How to make a powered amplifier for over the air tv?

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Michael Weaser

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I know the components i would need to make a amplifier like transistors and possibly op-amps, I want to design an amplifier that can also remove signals that can mess up the over the air signal like FM radio waves and certain cellular phone waves. I want various circuits that i could use to make the amplifier at the specs i want, The circuit could use transistors to amplify the circuit only, it could use op-amp to mainly amplify the circuit , and what type of op-amp would i need for the amplifier could i use lm386 or a ua741, or could i use a combination of transistors and op-amps? This is my first time making my own over the air tv amplifier , so i need some help designing it.
 

Forget it. You are in way over your head.

The range for US OTA digital transmission is approx 54 - 700MHz. There is no opamp that can handle those frequencies, so you're going to have to design it all using discrete components. The interferrers that you are talking about are usually in-band interferrers that you can do nothing about. Anyway, DTV is only minimally affected by these signals.

Your best bet would be to just purchase an antenna amplifier.
 

So i would have to do it with transistors? So that means that normal over the air amplifiers are made with discrete components, so mainly transistors? So i could design it with transistors? What about those amplifiers that block out those signals, they have amplifiers that say they block Fm signals and cell phone frequencies , I have seen allot of amplifiers block fm signals and now recently LTE filters that block LTE from cell phones.
 

Why do you want to add an RF amplifier to your TV that already has an RF amplifier? If your antenna is designed for the frequencies you want to receive, is high enough and is pointing at the transmitter then either the signal strength is high enough to work or it is too weak even if you amplify it (you would be amplifying the noise). The RF amplifier in a TV already has filters to block adjacent frequencies.
 

Why would they than come out with these devices like , that they have something called an lte filter that blocks lte signals apparently , and separate amplifiers that have fm radio frequencies filter , and also just separate amplifiers if the TV has an inbuilt one?
 

Old fashioned obsolete analog channel 6 in North America was beside the lowest FM broadcast band frequency. Old TV antenna amplifiers filtered out the FM broadcast band because it might over-amplify it causing the amplifier to be saturated and not amplify the signals you want.
Antenna amplifiers boosted the signal from the antenna to make up for the loss of the cable to the TV.
 

uA741 and lm386 are devices only suited to very low frequencies, less than 0.1% of the ones you are needing.

There are 'op-amp' like devices for broadband amplification, they are called MMIC (Monolithic Microwave Integrated Circuits) and they are cheap, plentiful and easy to use but they will not filter out any particular frequency passing through them. To do that you need inductors and capacitors to make filters or tuned circuits. It is possible, but tricky if you do not have test equipment, to make 'notch' filters that either block the passage of a particular frequency or 'short it out' to prevent it reaching the TV.

Probably the simplest notch filter is a length of co-axial cable, connected across the signal at one end and left open at the other. If made one electrical quarter wavelength of the signal you want to reject, it will help to remove it. Search for "quarter wave stub" for ideas.

Brian.
 

Yes i made filters for my speaker so i should know how to remove signals from an antenna line , I was just asking how would i put it into the amplifier circuit? Because op-amps can't be used , i want to do it with transistors, than, I Have seen different circuits online for it.
 

Not any device sold here and there does actually serve a reasonable purpose...

TV antenna amplifiers as well as cable TV amplifiers are needed in specific situations like compensating cable losses (e.g. for cables > 10 m), distributing a signal to multiple receivers without losses. Blocking of radio or GSM/LTE interferences is achieved by passive LC filters and doesn't require an amplifier.

Discrete wide amplifiers can be made by cascading single transistor amplifier stages (10-15 dB per stage, transistors with 5-8 GHz fT).
 

Can someone just help me design a simple powered amplifier for tv.

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What about this op-amp that has a 700 mhz bandwidth? wouldn't this work?
http://cds.linear.com/docs/en/datasheet/1886fa.pdf
 

700 MHz OP gain bandwidth product (GBW) means no gain around 700 MHz, negative gain above 700 MHz and very little gain in the interesting frequency range. OPs are just useless.

You can find suitable MMIC components as mentioned by betwixt. A large choice is e.g. offered by Mini-Circuits

But as also said, you can buy a plug-in antenna amplifier with power supply from a shop next door or order it from internet.
 


I was looking at another website about this op-amp and it says it can be used in over the air amplification, on what you are saying that website is wrong than? The website was a chinese website , and possiby where you can buy them from.
 

It would be a misnomer to call a UHF RF amp an Operational Amplifier

But beware that nearby signals may saturate it while trying to amplify weak signals.



Your goal will be fruitless if the Noise Figure of your preamp is greater than the Noise figure of your UHF TV.

Usually this is the limiting factor, not just signal strength.
Did you check the TV signal strength in your location? Where is that?

If you do not offer details , why ask. just Go buy it
 


I live within 8 miles of my over the air stations but I still get the signals very weak though, Where i live is i basically live in a forest with lots of trees around me and i live with mountains around me as well. no matter what i do, where i point the tv antenna though its outside i get nothing, It seems i get a very low signal.
 

You'll use an antenna with high directive (long Yagi antenna) and mount it on the roof, possibly on a high pole. Place an industry standard antenna amplifier near the antenna.
 

unless you can clear a path or raise antenna to destination. the moisture inside the trees will absorb the signal @ UHF.

Otherwise try to bounce off mountain on other side.,

I use a high gain butterfly wing-tip 20 element high gain antenna to get Buffalo over Lake Ontario which helps since I live over 100 miles from Buffalo.

THis year a neighbour's tree has grown past the direct path toward buffalo and those signals are not good, until, winter.
 
Last edited:

SunnySkyguy said:
unless you can clear a path or raise antenna to destination. the moisture inside the trees will absorb the signal @ UHF.

Otherwise try to bounce off mountain on other side.,
Click to expand...

Could i do a parabolic antenna design , using an old satellite dish and than pointing a antenna to the dish inwards, i have heard this can give a better signal than most other antenna, since the parabolic dish bounces the signals off the dish and concentrates them to the center, If you hardly get nothing. Does anyone know what the Db gain of if you use a yagi with a parabolic dish, Because the signal is concentrated to the center wouldn't that make the Db gain more?
 

If you have good internet I would recommend KODI with Pulse CCM addon to get live TV and all the rest.

At UHF , it needs to be line of sight or single skip.
 

SunnySkyguy said:
If you have good internet I would recommend KODI with Pulse CCM addon to get live TV and all the rest.

At UHF , it needs to be line of sight or single skip.
Click to expand...

I don't have that good of a internet connection, Back to parabolic dish antennas, I was looking at a website and it says it can have up 20 Db of gain or more based on how big the dish is ? So If i make a parabolic antenna would that mostly help pick up the weak over the air signal?
 

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