RF Modulator Kills my CATV Signal When Used w. DISH

Toggle sidebar
G

gilgul

New Member
Original poster
Nov 6, 2009
2
0
Las Vegas
I had Dish installed this past week and am having trouble finding an RF modulator that works properly. My regular CATV is through Cox Communication and I would like to add the DISH signal into the CATV signal.

I purchased 2 different RF Modulators (RadioShack & Fry's @ $20/pc) and on both I am having the same issue. The DISH signal works fine but the CATV shows at a very bad quality. Note that the CATV shows fine when I simply disconnect the DISH box. I added an amplifier on the CATV line before the modulator and picture improve but still is bad.

Is this a function of a low cost modulator? Can you suggest of a modulator that works?
 
I am by no means an expert on this, but I have some questions about your setup...

1) You have Dish AND Cox? Why?
2) You say you purchased two modulators, again why? The dish receivers come with built in Ch 3/4 modulator.
3) Regardless of which modulator you use, you need to put it on an unused channel, otherwise one signal will bleed into the other (ie: you modulate Dish on ch. 3 and use a simple splitter to combine it with the Cox signal. Whatever Cox puts on ch. 3 will cause the Dish signal to look bad. ) IIRC, you can take the Cox signal, put it to the "Antenna In" (NOT "Satellite In" on the Dish receiver, and then it puts out the signal on the appropriate channel. However, the receiver's modulator will generally blow out anything other than the Dish signal when the receiver is turned on.
 
You have to buy a filter that filters out a couple channels above and below the channel you are trying to modulate on. Channels that look like all snow are probably carrying a digital signal. You also have to be sure you are not feeding back into the cable system, if you do and it causes issues cox will disconnect you.
 
gilgul said:
I had Dish installed this past week and am having trouble finding an RF modulator that works properly. My regular CATV is through Cox Communication and I would like to add the DISH signal into the CATV signal.
Click to expand...
You need to offer some specifics:

1. What model(s) of DISH receiver(s)?

2. What are you using the modulators for?

3. What service(s) do you get from Cox?
 
@sam_gordon
1. Have had Cox for ages. Ordered Dish only for an an international package.
2. Bought 2 modulators because the first didn't work so I figured I'd try another (didn't use at the same time...)
3. Do not have antenna in on my Dish box

@kb7oeb
1. So, if I modulate at channel 3, I need a filter for channels 2-4 running before the modulator?

@harshness
1. Dish receiver is VIP222K
2. Used one modulator at a time to try and add Dish into my analog cox line at channel 3/4.
3. I get both digital and analog from Cox. However, need the modulator only in one analog room where antenna is plugged into my computer (using a capture card).

Thanks for the quick replies. Sounds like I may be doing something wrong. We'll see.
 
The 222k should provide a channel 3/4 out. No need for an external modulator. The problem is Cox is probably already using 3 and or 4 and has kb7oeb pointed out you'd need a filter for those channels. Or you can get a (much more expensive) frequency agile modulator that allows you to pick the channel, but you'd need to know a channel cox isn't using (even if it's a digital channel, they're still using that frequency).
 
You need to filter out the un-used channels on the cable. The problem is that many of them will just show "Snow" but are actually using that same frequency broadcasting digital.

I had a hotel we did this at to add an international channel on Dish that was using Comcast. We modulated it out on a higher channel we though was clear, but had the same issue.

Only after we got a notch filter and removed everything above the channel we where using then did everything work perfect..
 
Because all cable systems use channels 3 and 4, you don't want to use a modulator in that range (you would undoubtedly filter out something important). Fortunately, the ViP222K comes with built-in UHF/CATV modulators that should work better than the ones that you bought.

See page 90 of the manual for instructions on how to set it up. If you've burned your manual, they are available on the DISH Network website. You want chapter 12.
 
I have Cox cable and Dish Network on my cable system in the house. They are using the entire band for analog and digital so you have to notch out the channels to make a spot for yours. On my 722 I set the cable output for 76 and 79 (TV1 & TV2). I have a 75-80 notch filter. Here is how I have it hooked up.

Cable line comes in and splits 2 ways. One goes to the cable modem. The other leg goes into the notch filter then into a 2 way splitter placed backwards (using as a combiner). The 722 cable output then attaches to the other leg of the combiner. The output of the combiner then goes into a cable distribution amp. From there I split it out to the 6 TVs and 3 PC tuners.

Works great, any TV in the house can pick up either side of the DVR or pick a Cox cable channel to watch.
 
magnum2066 said:
222K does NOT have a CH3-4 output anyway, hence the OTA module option.
Click to expand...
The two are substantially unrelated other than that the built-in agile modulators can distribute OTA signals as well as satellite delivered content.

The channel 3-4 modulator built into the OTA module represents a second RF frequency for TV1 and is currently pretty useless.
 
As you are combining with an existing service (your CATV provider) they use professional grade modulators, you might not have to go that far ($2,500 and up) you will have to use commercial grade (rack mountable) units to band pass or block and to modulate, the price range of the project could be between $450 and $900
You might want to analyze first other options.

Among other options I would consider in running paralel wiring (wiring is cheapper) and use a remote control AB switch some TV sets bring two antenna inputs.

If you want to send (transmit) HDTV (Line A/V; composite, etc.) you could build up a CAT 5 or CAT 6 network and install a HDMI receiver to each TV set.

Other option could be install more IRD's from your satellite provider.

All these depend on the number of users you intend to feed with this service or signal.

If you still want to go for your first idea, in my personal opinion the best way to do it goes something like this:

This kind of combination need skills and some professional tools to make combination as good as possible, I will try to explain in the most simple way as possible.

Assuming your house is wired with RG-6 and you have a distribution center also called head end, this distribution center most likely is located near the first drop or division in your house, there you will feed, divide, split, combine, etc.

I would buy first a Agile CATV modulator, there are several manufacturers: Holland electronics, Blonder Tongue, Pico Macom, etc.

PLM860SAW : 860MHz Channelized-Agile PLL SAW Filtered A/V Modulator

This one from Pico Macom sells for over $210 plus S&H; the good thing from this one is it goes up to 860 MHz most cable operators will cover up to 750 MHz or even 850 MHz; don't know if they will go up to 1000 MHz; the tool needed for this is RF field strength meter (too expensive as you aren't going to use this so often) I have found used units at a good price in ebay (arround $250) of course there are units up to $5,000 that will cover even digital.....

The advantage you have of knowing the power you are receiving the signal from your cable operator and then you can combinate with your agile modulator evenly (balanced) so one wont fade or mask the other...

All this needs to be made in the first area the CATV enters the house (Your house headend), you will have to run a coax from your IRD to this headend (no splits), other coax cable should be run from this headend to your cable modem (directly, no splits) and then you have you old cable that serves all your users areas (tv's).

If you use Broadband (internet) from your cable operator, I personally would separate them first so you wouldn't affect the two way communication since you are TX from 5 - 50 MHz and Rx in any other frequency from 50 MHz to 850 MHz.
To separate Broadband from CATV I advice to use a Digital ready 2 way splitter:

Buy 2 Way Cable Splitter for Cable TV

The good thing from this unit is it has Blocking capacitors on each splitter port produce low intermodulation distortion figures that are essential in optimizing broadband network performance.

Connect broadband to the output labeled (S) it has red stipe.

The other port will be used to feed your house with images and combine with your private circuit (IRD).

This is the best splitter-combiner I would advice:

Channel Plus 2-Way Splitter/Combiner - 2512 - Smarthome

combine this with your agile modulator and your CATV provider.
you might need to power up signal levels from your CATV provider since most likely they will provide you with not more than +15 dBmV or at least +5 dBmV (this is when the meter is good) the agile modulator will give +55 dBmV differential is between 40 dBmV and 50 dBmV you have to buy at least a drop amplifier like this:

CDA-1P : 1 GHz 1 Out Bi-Directional Amp (Passive Reverse)

That unit covers 5 MHz to 1 GHz and has a max output of +23 dBmv.
I advice not to serve the house with more than +25 dBmv due to the fact it could create distored images on some TV sets, as a matter of fact all tv sets will be perfect with +0 dBmv but you have to consider insertion loss, cable run loss, etc.

To balance with +55 dBmv of the agile modulator, the unit has a potentiometer to adjust RF output levels, try not to adjust Aural carrier (hopefully it comes adjusted from factory to -15 dBmv from video carrier) the other potentiometer you can adjust is audio (for volume level) and video for clarity-darkness, I advice image to be set as dark as possible, clarity sometimes create audio distortion.

If after you combine you don't find free carriers (channels) that you can use with your agile modulator, then you might need a single channel eliminator like this:

CEF750 : 750 MHz Single Channel Elimination Filter

This must be requested due to the fact they manufacture them customized.
Here's a chart so you have an idea of frequency/channel:

http://200.78.236.213/catalog/Appendix.pdf

This is the only procedure I could state should give you a reliable combination.

Good Luck!!!!
 

Users Who Are Viewing This Thread (Total: 0, Members: 0, Guests: 0)

Who Read This Thread (Total Members: 1)

Share this page

Share this page
Top