Thread: RF Modulator Kills my CATV Signal When Used w. DISH

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.

Originally Posted by gilgul

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.

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.

Originally Posted by sam_gordon

The 222k should provide a channel 3/4 out.

The ViP222K has a two-channel high-band agile modulator that can output UHF (21-69) or higher numbered (73-125) cable channels.