need a transistor

I found on one site that my transistor is most likely the culprit of my superregen. the site states that FT should be at least 10 times the highest frequency I intend to receive.

Right now, I'm trying to optimize channel 11 which is at about 205Mhz. Multiply by 10, and I get 2050Mhz which is over 2Ghz.

The problem is that I only have access to a limited selection of transistors. For the selection, go to sayal.com, click on retail catalog, then click on transistors.

The transistor I have now is a Pn3563 which only goes up to 600Mhz for FT.

So someone please suggest to me a transistor having an FT of at least 2Ghz what starts wit 2N or PN or MPS.

thanks.

a search found 2N6618 microwave transistor
**broken link removed**

mstechca said:

I found on one site that my transistor is most likely the culprit of my superregen. the site states that FT should be at least 10 times the highest frequency I intend to receive.

Click to expand...

That's the least of your problems! :lol:

a search found 2N6618 microwave transistor

Click to expand...

thanks, but that is not available in the Sayal Retail Catalog. I don't buy items online.

Nigel Goodwin said:

That's the least of your problems! :lol:

Click to expand...

Let's put it this way, (Ft / frequency of interest) = transistor beta when dealing with RF. I discovered this at electronics-tutorials.com.

Since the best transistor I have on hand is rated at 600Mhz, I get: 600Mhz/200Mhz (200 Mhz is around my frequency of interest) = 3 which is less than the recomended value of 10!

Is there another transistor that has an Ft of at least 2Ghz?

mstechca said:

Nigel Goodwin said:

That's the least of your problems! :lol:

Click to expand...

Let's put it this way, (Ft / frequency of interest) = transistor beta when dealing with RF. I discovered this at electronics-tutorials.com.

Click to expand...

It's a nice theory, but NOT a requirement - for a super-regen it will either work, or not work at all, as it wouldn't have enough gain to oscillate. As your's work (at least to some extent), the transistor isn't likely to be a problem.

To make it work properly (at least as far as a super-regen can), try building it properly - don't make your random changes, use a proven working circuit!.

Nigel Goodwin said:

use a proven working circuit!.

Click to expand...

The problem is there is no proven working circuit! :lol:
Sure, they might have aircraft receivers, but they don't have transistor TV receivers, especially with the transistor numbers I use.

HOWEVER, I do use proven mini circuits in my design like a tank circuit, and common-emitter amplifier, etc.

I will make one stab at including an emiter resistor and connecting it with a capacitor (in parallel), just to see if it actually works. I begin to think that not enough resistance somewhere makes the actual mains hum sound.

I will add emitter resistors to every part of my old circuit whose NPN connects directly to ground.

Luckily, on a PCB, if it doesn't work, I'll just stick a blob of solder, and short the new circuit so that I can revert to the old design.

mstechca said:

Nigel Goodwin said:

use a proven working circuit!.

Click to expand...

The problem is there is no proven working circuit! :lol:
Sure, they might have aircraft receivers, but they don't have transistor TV receivers, especially with the transistor numbers I use.

Click to expand...

There are many proven and tested super-regen circuits, the only difference for a (VHF) TV receiver is to alter the coil slightly - either more turns for band I or less turns for band III.

The transistor number is largely irrelevent, pretty well any small signal silicon NPN will work fine.