[Elecraft] Re: K3 6m pre-amp

[Don Wilhelm]

Jack,

I understand the vanishing part syndrome.  I have a few remaining in my 
parts bin, and I am not about to give them up (similar feelings about my 
dual gate MOSFETs).

As an alternative to the U310, when laying out a PC board (or Manhatten 
construction board), one might consider the SMD version of the 
J310/U310.  It should be at least as good as the U310 and likely 
better.  A nice clean layout is critical to performance in a VHF/UHF 
amplifier.  A carrier board may be needed for Manhatten construction, 
but for 3 legged devices, a carrier board is simplicity itself - just a 
tiny scrap of rectangular PC board with the copper cut in half along the 
length and one of the remaining long rectangles cut in half across its 
width.  Caution - cut the copper on the corner of a larger piece of PC 
board and then cut out the result as the 'final act' - attempting to cut 
through the copper on a tiny board can result in injury to the fingers 
and hands.  With the demise of thru-hole parts and the advent af 
inexpensive SMD parts, we hams will have to learn how to deal with these 
tiny devices if we are to continue homebrewing and experimenting efforts 
at a reasonable price.

73,
Don W3FPR

Jack Smith wrote:
> Don:
>
> The U310's are not too easy to find these days. Vishay seems to be the 
> most common (only?) new production supplier and the one-off price is 
> about $14 from Mouser or Arrow.  Digikey, Allied and Newark only stock 
> the SOT23 plastic surface mount version. TO-92 plastic case parts, the 
> J310, are around 25 cents each. The U310 and J310 are supposed to have 
> the same die, so differences should be attributed to the case, but who 
> knows what goes inside the package these days, particularly if it is 
> from China.
>
> If I were building a pre-amp based upon a U310, I would start with a 
> J310 and get it thoroughly debugged before experimenting with U310's 
> at $14 a pop.
>
> It's something like the 40673 dual gate FET - once ubiquitous and now 
> difficult to find and expensive when found.
>
>
> Jack K8ZOA
>