[ARC5] JFET in ARC-5 TX oscillator socket

[mstangelo at comcast.net]

When the MOSFETS first came out the prices were high; I can believe it.

Dual gate mosfets followed the single gate 3N128 Insulated Gate mosfet. They were popular because the second gate could be to control gain in amplifiers. The Dual Gate MOSFETS were also used as mixers.

As someone mentioned, the thin insulation was susceptable to damage from static discharges. The FETS were packaged with a coil of wire shorting all leads. You were advised to remove the short after the transistor was installed in the circuit.

RCA came out wth a line of dual gate MOSFETS with input protective diodes, the most popular one being the 40673. This FET was a popular device in Heathkit solid state kits. It still is a popular part, and like lots of discontinued parts, fetches a premium price these days.

Mike,

N2MS

----- Original Message -----

From: sbjohnston at aol.com

To: ARC5 at mailman.qth.net

Sent: Thu, 9 Jul 2009 03:30:34 +0000 (UTC)

Subject: Re: [ARC5] JFET in ARC-5 TX oscillator socket



WA5CAB wrote:



>the last JFET's I actually bought were around $15 each.



That's exorbitant.  Sure those weren't dual-gate MOSFETs are something 

else really rare?



Right now Mouser has the MPF102 JFET for 10 cents each, single 

quantity.   Radio Shack has MPF102s on the wall for $1.29 each.

Newark sells 2N3819 JFETs for 11 cents each.



So I don't think you can really say that cost is the reason not to 

experiment with a JFET VFO using ARC5 parts.



Steve WD8DAS





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