Static discharge protection questions

Static discharge protection questions

Post by mike » Tue, 23 Sep 2003 05:25:22

Hey group,

I have a portable radio with no external ground.

Recently I built a PI network antenna tuner in a metal box and
included an output for earth ground. So the outer sheild of my coax
inputs as well as outputs and the variable capacitor frames are on
this ground to earth. The random wire input goes strait to the tuning
capacitor thus needs some kind of static drain off.

I have heard using a neon bulb and a 2 watt 2.2k ohm resistor in
between the inputs and ground would discharge static buildup and give
me some warning of build up conditions.

I am also concerned about limiting the voltage to the receiver front
end to prevent damage. I have heard installing back to back high speed
diodes between the imputs and ground would acheive this.

I understand everything but the diodes. What does back to back mean. I
recall diodes are one way, but which way goes where? Should I look for
a certain type or rating of diode?

Thanks for your help,

Mike

 
 
 

Static discharge protection questions

Post by Kiere » Tue, 23 Sep 2003 06:30:28


Back to back:  Take your two diodes and install them in parallel, but
with one 'pointing' in the opposite direction.  The idea is that, because  
each diode will conduct when the voltage rises above it's threashold, it
doesn't matter if the spike is positive or negative.  A radio signal is
highly unlikely to be powerful enough to force either diode to conduct
(and if it did, they'll protect the RX front end).

I don't think they'd help much however!  You only have to think about the
kind of potential in a static build-up to decide that you do not want to
rely on a pair of diodes to keep everything calm.  Far better to make
sure your aerial has a DIRECT path to earth - a low impedence one at
that.  Best way to avoid static damage?  Disconnect the hardware from the
wire when you think there's static about.  Oh - and avoid using
headphones....

Good luck.
K



Quote:> Hey group,

> I have a portable radio with no external ground.

> Recently I built a PI network antenna tuner in a metal box and
> included an output for earth ground. So the outer sheild of my coax
> inputs as well as outputs and the variable capacitor frames are on
> this ground to earth. The random wire input goes strait to the tuning
> capacitor thus needs some kind of static drain off.

> I have heard using a neon bulb and a 2 watt 2.2k ohm resistor in
> between the inputs and ground would discharge static buildup and give
> me some warning of build up conditions.

> I am also concerned about limiting the voltage to the receiver front
> end to prevent damage. I have heard installing back to back high speed
> diodes between the imputs and ground would acheive this.

> I understand everything but the diodes. What does back to back mean. I
> recall diodes are one way, but which way goes where? Should I look for
> a certain type or rating of diode?

> Thanks for your help,

> Mike

 
 
 

Static discharge protection questions

Post by mike » Tue, 23 Sep 2003 09:16:04


Quote:>Back to back:  Take your two diodes and install them in parallel, but
>with one 'pointing' in the opposite direction.  The idea is that, because  
>each diode will conduct when the voltage rises above it's threashold, it
>doesn't matter if the spike is positive or negative.  A radio signal is
>highly unlikely to be powerful enough to force either diode to conduct
>(and if it did, they'll protect the RX front end).

>I don't think they'd help much however!  You only have to think about the
>kind of potential in a static build-up to decide that you do not want to
>rely on a pair of diodes to keep everything calm.  Far better to make
>sure your aerial has a DIRECT path to earth - a low impedence one at
>that.  Best way to avoid static damage?  Disconnect the hardware from the
>wire when you think there's static about.  Oh - and avoid using
>headphones....

>Good luck.
>K

OK I get it now.

 As for an earth ground......I found a nice fat copper braided wire
coming off the metal roof lightning protectors (this is an old
farmhouse) down the side of the house going deep into the ground.

I suspect if I solder a nice fat 12 guage wire to my random wire where
it meets my coax it would suffice in this regard. Additionaly I will
run another wire to this ground from my tuner.

thanks,

mike

 
 
 

Static discharge protection questions

Post by Avery Finem » Tue, 23 Sep 2003 10:32:08



>Hey group,

>I have a portable radio with no external ground.

>Recently I built a PI network antenna tuner in a metal box and
>included an output for earth ground. So the outer sheild of my coax
>inputs as well as outputs and the variable capacitor frames are on
>this ground to earth. The random wire input goes strait to the tuning
>capacitor thus needs some kind of static drain off.

>I have heard using a neon bulb and a 2 watt 2.2k ohm resistor in
>between the inputs and ground would discharge static buildup and give
>me some warning of build up conditions.

   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.

Quote:>I am also concerned about limiting the voltage to the receiver front
>end to prevent damage. I have heard installing back to back high speed
>diodes between the imputs and ground would acheive this.

>I understand everything but the diodes. What does back to back mean. I
>recall diodes are one way, but which way goes where? Should I look for
>a certain type or rating of diode?

   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

 
 
 

Static discharge protection questions

Post by mike » Tue, 23 Sep 2003 22:52:43



Quote:>   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.

Quote:

>   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

 
 
 

Static discharge protection questions

Post by KA9CA » Wed, 24 Sep 2003 05:10:11

For Static control,  I have a 1 megaohm 1/2 watt resistor to ground from
each side of my antenna.  I do this because my balanced antenna tuner does
not have a DC path to ground.

Notice I said STATIC control, not Lightening arresting.

You can use a much lower value.  The resistor should be large compared to
the impeadence of your anteanna.  So if the antenna is 4,000 ohms, even a
400,000 ohm resistor would be 100 times the antenna value.

KA9CAR


Quote:> Hey group,

> I have a portable radio with no external ground.

> Recently I built a PI network antenna tuner in a metal box and
> included an output for earth ground. So the outer sheild of my coax
> inputs as well as outputs and the variable capacitor frames are on
> this ground to earth. The random wire input goes strait to the tuning
> capacitor thus needs some kind of static drain off.

> I have heard using a neon bulb and a 2 watt 2.2k ohm resistor in
> between the inputs and ground would discharge static buildup and give
> me some warning of build up conditions.

> I am also concerned about limiting the voltage to the receiver front
> end to prevent damage. I have heard installing back to back high speed
> diodes between the imputs and ground would acheive this.

> I understand everything but the diodes. What does back to back mean. I
> recall diodes are one way, but which way goes where? Should I look for
> a certain type or rating of diode?

> Thanks for your help,

> Mike

 
 
 

Static discharge protection questions

Post by Avery Finem » Wed, 24 Sep 2003 12:59:09





>>   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

 
 
 

Static discharge protection questions

Post by Avery Finem » Wed, 24 Sep 2003 14:09:01



>>   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.  :-)

Quote:>>   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...:-(

 
 
 

Static discharge protection questions

Post by Roy Lewalle » Wed, 24 Sep 2003 16:22:25

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


>    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.
> . . .

 
 
 

Static discharge protection questions

Post by mike » Wed, 24 Sep 2003 21:40:22



Quote:>   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.

Silly me, I put them all in parallel.<grin>. I am a mechanic with some
electrical knowledge, but not much electronics. So the resistor should
be in series with the diodes to limit current.

A side effect I noticed after installing the 1N914 diodes was images
scattered across the bands. For example, wwcr on 3200 was also on
2300. Another gentleman posted me link in the antenna group where he
found the same thing happening.

Might the resistor in series with the diodes reduce this side effect?

Quote:>   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.

I chose 2.2k ohm 1/4 watt resistors. Couldnt find any higher wattages
at Radio Shack. This was the latest resistance value recommended by
Arnie Coro at Radio Habana.

Quote:>   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.

I live in Vermont. We get some lightning but not that much. My main
concern is static buildup due to wind and the elements.

mike

 
 
 

Static discharge protection questions

Post by mike » Thu, 25 Sep 2003 00:10:28


>A side effect I noticed after installing the 1N914 diodes was images
>scattered across the bands. For example, wwcr on 3200 was also on
>2300. Another gentleman posted me link in the antenna group where he
>found the same thing happening.

>Might the resistor in series with the diodes reduce this side effect?

hmmm... might be my impedance mismatch causing reflections of imcoming
signals back and forth along the antenna, thus causing images.

probable?

mike

 
 
 

Static discharge protection questions

Post by Rob Jud » Thu, 25 Sep 2003 00:16:29

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
*** game in which he held a decided advantage while being able to
claim a totally impartial device. ;-)

Rob


> 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


> >    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.
> > . . .

 
 
 

Static discharge protection questions

Post by Dick Carrol » Thu, 25 Sep 2003 12:32:00



>>A side effect I noticed after installing the 1N914 diodes was images
>>scattered across the bands. For example, wwcr on 3200 was also on
>>2300. Another gentleman posted me link in the antenna group where he
>>found the same thing happening.

>>Might the resistor in series with the diodes reduce this side effect?

> hmmm... might be my impedance mismatch causing reflections of imcoming
> signals back and forth along the antenna, thus causing images.

> probable?

  It may be a mixing product due to mixing of RF signals in a diode.

Dick
  mike

 
 
 

Static discharge protection questions

Post by Dick Carrol » Thu, 25 Sep 2003 13:44:41


> Back to back:  Take your two diodes and install them in parallel, but
> with one 'pointing' in the opposite direction.  The idea is that, because  
> each diode will conduct when the voltage rises above it's threashold, it
> doesn't matter if the spike is positive or negative.  A radio signal is
> highly unlikely to be powerful enough to force either diode to conduct
> (and if it did, they'll protect the RX front end).

> I don't think they'd help much however!  You only have to think about the
> kind of potential in a static build-up to decide that you do not want to
> rely on a pair of diodes to keep everything calm.

  Once the static voltage builds to .7 volt one or the other diode will
conduct and "bleed" it off. Of course that assumes that we're not
talking of lightning-level static charge. In that case all bets are off.

  Many HF and MF installations use an RF ***of sufficient impedance
placed across the antenna terminals to provide a discharge path for all
static voltages to be immediately shunted to ground without disturbing
the received radio signal in any way. No static ever builds up on the
antenna. All it takes is a small RF ***of sufficient impedance to be
transparent at the frequency of interest.

Dick

  Far better to make

> sure your aerial has a DIRECT path to earth - a low impedence one at
> that.  Best way to avoid static damage?  Disconnect the hardware from the
> wire when you think there's static about.  Oh - and avoid using
> headphones....

> Good luck.
> K



>>Hey group,

>>I have a portable radio with no external ground.

>>Recently I built a PI network antenna tuner in a metal box and
>>included an output for earth ground. So the outer sheild of my coax
>>inputs as well as outputs and the variable capacitor frames are on
>>this ground to earth. The random wire input goes strait to the tuning
>>capacitor thus needs some kind of static drain off.

>>I have heard using a neon bulb and a 2 watt 2.2k ohm resistor in
>>between the inputs and ground would discharge static buildup and give
>>me some warning of build up conditions.

>>I am also concerned about limiting the voltage to the receiver front
>>end to prevent damage. I have heard installing back to back high speed
>>diodes between the imputs and ground would acheive this.

>>I understand everything but the diodes. What does back to back mean. I
>>recall diodes are one way, but which way goes where? Should I look for
>>a certain type or rating of diode?

>>Thanks for your help,

>>Mike

 
 
 

Static discharge protection questions

Post by Avery Finem » Fri, 26 Sep 2003 07:04:07





>Silly me, I put them all in parallel.<grin>. I am a mechanic with some
>electrical knowledge, but not much electronics. So the resistor should
>be in series with the diodes to limit current.

>A side effect I noticed after installing the 1N914 diodes was images
>scattered across the bands. For example, wwcr on 3200 was also on
>2300. Another gentleman posted me link in the antenna group where he
>found the same thing happening.

>Might the resistor in series with the diodes reduce this side effect?

   The effect should not be there with or without diodes, with or without
   any resistors...unless there is some VERY big RF source out of the
   receiver's tuning range that is supplying energy to the diodes and
   thus causing the "mixer" effect.

   It might be possible if you have some Local Oscillator energy leaking
   out to the antenna connection, but even that is unlikely given "modern"
   (in the last couple of decades) receiver design.

   The diodes should not have any effect on anything but a few millivolts
   of any signal arriving on your antenna.  A non-conducting diode simply
   shows a junction capacitance to the rest of the world.  That's a minor
   reactive discontinuity to the antenna connection.

   It might be possible that some unusual circuitry in your receiver presents
   a DC Voltage at the antenna port.  If so, it might cause one of the diodes
   to conduct.  It would be better then to AC-couple the back-to-back diodes
   to the receiver through a capacitor of 0.001 to 0.01 uFd to eliminate that
   possibility.  You should be able to measure any DC potential at the
   antenna port with a high impedance multimeter.

   Len Anderson
   retired (from regular hours) electronic engineer person