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Reducing K2 power below 1 watt (QRPp)

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andyatd

Reducing K2 power below 1 watt (QRPp)

I've been searching for the best methods to modify a K2 for QRPp levels but the pages recommended seem to have expired accounts.

Any suggestions would be very much appreciated.

Thanks!

Andy
N3LCW

Tom McCulloch

Re: Reducing K2 power below 1 watt (QRPp)

I never tried to go that low, but I thought it went down to zero. Have
you tried putting a watt meter on it?

Tom, WB2QDG
K2 #1103

On 2/7/2013 10:22 AM, andyatd wrote:

> I've been searching for the best methods to modify a K2 for QRPp levels but
> the pages recommended seem to have expired accounts.
>
> Any suggestions would be very much appreciated.
>
> Thanks!
>
> Andy
> N3LCW
>
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Reducing-K2-power-below-1-watt-QRPp-tp7569704.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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N0AZZ

Re: Reducing K2 power below 1 watt (QRPp)

I have a friend that built something where he works as low as .05w and lower
using WSPR most of the time. He is an extreme QRP op and has been so for
some time. In fact he was the person that steered me to the Oak Hills
Research WM-2 QRP wattmeter one of very few accurate at very low power QRP
levels.

My Elecraft and Alpha wattmeter's will read QRP levels but not as low as it
will and it's a fun kit to build. He uses a K2 and I do a lot of the time
but now use my KX3 for everything except digital modes like WSPR.

73,
Fred/N0AZZ

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Tom McCulloch
Sent: Thursday, February 07, 2013 9:40 AM
To: andyatd
Cc: [hidden email]
Subject: Re: [Elecraft] Reducing K2 power below 1 watt (QRPp)

I never tried to go that low, but I thought it went down to zero. Have you
tried putting a watt meter on it?

Tom, WB2QDG
K2 #1103

On 2/7/2013 10:22 AM, andyatd wrote:

> I've been searching for the best methods to modify a K2 for QRPp
> levels but the pages recommended seem to have expired accounts.
>
> Any suggestions would be very much appreciated.
>
> Thanks!
>
> Andy
> N3LCW
>
>
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/Reducing-K2-power-below-1-watt-QR
> Pp-tp7569704.html Sent from the Elecraft mailing list archive at
> Nabble.com.
> ______________________________________________________________
> 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
>

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Chip Stratton

Re: Reducing K2 power below 1 watt (QRPp)

In reply to this post by andyatd

Andy -

There are a number of pretty simple kits for reducing QRP to QRPp. I built
one from midnightscience.com that will attenuate as much as 20 dB in steps.
No need to hack on the K2!

Chip

On Thu, Feb 7, 2013 at 10:22 AM, andyatd <[hidden email]>wrote:

> I've been searching for the best methods to modify a K2 for QRPp levels but
> the pages recommended seem to have expired accounts.
>
> Any suggestions would be very much appreciated.
>
> Thanks!
>
> Andy
> N3LCW
>
>
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/Reducing-K2-power-below-1-watt-QRPp-tp7569704.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> 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
>

Lou Voerman W2ROW

Re: Reducing K2 power below 1 watt (QRPp)

In reply to this post by andyatd

There is an article on the Elecraft website:

Milliwatting with the K2

Lou W2ROW

andyatd wrote

I've been searching for the best methods to modify a K2 for QRPp levels but the pages recommended seem to have expired accounts.

Any suggestions would be very much appreciated.

Thanks!

Andy
N3LCW

Don Wilhelm-4

Re: Reducing K2 power below 1 watt (QRPp)

In reply to this post by andyatd

Andy,

There *was* a non-Elecraft mod to accomplish that, but I am certain the
links are no longer valid because the author has been SK for several
years, and the mod documentation was on his website.

As I recall, that mod changed the resistors in the base K2 RF Output
Detector. That solution would not work in general now with a K2 with
either the KAT2, the KPA100 or the KAT100 installed.

If I were to attempt a mod like that, I would want it to work even with
the wattmeters in the KAT2 (or KPA100 or KAT100). I would break the
path on the Control Board between R12 and U6 pin 2 and insert a gain
(non-inverting) op amp - hint remove R12 and add it back on the input of
the op amp piggyback board. I am going to guess that the op amp gain
would be 10 or close to it, but some experimenting may be in order to
make 1 watt fall at the 10 watt display and 0.1 watt fall at the 1 watt
display.

You would have to switch the op-amp out of the circuit to tune the KAT2
or KAT100, but other than that I can see no other operational difficulties.

A 10 dB attenuator with a power rating of at least 15 watts input would
also do the job, but it would need to be switched out for receive
somehow - a relay powered from an amp keying circuit should work to
switch the attenuator in on TX and out for RX if you wanted to go the
attenuator route.

For those who have the KPA100, you can always remove the power from the
KPA100 and power only the base K2. Doing that changes the power scale
from 1 watt to 100 watts down to 0.1 watt to 15.2 watts (but you will
find the power control will not be accurate much below 0.3 watts)

73,
Don W3FPR
.
On 2/7/2013 10:22 AM, andyatd wrote:

andyatd

Re: Reducing K2 power below 1 watt (QRPp)

Many excellent suggestions, I wish to thank you all.

I'll post an update of which route I decided to go.

73...

Andy
N3LCW