Elecraft › [K2]

KPA100 diodes blown...

Classic

List

Threaded

5 messages Options

Brett Gazdzinski

KPA100 diodes blown...

I turned my K2 on after is sat a while, and hit the tune button to tune the
antenna, and got crazy indications, D16 and D17 in the KPA100 are blown.

Is there nothing that can be done about these diodes blowing so easy?
I need to order a set from Elecraft, but I leave all the other radios hooked
up and nothing blows in them...

I disconnect the antenna's, and select the dummy load, plus I usually have
the homebrew receiver selected which has a 3 turn coil as an antenna input,
which should look like a short to any voltage, but enough voltage must get
through everything to blow the diodes in the K2...

How are other radios protected against static buildup on the antenna?

Brett
N2DTS

______________________________________________________________
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

Don Wilhelm-4

Re: KPA100 diodes blown...

Brett,

I do not know how many other radios have wattmeters directly at the
antenna jack, so I really can't compare others.

You can place a high value resistor (1k or greater - that is 20 times
the 50 ohm impedance) across the antenna and see if that helps. An RF
Choke could also be used for the same purpose. RFC10 (100 uHy) was
removed from inside the KPA100 because it can couple to parts of the
base K2 and cause out of band oscillations. You could add an RF choke
of 100 uHy or a little greater across the antenna external to the KPA100
if you want the protection it afforded back again.

I am confused because you state that you disconnect the antennas when
not in use, but then you refer to the 3 turn winding in your homebrew
receiver. The only certain cure for damaged diodes is to fully
disconnect the antenna connection when the K2 is not in use - I
certainly hope you do not operate during periods of thunderstorm
activity, sine that is a dangerous situation unless you have extensive
(and expensive) lightning protection (equal to that installed at a
broadcast station) installed in your ham station - a simple ground will
not perform that function. I have never had a diode failure in my
KPA100, but I disconnect the antennas and connect a dummy load directly
to the K2 when it is not in use.

The 1N5711 diodes are a bit on the fragile side, but they do provide the
best voltage response vs. frequency curve. If you want hardier
wattmeter diodes, you could replace them with 1N4148 diodes. The
accuracy of the wattmeter may suffer by 5 to 10% (and that may be band
dependent), and the readings below 3 watts may not be as accurate and
with the 1N5711s. Since you have to replace the diodes anyway, the
choice is yours to make - just be prepared to accept the consequences I
have outlined if you decide to use the 1N4148s, or if you choose the
1N5711s, understand that they are more sensitive to static discharges
and the take the necessary precautions so they are not damaged.

73,
Don W3FPR

Brett Gazdzinski wrote:

> I turned my K2 on after is sat a while, and hit the tune button to tune the
> antenna, and got crazy indications, D16 and D17 in the KPA100 are blown.
>
> Is there nothing that can be done about these diodes blowing so easy?
> I need to order a set from Elecraft, but I leave all the other radios hooked
> up and nothing blows in them...
>
> I disconnect the antenna's, and select the dummy load, plus I usually have
> the homebrew receiver selected which has a 3 turn coil as an antenna input,
> which should look like a short to any voltage, but enough voltage must get
> through everything to blow the diodes in the K2...
>
> How are other radios protected against static buildup on the antenna?
>
> Brett
> N2DTS
>
>

______________________________________________________________
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

AC7AC

Re: KPA100 diodes blown...

In reply to this post by Brett Gazdzinski

CONTENTS DELETED

The author has deleted this message.

Brett Gazdzinski

Re: KPA100 diodes blown...

In reply to this post by Don Wilhelm-4

Don,
Thanks for the info.
Everything connects through the station control, antenna's, receivers,
transmitters, mod monitor, etc, it also has the T/R contactors, muting
relays etc in it.

What I have done for the last 25 years is select the dummy load when not
operating, which leaves the antenna's connected to nothing, and the homebrew
receiver bridged with the 756 pro3 selected for the receiver (I only use the
band scope in the icom).
The K2, as a transceiver, gets connected to rx position 5.

Nothing else has ever blown out when hooked up this way, and I have had many
close strikes...

In that setup, you have a BIG antenna switch open (going to dummy load) 1
inch spacing or more between things, plus the K2 antenna is also open
(receiver switch selected to a short to ground from homebrew rx).

I have the kpa100 and the kat100 in one case, remote from the actual K2,
hooked up to the antenna port all the time as its out of the way behind
racks of big AM transmitters.

I think I will try the choke at the antenna 1 connector of the kat100.

That is another odd thing, that any voltage made it through the kat100 to
take out the diodes in the kpa100....

Brett
N2DTS

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
To: "Brett Gazdzinski" <[hidden email]>
Cc: <[hidden email]>
Sent: Saturday, May 02, 2009 9:41 PM
Subject: Re: [Elecraft] KPA100 diodes blown...

> Brett,
>
> I do not know how many other radios have wattmeters directly at the
> antenna jack, so I really can't compare others.
>
> You can place a high value resistor (1k or greater - that is 20 times the
> 50 ohm impedance) across the antenna and see if that helps. An RF Choke
> could also be used for the same purpose. RFC10 (100 uHy) was removed from
> inside the KPA100 because it can couple to parts of the base K2 and cause
> out of band oscillations. You could add an RF choke of 100 uHy or a
> little greater across the antenna external to the KPA100 if you want the
> protection it afforded back again.
>
> I am confused because you state that you disconnect the antennas when not
> in use, but then you refer to the 3 turn winding in your homebrew
> receiver. The only certain cure for damaged diodes is to fully disconnect
> the antenna connection when the K2 is not in use - I certainly hope you do
> not operate during periods of thunderstorm activity, sine that is a
> dangerous situation unless you have extensive (and expensive) lightning
> protection (equal to that installed at a broadcast station) installed in
> your ham station - a simple ground will not perform that function. I have
> never had a diode failure in my KPA100, but I disconnect the antennas and
> connect a dummy load directly to the K2 when it is not in use.
>
> The 1N5711 diodes are a bit on the fragile side, but they do provide the
> best voltage response vs. frequency curve. If you want hardier wattmeter
> diodes, you could replace them with 1N4148 diodes. The accuracy of the
> wattmeter may suffer by 5 to 10% (and that may be band dependent), and the
> readings below 3 watts may not be as accurate and with the 1N5711s. Since
> you have to replace the diodes anyway, the choice is yours to make - just
> be prepared to accept the consequences I have outlined if you decide to
> use the 1N4148s, or if you choose the 1N5711s, understand that they are
> more sensitive to static discharges and the take the necessary precautions
> so they are not damaged.
>
> 73,
> Don W3FPR
>
> Brett Gazdzinski wrote:
>> I turned my K2 on after is sat a while, and hit the tune button to tune
>> the antenna, and got crazy indications, D16 and D17 in the KPA100 are
>> blown.
>>
>> Is there nothing that can be done about these diodes blowing so easy?
>> I need to order a set from Elecraft, but I leave all the other radios
>> hooked up and nothing blows in them...
>>
>> I disconnect the antenna's, and select the dummy load, plus I usually
>> have the homebrew receiver selected which has a 3 turn coil as an antenna
>> input, which should look like a short to any voltage, but enough voltage
>> must get through everything to blow the diodes in the K2...
>>
>> How are other radios protected against static buildup on the antenna?
>>
>> Brett
>> N2DTS
>>

Don Wilhelm-4

Re: KPA100 diodes blown...

Brett,

What I can say for certain is that you experienced a surge of some
sort. Perhaps while you were operating and a thunderstorm was nearby -
and in that case, it was an unfortunate experience.

At least you do take precautions to disconnect the antennas when not
operating - some do not.

Do you have lightning surge suppressors on your antenna feedlines. If
you do not, I highly recommend them. I know they are expensive, but so
is a repair to your equipment. The surge suppressors will not guarantee
that the diodes will not be damaged, but they will help with other
catastrophes if you have a good grounding system in your shack. See the
PolyPhaser website for information about grounding your station (it is
not trivial, but may save your home, life and possibly equipment).

The choke at the KAT100 ant1 is a good idea IMHO.

73,
Don W3FPR

Brett Gazdzinski wrote:

> Don,
> Thanks for the info.
> Everything connects through the station control, antenna's, receivers,
> transmitters, mod monitor, etc, it also has the T/R contactors, muting
> relays etc in it.
>
> What I have done for the last 25 years is select the dummy load when not
> operating, which leaves the antenna's connected to nothing, and the homebrew
> receiver bridged with the 756 pro3 selected for the receiver (I only use the
> band scope in the icom).
> The K2, as a transceiver, gets connected to rx position 5.
>
> Nothing else has ever blown out when hooked up this way, and I have had many
> close strikes...
>
> In that setup, you have a BIG antenna switch open (going to dummy load) 1
> inch spacing or more between things, plus the K2 antenna is also open
> (receiver switch selected to a short to ground from homebrew rx).
>
> I have the kpa100 and the kat100 in one case, remote from the actual K2,
> hooked up to the antenna port all the time as its out of the way behind
> racks of big AM transmitters.
>
> I think I will try the choke at the antenna 1 connector of the kat100.
>
> That is another odd thing, that any voltage made it through the kat100 to
> take out the diodes in the kpa100....
>
>
>
> Brett
> N2DTS
>
> ----- Original Message -----
> From: "Don Wilhelm" <[hidden email]>
> To: "Brett Gazdzinski" <[hidden email]>
> Cc: <[hidden email]>
> Sent: Saturday, May 02, 2009 9:41 PM
> Subject: Re: [Elecraft] KPA100 diodes blown...
>
>
>
>> Brett,
>>
>> I do not know how many other radios have wattmeters directly at the
>> antenna jack, so I really can't compare others.
>>
>> You can place a high value resistor (1k or greater - that is 20 times the
>> 50 ohm impedance) across the antenna and see if that helps. An RF Choke
>> could also be used for the same purpose. RFC10 (100 uHy) was removed from
>> inside the KPA100 because it can couple to parts of the base K2 and cause
>> out of band oscillations. You could add an RF choke of 100 uHy or a
>> little greater across the antenna external to the KPA100 if you want the
>> protection it afforded back again.
>>
>> I am confused because you state that you disconnect the antennas when not
>> in use, but then you refer to the 3 turn winding in your homebrew
>> receiver. The only certain cure for damaged diodes is to fully disconnect
>> the antenna connection when the K2 is not in use - I certainly hope you do
>> not operate during periods of thunderstorm activity, sine that is a
>> dangerous situation unless you have extensive (and expensive) lightning
>> protection (equal to that installed at a broadcast station) installed in
>> your ham station - a simple ground will not perform that function. I have
>> never had a diode failure in my KPA100, but I disconnect the antennas and
>> connect a dummy load directly to the K2 when it is not in use.
>>
>> The 1N5711 diodes are a bit on the fragile side, but they do provide the
>> best voltage response vs. frequency curve. If you want hardier wattmeter
>> diodes, you could replace them with 1N4148 diodes. The accuracy of the
>> wattmeter may suffer by 5 to 10% (and that may be band dependent), and the
>> readings below 3 watts may not be as accurate and with the 1N5711s. Since
>> you have to replace the diodes anyway, the choice is yours to make - just
>> be prepared to accept the consequences I have outlined if you decide to
>> use the 1N4148s, or if you choose the 1N5711s, understand that they are
>> more sensitive to static discharges and the take the necessary precautions
>> so they are not damaged.
>>
>> 73,
>> Don W3FPR
>>
>> Brett Gazdzinski wrote:
>>
>>> I turned my K2 on after is sat a while, and hit the tune button to tune
>>> the antenna, and got crazy indications, D16 and D17 in the KPA100 are
>>> blown.
>>>
>>> Is there nothing that can be done about these diodes blowing so easy?
>>> I need to order a set from Elecraft, but I leave all the other radios
>>> hooked up and nothing blows in them...
>>>
>>> I disconnect the antenna's, and select the dummy load, plus I usually
>>> have the homebrew receiver selected which has a 3 turn coil as an antenna
>>> input, which should look like a short to any voltage, but enough voltage
>>> must get through everything to blow the diodes in the K2...
>>>
>>> How are other radios protected against static buildup on the antenna?
>>>
>>> Brett
>>> N2DTS
>>>
>>>
>
> ______________________________________________________________
> 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
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.325 / Virus Database: 270.12.20/2100 - Release Date: 05/06/09 06:04:00
>
>