[Elecraft] Re: K3 6m pre-amp

[Bob Tellefsen]

Don't think I've seen that kind of model number before, Jack.
What is it and who makes it?
Thanks and 73
Bob N6WG

----- Original Message ----- 
From: "Jack Colson" <jcolson7 at tampabay.rr.com>
To: "Jack Smith" <jack.smith at cliftonlaboratories.com>;
<w3fpr at arrl.net>
Cc: <elecraft at mailman.qth.net>
Sent: Wednesday, July 30, 2008 4:37 PM
Subject: Re: [Elecraft] Re: K3 6m pre-amp


> I personally would use a MGF-1302.
>
> 73
> Jack, W3TMZ
>
> ----- Original Message ----- 
> From: "Jack Smith" <jack.smith at cliftonlaboratories.com>
> To: <w3fpr at arrl.net>
> Cc: <elecraft at 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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