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Prevent Snow/Dirt Static damage to KPA100 after upgrade

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Kenneth Christiansen

Prevent Snow/Dirt Static damage to KPA100 after upgrade

40 years ago we had a windy dust storm in Bismarck ND and I lost the RF
amplifier in my new solid state Heathkit receiver three times that day
before I realized the dirt and high winds were putting a static charge
on my antenna. I found there was a capacitor between the antenna and the
RF amp and the static would arc across the capacitor and burn out the
RF amp. Of course tube type receivers did not have this problem. I found
out a 100K resistor from the antenna to ground would prevent this and
not load down the antenna.

Several years ago my friend I each bought a new IC-746PRO. The first
time we had a blizzard with 50 MPH winds and snow my friend and I both
burned out our new rigs with snow static trying to check into the ND
Weather Net. The K2 survived just fine. The IC-746PROs were both fixed
under warranty but it still cost both of us shipping. I found out the
IC-746PROs did not have any path to discharge the antenna charge from
the snow static.

I recently installed the KPA100 Upgrade and one of the steps was to
remove R10 the 100uh choke between the antenna jack and ground. There is
no other path to ground and I have read on the reflector about people
having their SWR and Power measuring diodes go bad and it was easy to
see why. I plan to use this rig to check into the ND Weather net this
winter so knew I needed to fix the problem.

MFJ on my remote tuner uses a 40 K resistor to protect their circuit.
That is less than the 100 K I have used over the years so it should
protect even better.

I put in the following change to fix my problem. I bought four 10K half
watt resistors in a package from Radio Shack for $1.99. I soldered them
in series and soldered one end to the center pint of the antenna jack J2
and the other end to ground. I calculate that the resistors would
withstand a 16 to 1 VSWR and I do not think the KPA100 would be able to
put out 100 watts to a 16 to 1 VSWR so the resistors should be safe. 40K
should protect the diodes from any problem and under normal conditions
should dissipate 0.2 watts.

There is an easy way to protect the amplifier without making a
modification to the amplifier it self. Buy a PL259 T adapter and a PL259
plug. Solder one end of the 40 K series resistor to the center of the
PL259 and the other end to the shell. The resistors can be covered by
tape to prevent an accidental RF burn. Screw the PL259 /40K assembly to
one side of the T adapter. Put the other two ports of the T adapter in
series with the coax to the antenna or the coax to the 50 ohm side of a
tuner.

The one remaining precaution is to touch both sides of the antenna lead
to ground just before hooking them up to discharge any static
electricity on the antenna. This fix will not protect the equipment from
a lightning strike but it does allow me to use my rig to check into the
ND Weather net during a blizzard.

I hope this can save someone else from having rig trouble after a high
wind snow or dust storm.

73 for now

Ken W0CZ

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N5GE

Re: Prevent Snow/Dirt Static damage to KPA100 after upgrade

On Sat, 23 Oct 2010 16:07:41 -0500, "Kenneth A. Christiansen"
<[hidden email]> wrote:

Thanks for that information Kenneth. I'll bet it works on Texas
spring rain static too!

Tom Childers
N5GE Antenna
4507 Branchview Drive
Arlington, TX 76017
[hidden email]
http://www.n5ge.com

>40 years ago we had a windy dust storm in Bismarck ND and I lost the RF
>amplifier in my new solid state Heathkit receiver three times that day
>before I realized the dirt and high winds were putting a static charge
>on my antenna. I found there was a capacitor between the antenna and the
>RF amp and the static would arc across the capacitor and burn out the
>RF amp. Of course tube type receivers did not have this problem. I found
>out a 100K resistor from the antenna to ground would prevent this and
>not load down the antenna.
>
>Several years ago my friend I each bought a new IC-746PRO. The first
>time we had a blizzard with 50 MPH winds and snow my friend and I both
>burned out our new rigs with snow static trying to check into the ND
>Weather Net. The K2 survived just fine. The IC-746PROs were both fixed
>under warranty but it still cost both of us shipping. I found out the
>IC-746PROs did not have any path to discharge the antenna charge from
>the snow static.
>
>I recently installed the KPA100 Upgrade and one of the steps was to
>remove R10 the 100uh choke between the antenna jack and ground. There is
>no other path to ground and I have read on the reflector about people
>having their SWR and Power measuring diodes go bad and it was easy to
>see why. I plan to use this rig to check into the ND Weather net this
>winter so knew I needed to fix the problem.
>
>MFJ on my remote tuner uses a 40 K resistor to protect their circuit.
>That is less than the 100 K I have used over the years so it should
>protect even better.
>
>I put in the following change to fix my problem. I bought four 10K half
>watt resistors in a package from Radio Shack for $1.99. I soldered them
>in series and soldered one end to the center pint of the antenna jack J2
>and the other end to ground. I calculate that the resistors would
>withstand a 16 to 1 VSWR and I do not think the KPA100 would be able to
>put out 100 watts to a 16 to 1 VSWR so the resistors should be safe. 40K
>should protect the diodes from any problem and under normal conditions
>should dissipate 0.2 watts.
>
>There is an easy way to protect the amplifier without making a
>modification to the amplifier it self. Buy a PL259 T adapter and a PL259
>plug. Solder one end of the 40 K series resistor to the center of the
>PL259 and the other end to the shell. The resistors can be covered by
>tape to prevent an accidental RF burn. Screw the PL259 /40K assembly to
>one side of the T adapter. Put the other two ports of the T adapter in
>series with the coax to the antenna or the coax to the 50 ohm side of a
>tuner.
>
>The one remaining precaution is to touch both sides of the antenna lead
>to ground just before hooking them up to discharge any static
>electricity on the antenna. This fix will not protect the equipment from
>a lightning strike but it does allow me to use my rig to check into the
>ND Weather net during a blizzard.
>
>I hope this can save someone else from having rig trouble after a high
>wind snow or dust storm.
>
>73 for now
>
>Ken W0CZ
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Amateur Radio Operator N5GE

AC7AC

Re: Prevent Snow/Dirt Static damage to KPA100 after upgrade

In reply to this post by Kenneth Christiansen

CONTENTS DELETED

The author has deleted this message.

Don Wilhelm-4

Re: Prevent Snow/Dirt Static damage to KPA100 after upgrade

In reply to this post by Kenneth Christiansen

Ken,

If you salvaged RFC10 from the KPA100 upgrade, I suggest you use it.
The only problem is that it cannot live inside the KPA100 because it
couples into the base K2 circuits causing spurious responses and all
kinds of "strange happenings".

You mentioned using a T connector - certainly, just mount the 100 uHy
choke in a PL-259 - one lead to the center conductor and the other to
the shell. Place that PL-259 on one side of the T adapter, and connect
the antenna to the other.

A resistor will do OK, but the choke provides a better low DC resistance
path than a resistor.

73,
Don W3FPR

On 10/23/2010 5:07 PM, Kenneth A. Christiansen wrote:

Kenneth Christiansen

Re: Prevent Snow/Dirt Static damage to KPA100 after upgrade

Hi Don

Thank you for your note. You answered a question that was on my mind and
in fact I did use the slavaged RFC10 in my own modification. I put it
across J4 the RF IN jack of the KAT100. It seems to work fine and I plan
to keep it that way. The only reason I did not put it in my note was
that I was not sure why it was removed from the KPA100 in the first
place. Now that I know I recommend either putting the RFC10 accross J4
of the KAT100 like I did or putting RFC10 from the center pin to ground
of the PL-259 and T adaptor.

Thanks for the info Don and I hope between our two notes we can save
many KPA100s from snow static this winter.

73

Ken W0CZ
+++++++++++++++++++++++++++++++++++++++++++++++
On 10/23/2010 7:25 PM, Don Wilhelm wrote:

> Ken,
>
> If you salvaged RFC10 from the KPA100 upgrade, I suggest you use it.
> The only problem is that it cannot live inside the KPA100 because it
> couples into the base K2 circuits causing spurious responses and all
> kinds of "strange happenings".
>
> You mentioned using a T connector - certainly, just mount the 100 uHy
> choke in a PL-259 - one lead to the center conductor and the other to
> the shell. Place that PL-259 on one side of the T adapter, and
> connect the antenna to the other.
>
> A resistor will do OK, but the choke provides a better low DC
> resistance path than a resistor.
>
> 73,
> Don W3FPR
>
> On 10/23/2010 5:07 PM, Kenneth A. Christiansen wrote:
>> 40 years ago we had a windy dust storm in Bismarck ND and I lost the RF
>> amplifier in my new solid state Heathkit receiver three times that day
>> before I realized the dirt and high winds were putting a static charge
>> on my antenna. I found there was a capacitor between the antenna and the
>> RF amp and the static would arc across the capacitor and burn out the
>> RF amp. Of course tube type receivers did not have this problem. I found
>> out a 100K resistor from the antenna to ground would prevent this and
>> not load down the antenna.
>>
>> Several years ago my friend I each bought a new IC-746PRO. The first
>> time we had a blizzard with 50 MPH winds and snow my friend and I both
>> burned out our new rigs with snow static trying to check into the ND
>> Weather Net. The K2 survived just fine. The IC-746PROs were both fixed
>> under warranty but it still cost both of us shipping. I found out the
>> IC-746PROs did not have any path to discharge the antenna charge from
>> the snow static.
>>
>> I recently installed the KPA100 Upgrade and one of the steps was to
>> remove R10 the 100uh choke between the antenna jack and ground. There is
>> no other path to ground and I have read on the reflector about people
>> having their SWR and Power measuring diodes go bad and it was easy to
>> see why. I plan to use this rig to check into the ND Weather net this
>> winter so knew I needed to fix the problem.
>>
>>
>

AC7AC

Re: Prevent Snow/Dirt Static damage to KPA100 after upgrade

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The author has deleted this message.