On 22 Sep 2003 01:32:08 GMT, (Avery Fineman)
wrote:


A small neon bulb was used in thousands of ARC-5 Command Set
receivers in WW2 for static bleed-off. Similar to an old NE-2 bulb.
No need to use a resistor. The neon will conduct somewhere around
70 Volts and shunt any static pickup to ground...then goes into non-
conducting state until the next static potential build-up.

Wow.....70 volts seems a tad high to be protective in my solid state
portable. I suspect the older vacuum tube sets were far more static
resistant. I've read the limit for my sony portable should be kept
below 0.7volts to keep the sensitive front end electronics safe.




You can use practically anything modern in the way of diodes there
but the high-speed types such as 1N914 and 1N4148 are very cheap
and available many places. Varistors could be used (GE "movisters")
or even 1N4000 series rectifier diodes. Diodes have a 0.6 to 0.7 VDC
forward conduction voltage if silicon.

Put them side by side with the anode of one to the cathode of the
other at each end. That will limit voltage input to about 1.4 V peak-to-
peak. You could put a small series resistor, say 22 Ohms or so,
between antenna input and the diodes to limit peak diode current on
conduction. Your option...since the series resistor will drop the RF
input level slightly.

You could also use a high-inductance RF "choke" in place of diodes
and neon bulb. 1 to 5 mHy would work at HF bands. That forms a
constant low-resistance DC path from antenna to ground and keeps
static accumulation bled off immediately.

Len Anderson
retired (from regular hours) electronic engineer person


I've read suggestions for resistors ranging from 2.2 k ohms to 56 k
ohms all the way up to 100 k ohms. The most recent information being
the lowest value resistors. From the schematics I have seen, the
resistors were placed in parralel between the antenna input and ground
input. Or in the case of a two wire unbalanced input, between each
wire and the case of the tuner which is grounded.

Guess I might have to just play resistor values and see what doesnt
hurt signal strenth (another suggestion I read).

good information though, thanks. - mike

In article , mike
writes:

On 22 Sep 2003 01:32:08 GMT, (Avery Fineman)
wrote:


A small neon bulb was used in thousands of ARC-5 Command Set
receivers in WW2 for static bleed-off. Similar to an old NE-2 bulb.
No need to use a resistor. The neon will conduct somewhere around
70 Volts and shunt any static pickup to ground...then goes into non-
conducting state until the next static potential build-up.

Wow.....70 volts seems a tad high to be protective in my solid state
portable. I suspect the older vacuum tube sets were far more static
resistant. I've read the limit for my sony portable should be kept
below 0.7volts to keep the sensitive front end electronics safe.




You can use practically anything modern in the way of diodes there
but the high-speed types such as 1N914 and 1N4148 are very cheap
and available many places. Varistors could be used (GE "movisters")
or even 1N4000 series rectifier diodes. Diodes have a 0.6 to 0.7 VDC
forward conduction voltage if silicon.

Put them side by side with the anode of one to the cathode of the
other at each end. That will limit voltage input to about 1.4 V peak-to-
peak. You could put a small series resistor, say 22 Ohms or so,
between antenna input and the diodes to limit peak diode current on
conduction. Your option...since the series resistor will drop the RF
input level slightly.

You could also use a high-inductance RF "choke" in place of diodes
and neon bulb. 1 to 5 mHy would work at HF bands. That forms a
constant low-resistance DC path from antenna to ground and keeps
static accumulation bled off immediately.

Len Anderson
retired (from regular hours) electronic engineer person


I've read suggestions for resistors ranging from 2.2 k ohms to 56 k
ohms all the way up to 100 k ohms. The most recent information being
the lowest value resistors. From the schematics I have seen, the
resistors were placed in parralel between the antenna input and ground
input. Or in the case of a two wire unbalanced input, between each
wire and the case of the tuner which is grounded.

Guess I might have to just play resistor values and see what doesnt
hurt signal strenth (another suggestion I read).

good information though, thanks. - mike

....[snip]....
I've read suggestions for resistors ranging from 2.2 k ohms to 56 k
ohms all the way up to 100 k ohms. The most recent information being
the lowest value resistors. From the schematics I have seen, the
resistors were placed in parralel between the antenna input and ground
input. Or in the case of a two wire unbalanced input, between each
wire and the case of the tuner which is grounded.

It just depends on how much power you want to "waste" in the paralleled
resistor. Think of it this way: IF you had a 50-ohm dipole antenna and
you used a 50-ohm resistor across the antenna (and ignoring the effect
of a 25-ohm load on your xmtr), half of your power go into the antenna
proper and half would be dissipated in the resistor.

That's probably too much, so try a 500-ohm resistor: now about 90% of
your xmtr power goes into the antenna and 10% into the resistor.

One more try: 5K-omn resistor: now about 99% goes into the antenna and
1% is wasted in the resistor.

This leads to one of the "rules of thumb" from a beginning EE class oh-
so- many years ago: the power loss from paralleling a 100*R-ohm resistor
with an R-ohm resistor is essentially negligible.

There is another GOOD effect of using any resistor across your feed line:
a simple ohm-meter check from inside the shack can tell you if your feed
line is intact!

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

....[snip]....
I've read suggestions for resistors ranging from 2.2 k ohms to 56 k
ohms all the way up to 100 k ohms. The most recent information being
the lowest value resistors. From the schematics I have seen, the
resistors were placed in parralel between the antenna input and ground
input. Or in the case of a two wire unbalanced input, between each
wire and the case of the tuner which is grounded.

It just depends on how much power you want to "waste" in the paralleled
resistor. Think of it this way: IF you had a 50-ohm dipole antenna and
you used a 50-ohm resistor across the antenna (and ignoring the effect
of a 25-ohm load on your xmtr), half of your power go into the antenna
proper and half would be dissipated in the resistor.

That's probably too much, so try a 500-ohm resistor: now about 90% of
your xmtr power goes into the antenna and 10% into the resistor.

One more try: 5K-omn resistor: now about 99% goes into the antenna and
1% is wasted in the resistor.

This leads to one of the "rules of thumb" from a beginning EE class oh-
so- many years ago: the power loss from paralleling a 100*R-ohm resistor
with an R-ohm resistor is essentially negligible.

There is another GOOD effect of using any resistor across your feed line:
a simple ohm-meter check from inside the shack can tell you if your feed
line is intact!

--Myron, W0PBV.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

In article , mike
writes:

A small neon bulb was used in thousands of ARC-5 Command Set
receivers in WW2 for static bleed-off. Similar to an old NE-2 bulb.
No need to use a resistor. The neon will conduct somewhere around
70 Volts and shunt any static pickup to ground...then goes into non-
conducting state until the next static potential build-up.

Wow.....70 volts seems a tad high to be protective in my solid state
portable. I suspect the older vacuum tube sets were far more static
resistant. I've read the limit for my sony portable should be kept
below 0.7volts to keep the sensitive front end electronics safe.

Allow me to correct a number. The strike voltage of a typical small
neon bulb is high but once struck, and a resistor is in series with it,
the bulb potential is around 50 VDC.

Yes, that IS a high voltage, but I encountered it on a (roughly) 200
foot long-wire that the previous apartment owner had put up to a
utility pole prior to 1947. The little bulb in the ARC-5 receiver DID
light. On learning some more about neon bulbs (I was 14 at the time),
I decided it was not a good thing to have the antenna connected during
electrical storm episodes. :-)

You can use practically anything modern in the way of diodes there
but the high-speed types such as 1N914 and 1N4148 are very cheap
and available many places. Varistors could be used (GE "movisters")
or even 1N4000 series rectifier diodes. Diodes have a 0.6 to 0.7 VDC
forward conduction voltage if silicon.

Put them side by side with the anode of one to the cathode of the
other at each end. That will limit voltage input to about 1.4 V peak-to-
peak. You could put a small series resistor, say 22 Ohms or so,
between antenna input and the diodes to limit peak diode current on
conduction. Your option...since the series resistor will drop the RF
input level slightly.

You could also use a high-inductance RF "choke" in place of diodes
and neon bulb. 1 to 5 mHy would work at HF bands. That forms a
constant low-resistance DC path from antenna to ground and keeps
static accumulation bled off immediately.

Len Anderson
retired (from regular hours) electronic engineer person

I've read suggestions for resistors ranging from 2.2 k ohms to 56 k
ohms all the way up to 100 k ohms. The most recent information being
the lowest value resistors. From the schematics I have seen, the
resistors were placed in parralel between the antenna input and ground
input. Or in the case of a two wire unbalanced input, between each
wire and the case of the tuner which is grounded.

Guess I might have to just play resistor values and see what doesnt
hurt signal strenth (another suggestion I read).

good information though, thanks. - mike

A resistor alone will only serve to bleed off any accumulated voltage
charge. Relatively slowly. It is NOT any sort of protection from a spike
of voltage created by a nearby lightning episode. Those can be anywhere
from a few Volts to 300 Volts peak amplitude, polarity either positive or
negative depending on what Mother Nature decides at that moment...

The "back-to-back" diodes serve as clamps to effect a sudden low-
impedance shunt across the input once they conduct past around 0.7
Volts forward (it's not sudden, but gradual, the Z curve has a lot of
slope steepness until it really begins to conduct). The reason I mentioned
a _series_ resistor between back-to-back diodes and antenna is for three
reasons: It limits the peak current in the diodes; it provides a slight
voltage-divider effect to reduce peaks (even on conduction) at receiver
input; it reduces the rise time of the static peak through a tiny R-C
filter effect using the diodes' junction capacitance.

In truth, NONE of the above is an guarantee of _protection_ of any
receiver input. A slow, gradual charge build-up on an antenna isn't
going anywhere as long as _all_ the components involved have
insulation breakdown voltages that are high. A resistor by itself will
bleed off such slow charge build-up attempts. At around 2.7 KOhms
or so, that resistance isn't going to affect high-impedance values much
at frequencies well away from resonance of the wire antenna.

Since I live in Southern California with a low incidence of electrical
storms, I've not concerned myself with electrostatic charges in wire
antennas. Being raised in northern Illinois, such were quite common
and I've been "bit" by one charge which was probably up around 50
Volts or so on that mentioned long-wire. Lightning storm areas NEED
additional protection for outside antennas.

Len Anderson
retired (from regular hours) electronic engineer person


My apologies for the previous posting without content...stupid cat
walked across the keyboard...:-(

Neon bulbs are curious critters. As you say, they have hysteresis -- a
higher strike voltage than sustaining voltage. The company I worked for
once used them as low current regulators here and there, as well as for
static protection, so they bought or selected them to various
specifications for strike and sustaining voltages. Strike voltages
varied from 55 minimum to 135 maximum, and sustaining specs went from a
minimum of 46 to a maximum of 78. They also exhibited a "dark effect",
which I believe was that the strike voltage was dependent on the ambient
light level. I recall that a trace radioactive material was added to
some -- to reduce the "dark effect", I think, by keeping the gas close
to ionization. I imagine the sustaining voltage was controlled by the
mixture and pressure of gas.

The bulbs were commonly used as pilot lamps, but not when the supply was
DC. (This lesson was learned the hard way, judging by company documents
and app notes.) Depending on the supply impedance, the pilot bulb could
become a relaxation oscillator, interfering with sensitive circuitry.

I came in just as their day was ending.

Roy Lewallen, W7EL

Avery Fineman wrote:

Allow me to correct a number. The strike voltage of a typical small
neon bulb is high but once struck, and a resistor is in series with it,
the bulb potential is around 50 VDC.
. . .

Roy,

I recall as a kid making a "Decision Maker" project that used two neons
to indicate Yes and No. My father thought it was pretty cool, especially
when I mentioned that I had noticed it came up on Yes more often. I told
him I'd fix it but he seemed insistent that I leave it the way it was.

I didn't see it much after that, but suspect it played a part in some
gambling game in which he held a decided advantage while being able to
claim a totally impartial device. ;-)

Rob


Roy Lewallen wrote:

Neon bulbs are curious critters. As you say, they have hysteresis -- a
higher strike voltage than sustaining voltage. The company I worked for
once used them as low current regulators here and there, as well as for
static protection, so they bought or selected them to various
specifications for strike and sustaining voltages. Strike voltages
varied from 55 minimum to 135 maximum, and sustaining specs went from a
minimum of 46 to a maximum of 78. They also exhibited a "dark effect",
which I believe was that the strike voltage was dependent on the ambient
light level. I recall that a trace radioactive material was added to
some -- to reduce the "dark effect", I think, by keeping the gas close
to ionization. I imagine the sustaining voltage was controlled by the
mixture and pressure of gas.

The bulbs were commonly used as pilot lamps, but not when the supply was
DC. (This lesson was learned the hard way, judging by company documents
and app notes.) Depending on the supply impedance, the pilot bulb could
become a relaxation oscillator, interfering with sensitive circuitry.

I came in just as their day was ending.

Roy Lewallen, W7EL

Avery Fineman wrote:

Allow me to correct a number. The strike voltage of a typical small
neon bulb is high but once struck, and a resistor is in series with it,
the bulb potential is around 50 VDC.
. . .

Roy,

I recall as a kid making a "Decision Maker" project that used two neons
to indicate Yes and No. My father thought it was pretty cool, especially
when I mentioned that I had noticed it came up on Yes more often. I told
him I'd fix it but he seemed insistent that I leave it the way it was.

I didn't see it much after that, but suspect it played a part in some
gambling game in which he held a decided advantage while being able to
claim a totally impartial device. ;-)

Rob


Roy Lewallen wrote:

Neon bulbs are curious critters. As you say, they have hysteresis -- a
higher strike voltage than sustaining voltage. The company I worked for
once used them as low current regulators here and there, as well as for
static protection, so they bought or selected them to various
specifications for strike and sustaining voltages. Strike voltages
varied from 55 minimum to 135 maximum, and sustaining specs went from a
minimum of 46 to a maximum of 78. They also exhibited a "dark effect",
which I believe was that the strike voltage was dependent on the ambient
light level. I recall that a trace radioactive material was added to
some -- to reduce the "dark effect", I think, by keeping the gas close
to ionization. I imagine the sustaining voltage was controlled by the
mixture and pressure of gas.

The bulbs were commonly used as pilot lamps, but not when the supply was
DC. (This lesson was learned the hard way, judging by company documents
and app notes.) Depending on the supply impedance, the pilot bulb could
become a relaxation oscillator, interfering with sensitive circuitry.

I came in just as their day was ending.

Roy Lewallen, W7EL

Avery Fineman wrote:

Allow me to correct a number. The strike voltage of a typical small
neon bulb is high but once struck, and a resistor is in series with it,
the bulb potential is around 50 VDC.
. . .

In article , Roy Lewallen
writes:

Neon bulbs are curious critters. As you say, they have hysteresis -- a
higher strike voltage than sustaining voltage. The company I worked for
once used them as low current regulators here and there, as well as for
static protection, so they bought or selected them to various
specifications for strike and sustaining voltages.

Tektronix. :-) I'm thoroughly familiar with the 53n and 54n Tek scopes
and their "seriesed" power supplies. A rather good design concept in
my later opinion. Used to calibrate them at Ramo-Wooldridge Standards
Lab 1959-1961.

According to the parts descriptions they were controlled-characteristic
miniature neon pilot bulbs. That worked out rather well since I only had
one problem among about 300 or so scopes at R-W...and that was due
to the error amplifier (tube circuit), not the voltage reference of the
neon.

Much smaller than the common "high grade" VR tube, a 5651.


The bulbs were commonly used as pilot lamps, but not when the supply was
DC. (This lesson was learned the hard way, judging by company documents
and app notes.) Depending on the supply impedance, the pilot bulb could
become a relaxation oscillator, interfering with sensitive circuitry.

Heh, Tektronix and several other manufacturers of the 1950-1960 period.

General Electric had that problem in one piece of broadcast TV thing.
Encountered that at WREX-TV in 1956, where it was messing about
with the local color sub-carrier generator.

I came in just as their day was ending.

I'm glad those are nearly gone. Neons are a nice AC pilot bulb or night
light where the minor heat and supply current is not a problem.

Today is a whole different ballgame with logic supply voltage dropping
to 3.3 VDC and rail supplies for op-amps down to 1.5 VDC. LEDs are
now cheap, take less power, and have different colors. Neon lamps are
rather fixed at orange.

ESD built into many MOS ICs makes it much easier on designers and
users and repair folks. Gotta love it now! :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article , Roy Lewallen
writes:

Neon bulbs are curious critters. As you say, they have hysteresis -- a
higher strike voltage than sustaining voltage. The company I worked for
once used them as low current regulators here and there, as well as for
static protection, so they bought or selected them to various
specifications for strike and sustaining voltages.

Tektronix. :-) I'm thoroughly familiar with the 53n and 54n Tek scopes
and their "seriesed" power supplies. A rather good design concept in
my later opinion. Used to calibrate them at Ramo-Wooldridge Standards
Lab 1959-1961.

According to the parts descriptions they were controlled-characteristic
miniature neon pilot bulbs. That worked out rather well since I only had
one problem among about 300 or so scopes at R-W...and that was due
to the error amplifier (tube circuit), not the voltage reference of the
neon.

Much smaller than the common "high grade" VR tube, a 5651.


The bulbs were commonly used as pilot lamps, but not when the supply was
DC. (This lesson was learned the hard way, judging by company documents
and app notes.) Depending on the supply impedance, the pilot bulb could
become a relaxation oscillator, interfering with sensitive circuitry.

Heh, Tektronix and several other manufacturers of the 1950-1960 period.

General Electric had that problem in one piece of broadcast TV thing.
Encountered that at WREX-TV in 1956, where it was messing about
with the local color sub-carrier generator.

I came in just as their day was ending.

I'm glad those are nearly gone. Neons are a nice AC pilot bulb or night
light where the minor heat and supply current is not a problem.

Today is a whole different ballgame with logic supply voltage dropping
to 3.3 VDC and rail supplies for op-amps down to 1.5 VDC. LEDs are
now cheap, take less power, and have different colors. Neon lamps are
rather fixed at orange.

ESD built into many MOS ICs makes it much easier on designers and
users and repair folks. Gotta love it now! :-)

Len Anderson
retired (from regular hours) electronic engineer person