Coax joiners, splitters etc and cable losses

[jaray]

I'm trying to put together a plan for a centralized wiring area in my house. This will be a common area where all my coax, Cat5, telephone etc will all run back to (or start from).

Up to this point I've stayed away from it in terms of my coax runs as I can already picture various coax switches, junction blocks, splitters etc that end up being used to start sending coax runs throughout the house. My thoughts are that there is nothing better than the direct runs of coax I already have from both my KU FTA dish, C-band dish and DBS dish which go directly from dish to my living room where all my receivers are.

So my question is, since everyone wants to always maximize signal quality/level and minimize any losses why would anyone bother to include coax in they're structure wiring plan? Every time a junction block, ground block etc is used it adds a loss to the overall SQ. What are your opinions on this stuff and what are the hobbyists generally doing in terms of structured coax wiring?

Right now, I have a grounding block in the garage not far from my dishes, then a straight run to the v-box (c-band) then out of the V-Box to the reciever. That's 3 joints already in that single run and the last thing I'd want to do is add any more.

 

[pendragon]

Worrying about properly terminated coax cable signal losses is one of the popular urban myths of FTA. Awhile back someone posted specs here for some compression connectors; I recall the signal loss being on the order of 0.05 dB or less for a single connection. This is completely meaningless in our domain.

Before you get worried about a bunch of these connectors adding up to something significant, it's important to note LNBs amplify satellite signals well above the thermal noise floor of a 75 ohm resistor. This essentially means signal losses will only affect signal level, not CNR or signal quality as it is often referred to. It's very unlikely you would ever be able to drop the signal level enough to make any material difference on reception, but if you did, a good quality amplifier at the appropriate point in the chain would solve that problem.

Those who claim otherwise either have very poor quality coax connections or are in dire need of understanding gain optimization.

 

[guapoharry]

Maybe those concerns are more appropriate for OTA antennas without amps.

 

[jaray]

Pendragon, that makes alot of sense. That probably explains why on my DSR-410 after about 120' of coax, 1 ground block and through my V-Box my signal level went from about 65 down to 52, but SQ hardly took a hit, if at all. I suppose if for some reason I was that worried about it, I'd throw in an amp but there's hardly any need.

Great way of putting it...

 

[PopcornNMore]

I was experimenting a little last night and found some interesting things about signal strength and what happens when barrel connectors and / or switches are in-line along with additional coax or if the dish and LNB are misaligned. I will be performing additional testing today.

Here are my odd findings from last night:

I had both my 6' and 8' prime focus dishes aligned to Galaxy 17 and performed a blind scan using the same receiver (Coolsat 4000).

1) On the 6' dish FUEL, SPEED, FOX Soccer and others scanned in as scrambled channels and a black screen appeared. On the 8' dish these same channels scanned in ITC with a beautiful picture. Both the 6' and 8' had about the same signal strength on that transponder.

2) National Geographic had a signal strength of 70% on the 6' and 72% on the 8' and was ITC with a beautiful picture.

3) The 8' scanned in several transponders that the 6' couldn't scan in, but the 6' scanned in a channel or two that the 8' wouldn't scan in.

4) Using the 8' dish with the receiver downstairs in the communications room FX East and FX West and some other channels scan in with a beautiful picture. When I add a barrel connector and an additional 50' coax to our master bedroom and move the receiver to the bedroom theses channels don't scan in (blind and manually), but all other transponders do scan in.

5) PBS channel NET1 from nearby Galaxy28 scans in as GEMS TV on Galaxy 17 using the 8' dish for some unknown reason. However, the other two NET channels don't scan in.

Like I said I will be performing additional testing today, but found these things interesting of what can happen if your dish isn't properly aligned and / or additional barrel connectors, switches and coax are added to the system.

 

[jaray]

lol, well that's just great! Now what am I supposed to think? hehe.

All I found so far was that signal strength drops as cable length increases and SQ didn't change much at all.
Best way to tell would be take SQ reading using all the same equipment, then add in a bunch of chunks of RG-6 joined with barrel connectors to make up the same cable length and compare the SQ difference.

 

[pendragon]

PopcornNMore: were your measurements for signal strength of signal quality? There is a critical difference between the two. It does sound as though you are on the ragged edge for reception of the channels you reported. Ordinarily one might suspect alignment issues, a long/weathered cable or perhaps a marginal LNB. If this isn't the case you would probably see more consistency with a high-quality amplifier located at your dishes.