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antennan preamp questions

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Anonymous
June 19, 2005 9:45:08 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

Would a pre-amp on the roof by the antenna help with the HDTV signal?

I am having antenna problems. We live in a valley. We just put up a new
$100 channelmaster directional antenna VHF 100 miles, UHF 60 miles with AN
AMPLIFIER down by the TV. We pointed the antenna as best we could using the
Directv off air digital signal meter. We did manage to find most stations,
but one of the worst stations, channel 4-1 (UHF channel), only comes in at
60% on the signal meter. The bad channel 4-1 drops in and out, and I would
like to get that channel. (Note, without the amplifier by the TV, the
signal strength is lousy.)

Since I already have an amplifier down by the TV, would a pre-amp on the
roof by the antenna help with the HDTV signal? Has anybody used a preamp? If
so, how well did it help with the signal?

Thanks in advance
noone
Anonymous
June 20, 2005 2:45:29 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"nonone" <noone@nowhere.com> wrote in
news:Eaite.988894$w62.216065@bgtnsc05-news.ops.worldnet.att.net:

> Would a pre-amp on the roof by the antenna help with the HDTV signal?

It might, or it might make matters worse.

> I am having antenna problems. We live in a valley. We just put up a
> new $100 channelmaster directional antenna VHF 100 miles, UHF 60 miles
> with AN AMPLIFIER down by the TV. We pointed the antenna as best we
> could using the Directv off air digital signal meter. We did manage to
> find most stations, but one of the worst stations, channel 4-1 (UHF
> channel), only comes in at 60% on the signal meter. The bad channel
> 4-1 drops in and out, and I would like to get that channel. (Note,
> without the amplifier by the TV, the signal strength is lousy.)

> Since I already have an amplifier down by the TV, would a pre-amp on
> the roof by the antenna help with the HDTV signal? Has anybody used a
> preamp? If so, how well did it help with the signal?

A good, CLEAN preamp at the antenna feedpoint is better than one at the
TV. The reason is that the preamp can drive the line, eliminating most
of the effect of line losses, whereas the preamp at the TV has to amplify
the signal AFTER it has lost strength in the line.

The caveat is that, in some environments where there are strong local
signal, a preamp that has bad intermod characteristics can actually
introduce interference.

But from the sound of your situation, a GOOD preamp at the antenna should
help some. How much will depend on what type of coax you have and how
much loss it's giving you now. REALLY good preamps (GaAsFETs) are not
easy to find for TV.


--
Dave Oldridge+
ICQ 1800667

A false witness is worse than no witness at all.
God is an evolutionist.
June 20, 2005 6:32:51 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

In article <Eaite.988894$w62.216065@bgtnsc05-news.ops.worldnet.att.net> "nonone" <noone@nowhere.com> writes:
>Would a pre-amp on the roof by the antenna help with the HDTV signal?
>
>I am having antenna problems. We live in a valley. We just put up a new
>$100 channelmaster directional antenna VHF 100 miles, UHF 60 miles with AN
>AMPLIFIER down by the TV. We pointed the antenna as best we could using the
>Directv off air digital signal meter. We did manage to find most stations,
>but one of the worst stations, channel 4-1 (UHF channel), only comes in at
>60% on the signal meter. The bad channel 4-1 drops in and out, and I would
>like to get that channel. (Note, without the amplifier by the TV, the
>signal strength is lousy.)
>
>Since I already have an amplifier down by the TV, would a pre-amp on the
>roof by the antenna help with the HDTV signal? Has anybody used a preamp? If
>so, how well did it help with the signal?


This has been discussed in great detail here. In fact, I believe it has
been discussed here since you started posting and asking questions.

For amplifiers: If you are going to use one, use a good one. Many of the
consumer ones vary from suspect to bad. They will add interference from
intermodulation from any strong signals, will re-transmit interference to
nearby receivers, etc.

Also, use one AT THE ANTENNA. The feedline loss will just weaken the
signal before it gets to the amp, and there is NOTHING you can do to get
the lost signal back. Once you have a good one at the antenna, you don't
need one at the bottom of the feedline.

Don't use one if you don't need it. You can overload the receiver/tv set
with strong signals through it.


Alan
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Anonymous
June 20, 2005 6:19:25 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

nospam@w6yx.stanford.edu (Alan) wrote in
news:D 959sj$nu6$1@news.Stanford.EDU:

> In article
> <Eaite.988894$w62.216065@bgtnsc05-news.ops.worldnet.att.net> "nonone"
> <noone@nowhere.com> writes:
>>Would a pre-amp on the roof by the antenna help with the HDTV signal?
>>
>>I am having antenna problems. We live in a valley. We just put up a
>>new $100 channelmaster directional antenna VHF 100 miles, UHF 60 miles
>>with AN AMPLIFIER down by the TV. We pointed the antenna as best we
>>could using the Directv off air digital signal meter. We did manage to
>>find most stations, but one of the worst stations, channel 4-1 (UHF
>>channel), only comes in at 60% on the signal meter. The bad channel
>>4-1 drops in and out, and I would like to get that channel. (Note,
>>without the amplifier by the TV, the signal strength is lousy.)
>>
>>Since I already have an amplifier down by the TV, would a pre-amp on
>>the roof by the antenna help with the HDTV signal? Has anybody used a
>>preamp? If so, how well did it help with the signal?
>
>
> This has been discussed in great detail here. In fact, I believe it
> has
> been discussed here since you started posting and asking questions.
>
> For amplifiers: If you are going to use one, use a good one. Many
> of the
> consumer ones vary from suspect to bad. They will add interference
> from intermodulation from any strong signals, will re-transmit
> interference to nearby receivers, etc.
>
> Also, use one AT THE ANTENNA. The feedline loss will just weaken
> the
> signal before it gets to the amp, and there is NOTHING you can do to
> get the lost signal back. Once you have a good one at the antenna,
> you don't need one at the bottom of the feedline.
>
> Don't use one if you don't need it. You can overload the
> receiver/tv set
> with strong signals through it.

Yes, though you can usually deal with that by just using inferior
feedline and coiling enough of it. I used to have a 144mhz transmitting
amplifier that wanted only a watt or so in. My radio put out 14 watts so
I put 50 feet of the cheapest RG-58 that I could find in the line between
the radio and the amp (switching it in only when transmitting).

But it's amazing what bad coax can do to reception. I thought I was
doing fine with that setup until one day I smelled a little smoke while
transmitting FM at about 600 watts output. Seems the little barrel
connecter that I had used to extend the good coax that came down from the
rooftop was smoking. It was the cheaper PL-259-style hardware. I went
out and got Mil-spec N connector hardware and got an immediate 6db
improvement on everything! Stupid connector was eating up fully 3/4 of
the signal!

--
Dave Oldridge+
ICQ 1800667

A false witness is worse than no witness at all.
God is an evolutionist.
Anonymous
June 20, 2005 7:08:30 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

> Also, use one AT THE ANTENNA. The feedline loss will just weaken the
> signal before it gets to the amp, and there is NOTHING you can do to get
> the lost signal back. Once you have a good one at the antenna, you don't
> need one at the bottom of the feedline.
>
> Don't use one if you don't need it. You can overload the receiver/tv
set
> with strong signals through it.
>
>
> Alan

Without the amplifier at the TV, I can't get anything, so I need some
amplification. Even with the amplifier at the TV, I am still having trouble
getting signals. I get the signal and find the channels, but the signal
drops in an out, so the signal at best is marginal. It is a pile of work to
put the preamp on the roof. Will the preamp at the roof have a good chance
of solving my problem? Has anybody used a preamp? If so, how much did it
help?

noone
Anonymous
June 20, 2005 11:58:45 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"nonone" <noone@nowhere.com> wrote:

>> Also, use one AT THE ANTENNA. The feedline loss will just weaken the
>> signal before it gets to the amp, and there is NOTHING you can do to get
>> the lost signal back. Once you have a good one at the antenna, you don't
>> need one at the bottom of the feedline.
>>
>> Don't use one if you don't need it. You can overload the receiver/tv
>> set with strong signals through it.
>>
>> Alan
>
>Without the amplifier at the TV, I can't get anything, so I need some
>amplification. Even with the amplifier at the TV, I am still having trouble
>getting signals. I get the signal and find the channels, but the signal
>drops in an out, so the signal at best is marginal. It is a pile of work to
>put the preamp on the roof. Will the preamp at the roof have a good chance
>of solving my problem? Has anybody used a preamp? If so, how much did it
>help?
>
>noone
>
Ditto what Alan said. You need more signal, which any amplifier can
provide, but more importantly you need a higher signal-to-noise ratio.
That's harder to come by. Noise rides in with the signal, it can
enter along the cable despite shielding, and even the best amplifier
generates some noise of its own. In any reasonable system the S/N
ratio is set by the first amplifier, because the amplified signal (and
noise) are much greater than any noise that will be added further on.
So you need a good quality low noise preamp mounted as close to the
antenna as possible. Usually it's mounted on the mast just below the
antenna, powered by DC from a separate unit at the other end of the
cable. If by "a pile of work" you mean just getting to the antenna,
then hire somebody. But once you're there installation is easy.

I can't say if a mast-mounted preamp would help in your particular
situation, but there's a good chance of it. Ask around to see if
others have done it. Whoever installs antennas in your area would
know.

I have good local reception so don't need a preamp. I do use a
4-output distribution amp to counter the losses of all the splitters I
would otherwise need. But I work at a satellite uplink site that also
has lots of receive dishes. Most have in-line amps at the dishes, and
it can make a big difference especially for the dishes a distance from
the building. The same amplifier mounted at the receiver instead of
the dish gives a stronger meter reading than no amp at all, but little
if any improvement in reception.

Del Mibbler
Anonymous
June 21, 2005 3:49:52 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Del Mibbler" <mibbler@nycap.rr.com> wrote in message
news:c85eb1lgv3o2dahvg5k2p53mu8ogmlsuse@4ax.com...
> "nonone" <noone@nowhere.com> wrote:
>
> >> Also, use one AT THE ANTENNA. The feedline loss will just weaken the
> >> signal before it gets to the amp, and there is NOTHING you can do to
get
> >> the lost signal back. Once you have a good one at the antenna, you
don't
> >> need one at the bottom of the feedline.
> >>
> >> Don't use one if you don't need it. You can overload the receiver/tv
> >> set with strong signals through it.
> >>
> >> Alan
> >
> >Without the amplifier at the TV, I can't get anything, so I need some
> >amplification. Even with the amplifier at the TV, I am still having
trouble
> >getting signals. I get the signal and find the channels, but the signal
> >drops in an out, so the signal at best is marginal. It is a pile of work
to
> >put the preamp on the roof. Will the preamp at the roof have a good
chance
> >of solving my problem? Has anybody used a preamp? If so, how much did it
> >help?
> >
> >noone
> >
> Ditto what Alan said. You need more signal, which any amplifier can
> provide, but more importantly you need a higher signal-to-noise ratio.
> That's harder to come by. Noise rides in with the signal, it can
> enter along the cable despite shielding, and even the best amplifier
> generates some noise of its own. In any reasonable system the S/N
> ratio is set by the first amplifier, because the amplified signal (and
> noise) are much greater than any noise that will be added further on.
> So you need a good quality low noise preamp mounted as close to the
> antenna as possible. Usually it's mounted on the mast just below the
> antenna, powered by DC from a separate unit at the other end of the
> cable. If by "a pile of work" you mean just getting to the antenna,
> then hire somebody. But once you're there installation is easy.
>
> I can't say if a mast-mounted preamp would help in your particular
> situation, but there's a good chance of it. Ask around to see if
> others have done it. Whoever installs antennas in your area would
> know.
>
> I have good local reception so don't need a preamp. I do use a
> 4-output distribution amp to counter the losses of all the splitters I
> would otherwise need. But I work at a satellite uplink site that also
> has lots of receive dishes. Most have in-line amps at the dishes, and
> it can make a big difference especially for the dishes a distance from
> the building. The same amplifier mounted at the receiver instead of
> the dish gives a stronger meter reading than no amp at all, but little
> if any improvement in reception.
>
> Del Mibbler

Thanks Del,

Any recommendations on what brand of preamp to get?

The coax cable from the antenna to the TV is probably 60 feet long. And your
noise logic makes sense to put a preamp on near the antenna. Of course, the
coax connection is at the very top of the antenna which is fifteen feet
above the roof. So the antenna on the roof will have to come down to be able
to put the preamp on. Argghs!!!

noone
June 21, 2005 1:27:06 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

nonone wrote:
>> Also, use one AT THE ANTENNA. The feedline loss will just weaken the
>>signal before it gets to the amp, and there is NOTHING you can do to get
>>the lost signal back. Once you have a good one at the antenna, you don't
>>need one at the bottom of the feedline.
>>
>> Don't use one if you don't need it. You can overload the receiver/tv
>
> set
>
>>with strong signals through it.
>>
>>
>>Alan
>
>
> Without the amplifier at the TV, I can't get anything, so I need some
> amplification. Even with the amplifier at the TV, I am still having trouble
> getting signals. I get the signal and find the channels, but the signal
> drops in an out, so the signal at best is marginal. It is a pile of work to
> put the preamp on the roof. Will the preamp at the roof have a good chance
> of solving my problem? Has anybody used a preamp? If so, how much did it
> help?
>
> noone
>
>
Simple rule:
Amps at the TV are for DISTRIBUTING the signal in the house
Amps at the Antenna are for BOOSTING the signal strength.
Anonymous
June 21, 2005 3:06:20 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

CM 7777 is a good preamp for VHF/UHF
"Curmudgeon" <curmudgeon@buzzoff.net> wrote in message
news:wyUte.42178$zm.1506@bignews4.bellsouth.net...
> nonone wrote:
>>> Also, use one AT THE ANTENNA. The feedline loss will just weaken the
>>>signal before it gets to the amp, and there is NOTHING you can do to get
>>>the lost signal back. Once you have a good one at the antenna, you don't
>>>need one at the bottom of the feedline.
>>>
>>> Don't use one if you don't need it. You can overload the receiver/tv
>>
>> set
>>
>>>with strong signals through it.
>>>
>>>
>>>Alan
>>
>>
>> Without the amplifier at the TV, I can't get anything, so I need some
>> amplification. Even with the amplifier at the TV, I am still having
>> trouble
>> getting signals. I get the signal and find the channels, but the signal
>> drops in an out, so the signal at best is marginal. It is a pile of work
>> to
>> put the preamp on the roof. Will the preamp at the roof have a good
>> chance
>> of solving my problem? Has anybody used a preamp? If so, how much did it
>> help?
>>
>> noone
>>
>>
> Simple rule:
> Amps at the TV are for DISTRIBUTING the signal in the house
> Amps at the Antenna are for BOOSTING the signal strength.
Anonymous
June 21, 2005 8:46:05 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Jim Riggs" <oljim@islc.net> wrote in message
news:D 99acv01i55@enews1.newsguy.com...
> CM 7777 is a good preamp for VHF/UHF

Thanks for the tip on the preamp. I am looking one up now.
Noone
Anonymous
June 22, 2005 12:28:37 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"nonone" <noone@nowhere.com> wrote (in part):

>Any recommendations on what brand of preamp to get?

No. I don't need one myself, so haven't researched it. Sounds like
all your signals are very weak, so you want high gain, low noise
figure. If you have to choose between them, go for the lower noise
figure. You can always boost the gain later. Match the preamp to the
antenna (UHF only, VHF only or both with combined or separate inputs,
300 ohm or 75 ohm in.
>
>The coax cable from the antenna to the TV is probably 60 feet long. And your
>noise logic makes sense to put a preamp on near the antenna. Of course, the
>coax connection is at the very top of the antenna which is fifteen feet
>above the roof. So the antenna on the roof will have to come down to be able
>to put the preamp on. Argghs!!!
>
>noone
>
If the antenna is 75 ohm out (rare) then you probably wouldn't lose
much to cut the cable at a more accessible place on the mast to
install the preamp (assuming you have enough slack). But if the
antenna is the more common 300 ohm with a balun to the coax, or
separate UHF/VHF outputs with a coupler, it's still worth it to match
the preamp to the antenna and eliminate the balun or coupler, which
means mounting the preamp as close to the antenna as possible. Any
antenna installers want to chime in with advice?

Del Mibbler
Anonymous
June 22, 2005 2:48:58 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

"Del Mibbler" <mibbler@nycap.rr.com> wrote in message
news:vbsgb1h1d7lhnam2pr5nqhe9fj0cbdglr9@4ax.com...
> "nonone" <noone@nowhere.com> wrote (in part):
>
> >Any recommendations on what brand of preamp to get?
>
> No. I don't need one myself, so haven't researched it. Sounds like
> all your signals are very weak, so you want high gain, low noise
> figure. If you have to choose between them, go for the lower noise
> figure. You can always boost the gain later. Match the preamp to the
> antenna (UHF only, VHF only or both with combined or separate inputs,
> 300 ohm or 75 ohm in.
> >
> >The coax cable from the antenna to the TV is probably 60 feet long. And
your
> >noise logic makes sense to put a preamp on near the antenna. Of course,
the
> >coax connection is at the very top of the antenna which is fifteen feet
> >above the roof. So the antenna on the roof will have to come down to be
able
> >to put the preamp on. Argghs!!!
> >
> >noone
> >
> If the antenna is 75 ohm out (rare) then you probably wouldn't lose
> much to cut the cable at a more accessible place on the mast to
> install the preamp (assuming you have enough slack). But if the
> antenna is the more common 300 ohm with a balun to the coax, or
> separate UHF/VHF outputs with a coupler, it's still worth it to match
> the preamp to the antenna and eliminate the balun or coupler, which
> means mounting the preamp as close to the antenna as possible. Any
> antenna installers want to chime in with advice?
>
> Del Mibbler

Del,
Thanks for answering my question. Your advice is greatly appreciated.

We connect coax cable to a device with a coax connector that is on the
antenna (300 ohm with a balun to the coax??).

Someone else recommended this preamp. Channel Master CM 7777 Titan2 VHF/UHF
Preamplifier with Power Supply (CM7777)
http://www.solidsignal.com/prod_display.asp?main_cat=03...

The web page says says:" Power supply and pre-amp are connected to the
antenna using RG6 coax cable. An RG6 cable is run from antenna to pre-amp,
from pre-amp to power supply, then from power supply to television. Power
supply does not have to be outdoors. "

For me, getting a short coax cable from the antenna to the preamp would be
easiest.

noone
!