[Lowfer] JFET (J310) Biasing

[n8tl]

Hi Clive:

I am currently working on w1vd's version of the e-probe.  You should 
adjust for 20-25 ma or 2.0-2.5
volts across the bias resistor which is 22 megohm in this case.

Good Luck and Cheers,

Tom N8TL

On 14-06-28 01:20 PM, Clive S Carver wrote:
> I am curious of the pro's and con's of three different ways of biasing a
> J310 for use as an e-Probe front end stage.
>
> 1. For example, the PA0RDT mini-whip uses two 1Mohm resistors in a potential
> divider across the +12ve to ground supply, with a third 1Mohm resistor
> between the potential divider mid-point and the J310 gate.
>
> 2. Some designs omit the third 1Mohm resistor referred to above, and connect
> the potential divider mid-point directly to the J310 gate.
>
> 3. I have also come across a design where there is a single 1Mohm resistor
> between the +12ve rail and the J310 gate.
>
> So, what are the advantages/disadvantages in the three methods (besides
> using less 1Mohm resistors!).
>
> 73's
>
> Clive
> GW4EYO
>
>
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