Outdoor diplexer keeps failing

[petermac]

I use a pair of standard one-port pass-thru diplexers to split and re-combine signals from directv/catv signals. The outdoor diplexer is an RCA D920 40-2150MHz/DC Pass. The inside diplexer is an Eagle Aspen D-2000LX.

The outdoor diplexer fails to work properly after a few weeks. This has happened several times now. It only fails passing the catv signal -- the sat signal is still good. The catv picture is snowy, so some signal is getting through.

I've replaced all the coaxials before the outdoor diplexer but not the one that goes through the wall. The indoor side of the coaxial goes from the diplexer/splitter to two inputs: cable and sat. The cable coaxial is then split to a box and the tv. Both of these cable inputs produce a snowy picture -- the sat picture is fine.

My directv hd-receiver recently went bad so they sent me a new one (Hughes). I get three sats (A,B and C). B and C are for high-definition. All these sats continue to work after the diplexer fails for catv.

The catv signal into the outdoor diplexer is always good -- I test it each time the catv picture goes snowy. The connections are taped up and protected from the elements, so i don't think water or sun is causing the problem.

The outdoor diplexer is failing more often lately. This last time, it failed after only two weeks. Would a high-performance diplexer make a difference? How about a dual-port diplexer? Is the sat signal somehow corrupting the catv side of the diplexer? Does splitting the catv line on the indoor side make a difference? The inside coaxials out of the diplexer have all been replaced.

If anybody has any ideas as to what the problem might be, I'd appreciate hearing them. Thanks.

 

[Cougar]

The only thing I can think of on this is, the problem may be caused by DC leakage to the outside antenna port. Though the design should prevent this kind of thing. You could try using a different brand of outside diplexer or put a DC block between the port and the antenna to see if that helps solve this problem.

If you have a voltmeter around you could see if you have any DC out of the ANT. port with everything normal and the antenna disconnected. If you do measure some then that is the problem I would say.

The only other thought I have is that some other external influence is causing this to happen.

Edit:
Another thought just came to mind. Since this is going to an outside CATV connection there may be some sort of a ground loop issue here. Is there a good ground to the outside diplexer?

 

[boba]

You might also check the cable line to see if it is passing voltage.