AVS › AVS Forum › HDTV › HDTV Technical › Preamp question
New Posts  All Forums:Forum Nav:

Preamp question

post #1 of 13
1/28/13 at 9:57am
Thread Starter 
Thinking about an RCA preamp to my RCA 751 antenna. How do I power it? I am assuming it looks like this:
1. short down wire coax from antenna to preamp.
2. one coax to television
3. other coax to wall outlet indoors via plug.

Let me know if this is right.
Thanks.
Reply
Reply

AVS Top Picks

post #2 of 13
1/28/13 at 10:49am
You are close. Look here:
http://www.solidsignal.com/p/?p=3535&d=How-to-properly-install-a-pre-amplifier
John
Reply
Reply
post #3 of 13
1/28/13 at 11:49am
And some Preamps (e.g.Winegard, et al) use a separate Power Injector and wall-wart Power Supply:
http://www.winegard.com/kbase/upload/2451964.pdf
Reply
Reply
post #4 of 13
1/29/13 at 7:42am
Thread Starter 
Thanks for the link. Is that a splitter I see? Or is it a power injector? Is there a differnce?
Reply
Reply
post #5 of 13
1/29/13 at 9:28am
Quote:
Originally Posted by airgwar View Post

Thanks for the link. Is that a splitter I see? Or is it a power injector? Is there a differnce?


It's a power injector and isn't interchangeable with a splitter. Although the physical case might look the same, the internals are completely different.
Reply
Reply
post #6 of 13
1/29/13 at 10:41am
Thread Starter 
Thanks, got it now. I am learning so much as I go. This is a great forum. Since this unit requires AC, what grounding rules should I follow. I am guessing everything remains the same. Coax to grounding block then to pre-amp...and so on?
Reply
Reply
post #7 of 13
1/29/13 at 12:07pm
Power Supply converts from 120 VAC to (usually) DC Voltage (12-24 VAC, depending on manufacturer),
which is a FLOATING output between center and outer coax shield....so no ground loop issues. The
only connection to GROUND for the coax is at the Grounding Block.....Mast Mounted Preamp end of
the coax is NOT grounded, although the Metal case for a few Preamps (e.g. CM-7777) may be connected
to GROUND by way of being attached to the Mast.

Coax from an EXTERNAL antenna must go through a Grounding Block close to the building entry point.
Grounding Block MUST have a relatively short connection to GROUND, such as AC Power Breaker Panel, etc.
Antenna MAST (or eave mount) MUST also have as short a connection to GROUND as possible.

I'm surprised the above links didn't show the National Electric Code (NEC) mandated Grounding Block.
Fol. Sat Dish Grounding Instructions also apply to OTA Antennas:
http://www.sadoun.com/Sat/Installation/Grounding.htm
http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/GroundingSatelliteDishandLead-InCables~20020303.htm

And why everything needs to be grounded:
http://www.keohi.com/keohihdtv/hdreception/antenna_grounding.html

Fol. Channel Master Installation Guide may also be of interest, although it is fairly old:
http://manuals.solidsignal.com/AntInstallGuide.pdf
Edited by holl_ands - 1/29/13 at 12:24pm
Reply
Reply
post #8 of 13
1/29/13 at 3:30pm
Ironically, NEC doesn't mandate a grounding block. You won't find that term (grounding block) in the text of the NEC.

What NEC does say (paraphrased) is that a listed lightning arrestor (when was the last time anyone saw one of those?) must be used unless the outer conductor of the cable is grounded. The code doesn't specify the hardware to be used on the coaxial cable side of the circuit.

One of these years, NFPA might update the Code to modern wiring techniques.
Edited by ProjectSHO89 - 1/29/13 at 3:36pm
Reply
Reply
post #9 of 13
1/29/13 at 5:41pm
Quote:
Originally Posted by ProjectSHO89 View Post

Ironically, NEC doesn't mandate a grounding block. You won't find that term (grounding block) in the text of the NEC.

What NEC does say (paraphrased) is that a listed lightning arrestor (when was the last time anyone saw one of those?) must be used unless the outer conductor of the cable is grounded. The code doesn't specify the hardware to be used on the coaxial cable side of the circuit.

One of these years, NFPA might update the Code to modern wiring techniques.
1) http://www.l-com.com/familylist.aspx?id=2082 (first Google hit)
2) Ground Block...
Reply
Reply
post #10 of 13
1/29/13 at 6:19pm
Sure, surge suppressors are easy to find, but does a coaxial surge suppressor meet the definition under the code of a "listed lighting arrestor"?

My point is that the Code does not specify or mandate that a grounding block be used, only that the coax shield be grounded.

Obviously, the use of a grounding block does fulfill this purpose, but, please, read the words that I specifically chose to use in my earlier post.
Edited by ProjectSHO89 - 1/29/13 at 6:24pm
Reply
Reply
post #11 of 13
1/30/13 at 7:58am
Be sure that the surge suppressor is designed to pass DC voltages, unless you just use it on the antenna (non-powered) side of the preamp.
Grounding the lead-in shield, where it comes indoors, is OK there. The S.S. would protect the input of the preamp from nearby lightning that enters the antenna.
(Of course, nothing will protect from a direct hit. That's what insurance is for.)
Reply
Reply
post #12 of 13
1/30/13 at 10:26am
Quote:
Originally Posted by ProjectSHO89 View Post

Sure, surge suppressors are easy to find, but does a coaxial surge suppressor meet the definition under the code of a "listed lighting arrestor"?

My point is that the Code does not specify or mandate that a grounding block be used, only that the coax shield be grounded.

Obviously, the use of a grounding block does fulfill this purpose, but, please, read the words that I specifically chose to use in my earlier post.
yes? http://www.l-com.com/content/RoHSCompliant.html?Item=AL-FFFF-9&Date=November%2029,%202007&type=plain Warning: Spoiler! (Click to show)
Certificate of Compliance

Date: November 29, 2007



To Whom It May Concern:


L-com hereby certifies that product

AL-FFFF-9

is in conformance with the requirements of the European RoHS Directive 2002/95EC, and that all materials referenced therein are in concentrations below the maximum allowable levels specified.

Our statements in this letter regarding RoHS compliance do not extend to, or apply to any product subjected to unintended contamination, misuse, neglect, accident, improper installation, or to use in violation of instructions furnished by L-com.


Sincerely,


L-com Global Connectivity

The information contained in this letter is being provided for informational purposes only and to clarify certain information concerning L-com products. Nothing provided in this letter is (i) a representation, warranty or agreement to indemnification by L-com, (ii) a statement which may form the basis of reliance by L-com, (iii) a modification of any of the terms and conditions of sale agreed to in writing between L-com and its customers with respect to any L-com products, whether previously sold or to be sold in the future.
for this device: http://www.l-com.com/item.aspx?id=20928.
Reply
Reply
post #13 of 13
1/30/13 at 1:28pm
Quote:
yes?

No.

ROHS is something completely and entirely different from the NEC definition of "Listed".

ROHS is why solder doesn't use lead like it used to (and a whole lot more). http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive

NEC excerpt
Quote:
NEC, Article 100 -- Definitions
Listed. Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that either the equipment, material, or services meets identified standards or has been tested and found suitable for a specified purpose.

For more details, see section in http://en.wikipedia.org/wiki/National_Electrical_Code

Since electrical and other building codes are sometimes incorporated in their entirety by state and local governments, you can usually catch a "free" copy online with some persistence. For example, if you download Oregon's electrical code from https://bulk.resource.org/codes.gov/or_electrical_2011.pdf you'll have a copy of the 2011 NEC.

Antenna grounding and coaxial cable wiring stuff is in sections 810 & 820 (which don't perfectly match each other in all regards). You'll also need to refer to section 250 and section 100 as needed.

Cheers!
Edited by ADTech - 1/30/13 at 1:41pm
Reply
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: HDTV Technical

AVS Top Picks

AVS › AVS Forum › HDTV › HDTV Technical › Preamp question