What kind of LNA transistor to use?

[Jane]

I have a satellite tuner where an input transistor needs to be replaced. It is SMD transistor so it has only a marking code such as GT.
It has 4 pins( probably 2 emitters).
Can anyone suggest a transistor that can be a suitable for the replacement?
Thank you

[rfeecs]

That's not a lot of information.  Typical 12GHz satellite receiver uses low noise HEMT.  Something like this:
http://www.cel.com/pdf/datasheets/CE3512K2.pdf

[Jane]

Thanks for your reply.
In my tuner there is a transistor ( of a shape ) like this
http://www.nxp.com/documents/data_sheet/BFG425W.pdf

But not sure if that kind transistor can be used.
Does anyone know?

[KE5FX]

Can you post a reasonably-detailed photo of the area of the PCB surrounding the part you need to replace?  That might provide some clues.

Unfortunately a lot of those discrete microwave transistors are no longer available.  NXP in particular has killed a lot of nice parts over the past few years. 

[rfeecs]

Thanks for your reply.
In my tuner there is a transistor ( of a shape ) like this
http://www.nxp.com/documents/data_sheet/BFG425W.pdf

But not sure if that kind transistor can be used.
Does anyone know?

Well that's a different package, an SOT-343.  Still doesn't say much.
If it really is an LNA, it's more likely to be a HEMT.  Definitely not interchangeable with a bipolar.
NEC(CEL) and Mitsubishi are common manufacturers.
Here's another one in an SOT-343 compatible package:
http://www.cel.com/pdf/datasheets/CE3514M4.pdf

[chrisl]

post some pics so we can see the part.
CE3514M4 from CEL or MGF4937AM from Mitsubish may fit the package description.
However, you cannot just drop in an alternate part and expect it to work at this frequency.
 

[Jane]

Here is a picture of the tuner and I marked by red arrow the transistor.
Thanks for help

[BigBoss]

What is the SMD marking on the transistor ?? It might still be available.

[Jane]

In the original tuner made by ALPS the  marking is  IYU  while in a clone tuner made by Earda Electronics Ltd( brand  Eardatek) is  marking GT.

Any idea how to source that transistor?
Thanks

[Gribo]

Try looking for the Conexant reference design.
This transistor is connected to a type F connector, I don't think it is a 25GHz part. Usually, the LNB is located near the dish.

[PA0PBZ]

No, this is not an LNA or LNB, it's the tuner where the LNB connect to and it works roughly from 1-2GHz.

[chrisl]

Looks like L-band stuff.  No Ku  or X for sure.

[Jane]

No, not  for Ku band, but how can I find an equivalent?