[mythtv-users] General Set-Up Question

sschaefer1 at woh.rr.com sschaefer1 at woh.rr.com
Fri Jun 2 16:09:37 UTC 2006


My infrared distribution over coax is a 12 volt system.

> do you mind me asking what hardware
> do you use for the IR distribution 
> and how much did it cost?

At one time I was trying to keep track of what I bought and how much, 
but didn't
keep up with it.

I don't mind you asking. There are many different offerings for 
infrared distribution
and a few different ways to accomplish it. Most the material I read 
suggested the
non-installer (do-it-yourselfer, that's me) to avoid infrared 
distribution over coax.
Just keep in mind that regardless of what type or manufacturer you 
buy, when you are
stuck and trying to troubleshoot, undoubtly there will be no one to 
call or probably
even hire to get it installed for you.

I wound up buying Channel Plus equipment.
http://www.channelplus.com/products_ir.html

At the computer rack I have (2) 2174 emitter expansion blocks, a 2100
to provide the power to the infrared system.
I have a 2100A and a 2132 at each television.
I bought a set of clear single head emitter leds from some other 
source,
cause the Channel Plus ones I could find were way too expensive.
They have self adhesive tape already on them that are supposed to pass
the signal through, so I didn't have to buy any. Eventually I will
tape over them and only rely on the distribution to signal with the
remote. I bought a pack of DC blocking capacitors 2501-10, which
you will need for any coax connection that doesn't have a 2100A on it.
Also, any coaxial combiner/splitter you have in between the path of
the infrared distribution's path has to be DC passing.
I just have some passive 2/3 and 4 ports I bought at the electronic
surplus store for $1-$2 each.

One of the reasons I bought into Channel Plus, was that I was 
interested
in there SVM-24, which has 4 RF modulators in the one rackmount unit.

http://www.channelplus.com/product_detail.php?productId=81

The only consumer modulator(s) that support stereo audio and is 
rackmount.
There are other single modulators that support stereo, but you have to
buy a seperate rack kit for them... multiply that by 4 and you have 
spent
the same price as SVM-24 which only takes up one space...
Also, it has jacks for 4 IR emitters and also acts as a power source
for the coaxial infrared distribution, which means I would not have
had to buy the 2100 with its power transformer. Another benefit is that
it has native pass through, so I can easily connect up my security
cameras to a RF channel and then on to the capture card with motion
detecting software... instead I have had to buy a range of cables 
adapters
with the setup I have now, thanks to the surplus store they were 
affordable.
However, the cheapest SVM-24 I could find was $535 + shipping.
Most of my televisions are mono audio, so I wouldn't get much benefit
from the modulator's stereo feature anyway.

The consumer modulators that I wound up purchasing were a Radio Shack 
UHF
brand, product ID 15-1243 sometimes found as 150-1243. They 
discontinued them
about a year and a half ago and I bought (12) of them for $25 each.
This modulator is nothing more than CELabs model 1001F with a Radio 
Shack
label instead of CELabs. I have (3) sets of 4 modulators connected via
4 port passive combiners, in turn connected via a 3 port combiner, then
passes through a 25 dB booster bought at Home Depot, then combined with
filtered antenna signal. The Radio Shack modulators have a stereo 
connection
but only broadcast a mono audio signal.

model        frequency range   output gain
-----        ---------------   -----------
SVM24        20 Hz - 12 kHz     ~25 dB
15-1243      1 kHz - 10 kHz     ~20 dB
  ...the best commercial, I found...
commercial   10 Hz - 15 kHz     35-65dB


> In addition to the audio limitations
> that you mention there are also  
> video limitations. First of all you
> are pretty much limited to SD  
> material, as creating your own ATSC
> RF signal would be expensive and  
> non-trivial.

I have a HD ATSC tuner card, but I play back the video
in SD resolution which goes out to RF modulator. The
result is a SD signal that is better than the SD
broadcast of the same show. For example, if I were to
watch Smart Gardening on PBS on their SD broadcast
channel, then watch the same show that was broadcast
on their HD channel as it is played back from my
computer through the RF modulator in SD... the played
back signal is much better! Of course, it is no where
near the quality of a HDTV display of the HD signal.

> Even with SD video, the quality of
> consumer grade modulators is  
> pretty limited. You could purchase
> a modulator of the type used in  
> CATV headends, but those cost around
> $3000, even more if you want to  
> have MTS audio, and that's per-channel,
> probably cheaper to purchase a separate PC.

I disagree, true the commercial modulators are technically
better, but I get a great signal that I've
boosted from my (low end) consumer modulators. If I were
to get a set of commercial modulators I would have to do
the reverse and buy those resistor things that degrade
the incoming signal at each TV enough so that I don't
have a distorted picture. Probably wouldn't have to do
that if the commercial modulator had a dial to turn
down the gain, which some don't. If all you had was
one consumer modulator, there would be no reason to
use a booster, cause the signal would not have that
many combinations to pass through to degrade it.

> Still, if the quality available is
> adequate for your purposes you are  
> quite correct about the flexibility
> of in-home RF distribution  
> systems. You can also put things
> like outside security cameras, baby  
> monitors etc. on the system, and you
> can distribute material other  
> than TV signals, like FM audio,
> custom data, intercom channels and  
> even modulated IR control for your RoboSapien.

That's exactly what I'm doing, except for the RoboSapien.
The wife doesn't like clutter, and it's easier to get
away with more clutter in the rack where there is already
clutter than have a frontend at each television, not
to mention I've already have the RF modulators for the
security cameras, why not just plug in the MythTV, DVD,
VCR? When I do finally buy a HDTV then I'll probably
consider one frontend.

The remaining text is discussing the differences
between a 5 and 12 volt infrared distribution system
over coaxial cabling, I don't remember where I found it.

We sell two over-the-coax IR repeating systems.
The 12V system is very versatile.
The 5V system is designed for the hobbyist. It is easy to use and low 
cost.
intended for professional installation and is

12 Volt IR system.
! Works with industry standard Xantech IR receivers (targets).
! Requires 2100A wall plate to interface with IR receiver. (One 2100A 
per receiver.)
! Requires a DC block on all output ports that do not have a 2100A.
! 12V IR coax panel models; 3100, 3208, 3212, 3308, DA-550BID, DA-
550HHR.

5 Volt IR system.
! Works with model 2133 IR receivers (target).
! Does not require special wall plates.
! Does not requires DC blocks on unused ports.
! 5V IR coax panel models; 3025, 8200, DA-8200HHR, DA-8200BID.

Notes:
! There is no such thing as 5V or 12V emitters. ChannelPlus and 
Xantech Emitters are
compatible with both systems.
! 12V IR receivers cannot be used on 5V systems.
! 5V IR receivers cannot be used on 12V systems.
! All ChannelPlus 5600 and SVM series modulators are compatible with 
both 5V and 12V
IR systems.



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