20db Amplifier w/ FM trap & gain control

[acuevas]

Hi All,

I set up smaller and older antenna( the clothes line type )and I also set up a small square, 12"x12", ota antenna. Both antennas work separately but I decided to use them together by using a splitter. I placed them both on the roof and turned( adjusted) them for best picture. My converter box is about 50' from the antennas.

I don't get the best signal though. Some channels come in, others come and go and some pixilate. I bought above mentioned amp but it does not make any difference all. I may not be using amp incorrectly but I think it is pretty straight forward. I live in Brea, CA 92821. Any suggestions are most welcomed.

 

[DRCars]

More info on the amplifier and antennas such as name, type would be helpful. Anyway, this might help.

From:

hdtvprimer.com/ANTENNAS/basics.html

Signal Amplifiers, Preamplifiers, part 2

There are two types of signal amplifiers:
[FONT=&quot]Preamplifiers [/FONT][FONT=&quot] (Mast-mounted amplifiers) - These should be mounted as close to the antenna as possible. Usually the amplifier comes in two parts: [/FONT]

• • [FONT=&quot]The amplifier. This is an outdoor unit that is normally bolted to the antenna mast. It must have a very low noise figure, and enough gain to overcome the cable loss and the receiver’s noise figure.[/FONT]
  • [FONT=&quot]The power module (power injector). This is an indoor unit that commonly lies on the floor behind the TV. It is inserted into the antenna cable between the amplifier and the TV. This module injects some power, usually DC, into the coaxial cable where the amplifier can use it. The power injector is the amplifier’s power supply.[/FONT]

[FONT=&quot]Distribution amplifiers[/FONT][FONT=&quot] - These are simple signal boosters. They are often necessary when an antenna drives multiple TVs or when the antenna cable is longer than 150 feet. Distribution amplifiers don’t need to have a low noise figure, but they need to be able to handle large signals without overloading. Commonly, distribution amplifiers have multiple outputs. (Unused outputs usually do not need to be terminated.)[/FONT]

Also, combining 2 antennas can lose more than half the signal from each antenna. This link probably has more than you want to know, but don't let the math distract you. There is less technical info there also:

hdtvprimer.com/ANTENNAS/merging.html

What is your goal in combining the antennas? For instance, are the TV stations you are trying to receive in 2 different directions?

There is a lot more information to be had at:

http://hdtvprimer.com/

DRCars

 

[Jim5506]

Combining two different antennas can be worse than using one. Signals are fed to them at different strengths so a signal received on antenna A , but not on antenna B will come in on A but radiate out on B and less than half goes down you wire.

It sounds like you have VHF and UHF antennas. You need a joiner that accepts seperate frequencies like a UVSJ (UHF/VHF signal joiner) or a pre amp with seperate UHF and VHF inputs.

 

[freezy]

that multi bay with the aim-able side looked very promising. also there are super easy to install antennas with rotors available for close range $25 ebay

 

[acuevas]

Thanks to all of you.

Lots of great info from all. The names on the antennas are faded and can't tell even the model numbers. The purpose for using two antennas was to get better signal - or so I thought.

Obviously, I had no idea. I will have to reconfig my set up based on info provided. Thanks again.

 

[Vorg]

Another thing about amps. They are not really for boosting weak signals, they are for over coming long cable lengths and distributing the signal to more sources. When they boost, they boost both signal and noise. If you don't have a good signal to drive one tuner from the start, the increased noise along with signal will mean you still have a bad signal.

 

[Jim5506]

Actually pre-amps do boost weak signals, if your antenna is gettiing a signal that is too weak for your tuner to decode and you insert a pre-amp, the chances improve that you can now watch that channel, even with very short cable runs.

Pre-amps also allow you to extend the distance the antenna can be from the tuner and allow you to split signals to multiple tuners, but the idea that they do not boost weak signals into usable territory is not necessarily true.

 

[Mr Tony]

I agree Jim
I had a preamp setup on my distant VHF antenna because the signal was "low" during the day and the pre-amp helped greatly. The only drawback was at night without the pre-amp the signal was up near 100 so with the pre-amp it made it worse.

Most of my viewing of that station is at night anyways so I removed the preamp

 

[DRCars]

These excerpts from hdtvprimer.com/ANTENNAS/basics.html offers an explanation as to how a pre-amp might be of benefit even though there is a short cable run.

[FONT=&quot]Normally the signal to noise ratio will be set by the receiver’s first transistor. But if an external amplifier is added, the first transistor in that amplifier determines the S/N ratio. (Since the external amp will greatly magnify its own noise as well as the signal, the receiver’s noise becomes insignificant.) Since there is no reason to think the external amp’s first transistor is quieter than the receiver’s first transistor, there is generally no benefit to the S/N ratio from an external amplifier.

[/FONT][FONT=&quot]But an external amplifier will compensate for signal loss in the cable if the amplifier is mounted at the antenna. Without this amplifier, a weak signal, just above the noise level at the antenna, could sink below the noise level due to loss in the cable, and be useless at the receiver.[/FONT]
[FONT=&quot]
..... snip .....

[/FONT][FONT=&quot]Actually there is a reason to think the external amplifier is quieter than the receiver. Long ago designers made an effort to make the TV’s first amplifier stage very quiet. But now 90% of homes use cable or satellite boxes (strong sources) and most of the rest are rural homes using antennas that have mast-mounted amplifiers. So the TV’s noise is rarely a factor. Some TV makers no longer put any effort into making their sets quiet.[/FONT]

[FONT=&quot]

DRCars
[/FONT]

 

[No Static At All]

Actually pre-amps do boost weak signals

Yup & quality distribution amps can do a great job with weak signals too. They really shine in mixed strong/weak signal areas where a preamp would overload.