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Low Power ?

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Larry Dodson

Low Power ?

I wonder if my K2 (Serial # 2424 with latest mods and software) is set up correctly and would appreciate comments. Output power with CAL CURR set at 3.0 amps is as below. Increasing CAL CURR to 5 amps makes little difference. I know that the K2 is basically a 10 watt rig and I get more on some bands, but the upper bands do not achieve this. When using the K2 with my KW1000 Linear Amplifier a watt or two makes a difference.
80 Meters = 13.0 watts out
40 Meters = 10.0 watts out
30 Meters = 12.0 watts out
20 Meters = 11.0 watts out
15 Meters = 8.0 watts out
12 Meters = 9.5 watts out
10 Meters = 7.0 watts out

Thanks in advance for your advice - Larry (G0IKE)
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John Lonigro

Re: Low Power ?

Larry:

I haven't measured my K2 output power for a while, but I recall I can
get 10 Watts out on 10 meters and at least 15 on 80 meters when I'm
using a 13.8 volt power supply. A 12 volt gelcell doesn't allow for
full output, especially at the higher frequencies. If you are using
13.8 volts, you might try to go through the alignment procedure one more
time. With your readings, it's hard to imagine there is much wrong with
the rig. Of course, you also need to be fairly confident your power
meter is accurate at these levels.

73's

John AA0VE

Larry Dodson wrote:

>I wonder if my K2 (Serial # 2424 with latest mods and software) is set up correctly and would appreciate comments. Output power with CAL CURR set at 3.0 amps is as below.
>40 Meters = 10.0 watts out
>30 Meters = 12.0 watts out
>20 Meters = 11.0 watts out
>15 Meters = 8.0 watts out
>12 Meters = 9.5 watts out
>10 Meters = 7.0 watts out
>
>
>

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Don Wilhelm-3

Re: Low Power ?

In reply to this post by Larry Dodson

Larry,

The K2 is speced for 10 watts out on all bands with a 13.8 volt power
supply, and most are capable of about 12 watts on the higher bands (10/12
meters) and 15 watts on 17 meters and below. Recall that there is a menu
entry (secondary menu) that sets the power limit on 10 meters - it defaults
to 10 watts. If you are checking for maximum power on that band, you may
want to temporarily set that value to 15 watts.

You could first try repeaking the bandpass filters - the K2 typically has
more gain on 40 and 30 meters, so your low 40 meter output gives me
suspicion.

The most common reason for low power output is T2. T2 should be wound so
that the secondary (green wire) is spread over most of the primary turns,
and it should be mounted above the board by about 1/16 inch (2mm). You may
want to download the latest manual and look at the illustration for T2.

Also check T4 - make certain it has the proper number of turns and that it
was not wound for maximum efficiency at 5 watts.

Last but not least, be certain your wattmeter is correct - many are not, and
be certain your dummy load is actually 50 ohms resistive on the band you are
investigating. If you have a calibrated 'scope with a frequency limit of 50
MHz or more, you can check the wattmeter by observing the RF voltage across
the dummy load. Power can be calculated as the square of the Peak to Peak
Voltage divided by 400 for a 50 ohm load (yes, you can do all the peak to
RMS conversions and arrive at the same thing - I will leave the proof to the
'student'). An RF probe can also be used to measure the RF voltage, and in
that case the probe shows RMS voltage and the power is calculated as V**2/R.

73,
Don W3FPR

----- Original Message -----

I wonder if my K2 (Serial # 2424 with latest mods and software) is set up
correctly and would appreciate comments. Output power with CAL CURR set at
3.0 amps is as below. Increasing CAL CURR to 5 amps makes little
difference. I know that the K2 is basically a 10 watt rig and I get more on
some bands, but the upper bands do not achieve this. When using the K2 with
my KW1000 Linear Amplifier a watt or two makes a difference.
80 Meters = 13.0 watts out
40 Meters = 10.0 watts out
30 Meters = 12.0 watts out
20 Meters = 11.0 watts out
15 Meters = 8.0 watts out
12 Meters = 9.5 watts out
10 Meters = 7.0 watts out

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Tom Mc

Re: Low Power ?

In reply to this post by Larry Dodson

Larry,
I wasn't aware of a menu entry limiting power. I have seen and used "Hi
Cur" for current monitoring/limiting. Can you tell me where the power
limiter (and what version of firmware you see it on, perhaps I am using an
earlier version.

Thanks
Tom, WB2QDG
k2 1103

"Today's problems are caused by yesterday's solutions"

-----Original Message-----
From: W3FPR - Don Wilhelm <[hidden email]>
To: Larry Dodson <[hidden email]>; Elecraft reflector
<[hidden email]>
Date: Sunday, September 19, 2004 9:27 AM
Subject: Re: [Elecraft] Low Power ?

Larry,

The K2 is speced for 10 watts out on all bands with a 13.8 volt power
supply, and most are capable of about 12 watts on the higher bands (10/12
meters) and 15 watts on 17 meters and below. Recall that there is a menu
entry (secondary menu) that sets the power limit on 10 meters - it defaults
to 10 watts. If you are checking for maximum power on that band, you may
want to temporarily set that value to 15 watts.

You could first try repeaking the bandpass filters - the K2 typically has
more gain on 40 and 30 meters, so your low 40 meter output gives me
suspicion.

The most common reason for low power output is T2. T2 should be wound so
that the secondary (green wire) is spread over most of the primary turns,
and it should be mounted above the board by about 1/16 inch (2mm). You may
want to download the latest manual and look at the illustration for T2.

Also check T4 - make certain it has the proper number of turns and that it
was not wound for maximum efficiency at 5 watts.

Last but not least, be certain your wattmeter is correct - many are not, and
be certain your dummy load is actually 50 ohms resistive on the band you are
investigating. If you have a calibrated 'scope with a frequency limit of 50
MHz or more, you can check the wattmeter by observing the RF voltage across
the dummy load. Power can be calculated as the square of the Peak to Peak
Voltage divided by 400 for a 50 ohm load (yes, you can do all the peak to
RMS conversions and arrive at the same thing - I will leave the proof to the
'student'). An RF probe can also be used to measure the RF voltage, and in
that case the probe shows RMS voltage and the power is calculated as V**2/R.

73,
Don W3FPR

----- Original Message -----

I wonder if my K2 (Serial # 2424 with latest mods and software) is set up
correctly and would appreciate comments. Output power with CAL CURR set at
3.0 amps is as below. Increasing CAL CURR to 5 amps makes little
difference. I know that the K2 is basically a 10 watt rig and I get more on
some bands, but the upper bands do not achieve this. When using the K2 with
my KW1000 Linear Amplifier a watt or two makes a difference.
80 Meters = 13.0 watts out
40 Meters = 10.0 watts out
30 Meters = 12.0 watts out
20 Meters = 11.0 watts out
15 Meters = 8.0 watts out
12 Meters = 9.5 watts out
10 Meters = 7.0 watts out

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Don Wilhelm-3

Re: Low Power - 10 meter power limit

Tom,

If you have version 2.xx firmware, the 10 meter power limit setting will be
found in the secondary menu. Check the version 2.xx firmware documentation
for details.

73,
Don W3FPR

----- Original Message -----

> I wasn't aware of a menu entry limiting power. I have seen and used "Hi
> Cur" for current monitoring/limiting. Can you tell me where the power
> limiter (and what version of firmware you see it on, perhaps I am using an
> earlier version.

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Ken Wagner K3IU

Re: Low Power - 10 meter power limit

Hi:
I could be wrong but I think that the power limiting on 10 meters is only
active for SSB or Digital modes and not CW.
73,
Ken K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 09:59 AM 9/19/2004, W3FPR - Don Wilhelm wrote:

>Tom,
>
>If you have version 2.xx firmware, the 10 meter power limit setting will
>be found in the secondary menu. Check the version 2.xx firmware
>documentation for details.
>
>73,
>Don W3FPR
>
>----- Original Message -----
>>I wasn't aware of a menu entry limiting power. I have seen and used "Hi
>>Cur" for current monitoring/limiting. Can you tell me where the power
>>limiter (and what version of firmware you see it on, perhaps I am using an
>>earlier version.
>
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

Don Wilhelm-3

Re: Low Power - 10 meter power limit

Ken,

OK, I just checked the docs - you are correct. I do move it up when
checking for max power out because I also do a check on the SSB peaks - I
have done this so often when setting up K2s that it is simply routine for
me. It is not necessary for CW!!

73,
Don W3FPR

----- Original Message -----

> Hi:
> I could be wrong but I think that the power limiting on 10 meters is only
> active for SSB or Digital modes and not CW.
> 73,
> Ken K3IU
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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Bill Coleman-2

Re: Low Power ?

In reply to this post by Larry Dodson

On Sep 19, 2004, at 6:27 AM, Larry Dodson wrote:

> I wonder if my K2 (Serial # 2424 with latest mods and software) is set
> up correctly and would appreciate comments. Output power with CAL
> CURR set at 3.0 amps is as below. Increasing CAL CURR to 5 amps makes
> little difference. I know that the K2 is basically a 10 watt rig and
> I get more on some bands, but the upper bands do not achieve this.
> When using the K2 with my KW1000 Linear Amplifier a watt or two makes
> a difference.
> 80 Meters = 13.0 watts out
> 40 Meters = 10.0 watts out
> 30 Meters = 12.0 watts out
> 20 Meters = 11.0 watts out
> 15 Meters = 8.0 watts out
> 12 Meters = 9.5 watts out
> 10 Meters = 7.0 watts out

I had this problem, too. Mine didn't affect 15m, but I barely had 10
watts on 12m, and just 9.3 watts at the bottom of 10m, with even less
higher in the band.

Gary Surrency suggested a number of things. The first thing is to
re-align the transformers for 17/15m and 12/10m. Make sure they ware
well peaked according to the manual. This got half a watt on 10m.

Next was to re-wind T4, the binocular core in the output of the finals.
Orignally, I had wound it according to the instructions, but since then
they suggested the white and green winding be interleaved on the core.

At this point, I got 9.9 watts at the bottom of 10m, and had little
more to try. Make sure T2 and T1 are wound neatly and spaced slightly
off the board. That will improve high-band performance as well.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Tom Mc

Re: Low Power ?

In reply to this post by Larry Dodson

Hi Bill,
I've read this before about interleaving the windings of T-4, but I didn't
realize that Gary was "officially" suggesting it. Can someone tell me what
"interleaving" means? I must have played hooky that day in class. Is it
sort of twisting the wires like on a bi-filar winding? As I recall the
space inside of T-4 was really pretty tight to begin with.

Thanks
Tom
WB2QDG

When a clock is hungry, does it goes back four seconds?

-----Original Message-----
From: Bill Coleman <[hidden email]>
To: Larry Dodson <[hidden email]>
Cc: [hidden email] <[hidden email]>
Date: Tuesday, September 21, 2004 9:23 PM
Subject: Re: [Elecraft] Low Power ?

On Sep 19, 2004, at 6:27 AM, Larry Dodson wrote:

I had this problem, too. Mine didn't affect 15m, but I barely had 10
watts on 12m, and just 9.3 watts at the bottom of 10m, with even less
higher in the band.

Gary Surrency suggested a number of things. The first thing is to
re-align the transformers for 17/15m and 12/10m. Make sure they ware
well peaked according to the manual. This got half a watt on 10m.

Next was to re-wind T4, the binocular core in the output of the finals.
Orignally, I had wound it according to the instructions, but since then
they suggested the white and green winding be interleaved on the core.

At this point, I got 9.9 watts at the bottom of 10m, and had little
more to try. Make sure T2 and T1 are wound neatly and spaced slightly
off the board. That will improve high-band performance as well.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Bill Coleman-2

Re: Low Power ?

On Sep 21, 2004, at 9:34 PM, Tom Mc wrote:

> I've read this before about interleaving the windings of T-4, but I
> didn't
> realize that Gary was "officially" suggesting it. Can someone tell me
> what
> "interleaving" means? I must have played hooky that day in class. Is
> it
> sort of twisting the wires like on a bi-filar winding? As I recall the
> space inside of T-4 was really pretty tight to begin with.

No, not twisting. Interleaving is simple. Pass one wire through each
hole, then pass the other wire through each hole. Keep alternating
until all the windings are done. As I remember, one winding has more
turns, so start with that wire first.

This is different from the original manual, which suggests you wind one
layer, then the other.

Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901

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Mike Harris-9

Re: Low Power ?

G'day,

> No, not twisting. Interleaving is simple. Pass one wire through each
> hole, then pass the other wire through each hole. Keep alternating
> until all the windings are done. As I remember, one winding has more
> turns, so start with that wire first.
>
> This is different from the original manual, which suggests you wind one
> layer, then the other.

Well this seems overly complicated. What has changed? #1400 has been
throbbing at full power 10W+ on 10 metres since day one.

Another suggestion I have made is not to try and align the BPF's with the
built in power metering. Much easier to get it on the nose with an
external analogy meter like the WM-2 or similar. The meter swing is so
much easier to interpret than dancing digits.

Regards,

Mike VP8NO
#1400

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