622 and OTA preamp

[joshbish]

Currently I have a DB8 from antennasdirect in the attic. The line runs outside and is merged with the sat line using a diplexer. then the single line goes into the house and there is another diplexer inside that splits back out the ant and sat signals. One tv/box. Fairly straight forward.

My question is, if I use a Channel Master 0065DSB preamp and change my in-house diplexer to one that will pass power on both sides, will my 622 sat box power the 0065DSB?

 

[ats7627]

Welcome to SatelliteGuys.

The Channel Master 0065DSB is designed to run off of the satellite receivers LNBF power supply. The 100mA current draw of the preamp should not be a problem with a 622.

 

[bhelms]

The diplexer you need to change to power-passing both output ports is the outside one so both the preamp and LNBF are getting power. There is no need to change the inside diplexer as long as it is passing power from the sat. input jacks through the diplexer and on to the outside equipment. Note that the 622 does not provide any power from the OTA antenna input. If you are using a separator to feed one sat. cable to both inputs, make sure your inside diplexer is between that separator and the cable leading to the outside equipment...

Welcome from me as well...!

 

[joshbish]

Terrific. Thanks both for your help.

I've read around and it seems to be preferred to use separate runs for the ant and sat rather than using diplexers. Why is that? What is the negative to setting things up how I have mentioned?

 

[bhelms]

The diplexers impart a certain amount of loss (~0.5 to 1dB ea.?) and reflections. That will almost never be an issue with the sat. signals but could contribute to weaker/less reliable reception on the OTA signals if you're in a fringe area like I am. If you can run an independent cable for the OTA signals I would advise doing it. That also gives you more flexibillity for future expansion or changes. Also - there are better preamps if you really need the best performance that will need their own PSs. For instance, the CM 0065DSB's 3dB noise figure is good, but the 7777 at 2.0dB is better.

PS - You asked so I answered. There is really no reason to change what you have if it's working OK for you. Just my 2-cents worth...!

 

[joshbish]

if I used a preamp that had its own PS like the 7777 you mentioned and still used the diplexer setup, where would I put the PS? could I put it in-house or will that be bad running that power through the diplexer? the reason I'm asking is because I don't have any power outlets outside where the sat and ant cables meet or in the attic.

I'll definitely have to give some thought to running two separate cables. I just got installed a couple of days ago and the Dish guy said the best way was to use the diplexer setup and use the existing cable running into the house --- however, I'm thinking now it was because he didn't want to get up into the attic and drop another line in. I guess I don't blame him --- it was 98 degrees yesterday!

 

[bhelms]

That's a situation where you can't diplex. I'm not sure what power the 7777 needs (I just ordered one myself, coincidentally - I'll be able to tell for sure in a couple of days!) and it may be different than what the LNBs/0065DSB need. You can diplex (combine) RF signals - they don't interfere since they're in different frequency bands - but you can't mix two different power types on the same cable.

Again - if what you have is working OK, no need to change it until you need to make other changes...