[ARC5] JFET in ARC-5 TX oscillator socket

[wf2u at ws19ops.com]

I never paid more than $3 for 1625's at hamfests, typically 2 for $5 .

73, Meir WF2U
Landrum, SC

Quoting mstangelo at comcast.net:

> Where can you get cheap 1626's.
>
> Mike N2MS
>
> ----- Original Message -----
>
> From: WA5CAB at cs.com
>
> To: ARC5 at mailman.qth.net
>
> Sent: Wed, 8 Jul 2009 04:05:39 +0000 (UTC)
>
> Subject: Re: [ARC5] JFET in ARC-5 TX oscillator socket
>
>
>
> 1626's are cheaper than JFET's.  And for some strange reason work
>
> surprisingly well in Command Set transmitters.  You'd almost think   
> that the sets had
>
> been designed to use them.
>
>
>
> In a message dated 7/7/2009 10:32:03 PM Central Daylight Time,
>
> dennis.monticelli at gmail.com writes:
>
>> I forgot that it was a Hartley configuration.  You're right.  Output
>
>> would
>
>> probably be low at the source node.
>
>>
>
>> One way around that would be to choose a high Vp (pinchoff) JFET with a
>
>> high
>
>> Idss rating and still protect it with a cascode device or else bias the
>
>> drain from a separate voltage source.   I think the appropriate choice
>
>> would
>
>> be a J111 (2N4856 or PN4856 is the same) or J108 (PN5432 is the same)  The
>
>> latter is the most beefy.  In all cases the BV is at least 25V.  But these
>
>> JFETs have more transconductance than the 1626 so the gate-source swing
>
>> will
>
>> be less than the grid-cathode swing for a given current draw.  The optimum
>
>> would be to change the tap on the coil but this is something most of us
>
>> would prefer not to do.
>
>>
>
>> Dennis AE6C
>
>>
>
>> On Sat, Jul 4, 2009 at 10:31 AM, Ian Wilson
>
>> wrote:
>
>>
>
>> >Not sure that beefing up the voltage dropped across a composite device
>
>> >would
>
>> >help, since it's a Hartley oscillator. The voltage swing is determined by
>
>> >the
>
>> >current through the device and the magnitude of the grid bias voltage
>
>> >developed
>
>> >(I think). Some other SS compound might have the right characteristics,
>
>> >though?
>
>> >
>
>> >73, ian K3IMW
>
>>
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