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1uW to 1mW UHF TV amplifier schematic?

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neazoi

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Hello, I have a uhf 470MHz TV modulator that outputs 1uW (1 microwatt).
I would like to amplify it to 1mW (1 milliwatt).

Any suitable schematics for this 30db amplification?
Discrete are preffered if possible.
 

using discrete components for something like that these days is pointless and a waste of time and resources

There's a dozen and one MMIC's that are dead easy to use eg a MAR8 31dB gain
and it would be wise to cascade a couple to keep the gain under control in each by using some of the other lower gain types

a tiny handful of components compared to discrete transistors
 

using discrete components for something like that these days is pointless and a waste of time and resources

There's a dozen and one MMIC's that are dead easy to use eg a MAR8 31dB gain
and it would be wise to cascade a couple to keep the gain under control in each by using some of the other lower gain types

a tiny handful of components compared to discrete transistors

Are these MAR/ERA MMICs suitable for TV signal amplification? In other words do they operate in class-A in their linear region?

How may stages would it require to do it discrete?

- - - Updated - - -

For example I made the first stage of this circuit http://www.next.gr/uploads/77/Tvtx1.gif but I see no improvement on the signal output, on my spectrum analyzer.
 
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15 dB@ 470 MHz per single transistor stage sounds like a good starting point if you have transistors with fT > 5 GHz, e.g. BFR93 (or legacy parts like BFR90, if you have it in your drawer).

For example I made the first stage of this circuit http://www.next.gr/uploads/77/Tvtx1.gif but I see no improvement on the signal output, on my spectrum analyzer.
BFY90 datasheet promises 9.5 dB |S21| at 500 MHz. So it's probably the circuit/layout.
 
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    neazoi

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15 dB@ 470 MHz per single transistor stage sounds like a good starting point if you have transistors with fT > 5 GHz, e.g. BFR93 (or legacy parts like BFR90, if you have it in your drawer).


BFY90 datasheet promises 9.5 dB |S21| at 500 MHz. So it's probably the circuit/layout.

I have found this one.
https://www.qsl.net/va3iul/Homebrew_RF_Circuit_Design_Ideas/AV_UHF_TV_modulator.gif
See the output amplifier, I think it won't hurt to try this one and see if I can achieve any amplification on my modulator. I think increasing VCC a bit won't hurt. Also can I directly replace this with a bfr93, or even better bfr90, since I see it has a bit higher gain?
It this works I could probably add another identical stage in series?

Finally, how about this discrete mmic? http://obrazki.elektroda.pl/11_1296043527.jpg
But it is for 50R :(
 
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Use this to amplify this signal..
https://www.macom.com/products/product-detail/MAAM-010373

It's pretty linear and input/output is perfectly matched to 75 ohm.


yeah, sweet device ...

was going to do another post aiming along similar lines after Neazoi posted the circuit he was playing with in post #3 and I realised then what he was doing.

There are a bunch of MMIC's like the one you have linked to that are ideal for this activity and have a tiny added component count and simple board layout


Dave
 

yeah, sweet device ...

was going to do another post aiming along similar lines after Neazoi posted the circuit he was playing with in post #3 and I realised then what he was doing.

There are a bunch of MMIC's like the one you have linked to that are ideal for this activity and have a tiny added component count and simple board layout


Dave

How would they do it discrete back then?
I have not tried this circuit yet https://obrazki.elektroda.pl/11_1296043527.jpg
This is 50R but I do not know how it will behave on 75R
 

Consider the difference between 50 and 75 ohm impedance as insignificant in a first order, resulting in worst case 1 to 2 dB gain drop.
 

How would they do it discrete back then?
I have not tried this circuit yet https://obrazki.elektroda.pl/11_1296043527.jpg
This is 50R but I do not know how it will behave on 75R
If you still intend to implement an CATV amplifier with discrete components;

**Cascode topology will give you the best result
**NXP Wideband BJT Transistors ( BFX series) are very suitable for that application
**If you are able to use a simulator ( any kind linear/nonlinear) you can reach very nice results because wideband amplifiers need optimization process.
**Cascade topology will also give you a result but it won't be very wideband ( it's up to you, if you don't need no more than one octave..)
Design will be a bit tedious..
 

If you still intend to implement an CATV amplifier with discrete components;

**Cascode topology will give you the best result
**NXP Wideband BJT Transistors ( BFX series) are very suitable for that application
**If you are able to use a simulator ( any kind linear/nonlinear) you can reach very nice results because wideband amplifiers need optimization process.
**Cascade topology will also give you a result but it won't be very wideband ( it's up to you, if you don't need no more than one octave..)
Design will be a bit tedious..

I wonder if these UHF TV preamplifiers (BFRxx transistors), that were used to amplify the antenna signal to the TV set, can be also used the other way round, to amplify the modulator signal?
I do not see why not, the only reason that would prohibit this would be a high input signal that would overload the amp.
My modulator output is 1uW, so how is that compared to the antenna received signal?
 

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