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VHF booster

Miguel Lopez

Jan 25, 2012
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Hi all

I need to build a TV booster for the VHF range (channels 2 to 12). I thought on a self-biased stage with a capacitor across the emitter resistor, using a Soviet 1T311 NPN transistor (Ge), because it is the only HF transistor that I have.

My cuestion is about the configuration of the circuit. The self-bias configuration is stable and provide good amplification, but as I have never worked with HF, I don't know if there is a more suitable bias configuration.

Any help welcomed

Thanks

Miguel
 

CDRIVE

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Personally, I don't know why anyone would bother building one. They're very inexpensive to purchase (off the shelf) but if you insist on building it post the schematic.

Edit: Oops, I just saw your location. You folks are still driving around in 1957 Chevy's that look like they just rolled off the showroom floor! Post the schematic.
 
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CDRIVE

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Oh, really!!?? I challenge you to find any in a Cuban shop.

You were too fast on the trigger. Go back and read my edit. BTW, Little Havana in Miami has lots of them. . :D
 

CDRIVE

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Are import restrictions that bad, that it makes ordering and importing one from say China that complicated?

I wasn't kidding about the 57 Chevy. ;) Isn't Communism wonderful? :rolleyes:

Chris
 

CocaCola

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I wasn't kidding about the 57 Chevy. ;) Isn't Communism wonderful? :rolleyes:

Well I know there is a US trade embargo, but Cuba does do business with the rest of the world, including our neighbors to the North and South that enjoy cheap cane sugar that makes my drink of choice that much better vs the US stuff...

I'm just hazarding a guess, but I suspect that sales between the Cuba and many other foreign countries would be nearly painless, as it's mainly a silly US policy only...
 

CDRIVE

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Most U.S. grown sugar is grown here in Florida and Hawaii. The price is high because of the EPA. No matter how you slice it, it isn't easy to get a lot of common things in Cuba and I don't think the US embargo has much to do with it. Hell, we don't make anything here anymore!
 

Miguel Lopez

Jan 25, 2012
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Please, keep focussed.

This is about a VHF booster, not about Cuba-US relationship. Open a thread in the Off-Topic Members Lounge section to talk about that

I will post the schematic today.

PS: Old cars (1940s - 1950s) in Cuba are as common as air.
 

Miguel Lopez

Jan 25, 2012
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Transistor is 1T311 Germanium NPN (Soviet)
 

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CDRIVE

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Transistor is 1T311 Germanium NPN (Soviet)

A Germanium! Good grief! Actually, whether, Germanium, Silicon, BJT, FET or Vacuum Tube, that's not an RF amplifier by any definition.
 

Miguel Lopez

Jan 25, 2012
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Ok, and what's the solution?

Any suggestion?

And, what's the problem with Germanium?
 

CocaCola

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Please, keep focussed.

My post were focused on the topic at hand, and were not off-topic... You simply ignored the on topic portions and twisted the remainder into something it wasn't...
 
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CDRIVE

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Ok, and what's the solution?

Any suggestion?

And, what's the problem with Germanium?

For the rest of the planet they were superseded by silicon by 1970. I can't find a data sheet for your transistor and I'm not surprised. It's difficult to design around a transistor that you have no data for. Your transistor is a child of the Iron curtain era, which is not merely ancient history for me. I lived it. Fact: I can Google a 1930's vacuum tube data sheet and get hits. Soviet Germaniums?... Not so much.
 

Miguel Lopez

Jan 25, 2012
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I'm agree with you that this is a dinosaur, but it is what I have. I've got some characteristic of this transistor that I can post here, basically maximun ratings.
Would that be useful?
And what about the circuit configuration?

PS: This type was massively used on Soviet precision laboratory instruments such as frequency generators in early 90s. I retrieved them from one of these.
 

CDRIVE

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Post what data you have. Let's see what we can do with it. How many of them do you have?

Curious,.. Are you trying to receive channel 7 in Miami?
 

Miguel Lopez

Jan 25, 2012
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UCEmax = 12V
UCBmax = 12V
UEB = 2V
Pmax = 150mW
Ic = 50mA
Hie = 30...180
Fmax = 300 MHz


CDRIVE said:
How many of them do you have?
Plenty

CDRIVE said:
Are you trying to receive channel 7 in Miami?
Nop. I'm just trying to see channels 2, 4, 6 of national TV which are seen very poorly in my town. Channel 7 in Cuba is "Cubavisión" broadcasted from Pinar del Río.
 

CDRIVE

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UCEmax = 12V
UCBmax = 12V
UEB = 2V
Pmax = 150mW
Ic = 50mA
Hie = 30...180
Fmax = 300 MHz

OK, I believe it should read like the following:

Vceo Max: 12V
Vcbo Max: 12V
Vebo Max: 2V
Pd Max: 150mW
Ic Max: 50mA
hFE: Min 30 Max 180
fT: 300MHz ( Where gain = unity)

Is this an NPN and do you know the noise figure?

Chris
 

Miguel Lopez

Jan 25, 2012
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CDRIVE said:
OK, I believe it should read like the following:
Vceo Max: 12V
Vcbo Max: 12V
Vebo Max: 2V
Pd Max: 150mW
Ic Max: 50mA
hFE: Min 30 Max 180
fT: 300MHz ( Where gain = unity)
Yes

CDRIVE said:
Is this an NPN and do you know the noise figure?
It is an NPN and I don't know the noise figure.
 
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