[ARC5] Receiver Voltages.

[Clare Owens]

And the GAP/R Model K2-W op amp plug in units from Philbrick (no, not Herb
), see here: http://www.philbrickarchive.org/ and search the page for
"radium" are radioactive, having radium paint smeared on the outside of the
two neon bulbs hiding inside, also to help them fire at the right voltage.
Much longer half life than the Kr85, which is mostly gone from really old
stock VR tubes by now.  I have three of the K2-W and all three are still
"hot."

You can test your old Geiger counter with a K2-W to see if it still
responds.

Clare

On Sat, May 2, 2015 at 9:31 AM, don davis <dxguy at earthlink.net> wrote:

> Brian:
>
> Following based on circuit design experience for Space tube / lamp
> applications over 40 years.  Yes, they still are using them in some limited
> applications.  VR tubes may, indeed, cycle briefly during start-up while
> circuit C is charging, but once charged should never cycle as you state.
> In a properly designed circuit there is enough head-room to ensure that
> once struck the tube will remain in conduction.  This is the reason why VR
> circuits are such power hogs during normal operation.  As an example (using
> a 0A2 from the RCA HB-3 data sheets) normal output is 73 v with 15 mA
> through the tube.  The tube requires 105 v to start, yielding 108 v
> assuming 130 v input, Iout = 5 mA, 2850 Ohms dropping R, 14.6 kOhm load.
> For reliable operation the Vin would have to increase or dropping R would
> decrease.
>
> Yes, VR tube circuits provide power supply noise rejection.  By "noise" I
> mean 60-400 Hz plus some reasonable range of audio (similar to MIL-SPEC-461
> CE-01/-02 limits).  In the instant example the dynamic resistance of the
> tube is about 120 Ohms.  When considered in the circuit the rejection from
> Vin to Vout is ~25X.  Any simulations I've made in the past have assumed an
> ideal voltage source in series with a resistor representing the dynamic
> impedance of the tube.  My understanding of the RF / uwave noise is due to
> individual atoms turning on / off or changing orbit to other excited
> states.  But my notion of this is hazy, having last studied gases in the
> '60s...  These effects can be reduced by bypassing, but one has to be
> careful since a parallel C across the VR tube will make a relaxation
> oscillator at some conditions.   Note that Zener diodes have the same noise
> issues and are used for RF noise sources, like the tubes were / are.
>
> BTW:  The firing voltage is dramatically influenced by light / photon
> sources.  I troubleshot a subcontractor's neon calibration cell circuit for
> the xxxx Space Sensor system for xxxx where we had the wrong bulbs
> installed.  Correct ones were doped with (some isotope of...) Kr to provide
> Alpha stimulation.  With the wrong bulbs we had intermittent firings.
>
> 73 de don ad6pb
>
> -----Original Message-----
> From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Brian
> Sent: Friday, May 01, 2015 7:17 PM
> To: Ian Wilson; Mike Feher
> Cc: ARC-5 Maillist; AKLDGUY .
> Subject: Re: [ARC5] Receiver Voltages.
>
>
> A VR tube works in cycles: as the Voltage applied reaches striking
> Voltage, the glow starts; but this causes a heavy current to flow and drops
> the Voltage across the tube below ignition and the low impedance becomes
> high impedance again ... and the cycle repeats. This is truly a noise
> generator, not a power supply noise attenuator.
>
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