K2: Heat On Digital Modes

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K2: Heat On Digital Modes

jperelst
This is a follow-up to a post about two months ago.

I'm still getting pretty high heat on my K2 when running digital modes such as
PSK, Olivia, etc.  Per the recommendation of Don and a few others, I'm adjusting
the K2 so that my desired power output is set on the Power control (25 watts),
and then I'm setting my input gain (using a Signalink) so that (a) I do not
exceed that power on the display and (b) I have one bar on the ALC.

Despite that, the K2 heats up rapidly.  After one or two transmissions of 2-3
minutes each, the K2's fan will stay on high speed for all transmissions and the
top of the K2 is hot to the touch.  As it heats up, people notice drift of +/-
20 Hz (on 20 meters) as the rig warms up during transmit, even with the fan
kicking in.  

The K2 does cool down on long receives, which indicates that the fan is having
some impact, but obviously not enough.  For now I have aimed a desk fan at the
K2 when operating digital and it has reduced the heat and the drift.  

Is all this normal for digital on the K2?  Are there things I should be looking
at that might perhaps be indicating a problem in my build?

 My FT-897, for comparison, does not have any noticeable heat spots even after
long digital transmits of 20 minutes or so (at 25 watts).  Also, on the FT-897 I
can get the ALC down below one bar while still keeping it at 25 watts; on the K2
I can never get it below 1-2 bars of ALC.
 
Note to others -- if you're going to aim a desk fan at the K2, make sure that
you dust first.  It may take a couple of days for me to get all the dust out of
my mouth from when I first turned on the fan.

Jon
KB1QBZ
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Re: K2: Heat On Digital Modes

Don Wilhelm-4
  Jon,

I do not believe your condition has anything to do with digital modes,
but rather sounds like you have a power control problem - it should not
heat up that it is too hot to touch, and not as fast as you indicate.
I assume a K2/100.  If so, please use an external wattmeter to determine
just how much power it is really producing.  Also, see if the power
control properly controls the power?  I am suspecting that you have some
problem with the KPA100 wattmeter (like damaged diodes from a lightning
surge) and it is developing full uncontrolled power output, which for
some KPA100s can be as high as 180 watts.

73,
Don W3FPR

On 9/26/2010 11:42 AM, Jon Perelstein wrote:

> This is a follow-up to a post about two months ago.
>
> I'm still getting pretty high heat on my K2 when running digital modes such as
> PSK, Olivia, etc.  Per the recommendation of Don and a few others, I'm adjusting
> the K2 so that my desired power output is set on the Power control (25 watts),
> and then I'm setting my input gain (using a Signalink) so that (a) I do not
> exceed that power on the display and (b) I have one bar on the ALC.
>
> Despite that, the K2 heats up rapidly.  After one or two transmissions of 2-3
> minutes each, the K2's fan will stay on high speed for all transmissions and the
> top of the K2 is hot to the touch.  As it heats up, people notice drift of +/-
> 20 Hz (on 20 meters) as the rig warms up during transmit, even with the fan
> kicking in.
>
> The K2 does cool down on long receives, which indicates that the fan is having
> some impact, but obviously not enough.  For now I have aimed a desk fan at the
> K2 when operating digital and it has reduced the heat and the drift.
>
> Is all this normal for digital on the K2?  Are there things I should be looking
> at that might perhaps be indicating a problem in my build?
>
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Re: K2: Heat On Digital Modes

jperelst
Don

Thanks for the quick reply.  Fortunately, it appears that uncontrolled power
output is not the problem.

And yes, it is a K2/100.

I connected the rig to an MFJ-941E Versatuner II and connected the Versatuner to
my antenna.  I tuned to a 1.1:1 SWR using the Versatuner and then measured
forward power on CW key down at various power settings.  The forward power
transitioned smoothly from just under 20 watts with the rig set to 20 watts to
just over 90 watts with the rig set to 100 watts.  I probably need to do some
calibration, but it appears that the power control is working.  

I also tried it with PSK and Olivia transmissions and the Versatuner was showing
around 25 watts when I had 25 watts set on the K2's power control.  I upped the
K2s power control to 40 watts and saw an increase in forward power on the
Versatuner to about 35 watts or so.

I can get my hands on a real wattmeter in the next few days if you think it
necessary, but these tests would imply that I am not experiencing uncontrolled
power.

Jon
KB1QBZ
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Re: K2: Heat On Digital Modes

Don Wilhelm-5
  Jon,

Your quick tests are sufficient to negate my initial suspicion.

I would say your next step is to re-do the KPA100 bias adjustment.  If
you have the bias set too high, the PA transistors will heat more than
normal.

Meter the current into the KPA100 - put the K2 into CW test (hold the
VOX button) and make sure the "C" indicator in the display is blinking -
connect a dummy load to the KPA100 'just in case'.  Set power to greater
than 11 watts.  The current draw will be in the vicinity of 500 ma.  
Whatever your external ammeter says, add 400 ma to that - this is your
target value.
The hold TUNE, and look at the ammeter -  If it is a digital meter, wait
until the 2nd reading (blink) because the first value shown may be too
low due to the relative timing of the meter vs the time you pushed the
TUNE button.
The current will go up the longer you remain in TUNE, so obtain the
reading and exit tune - adjust the KPA100 bias up or down a bit and try
again.  Once you have hit your target value, you are done - be sure to
remove the ammeter from the power line.

While you have the shield off the KPA100, you may want to check the
balance on the wattmeter (C1 adjustment) and the power calibration with
reference to a wattmeter that you are willing to trust.

You should be ale to operate the KPA100 at 35 watts continuously without
it getting too hot to touch - yes it will get quite warm, but not too
hot to touch unless you have more sensitive fingers than average.  RTTY
can be considered continuous, PSK31 should be OK up to 50 watts since
the PSK idle has a shorter duty cycle.

If the bias and wattmeter are correct, and you still feel it is getting
warmer than you would like, you might want to try a supplemental fan -
find one from a defunct computer, and run it with a resistor in series
to slow it down so the noise does not irritate.  It can be placed on top
of the heat sink, moving air away and will be quite effective.  See Tom
Hammond's website www.n0ss.net for his implementation.

73,
Don W3FPR

On 9/26/2010 6:49 PM, Jon Perelstein wrote:

> Don
>
> Thanks for the quick reply.  Fortunately, it appears that uncontrolled
> power output is not the problem.
>
> And yes, it is a K2/100.
>
> I connected the rig to an MFJ-941E Versatuner II and connected the
> Versatuner to my antenna.  I tuned to a 1.1:1 SWR using the Versatuner
> and then measured forward power on CW key down at various power
> settings.  The forward power transitioned smoothly from just under 20
> watts with the rig set to 20 watts to just over 90 watts with the rig
> set to 100 watts.  I probably need to do some calibration, but it
> appears that the power control is working.
>
> I also tried it with PSK and Olivia transmissions and the Versatuner
> was showing around 25 watts when I had 25 watts set on the K2's power
> control.  I upped the K2s power control to 40 watts and saw an
> increase in forward power on the Versatuner to about 35 watts or so.
>
> I can get my hands on a real wattmeter in the next few days if you
> think it necessary, but these tests would imply that I am not
> experiencing uncontrolled power.
>
> Jon
> KB1QBZ
>
>
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Re: K2: Heat On Digital Modes

jperelst
Don,

Again, thanks for quick reply.

Guess I know what I'll be doing this weekend.  That's okay, I was going to open
it up anyway to adjust the SSB filters to get narrow filtering for use in
digital modes.

Jon
KB1QBZ



________________________________
From: Don Wilhelm <[hidden email]>
To: Jon Perelstein <[hidden email]>
Cc: elecraft reflector <[hidden email]>
Sent: Sun, September 26, 2010 7:12:49 PM
Subject: Re: [Elecraft] K2:  Heat On Digital Modes

Jon,

Your quick tests are sufficient to negate my initial suspicion.

I would say your next step is to re-do the KPA100 bias adjustment.      If you
have the bias set too high, the PA transistors will heat more     than normal.

Meter the current into the KPA100 - put the K2 into CW test (hold     the VOX
button) and make sure the "C" indicator in the display is     blinking - connect
a dummy load to the KPA100 'just in case'.  Set     power to greater than 11
watts.  The current draw will be in the     vicinity of 500 ma.  Whatever your
external ammeter says, add 400 ma     to that - this is your target value.
The hold TUNE, and look at the ammeter -  If it is a digital meter,     wait
until the 2nd reading (blink) because the first value shown may     be too low
due to the relative timing of the meter vs the time you     pushed the TUNE
button.
The current will go up the longer you remain in TUNE, so obtain the     reading
and exit tune - adjust the KPA100 bias up or down a bit and     try again.  Once
you have hit your target value, you are done - be     sure to remove the ammeter
from the power line.

While you have the shield off the KPA100, you may want to check the     balance
on the wattmeter (C1 adjustment) and the power calibration     with reference to
a wattmeter that you are willing to trust.

You should be ale to operate the KPA100 at 35 watts continuously     without it
getting too hot to touch - yes it will get quite warm,     but not too hot to
touch unless you have more sensitive fingers than     average.  RTTY can be
considered continuous, PSK31 should be OK up     to 50 watts since the PSK idle
has a shorter duty cycle.

If the bias and wattmeter are correct, and you still feel it is     getting
warmer than you would like, you might want to try a     supplemental fan - find
one from a defunct computer, and run it with     a resistor in series to slow it
down so the noise does not     irritate.  It can be placed on top of the heat
sink, moving air away     and will be quite effective.  See Tom Hammond's
website www.n0ss.net for his implementation.

73,
Don W3FPR

On 9/26/2010 6:49 PM, Jon Perelstein wrote:
Don

>
>
>Thanks for the quick reply.  Fortunately, it appears that           uncontrolled
>power output is not the problem.
>
>
>And yes, it is a K2/100.
>
>
>I connected the rig to an MFJ-941E Versatuner II and           connected the
>Versatuner to my antenna.  I tuned to a 1.1:1           SWR using the Versatuner
>and then measured forward power on CW           key down at various power
>settings.  The forward power           transitioned smoothly from just under 20
>watts with the rig           set to 20 watts to just over 90 watts with the rig
>set to 100           watts.  I probably need to do some calibration, but it
>appears           that the power control is working.  
>
>
>I also tried it with PSK and Olivia transmissions and the           Versatuner
>was showing around 25 watts when I had 25 watts set           on the K2's power
>control.  I upped the K2s power control to           40 watts and saw an
>increase in forward power on the           Versatuner to about 35 watts or so.
>
>
>I can get my hands on a real wattmeter in the next few days           if you
>think it necessary, but these tests would imply that I           am not
>experiencing uncontrolled power.
>
>
>Jon
>KB1QBZ
>
>
>
>
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Re: K2: Heat On Digital Modes

Don Wilhelm-4
  John,

Rather than changing the SSB filters for digital modes, activate the
RTTY filter set in the secondary menu.  That gives you a set of filters
(just like the SSB set but with the important difference that the SSBC
menu parameter is independent - always set to 1:1 for digital modes).

I set the RTTY FL1 filter the same as the SSB OP1 for use with a wide
waterfall display, but I set the other 3 to widths of 1.00, 0.70 and
0.40 each centered at 1000 Hz to be able to deal with QRM if the need be
- just tune the desired signal in (with the VFO) to about 1000 Hz on the
waterfall display and switch to the more narrow filters.  With PSK the
narrow filters are seldom necessary, the for RTTY it is often needed -
set the application's mark frequency to 915 Hz and you should be good.

73,
Don W3FPR

On 9/26/2010 9:53 PM, Jon Perelstein wrote:

> Don,
>
> Again, thanks for quick reply.
>
> Guess I know what I'll be doing this weekend.  That's okay, I was going to open
> it up anyway to adjust the SSB filters to get narrow filtering for use in
> digital modes.
>
> Jon
> KB1QBZ
>
>
>
> ________________________________
> From: Don Wilhelm<[hidden email]>
> To: Jon Perelstein<[hidden email]>
> Cc: elecraft reflector<[hidden email]>
> Sent: Sun, September 26, 2010 7:12:49 PM
> Subject: Re: [Elecraft] K2:  Heat On Digital Modes
>
> Jon,
>
> Your quick tests are sufficient to negate my initial suspicion.
>
> I would say your next step is to re-do the KPA100 bias adjustment.      If you
> have the bias set too high, the PA transistors will heat more     than normal.
>
> Meter the current into the KPA100 - put the K2 into CW test (hold     the VOX
> button) and make sure the "C" indicator in the display is     blinking - connect
> a dummy load to the KPA100 'just in case'.  Set     power to greater than 11
> watts.  The current draw will be in the     vicinity of 500 ma.  Whatever your
> external ammeter says, add 400 ma     to that - this is your target value.
> The hold TUNE, and look at the ammeter -  If it is a digital meter,     wait
> until the 2nd reading (blink) because the first value shown may     be too low
> due to the relative timing of the meter vs the time you     pushed the TUNE
> button.
> The current will go up the longer you remain in TUNE, so obtain the     reading
> and exit tune - adjust the KPA100 bias up or down a bit and     try again.  Once
> you have hit your target value, you are done - be     sure to remove the ammeter
> from the power line.
>
> While you have the shield off the KPA100, you may want to check the     balance
> on the wattmeter (C1 adjustment) and the power calibration     with reference to
> a wattmeter that you are willing to trust.
>
> You should be ale to operate the KPA100 at 35 watts continuously     without it
> getting too hot to touch - yes it will get quite warm,     but not too hot to
> touch unless you have more sensitive fingers than     average.  RTTY can be
> considered continuous, PSK31 should be OK up     to 50 watts since the PSK idle
> has a shorter duty cycle.
>
> If the bias and wattmeter are correct, and you still feel it is     getting
> warmer than you would like, you might want to try a     supplemental fan - find
> one from a defunct computer, and run it with     a resistor in series to slow it
> down so the noise does not     irritate.  It can be placed on top of the heat
> sink, moving air away     and will be quite effective.  See Tom Hammond's
> website www.n0ss.net for his implementation.
>
> 73,
> Don W3FPR
>
> On 9/26/2010 6:49 PM, Jon Perelstein wrote:
> Don
>>
>> Thanks for the quick reply.  Fortunately, it appears that           uncontrolled
>> power output is not the problem.
>>
>>
>> And yes, it is a K2/100.
>>
>>
>> I connected the rig to an MFJ-941E Versatuner II and           connected the
>> Versatuner to my antenna.  I tuned to a 1.1:1           SWR using the Versatuner
>> and then measured forward power on CW           key down at various power
>> settings.  The forward power           transitioned smoothly from just under 20
>> watts with the rig           set to 20 watts to just over 90 watts with the rig
>> set to 100           watts.  I probably need to do some calibration, but it
>> appears           that the power control is working.
>>
>>
>> I also tried it with PSK and Olivia transmissions and the           Versatuner
>> was showing around 25 watts when I had 25 watts set           on the K2's power
>> control.  I upped the K2s power control to           40 watts and saw an
>> increase in forward power on the           Versatuner to about 35 watts or so.
>>
>>
>> I can get my hands on a real wattmeter in the next few days           if you
>> think it necessary, but these tests would imply that I           am not
>> experiencing uncontrolled power.
>>
>>
>> Jon
>> KB1QBZ
>>
>>
>>
>>
> ______________________________________________________________
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>
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K2: Filter and BFO Settings for RTTY

jperelst
In reply to this post by jperelst
I'm having a problem with the BFO settings for RTTY.  The outputs on the
different filters are centered at significantly different places in the
waterfall.  For R-Reverse, they're as follows:

Filter      Width            Center on Waterfall
-------      --------             ---------------------------
FL1        2.5 KHz            1.1 KHz
FL2        1.3 KHz            2.0 KHz
FL3        0.6 KHz            1.6 KHz
FL4        0.3 KHz            1.1 KHz


Thus, a station centered at 1.0 KHz on my waterfall when using FL1 is not
visible in the waterfall when using FL2 or FL3, but is again visible when using
FL4.

My understanding from the main K2 manual is that R-Normal is LSB, and R-Reverse
is USB.  Based on that, I used the KSB2 LSB BFO settings for R-Normal and the
KSB2 USB BFO settings for R-Reverse.  The settings for R-Reverse were:

Filter  Width   BFO
-------  --------    ---------
FL1    Op1     4916.3
FL2    1.40     4916.1
FL3    0.70     4915.5
FL4    0.20     4914.7

These R-Reverse BFO settings are the same as I have set with USB.

By comparison, for USB, using the same BFO settings, I get all four filters
centered at about 1.1 KHz.  A station at 1.0 KHz on my waterfall is visible on
FL1, FL2, FL3, and FL4.

I took the measurements with a straight stereo cable from the headphone out to
the line in on my computer.  I also re-did them with a SignaLink USB and got the
same results.  Similarly, I tried both fldigi and DM-780 as my software and got
the same results.

What am I doing wrong?  I didn't find anything in either the K2 Operating Guide
or the KSB2 Operating Guide for any BFO calibrations related  to the RTTY mode.

By the way, I re-did the KPA-100 bias adjustment on my rig and it was pretty
close to correct to begin with.  I did notice that the K2 Operating Guide
recommends against transmitting at more than 10w for more than 1-2 minutes at a
time for continuous duty cycle RTTY/data modes.

As always, thanks for your help,

Jon
KB1QBZ
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Re: K2: Filter and BFO Settings for RTTY

Don Wilhelm-4
  Jon,

The default BFO frequencies for the RTTY filter set will not be optimum
for your K2, you will have to optimize them the same as you must do for
SSB and CW if you are to achieve decent filters.  A note of interest -
due to the varactors that were supplied with K2s over the past year, the
wide (greater than 1.00) filter widths are much greater than that
indicated by the K2 display.  The "cure" is to use Spectrogram (or other
audio spectrum analyzer) to measure the actual width of the filters for
SSB and possibly for RTTY.

I suggest you use Spectrogram to set the filters.  RTTY is not much
different than either the SSB or the CW filters.  See part 3 of the K2
Dial Calibration article on my website www.w3fpr.com for information
about using Spectrogram for filter alignment.

Set FL1 to the OP1 filter since the OP1 filter will be always be used
for transmit.  Set the BFOs for FL1  the same as you have for SSB - yes,
RTTY should be the same as LSB and RTTYr should be the same as USB.  The
low frequency -3dB corner of the filter passband should ce located at
300 Hz.   That will provide you with a full width filter for use with
most PSK31 applications.

I usually set FL2 at a 1.00 kHz bandwidth, FL3 at 0.70, and FL4 at
0.40.  You may vary those if you prefer different widths.
Whatever your chosen widths, set the BFOs for those filters to center on
1000 Hz.  Use Spectrogram to see the filter passband and where it is
positioned.

Those settings will give you narrow filters for PSK31 when there are
strong signals nearby and good narrow filters for RTTY (set the RTTY
application to use 915 Hz as the mark frequency).  When using the narrow
filters, tune the desired signal to the vicinity of 1000 Hz on the
waterfall display using the K2 VFO.

If you have the KDSP2 installed, you must change the DSP RTTY filter AF2
through AF4 center frequencies to center on 1000 Hz to agree with the IF
filter frequencies.  Leave the AF1 setting at LO PASS.

On the RTTY power question, that recommendation you referenced is for
the base K2 without the KPA100.  With the KPA100, you can operate
continuously at 35 watts, or for 1 to 2 minute periods at 70 watts with
no harm.

73,
Don W3FPR


On 10/1/2010 11:20 PM, Jon Perelstein wrote:

> I'm having a problem with the BFO settings for RTTY.  The outputs on the
> different filters are centered at significantly different places in the
> waterfall.  For R-Reverse, they're as follows:
>
> Filter      Width            Center on Waterfall
> -------      --------             ---------------------------
> FL1        2.5 KHz            1.1 KHz
> FL2        1.3 KHz            2.0 KHz
> FL3        0.6 KHz            1.6 KHz
> FL4        0.3 KHz            1.1 KHz
>
>
> Thus, a station centered at 1.0 KHz on my waterfall when using FL1 is not
> visible in the waterfall when using FL2 or FL3, but is again visible when using
> FL4.
>
> My understanding from the main K2 manual is that R-Normal is LSB, and R-Reverse
> is USB.  Based on that, I used the KSB2 LSB BFO settings for R-Normal and the
> KSB2 USB BFO settings for R-Reverse.  The settings for R-Reverse were:
>
> Filter  Width   BFO
> -------  --------    ---------
> FL1    Op1     4916.3
> FL2    1.40     4916.1
> FL3    0.70     4915.5
> FL4    0.20     4914.7
>
> These R-Reverse BFO settings are the same as I have set with USB.
>
> By comparison, for USB, using the same BFO settings, I get all four filters
> centered at about 1.1 KHz.  A station at 1.0 KHz on my waterfall is visible on
> FL1, FL2, FL3, and FL4.
>
> I took the measurements with a straight stereo cable from the headphone out to
> the line in on my computer.  I also re-did them with a SignaLink USB and got the
> same results.  Similarly, I tried both fldigi and DM-780 as my software and got
> the same results.
>
> What am I doing wrong?  I didn't find anything in either the K2 Operating Guide
> or the KSB2 Operating Guide for any BFO calibrations related  to the RTTY mode.
>
> By the way, I re-did the KPA-100 bias adjustment on my rig and it was pretty
> close to correct to begin with.  I did notice that the K2 Operating Guide
> recommends against transmitting at more than 10w for more than 1-2 minutes at a
> time for continuous duty cycle RTTY/data modes.
>
> As always, thanks for your help,
>
> Jon
> KB1QBZ
>
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Re: K2: Filter and BFO Settings for RTTY

jperelst
Don,

Thanks for the response and info.  

The wording in the Operating Manual made me think that the same values are used
for RTTY as for SSB, my mistake.  I used Spectogram (surprisingly easy) and have
everything working nicely now.

On the digital transmission heat issue.  The rig is ok on 1-2 minute digital
transmissions (e.g., 1-2 minutes of PSK at 30 watts).  It'll warm up a bit,
although nothing uncomfortable, and the internal fan can handle it.  The problem
is longer transmissions.  For example, I do a lot of file sending for EmComm
simulations and those transmissions can run 5-10 minutes at a time.  The area
above the power transistors gets very uncomfortable on a long transmission like
that and people notice drift in my transmissions.

For now I've got a desk fan pointed at the rig when doing longer transmissions
and that's keeping the rig cool and stable.   I'll find myself a muffin fan or
smaller desk fan at the next hamfest.

Jon
KB1QBZ



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Re: K2: Filter and BFO Settings for RTTY

Don Wilhelm-4
  Jon,

Look to computer shops for fans from defunct computers - often you can
get them for free.

Put a resistor in series to reduce the fan speed (and noise), and place
the fan over the PA transistor area of the heat sink.  The fan should
pull air away from the heat sink for the most effective cooling.

73,
Don W3FPR

On 10/2/2010 8:54 PM, Jon Perelstein wrote:

> Don,
>
> Thanks for the response and info.
>
> The wording in the Operating Manual made me think that the same values are used
> for RTTY as for SSB, my mistake.  I used Spectogram (surprisingly easy) and have
> everything working nicely now.
>
> On the digital transmission heat issue.  The rig is ok on 1-2 minute digital
> transmissions (e.g., 1-2 minutes of PSK at 30 watts).  It'll warm up a bit,
> although nothing uncomfortable, and the internal fan can handle it.  The problem
> is longer transmissions.  For example, I do a lot of file sending for EmComm
> simulations and those transmissions can run 5-10 minutes at a time.  The area
> above the power transistors gets very uncomfortable on a long transmission like
> that and people notice drift in my transmissions.
>
> For now I've got a desk fan pointed at the rig when doing longer transmissions
> and that's keeping the rig cool and stable.   I'll find myself a muffin fan or
> smaller desk fan at the next hamfest.
>
> Jon
> KB1QBZ
>
>
>
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> Please help support this email list: http://www.qsl.net/donate.html
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Re: K2: Filter and BFO Settings for RTTY

George Winship, NC5G
In reply to this post by jperelst
<quote author="jperelst">

<For now I've got a desk fan pointed at the rig when doing longer transmissions
<and that's keeping the rig cool and stable.   I'll find myself a muffin fan or
<smaller desk fan at the next hamfest.

Jon,

You might want to check out Tom Hammond's web site at www.n0ss.net.  Click on the Elecraft K2 related files, then scroll down to the Auxillary fan for the K2. Might be something that would work for you.

73,

George, NC5G, K2-2217


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</quote>