Or BF981 would work nicely. However don´t know how hard to
get they are these days.
A preamp with NF below 1 can easily be built with a BF981,
forexample the YU1AW cavity design with BF981.
73 Jim SM2EKM
-------------------------
Jack Colson wrote:
I personally would use a MGF-1302.
73
Jack, W3TMZ
----- Original Message ----- From: "Jack Smith"
<[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Cc: <elecraft@mailman.qth.net>
Sent: Wednesday, July 30, 2008 6:48 PM
Subject: Re: [Elecraft] Re: K3 6m pre-amp
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
Don Wilhelm wrote:
Bob,
While I cannot speak from my own measurements, but in EMRFD, Wes
Hayward recommends the U310s for VHF/UHF rather than the J310. The
case of the U310 is connected to the gate, and when used in a
grounded gate configuration, the case can be mounted (upside down)
into a hole in the PC board, and I believe that alone should provide
better input to output isolation. The Vishay data sheet indicates a
slightly lower noise figure for the U310.
I would suggest that you try the J310s. If you find them lacking, it
should be easy to change to U310s, I would guess that at 50 MHz, it
may be a 'toss-up' decision.
73,
Don W3FPR
Bob Tellefsen wrote:
Hi John
I've been looking at this circuit for some time.
I have a number of J310s, but no U310s.
Do you know whether they are the same
animal, just in different casings?
73, Bob N6WG
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