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KPA500 - Advantage of min fan speed?

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ANDY DURBIN

KPA500 - Advantage of min fan speed?

The KPA500 offers a minimum fan speed setting which is settable by menu or serial command. Some posters have advocated setting a minimum fan speed higher than zero, presumably thinking it offers some advantage in thermal management.

Does anyone have any hard data that shows that the KPA500 runs cooler, or with lower peak fan speed, when minimum fan speed is set above zero.

Running a rigorous test may not be easy since it would seem to require the same ambient temperature, same finals starting temperature, same TX periods, and same antenna system load.

I'm curious because, before CQ-WW-RTTY I configured my KPA500 to set min fan speed to 1 at start of TX and reset min speed to zero 30 seconds after stop of TX. Of course the fans ran faster than min speed during TX but I don't have any feel for whether the higher speeds were any more protracted than before the min speed change.

Please share you experience of using min fan speed greater than zero, and any data if you have it.

73,
Andy, k3wyc

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Michael Walker

Re: KPA500 - Advantage of min fan speed?

Here are the thresholds

level 1: 50 degrees
level 2: 55 degrees
level 3: 60 degrees
level 4: 65 degrees
level 5: 70 degrees
level 6: 80 degrees

if the temperature gets above 90 degrees we throw a fault and drop into standby (with fault showing).

Mike va3mw

> On Sep 29, 2019, at 10:38 PM, Andy Durbin <[hidden email]> wrote:
>
> The KPA500 offers a minimum fan speed setting which is settable by menu or serial command. Some posters have advocated setting a minimum fan speed higher than zero, presumably thinking it offers some advantage in thermal management.
>
> Does anyone have any hard data that shows that the KPA500 runs cooler, or with lower peak fan speed, when minimum fan speed is set above zero.
>
> Running a rigorous test may not be easy since it would seem to require the same ambient temperature, same finals starting temperature, same TX periods, and same antenna system load.
>
> I'm curious because, before CQ-WW-RTTY I configured my KPA500 to set min fan speed to 1 at start of TX and reset min speed to zero 30 seconds after stop of TX. Of course the fans ran faster than min speed during TX but I don't have any feel for whether the higher speeds were any more protracted than before the min speed change.
>
> Please share you experience of using min fan speed greater than zero, and any data if you have it.
>
> 73,
> Andy, k3wyc
>
>
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Jim Brown-10

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

On 9/29/2019 7:38 PM, Andy Durbin wrote:
> Please share you experience of using min fan speed greater than zero, and any data if you have it.

Lots of experience, but I've never bothered to take data. I used my
KPA500 (replaced by KPA1500) a lot for WSJT modes on 6M. The KPA500 fan
gets pretty loud after 15-20 minutes of near constant calling on FT8 or
MSK144, but it takes a lot longer to get that way if a higher minimum
speed is set. The KPA1500 works the same way, except that it gets a LOT
LOUDER at LOT sooner.

Neither amp is noisy enough to be an issue on CW or SSB, even with
fairly heavy HF contest operation. I used the KPA1500 for the first time
in a RTTY contest this weekend. I started hearing the fans speed up
after 10-15 minutes of CQing with not many responses, but they never got
anywhere near the SCREAMING level they hit with digital on 6M.

The fan noise is tolerable because I do 100% of my CW and SSB operation
with headphones, and for SSB it's a Yamaha CM500 with an attached boom
mic. And for serious RTTY contesting, I'm running SO2R, wearing a
headset with one ear dedicated to each radio to help me keep track of
what's happening on each radio.

The significance of 6M is that both amps are least efficient there.

73, Jim K9YC

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Irwin KD3TB

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

During CQWW RTTY this weekend I ran mine at level 3. Normally I keep it at
the NOR setting. When I was in the S&P mode the KPA500 stayed at this
level. When I was in Run mode the KPA500 would occasionally go to the
highest speed when working a pile up. My antennas are pretty much tuned and
I kept my output between 300 & 400 W.

Irwin KD3TB

On Sun, Sep 29, 2019 at 10:40 PM Andy Durbin <[hidden email]> wrote:

> The KPA500 offers a minimum fan speed setting which is settable by menu or
> serial command. Some posters have advocated setting a minimum fan speed
> higher than zero, presumably thinking it offers some advantage in thermal
> management.
>
> Does anyone have any hard data that shows that the KPA500 runs cooler, or
> with lower peak fan speed, when minimum fan speed is set above zero.
>
> Running a rigorous test may not be easy since it would seem to require the
> same ambient temperature, same finals starting temperature, same TX
> periods, and same antenna system load.
>
> I'm curious because, before CQ-WW-RTTY I configured my KPA500 to set min
> fan speed to 1 at start of TX and reset min speed to zero 30 seconds after
> stop of TX. Of course the fans ran faster than min speed during TX but I
> don't have any feel for whether the higher speeds were any more protracted
> than before the min speed change.
>
> Please share you experience of using min fan speed greater than zero, and
> any data if you have it.
>
> 73,
> Andy, k3wyc
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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--
Irwin KD3TB
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Mike Maloney

Re: KPA500 - Advantage of min fan speed?

In reply to this post by Michael Walker

Thanks Mike for the KPA-500 fan level settings. That answers the question I was going to ask. Could find no fan level info in the owners manual or from previous posts.I don't suppose any record kept of SPL readings at the different levels? Anyone done that?
73, Mike AC5P

On Sunday, September 29, 2019, 10:08:41 PM CDT, Michael Walker <[hidden email]> wrote:

Here are the thresholds

level 1: 50 degrees
level 2: 55 degrees
level 3: 60 degrees
level 4: 65 degrees
level 5: 70 degrees
level 6: 80 degrees

if the temperature gets above 90 degrees we throw a fault and drop into standby (with fault showing).

Mike va3mw

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Michael Walker

Re: KPA500 - Advantage of min fan speed?

I got the thresholds from Elecraft directly.

I never worried too much about them since the Elecraft guys are pretty
smart people and likely have done a lot more research on this than most of
us.

Mike va3mw

On Mon, Sep 30, 2019 at 9:28 AM Mike Maloney <[hidden email]> wrote:

> Thanks Mike for the KPA-500 fan level settings. That answers the question
> I was going to ask. Could find no fan level info in the owners manual or
> from previous posts.
> I don't suppose any record kept of SPL readings at the different levels?
> Anyone done that?
>
> 73, Mike AC5P
>
>
> On Sunday, September 29, 2019, 10:08:41 PM CDT, Michael Walker <
> [hidden email]> wrote:
>
>
> Here are the thresholds
>
>
> level 1: 50 degrees
> level 2: 55 degrees
> level 3: 60 degrees
> level 4: 65 degrees
> level 5: 70 degrees
> level 6: 80 degrees
>
> if the temperature gets above 90 degrees we throw a fault and drop into
> standby (with fault showing).
>
> Mike va3mw
>
> > On Sep 29, 2019, at 10:38 PM, Andy Durbin <[hidden email]> wrote:
> >
> > The KPA500 offers a minimum fan speed setting which is settable by menu
> or serial command. Some posters have advocated setting a minimum fan speed
> higher than zero, presumably thinking it offers some advantage in thermal
> management.
> >
> > Does anyone have any hard data that shows that the KPA500 runs cooler,
> or with lower peak fan speed, when minimum fan speed is set above zero.
> >
> > Running a rigorous test may not be easy since it would seem to require
> the same ambient temperature, same finals starting temperature, same TX
> periods, and same antenna system load.
> >
> > I'm curious because, before CQ-WW-RTTY I configured my KPA500 to set min
> fan speed to 1 at start of TX and reset min speed to zero 30 seconds after
> stop of TX. Of course the fans ran faster than min speed during TX but I
> don't have any feel for whether the higher speeds were any more protracted
> than before the min speed change.
> >
> > Please share you experience of using min fan speed greater than zero,
> and any data if you have it.
> >
> > 73,
> > Andy, k3wyc
> >
> >
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]
>
> ______________________________________________________________
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ANDY DURBIN

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

"I got the thresholds from Elecraft directly.
I never worried too much about them since the Elecraft guys are pretty smart people and likely have done a lot more research on this than most of us."

That's possible but they only gave you half the information. The thresholds you quoted are for increasing temperature. The fan speed step down thresholds are lower than the step up thresholds. (I have experimental data for fan speeds up to, and including, 5 but have never seen 6 except when I set min speed to 6 to hear how loud it was.)

I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed greater than zero.

73,
Andy, k3wyc

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Don Wilhelm

Re: KPA500 - Advantage of min fan speed?

Andy,

Physical fact related to any heat dissipating object -- if you apply an
air stream across the object, it will not come up to a given temperature
as quickly as having no air stream across it.

Specifically for the amp, if you run the fan speed minimum at 1, it will
heat to the 55 degC threshold more slowly before switching to level 2.
Of course, from there on up to higher temperatures, there will be the
same time period between the higher fan speed steps.

In other words, the fan minimum will NOT shift the entire range of
thresholds, but it WILL delay the time to reach the level 2 threshold.

73,
Don W3FPR

On 9/30/2019 1:13 PM, Andy Durbin wrote:
>
> I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed greater than zero.
>
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George Thornton

Re: KPA500 - Advantage of min fan speed?

From a physics standpoint, heat is radiated from an object either by direct radiation of heat into space (photons) or by transfer of heat to an adjacent object with lower temperature.

For heat transfer to another object, the amount transferred depends substantially on the heat absorbing characteristics of the object. Some objects are natural insulators and will result in little heat transfer. Air is not an insulator but it is not as effective as water, which is 24 times as heat absorbing as air.

The surface area of contact is also important. Moving air across a hot surface increases the exposure of cooler air to the hot surface resulting in faster cooling. In other words a faster fan will always cool more than a slower fan.

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Don Wilhelm
Sent: Monday, September 30, 2019 10:28 AM
To: Andy Durbin <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] KPA500 - Advantage of min fan speed?

Andy,

Physical fact related to any heat dissipating object -- if you apply an air stream across the object, it will not come up to a given temperature as quickly as having no air stream across it.

Specifically for the amp, if you run the fan speed minimum at 1, it will heat to the 55 degC threshold more slowly before switching to level 2.
Of course, from there on up to higher temperatures, there will be the same time period between the higher fan speed steps.

In other words, the fan minimum will NOT shift the entire range of thresholds, but it WILL delay the time to reach the level 2 threshold.

73,
Don W3FPR

On 9/30/2019 1:13 PM, Andy Durbin wrote:
>
> I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed greater than zero.
>
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Michael Walker

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

Andy

I would call Elecraft and ask them directly. Unless they respond directly here in the forum everyone is just guessing

Mike

> On Sep 30, 2019, at 1:13 PM, Andy Durbin <[hidden email]> wrote:
>
> "I got the thresholds from Elecraft directly.
> I never worried too much about them since the Elecraft guys are pretty smart people and likely have done a lot more research on this than most of us."
>
> That's possible but they only gave you half the information. The thresholds you quoted are for increasing temperature. The fan speed step down thresholds are lower than the step up thresholds. (I have experimental data for fan speeds up to, and including, 5 but have never seen 6 except when I set min speed to 6 to hear how loud it was.)
>
> I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed greater than zero.
>
> 73,
> Andy, k3wyc
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
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k6dgw

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

When running RTTY with the KPA500 I no longer have, I noticed that, with
a minimum fan speed greater than zero, the temp tended to fall lower
during RX periods than when the min speed was zero. During the
subsequent TX period, having started from a lower temp, it would not
rise as high, keeping the fan speed one step lower by the end of the TX
period. I assume this was because there is significant thermal
"inertia" in the amplifier but thermodynamics was never my best
subject. RTTY operation tends to have a regular-ish pattern of on-off,
I never noticed the fan going to high on CW. I suppose the FT modes
would present an even more regular pattern.

All anecdotal Andy, I didn't bother to take any data.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 9/29/2019 7:38 PM, Andy Durbin wrote:

> The KPA500 offers a minimum fan speed setting which is settable by menu or serial command. Some posters have advocated setting a minimum fan speed higher than zero, presumably thinking it offers some advantage in thermal management.
>
> Does anyone have any hard data that shows that the KPA500 runs cooler, or with lower peak fan speed, when minimum fan speed is set above zero.
>
> Running a rigorous test may not be easy since it would seem to require the same ambient temperature, same finals starting temperature, same TX periods, and same antenna system load.
>
> I'm curious because, before CQ-WW-RTTY I configured my KPA500 to set min fan speed to 1 at start of TX and reset min speed to zero 30 seconds after stop of TX. Of course the fans ran faster than min speed during TX but I don't have any feel for whether the higher speeds were any more protracted than before the min speed change.
>
> Please share you experience of using min fan speed greater than zero, and any data if you have it.
>
> 73,
> Andy, k3wyc
>

Elecraft mailing list

Re: KPA500 - Advantage of min fan speed?

In reply to this post by Michael Walker

All you guys had to do was ask. When going down, the hysteresis is 3 degrees. That means that each threshold is shifted down 3 degrees.
The hysteresis is necessary to keep the fan speed from bouncing up and down when the temperature is at one of the switch points.

73!
Jack, W6FB

> On Sep 30, 2019, at 10:57 AM, Michael Walker <[hidden email]> wrote:
>
> Andy
>
> I would call Elecraft and ask them directly. Unless they respond directly here in the forum everyone is just guessing
>
> Mike
>
>
>
>> On Sep 30, 2019, at 1:13 PM, Andy Durbin <[hidden email]> wrote:
>>
>> "I got the thresholds from Elecraft directly.
>> I never worried too much about them since the Elecraft guys are pretty smart people and likely have done a lot more research on this than most of us."
>>
>> That's possible but they only gave you half the information. The thresholds you quoted are for increasing temperature. The fan speed step down thresholds are lower than the step up thresholds. (I have experimental data for fan speeds up to, and including, 5 but have never seen 6 except when I set min speed to 6 to hear how loud it was.)
>>
>> I measured the fan speed thresholds over a year ago but that information doesn't answer the question about any operation advantage of running min speed greater than zero.
>>
>> 73,
>> Andy, k3wyc
>>
>>
>>
>>
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> ______________________________________________________________
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ANDY DURBIN

Fw: KPA500 - Advantage of min fan speed?

In reply to this post by Don Wilhelm

Don,

Two test cases -

Case 1:
Ambient temperature 28 deg C, KPA500 OPER mode but no TX in over 12 hours, fan speed zero, PA temp 35 deg C.

Case 2:
Ambient temperature 28 deg C, KPA500 OPER mode but no TX in over 12 hours, fan speed 1 run for long enough to stabilize PA temperature, PA temp 29 deg C.

Fan 1 continuous operation has pre-cooled the KPA500 PA by 6 deg C (measured data).

It's obvious that that the start of the the first high power "run" cycle will have a later onset of fan 2 if the KPA500 has been pre-cooled at FS 1. What is not obvious is whether there will be any sustained advantage if the "run" continues. If the "run" never allows the temperature to drop to fan speed 1 there would appear to be no operational advantage to the pre-cool at fan speed 1.

For a S&P duty cycle each TX would likely have delayed fan speed increases. However, that advantage has to be offset by the noise of fan 1 when no cooling was required.

Andy, k3wyc

________________________________
From: Don Wilhelm <[hidden email]>
Sent: Monday, September 30, 2019 10:28 AM
To: Andy Durbin <[hidden email]>; [hidden email] <[hidden email]>
Subject: Re: [Elecraft] KPA500 - Advantage of min fan speed?

Andy,

Physical fact related to any heat dissipating object -- if you apply an
air stream across the object, it will not come up to a given temperature
as quickly as having no air stream across it.

Specifically for the amp, if you run the fan speed minimum at 1, it will
heat to the 55 degC threshold more slowly before switching to level 2.
Of course, from there on up to higher temperatures, there will be the
same time period between the higher fan speed steps.

In other words, the fan minimum will NOT shift the entire range of
thresholds, but it WILL delay the time to reach the level 2 threshold.

73,
Don W3FPR

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ANDY DURBIN

Re: KPA500 - Advantage of min fan speed?

Thanks to everyone who contributed their experience of operating with min fan speed set above 0.

I have some ideas for a test series and I'll share anything I learn from it.

Here is a teaser for those interested in KPA500 thermal management. Did you know that, for a KPA500 that has not transmitted for a long time, the Z bracket is hotter than the heat sink and the heat sink is hotter than the finals. For that condition the heat flow is from the Z bracket, into the heat sink, and then it heats the finals. The heat flow reversed during TX as the finals heat up.

73,
Andy, k3wyc
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Lyn WØLEN

Re: KPA500 - Advantage of min fan speed?

I have been following this discussion with some interest. This morning I
set the idling fan speed to 1, and after sitting at the same desk with it
for a couple hours, I am really no longer conscious of the noise (I have
other things happening).

The non-operating temp has settled in at 28ºC.

And now, after 5 consecutive 15 second JS8 transmissions, and running at 275
watts, the temp has risen to 59ºC and no change in fan speed. After the 6th
consecutive transmission, the temp rises to 62ºF and the fan goes to #2.

Temps after each 15 second interval are 37, 44, 50, 55, 59 and 62ºC
respectively.

With the fan at "Norm," the temp settles in at 31ºC.

Running the same test, temps after each 15 second interval are 39, 44, 49,
53 56 and 59ºC - so it never goes to #2.

The bottom line seems to be that there is nothing gained by setting the
minimum fan speed at #1. In fact, you might make the case that running the
fan unnecessarily will just add more dust to the interior over time and thus
reduce the long-term cooling efficiency.

Of course, the ambient temp in your environment will skew these results.

73,
Lyn, WØLEN

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Andy Durbin
Sent: Tuesday, October 01, 2019 11:52 AM
To: [hidden email]
Subject: Re: [Elecraft] KPA500 - Advantage of min fan speed?

Thanks to everyone who contributed their experience of operating with min
fan speed set above 0.

I have some ideas for a test series and I'll share anything I learn from it.

Here is a teaser for those interested in KPA500 thermal management. Did you
know that, for a KPA500 that has not transmitted for a long time, the Z
bracket is hotter than the heat sink and the heat sink is hotter than the
finals. For that condition the heat flow is from the Z bracket, into the
heat sink, and then it heats the finals. The heat flow reversed during TX
as the finals heat up.

73,
Andy, k3wyc
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Bob McGraw - K4TAX

Re: KPA500 - Advantage of min fan speed?

In reply to this post by ANDY DURBIN

For SSB voice operation and CW operation I leave the fan speed at
NORMAL.   For digital modes, which all have a higher duty cycle, I
usually set the fan speed to 1.   I do find the fan speed increments up
and down as needed and as driven by the temperature.   When running 400
to 500 watts most of the time for digital modes, I occasionally see 60
degrees.   The fan speed at 1 does not elevate the room noise at all.
In fact, I don't hear it, although I do have sound damping material on
the wall immediately behind the equipment. Usually something in the
house or shack is making more noise.

As to if setting the fan speed to 1 for digital modes, it seems to keep
the amp temperatures overall a bit lower. No scientific study conducted.

73

Bob, K4TAX

On 10/1/2019 11:51 AM, Andy Durbin wrote:

> Thanks to everyone who contributed their experience of operating with min fan speed set above 0.
>
> I have some ideas for a test series and I'll share anything I learn from it.
>
> Here is a teaser for those interested in KPA500 thermal management. Did you know that, for a KPA500 that has not transmitted for a long time, the Z bracket is hotter than the heat sink and the heat sink is hotter than the finals. For that condition the heat flow is from the Z bracket, into the heat sink, and then it heats the finals. The heat flow reversed during TX as the finals heat up.
>
> 73,
> Andy, k3wyc
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

WB4SON

Re: KPA500 - Advantage of min fan speed?

Personally, I wish Elecraft offered a slightly different approach, rather
than a minimum fan speed setting, how about a RX minimum and TX minimum?
This would allow quiet operation on RX, but would anticipate a higher
demand for cooling on TX.

There is quite a bit of thermal mass and overshoot that happens in TX on
digital modes. By the time the fan turns on, it tends to be running behind
the curve trying to catch up. Starting the fan running as soon as the rig
goes into TX would help considerably and allow things to go back to quiet
in RX.

73, Bob, WB4SON

On Tue, Oct 1, 2019 at 4:58 PM Bob McGraw K4TAX <[hidden email]> wrote:

> For SSB voice operation and CW operation I leave the fan speed at
> NORMAL. For digital modes, which all have a higher duty cycle, I
> usually set the fan speed to 1. I do find the fan speed increments up
> and down as needed and as driven by the temperature. When running 400
> to 500 watts most of the time for digital modes, I occasionally see 60
> degrees. The fan speed at 1 does not elevate the room noise at all.
> In fact, I don't hear it, although I do have sound damping material on
> the wall immediately behind the equipment. Usually something in the
> house or shack is making more noise.
>
> As to if setting the fan speed to 1 for digital modes, it seems to keep
> the amp temperatures overall a bit lower. No scientific study conducted.
>
> 73
>
> Bob, K4TAX
>
> On 10/1/2019 11:51 AM, Andy Durbin wrote:
> > Thanks to everyone who contributed their experience of operating with
> min fan speed set above 0.
> >
> > I have some ideas for a test series and I'll share anything I learn from
> it.
> >
> > Here is a teaser for those interested in KPA500 thermal management. Did
> you know that, for a KPA500 that has not transmitted for a long time, the Z
> bracket is hotter than the heat sink and the heat sink is hotter than the
> finals. For that condition the heat flow is from the Z bracket, into the
> heat sink, and then it heats the finals. The heat flow reversed during TX
> as the finals heat up.
> >
> > 73,
> > Andy, k3wyc
> > ______________________________________________________________
> > 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
> > Message delivered to [hidden email]
> >
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

73, Bob, WB4SON

Bob McGraw - K4TAX

Re: KPA500 - Advantage of min fan speed?

Personally I think it works great as designed. Yes there could be changes but I doubt we'd see much, if any difference in performance.

Hams today in general seem to delight in complaining. I find many should look in a mirror to identify the source of an issue. I'm one that believes in keeping things simple.

Bob, K4TAX

Sent from my iPhone

> On Oct 2, 2019, at 9:12 AM, Bob <[hidden email]> wrote:
>
> Personally, I wish Elecraft offered a slightly different approach, rather
> than a minimum fan speed setting, how about a RX minimum and TX minimum?
> This would allow quiet operation on RX, but would anticipate a higher
> demand for cooling on TX.
>
> There is quite a bit of thermal mass and overshoot that happens in TX on
> digital modes. By the time the fan turns on, it tends to be running behind
> the curve trying to catch up. Starting the fan running as soon as the rig
> goes into TX would help considerably and allow things to go back to quiet
> in RX.
>
> 73, Bob, WB4SON
>
>
>> On Tue, Oct 1, 2019 at 4:58 PM Bob McGraw K4TAX <[hidden email]> wrote:
>>
>> For SSB voice operation and CW operation I leave the fan speed at
>> NORMAL. For digital modes, which all have a higher duty cycle, I
>> usually set the fan speed to 1. I do find the fan speed increments up
>> and down as needed and as driven by the temperature. When running 400
>> to 500 watts most of the time for digital modes, I occasionally see 60
>> degrees. The fan speed at 1 does not elevate the room noise at all.
>> In fact, I don't hear it, although I do have sound damping material on
>> the wall immediately behind the equipment. Usually something in the
>> house or shack is making more noise.
>>
>> As to if setting the fan speed to 1 for digital modes, it seems to keep
>> the amp temperatures overall a bit lower. No scientific study conducted.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>> On 10/1/2019 11:51 AM, Andy Durbin wrote:
>>> Thanks to everyone who contributed their experience of operating with
>> min fan speed set above 0.
>>>
>>> I have some ideas for a test series and I'll share anything I learn from
>> it.
>>>
>>> Here is a teaser for those interested in KPA500 thermal management. Did
>> you know that, for a KPA500 that has not transmitted for a long time, the Z
>> bracket is hotter than the heat sink and the heat sink is hotter than the
>> finals. For that condition the heat flow is from the Z bracket, into the
>> heat sink, and then it heats the finals. The heat flow reversed during TX
>> as the finals heat up.
>>>
>>> 73,
>>> Andy, k3wyc
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>>
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Don Wilhelm

Re: KPA500 - Advantage of min fan speed?

In reply to this post by WB4SON

Bob,

The problem with that is the fan must continue to run for some time
after the return to RX so the residual heat from the TX cycle can be
reduced.

73,
Don W3FPR

On 10/2/2019 10:12 AM, Bob wrote:

> Personally, I wish Elecraft offered a slightly different approach, rather
> than a minimum fan speed setting, how about a RX minimum and TX minimum?
> This would allow quiet operation on RX, but would anticipate a higher
> demand for cooling on TX.
>
> There is quite a bit of thermal mass and overshoot that happens in TX on
> digital modes. By the time the fan turns on, it tends to be running behind
> the curve trying to catch up. Starting the fan running as soon as the rig
> goes into TX would help considerably and allow things to go back to quiet
> in RX.
>

Bob McGraw - K4TAX

Re: KPA500 - Advantage of min fan speed?

Thermal lag exists and likely always will. The hysteresis is reasonably adequate in the present configuration.

I find no objection to the performance of the present method of cooling.

Bob, K4TAX

Sent from my iPhone

> On Oct 2, 2019, at 9:46 AM, Don Wilhelm <[hidden email]> wrote:
>
> Bob,
>
> The problem with that is the fan must continue to run for some time after the return to RX so the residual heat from the TX cycle can be reduced.
>
> 73,
> Don W3FPR
>
>> On 10/2/2019 10:12 AM, Bob wrote:
>> Personally, I wish Elecraft offered a slightly different approach, rather
>> than a minimum fan speed setting, how about a RX minimum and TX minimum?
>> This would allow quiet operation on RX, but would anticipate a higher
>> demand for cooling on TX.
>> There is quite a bit of thermal mass and overshoot that happens in TX on
>> digital modes. By the time the fan turns on, it tends to be running behind
>> the curve trying to catch up. Starting the fan running as soon as the rig
>> goes into TX would help considerably and allow things to go back to quiet
>> in RX.
> ______________________________________________________________
> 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
> Message delivered to [hidden email]