Switch problems with dual LNB

[slb04786]

I have a legacy 18" RCA dish with 2 older RCA receivers on a DirecTv dual LNB system. I believe they are model DR310. Everything was working flawlessly until about 6 months ago I wanted to add a third receiver. I bought a 2x4 way RCA multiswitch and installed it in the attic where the 2 cables came in from the LNB. I bought a Samsung reveiver from DirecTv and installed it along with the 2 RCA reveivers to ports 1-3 of the multiswitch. Every since then I have been getting momentary lockups (freeze) of the video and audio. At times it would be worse than at others. I checked everything. Alignment, cabling, connectors, etc. Nothing helped. This weekend I was in my sons room when it was locking up and noticed that the receiver in the living room would lock up for about 2-3 seconds whenever he changed channels on his Samsung receiver and his would sometimes lockup when the RCA in the living room changed channels. So, I've narrowed it down to what is causing the problem and I'm hoping someone can shed some light on this. Hopefully it won't involve trashing everything and going to one of the newer Phase III dishes and quad LNB. Sorry for the long post and thanks in advance for any help.
Stan

 

[slb04786]

Additional info

I don't have an OTA antenna connected to the switch even though there is a jack for one. For that reason I didn't install diplexers in the receiver lines to split the signal between the receiver and tv. Could this be causing the above mentioned problem?
Stan

 

[CablerMN]

Sounds more like the voltages each receiver puts on the line to change transponders and polarization are not playing well together. I would start by disconnecting one receiver and seeing how the other two react, and so on for the other other two. May help isolate the problem or further complicate things. If you have a volt meter you can also test the voltages on each cable at the multi-switch. If you are getting more then +18 or less then +13 (depends on transponders) may help to isolate it as well.

 

[Cougar]

I would try a different switch. It sounds like the RCA unit is not working like it should.