The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by ghost307
Today at 06:25 AM
International Wire Colour Codes
by Tjia1981
Yesterday at 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
ghost307 7
HotLine1 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 290 Guests and 4 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#127113 - 04/29/01 03:55 PM Voodoo Magic?
Webmaster Offline


Registered: 10/07/00
Posts: 3142
Loc: NY, USA

Submitted by Ken Mendelson
How does this amplify the signal if there is no external power or batteries?
Radio Shack part #16-1156

Ken Mendelson (KEMendelson)

#127114 - 04/29/01 03:57 PM Re: Voodoo Magic?
sparky Offline

Registered: 10/18/00
Posts: 5545
using the 'force' ?

#127115 - 04/29/01 05:59 PM Re: Voodoo Magic?
sparky66wv Offline

Registered: 11/17/00
Posts: 2334
Loc: West Virginia
I was wondering the same thing with pole mounted CATV amplifiers... Where do they draw their power to boost?

#127116 - 04/29/01 10:04 PM Re: Voodoo Magic?
Scott35 Offline

Broom Pusher and

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Kind of depends on the system used.

CATV systems will have some DC coupled to each loop, which is to drive line amps at nodes, so they could also use that DC to power a small in-line preamp, such as the one pictured.

DSB [Satellite broadcast] will drive the LNB / LNBF at the "Dish" receiving antenna with DC power, which is coupled to the coax feed [the cable coming from the dish].

As to regular Yagi / Parasitic Yagi antennas used for VHF / UHF television, these two types of preamps can be used - without external power source / coupled DC:

1: Cable Bootstrapping [via Op-Amp LH2011].
This reduces cable Capacitance, leakage and spurious voltages. Stability is increased with a small Capacitor connected at the input.

2: Wideband Unity Gain Inverting Amplifier.
This one compensates for the normal 6dB loss on 75 ohm coax runs. The one pictured above in the posted image states 13dB amplification, which sounds like this type of Inverting Amp.
13dB would be lossed over 3 RF inputs [3 TV sets], run through a "4 way splitter", more if two "3 way splitters" were used.

Judging from the frequencies listed on that amp, it would be used on high frequency CATV [capable of Analog with compressed Digital services], but more likely for a DSB type system.
950 - 2050 MHz is the bandwith of my DSB feed, however, I have noticed some newer CATV with Compressed Digital feed had this bandwith listed on the receiver.

Scott SET
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals