L1, L2 - two turns, self supporting
L3, L4 - ten turns on ferrite core

What's so hard about that?

 

L1, L2 - two turns, self supporting
L3, L4 - ten turns on ferrite core

What's so hard about that?

I think the L1 and L2 I can make, but the L3 on the ferrite core is a mystery. Can you shed some light how to make it and what it looks like?

 

You can get plastic RF coil forms with ferrite slugs.
(I will post a picture when I get to a PC).

 

btw please change your avatar.

 

Here are some examples:

 

At that frequency it isn't getting the right components that's the problem, it's placing them properly on a circuit board with a good ground plane using the proper RF layout techniques.
Otherwise you're just spinning your wheels.

 

I thought I'd find a take-apart of one of the commercial TV antenna amplifiers from Mohu, RCA or others, but I was surprised that nothing showed up. I'm not in the mood to tear mine apart, so no reverse-engineering.

 

At that frequency it isn't getting the right components that's the problem, it's placing them properly on a circuit board with a good ground plane using the proper RF layout techniques.
Otherwise you're just spinning your wheels.

That was my drift in post #8. Now if you look at the transistor data sheet from the transistor cited in post #20 mounting it will be a truly entertaining experience. So while building can be a educational and rewarding experience sometimes a man has to know his limitations.

Ron

 

That circuit has more promise, but as you have observed you now have to fabricate some of the components.

 

L1, L2 - two turns, self supporting
L3, L4 - ten turns on ferrite core

What's so hard about that?

Nothing if you've done it before, and everybody has to start somewhere.

 

Good time to learn about Manhattan style circuit construction.

http://www.cliftonlaboratories.com/Prototyping.htm

 

Good time to learn about Manhatten style circuit construction.

http://www.cliftonlaboratories.com/Prototyping.htm

Note that they are mounted on a copper ground plane to give a good RF ground.

 

Good time to learn about Manhatten style circuit construction.

http://www.cliftonlaboratories.com/Prototyping.htm

Thanks for that link!

 

Hello,

You might want to look at the MMIC amplifiers on this site:
http://www.qsl.net/ok1cfp/ok1cfp-vhf-uhf-zesilovac-amplifier-mar-3.htm

Bertus

 

Thanks for all the great info. Manhattan style circuit construction is something I am familiar with. I did manage to build a FM transmitter before, that connects to my smartphone and let's me hear music on a frequency 95 - 105Mhz on the radio in the car. It worked pretty good I know these can be bought for a few bugs, but the joy of having constructed one yourself is just awesome.

Bertus posted some great options to build a UHF amp, especially this one looks simple and promising.

VHF/UHF amplifier with MAR-3
There is 5Volt Ucc power supply. The gain is about 12dB in all television bands (50-800MHz). The current to MAR-3 is about 35mA. NF=6dB. IP3=23dBm. The maximum output power can be 10dBm (=10mW). The Monolithic amplifier MAR-3.

Does anyone have an idea what L1 is in this circuit?

Perhaps this circuit might perform better Manhattan style?

Somebody else shared the information that tv channels that already come in strong might overload the transistor. What would happen in that case?

 

Hello,

The choke can be made with a resistor where about 20 turns of isolated wire around it.
The ends of the coils can be soldered to the wires if the resistors.

Bertus

 

Hello,

The choke can be made with a resistor where about 20 turns of isolated wire around it.
The ends of the coils can be soldered to the wires if the resistors.

Bertus

I just had a look at the MAR-3 datasheet and it seems to require a biasing resistor http://www.minikits.com.au/doc/MMICSc.pdf (see page 3).

How come this UHF amp circuit does not have this biasing resistor?

 

Hello,

At 5 Volts no resistor is needed.
When your supply voltage is higher, use the value given in the table.

Bertus

 

Hello,

At 5 Volts no resistor is needed.
When your supply voltage is higher, use the value given in the table.

Bertus

Yes, it shows that under "SUGGESTED RESISTOR BIAS VALUE". Makes perfect sense now. You rock! I look very much forward to constructing this circuit and testing it.

 

and that circuit posted in #20 will probably work, the first one you called a class a amplifier has no bias so cant be called class a, also the incoming signal isnt through a capacitor, so the bias will be affected by the circuit before it.