
Originally Posted by jcm View Post

In that case, you use a combiner and a low pass filter, you don't need to run the modulated signal through the amp. An Rf meter will help you get the amp and modulator gain (cut) settings in balance. Channel Vision will help you design the solution if you can't do it yourself.

jcmitch

http://www.channelplus.com/product_d...p?productId=19

I see now where you were going. However, if I use a seperate combiner (the DA-550 has it built in as input "A" and "B") I would then connect this combiner to the ANT/CABLE input side of the DA-550.
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post #16 of 19
2/28/09 at 6:27pm
No, you would connect the output side of the amp and the modulator to different legs of the combiner, and the output of the combiner to the Rf distribution system.

jcmitch
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post #17 of 19
3/1/09 at 9:00pm
OK, going on the assumption that your modulator is overdriving the system (my specs says its output gain is 25dBm, pretty high) there are basically two ways to fix it.

First buy a stand alone amp for your incoming CATV signal, then combine this signal with the modulator signal with a two way splitter, then distribute it with a passive 8 way splitter. Sell your Channel Plus on ebay and call it good :-)

Or you could try putting an attenuator in the line between the modulator and your distribution amp. This is probably the cheapest and quickest way to solve the problem, they are only a few $ each. I think I may even have a couple different strengths of attenuators lying around. PM me if interested.

This is why I am not a big fan of the "all in one" combiner/amp/splitter deals. I generally prefer to "roll your own" with a combination of amp and quality splitters since it gives more flexibility to change the system.
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post #18 of 19
3/2/09 at 6:41am
Quote:
Originally Posted by lorenkoeman View Post

OK, going on the assumption that your modulator is overdriving the system (my specs says its output gain is 25dBm, pretty high) there are basically two ways to fix it.

First buy a stand alone amp for your incoming CATV signal, then combine this signal with the modulator signal with a two way splitter, then distribute it with a passive 8 way splitter. Sell your Channel Plus on ebay and call it good :-)

Or you could try putting an attenuator in the line between the modulator and your distribution amp. This is probably the cheapest and quickest way to solve the problem, they are only a few $ each. I think I may even have a couple different strengths of attenuators lying around. PM me if interested.

This is why I am not a big fan of the "all in one" combiner/amp/splitter deals. I generally prefer to "roll your own" with a combination of amp and quality splitters since it gives more flexibility to change the system.

Lorenkoeman's suggestion makes the most sense so far, and I agree with him 100%. Either that or combine the modulator with the CATV feed utilizing a DC-12 (modulator on the TAP leg, CATV feed on the OUT leg, and the amp connecting to the IN leg).

Without knowing exactly how a combining network is setup, there's no way you can accurately design a distribution system.

LPF is on the CATV feed, I assume.
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post #19 of 19
3/2/09 at 8:48pm
Thread Starter 
Quote:
Originally Posted by lorenkoeman View Post

OK, going on the assumption that your modulator is overdriving the system (my specs says its output gain is 25dBm, pretty high) there are basically two ways to fix it.

First buy a stand alone amp for your incoming CATV signal, then combine this signal with the modulator signal with a two way splitter, then distribute it with a passive 8 way splitter. Sell your Channel Plus on ebay and call it good :-)

Or you could try putting an attenuator in the line between the modulator and your distribution amp. This is probably the cheapest and quickest way to solve the problem, they are only a few $ each. I think I may even have a couple different strengths of attenuators lying around. PM me if interested.

This is why I am not a big fan of the "all in one" combiner/amp/splitter deals. I generally prefer to "roll your own" with a combination of amp and quality splitters since it gives more flexibility to change the system.

Bingo...decided to call Channel Vision (again) today and was told all I needed was their model #3000-6. It's a 6db Attenuator. The tech was "positive" this would solve my problem. I'll let you know how it goes. Thanx for all the great advice
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