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
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