[Elecraft] Re: K3 6m pre-amp

[Jack Colson]

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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