Possible to disable receiver backfeed? Messing with my Cable channels

Spooon69

Active SatelliteGuys Member
Original poster
Aug 25, 2006
17
0
Hi,

I hooked up a 625 today to a room. I've got the dish sending a signal into my home, combining it onto the single line into my house, then diplexing it and sending one line to the 625 and the other to my Comcast cable box. Problem is, when I hook up the 625, some of my cable channels don't work and some of them come in pretty garbled (the digital channels, I think all the analog channels are fine, haven't checked em all though).

Weird part is that all I have to do is unplug the line from the diplexer to the 625 and not mess with anything else and everything works fine. I'm guessing it's backfeed problem, why else would the cable box be affected unless the 625 was sending a signal backwards. The 625 is currently in single mode and no separator is hooked up to it (will buy a switch later to make use of the separator).

Is there any way to stop/filter/trap the backfeed from the 625 onto the regular house line? I've messed with the modulator settings in the 625 menu and changed it from Air to Cable and set the TV2 (even though there is no line coming into TV2 right on the box) to a high channel hoping it would fix the problem, no go. Any tips?
 
r_childress said:
The satellite signal is also digital. I don't think the way you have things set up will work. You need a separate line directly to your 625.
Works fine with my older 2800 receiver, it's the 625 that's causing the problems with a few channels. It should work since cable and Dish are on separate frequencies, I don't understand why it wouldn't work.
 
Your post dosen't make a lot of sense to me. Are you sending TV2s output back into the cable line? That could mess up your cable signal. Do you have the two diplexars connected correctly? The 625 sends out 18 volts to power the LNB if your diplexer isn't blocking this from the cable line it could cause problems. You need inputs to both tuners on a 625 for it to work correctly, put your 2800 back in until you get the DPP Twin or DPP44 switch.
 
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OK, some clarification, guess I typed it out too fast.

The 625 has 2 inputs, TV1 and TV2. Right now I only have TV1 hooked up via the diplexer, TV2 isn't hooked up at all, will install the separater once I get a DPP44 switch. So right now I have the 625 set to single mode.

The problem is that some of my cable channels (on the box hooked up the same diplexer above) aren't working or are garbled (about 4 or 5, but I haven't checked all the channels yet, the rest are coming in perfectly). If I just unhooked the 625 from the diplexer (ONLY doing that), the garbled/non-working channels on the cable box start working again.

So I guess it's an issue of the 18 volts of power the 625 is sending and the diplexer isn't blocking that? I'm using a Perfect Vision PVDP3 diplexer and they're hooked up correctly. Guess it wasn't backfeed after all.

So what diplexer do you recommend that block the 18 volts from going into my cable box? Strange though, thought it was only power passing on the satellite end of the diplexer.
 
ok strike that. Have you tried more than one diplexer?

And tV1 is hooked up via the diplexer. The TV1 input should be connected to the tv or vcr. The sat lines(should be two from dish if you do not have a seperator) should go in the sat1 and sat2 inputs.

is that how it is? And you have the diplexer in-line with one of the sat lines, and the cable coming from the tv/ant/whatever side? And you have one outside in the cable box, with the correct cables going to the corresponding ports?
 
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Another thing to keep in mind is that the RF modulator for TV 2 on the 625 can output on UHF and/or cable channels. TV 1's RF output is limited to channels 3 or 4. As long as you are in single mode and you are using the RF output for TV1 going into the TV side of your diplexer it should work just as it did with your 2800. If you are using the output for TV 2 make sure you have it set to a channel that is not in use. While your cable system may not have any analog channels on the frequency you choose they could be putting the digital channels there which could be the source of your problems. Some experimentation with the channel setting on your 625 should clear up the problem.

Just to be sure, you are connecting the TV out from the 625 to the TV side of the diplexer, correct? And on the other end you have another diplexer, with the TV side connected to some sort of combiner so that the signal can be distributed throughout the house?
 
I think spoon69 has a terminology problem. If I am guessing right he is trying to use a dual tuner 625 with only 1 tuner connected he thinks single mode means it will work this way. A dual tuner DISH receiver needs 2 lines from the dish to the 2 inputs on the back of the satellite receiver to work correctly.
 
Problem fixed, I replaced the PVDP3 diplexers with Holland Blues, I guess the PVDP3s bleed a little on their power passing? Not sure, but at least my cable channels are fine now and the 625 works great too with no other changes.
 
Link Please

Spooon69 said:
Problem fixed, I replaced the PVDP3 diplexers with Holland Blues, I guess the PVDP3s bleed a little on their power passing? Not sure, but at least my cable channels are fine now and the 625 works great too with no other changes.


Can your provide a link and/or part number for those diplexers
 
Interesting. I'm still a little surprised you're getting away with this.

What are frequency ranges of Cable and DBS over the coax?

You'll have to post again when you get your Pro-Plus. The two-tuner stacking is going to suck twice as much bandwidth.
 
Holland DPD2
I bought them from http://www.swidendist.com, they had them cheaper than on eBay.

As for the frequency ranges, I assume they're the normal Cable and Dish ranges (e.g. ~40-850 & ~950-2150 respectively).

I'm not installing a Pro Plus but a DPP44 switch, so once that's done (installing as we speak by the satellite guy) I'll see how it goes with the tuner-stacking.
 
Spooon69 said:
Holland DPD2
I bought them from http://www.swidendist.com, they had them cheaper than on eBay.

As for the frequency ranges, I assume they're the normal Cable and Dish ranges (e.g. ~40-850 & ~950-2150 respectively).

I'm not installing a Pro Plus but a DPP44 switch, so once that's done (installing as we speak by the satellite guy) I'll see how it goes with the tuner-stacking.

DPP44 = Dish Pro Plus 44.
I was thinking that some of the expanded cable systems might have gone beyond 850, but perhaps not.
 
Ah OK, misunderstood then about the Pro Plus.

So it's all set up now and everything works great, even the two tuners in the 625. So right now I've got a 625 (2 tuners), a 2800, and cable (Analog, Digital, Internet, & HD) all working fine. The cable amplifier and the 625 line is using Holland Blue diplexers and the 2800 is hooked up via PVDP3 diplexers. The DPP44 is being powered by a clean line from the house and the LNBF is going into port #3 in the DPP44 (for 2800 61.5 compatiblity according to the DPP44 quick fact sheet).

Here is a diagram of what I did:
 

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