[time-nuts] HP 117/10509a

J. Forster jfor at quikus.com
Thu Jul 5 13:31:03 UTC 2012


You do know that neither a 117A or a 207 will work when WWVB changes to
BPSK fairy soon?

-John

===============


> Thanks Charles:
> I will consider your ideas as they seem to be excellent!
>
> I wonder if I could just make the whole unit run off of +24VDC or +12
> VDC.
> I need to look at the schematics and see what would be the best way to
> proceed.
>
> I currently do not have an antenna for WWVB and need to get up and
> running before I do anything with it.
>
> If successful, would anyone want information on my conversion? I also
> have a fluke 207 that needs to be recapped.
> Thanks,
> Ron
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Charles P. Steinmetz
> Sent: Wednesday, July 04, 2012 11:10 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] HP 117/10509a
>
> Don wrote:
>
>>the fet breakdown voltage has of course got to be high enough.
>
> If the nuvistor is used as a common-cathode or common-grid amplifier,
> you can cascode the fet with a bipolar to extend its drain voltage
> range.  You will need to come up with an appropriate bias source for
> the bipolar.  Generally, you would want at least 10-15 volts across
> the FET channel.
>
> Choose an appropriate JFET (transconductance, drain current, and
> gate-drain voltage similar to the nuvistor at the nuvistor's
> operating point).  You can add degeneration (source resistance) to
> lower the FET's transconductance if it is higher than the nuvistor's.
>
> Best regards,
>
> Charles
>
>
>
>
>
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