Can I use one part of a two-part TV signal Amp?
DJW
that is 300 ohm in to 75 oh out that is to go on at the antenna
location. Can I use the amp as an inline unit without the thing that
is put at the outdoor antenna? The thing to be used at the antenna
looks and I guess part of it’s job is to be a transformer from 300 to
75 ohm. But what exactly is it? I am only trying to boost my UHF
signal
Guru
"DJW" <dd...@hotmail.com> wrote in message
news:1b72668f-9ee7-4441...@r36g2000vbn.googlegroups.com...
Yes...you can use the amp without the 300:75 ohm transformer.
Kimba W Lion
Most likely the part that goes at the outdoor antenna is the amplifier itself,
and the other part is the power supply. So, no, you can't use one without the
other.
--
Intelligent Life Is All Around Us
http://intelligentlife.info/
Sal M. Onella
"DJW" <dd...@hotmail.com> wrote in message
news:1b72668f-9ee7-4441...@r36g2000vbn.googlegroups.com...
Sounds like No. What you describe is an amplifier SYSTEM that comes in two
parts. The part with the two 75 ohm connections is probably just the power
supply. (It has a power cord, right?) It stays in the house, obviously.
It provides a low-voltage to the outside part (the actual amplifier circuits
at the antenna) through the coaxial cable. The system has special circuits
in it to keep the power and TV signals separated, except on the coaxial
cable.
The power supply box doesn't amplify anything by itself and shouldn't be
connected except when the outsdide unit (the real amplifier) is also
installed.
On the power supply box,, the two 75-ohm connections are NOT
interchangeable. One says to "TO TV" and one says "TO ANTENNA" (or maybe
"TO AMP"). Backwards doesn't work.
These two-part systems are common and some are very good at improving
reception. Archer (Radio Shack) has made some good ones and some
not-so-good ones. Cross fingers for luck, please. ;-)
Sal
Techcom
the output of a 75 ohm fitting and is marked output/ 12 vdc. I think it's
powered by a power inserter. Do you have a schematic diagram of a power
inserter? Want to put one together to power up this amp. Thank you for your
help.
--
Techcom
"Sal M. Onella" <salmo...@food.poisoning.org> wrote in message
news:bhu2m.9071$6Q3....@newsfe22.iad...
GMAN
>Hey Sal, I have a 20 db drop amplifier that was given me. It's powered on
>the output of a 75 ohm fitting and is marked output/ 12 vdc. I think it's
>powered by a power inserter. Do you have a schematic diagram of a power
>inserter? Want to put one together to power up this amp. Thank you for your
>help.
>
Sal M. Onella
"Techcom" <tec...@sonic.net> wrote in message
news:4a4aa95d$0$1671$742e...@news.sonic.net...
> Hey Sal, I have a 20 db drop amplifier that was given me. It's powered on
> the output of a 75 ohm fitting and is marked output/ 12 vdc. I think it's
> powered by a power inserter. Do you have a schematic diagram of a power
> inserter? Want to put one together to power up this amp. Thank you for
your
> help.
Sure. The power inserter has an odd name in the business, so once you know
it, the rest should be easy. It's known as a "three port device" and it's
called a Bias Tee.
http://www.qsl.net/n9zia/wireless/pics/bias_tee.png
If you Google for bias tee schematic, you will be rewarded.
The path of the receive TV signals is from right to left across the top ot
the TEE. The signals pass through the capacitor from the antenna (off the
right port) to the TV (off the left port). They do not flow down the TEE
because the coils block them.
The path of the DC, the real power in "Power Supply," flows up the TEE from
the bottom. It goes through the coils but at the top it doesn't flow to the
TV because the capacitor blocks it. It does flow out the right side, though
your downlead and up onto the roof (or attic -- whatever).
The bias tee pictured in that schematic looks to be "overdesigned." One I
built a few years ago was much simpler and only used the one capacitor at
the top, the one marked 0.1 uF and just one choke coil in the line to the
bias port.
Don't worry that it says 50-ohm stripline. Just keep the wiring clean and
direct inside a little metal box and you'll be fine. The enclosure I used
for mine was the metal case for a TV/Game switch, left over from the olden
days when video games were played on TV sets. A box with two F-connectors
on it (the standard TV connectors) would be ideal, but almost any little
metal box will do. If you use a plain box. ground the coaxial cable shields
to the box for the RF. The power is just wired-in directly.
For the actual DC source, grab any 12-volt wall wart power supply left over
from a tape recorder, MP-3 player, answering machine, etc. Be sure to
observe the polarity when connecting. Figure out in advance whether the
coax center conductor wants plus or minus to the amp box and wire it
accordingly. If you don't have a multimeter to determine polarity, this
would be a good time to hit the Home Depot, Lowes, Tru-Valu, Radio Shack and
grab a cheapie meter. Less than $20 is easy; less that $10 is sometimes
doable.
More info on request if this much does not quite get you going.
Sal
Techcom
find them.You gave a good description of how the Bias Tee works and it's
functions.I looked at the other links and found a smaller version where I
can build it in a old two-way splitter.The power supply that came with the
amp is a wall wort with a 75 ohm female port.
Took an old two-way RadioShack splitter and removed the rear cover and
gutted out the insides. I used one of the ferrite beads to wind the inductor
and installed two capacitors, one for the D.C. Block and the other one for
the R.F. Shunt. I checked the polarity on the wall wort with a digital
voltmeter and got a plus on the middle part of the 75 ohm port.
Connected up the wall wort with the Bias Tee and the Drop Amp to the antenna
system and checked levels with a signal level meter. Drop Amp working with
32dbmv out of it. Enough signal to power up a mansion. Too much signal for
two tv sets and a fm receiver to use. I'll keep it as a spare.Thank you
again Sal for your help. You have been very helpful.
--
Techcom
"Sal M. Onella" <salmo...@food.poisoning.org> wrote in message
news:O_A2m.47$DA1...@newsfe25.iad...
Sal M. Onella
> Thank you Sal for sending the schematic of the Bias Tee and the links to
> find them.You gave a good description of how the Bias Tee works and it's
> functions.I looked at the other links and found a smaller version where I
> can build it in a old two-way splitter.The power supply that came with the
> amp is a wall wort with a 75 ohm female port.
>
> Took an old two-way RadioShack splitter and removed the rear cover and
> gutted out the insides. I used one of the ferrite beads to wind the
inductor
> and installed two capacitors, one for the D.C. Block and the other one for
> the R.F. Shunt. I checked the polarity on the wall wort with a digital
> voltmeter and got a plus on the middle part of the 75 ohm port.
>
> Connected up the wall wort with the Bias Tee and the Drop Amp to the
antenna
> system and checked levels with a signal level meter. Drop Amp working with
> 32dbmv out of it. Enough signal to power up a mansion. Too much signal for
> two tv sets and a fm receiver to use. I'll keep it as a spare.Thank you
> again Sal for your help. You have been very helpful.
> --
> Techcom
Understood & thanks for the kind words. Glad you got it working. Two-way
splitter was a good choice.
If you truly have so much signal that it's overdriving your sets, you can
get inline signal attenuators. They come in values of 3, 6, 10 and 20 dB.
They are all-metal, about the size and shape of a piece of chalk, with a
male one end and a female on the other so they can be inserted inline
anywhere. Some will pass DC, but not all, so it's better to insert it/them
on the "TV" side of the bias tee, rather than in the downlead.
Sal
Techcom
I have some 3,6,10, and some 20db in-line attenuators and some in-line DC
blocks to work with it. The in-line pads that I have won't pass DC ,because
they are the resistive"t'' types.Do you know how much signal that the DTV
converter should get before it goes to overdrive?
I'm just curious.news:miA3m.6485$IU6....@newsfe05.iad...
Sal M. Onella
> Thank you for your response Sal . I may use that amp down the road
sometime.
> I have some 3,6,10, and some 20db in-line attenuators and some in-line DC
> blocks to work with it. The in-line pads that I have won't pass DC
,because
> they are the resistive"t'' types.Do you know how much signal that the DTV
> converter should get before it goes to overdrive?
> I'm just curious.
Nope. They're all different. It's in the design.
If you did deep enough, some of them will have a spec for 3rd order
intermodulation distortion, IMD. I forget the exact units in the spec.
For example, at rated output, the IMD is supposed to be no higher than, say,
1 percent.
There is also the "third order intercept point, which you want to have be as
high as possible, numerically.
Good luck finding the specs on a reasonable-priced consumer amplifier.
Sal
Techcom
--
Techcom
"Sal M. Onella" <salmo...@food.poisoning.org> wrote in message
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