Some "Cool" heat sink info.

[hhoyt]

Hi all,

Johnny, VR2XMC wrote:

>>It should not?be any rocket science, all you need is a piece of thick metal plate
>>to suck the heat from the PA transistors and with fins to facilitate air circulation.


You are right: a thick piece of metal will sink the heat from the PA
transistors.  But how thick?  Too thin and there is little benefit. Too
thick and the stored heat in the metal mass actually inhibits recovery
time after a heating event.

How many fins?  How tall? How far apart?  And what combination of all of
these gives the most benefit at a targeted small size?

You are right: it is not rocket science, but a dismissive attitude
towards the importance of learning the interaction between the variables
leads to some of the poorly-performing (not to mention ugly) designs I
have seen hung off of several KX3s.  I also happen to agree with
Elecraft's design criteria which is the same as just about all
amateur-radio gear made:  100% power on CW and SSB, 50% power on digital
modes.  To upgrade this to commercial broadcast equipment performance of
100% duty cycle in all modes would greatly increase the price and size.  
If someone wants more power and xmit time in digital they can always buy
a heatsink, and the cost of doing so is not added to the KX3 for 90% of
the purchasers who do not need it.

More info on my website www.proaudioeng.com if you are interested,

Howie - WA4PSC

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[Fred Townsend-2]

Howard you and Johnny are right. It is not rocket science but it is thermodynamics. There are many nuances... conduction, radiation, and convection. Often optimizing for one may diminish another characteristics. There are many trade-offs. Copper is a better conductor of heat flux than aluminum but it adds more weight. Black bodies radiate heat faster than than bare metal but they also absorb heat from sunlight faster so do you optimize for dark or sunlight?

I think the good news take away is this an easy area to do your own experiments and homebrew. You don't even need a thermometer. It's already there. Thank you Elecraft.
73
Fred, AE6QL (The other Fred)

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

>From: Howard Hoyt <[hidden email]>
>Sent: Aug 13, 2014 10:55 AM
>To: [hidden email]
>Subject: [Elecraft] Some "Cool" heat sink info.
>
>Hi all,
>
>Johnny, VR2XMC wrote:
>
>>>It should not?be any rocket science, all you need is a piece of thick metal plate
>>>to suck the heat from the PA transistors and with fins to facilitate air circulation.
>
>
>You are right: a thick piece of metal will sink the heat from the PA
>transistors.  But how thick?  Too thin and there is little benefit. Too
>thick and the stored heat in the metal mass actually inhibits recovery
>time after a heating event.
>
>How many fins?  How tall? How far apart?  And what combination of all of
>these gives the most benefit at a targeted small size?
>
>You are right: it is not rocket science, but a dismissive attitude
>towards the importance of learning the interaction between the variables
>leads to some of the poorly-performing (not to mention ugly) designs I
>have seen hung off of several KX3s.  I also happen to agree with
>Elecraft's design criteria which is the same as just about all
>amateur-radio gear made:  100% power on CW and SSB, 50% power on digital
>modes.  To upgrade this to commercial broadcast equipment performance of
>100% duty cycle in all modes would greatly increase the price and size.  
>If someone wants more power and xmit time in digital they can always buy
>a heatsink, and the cost of doing so is not added to the KX3 for 90% of
>the purchasers who do not need it.
>
>More info on my website www.proaudioeng.com if you are interested,
>
>Howie - WA4PSC
>
>______________________________________________________________
>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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[Edward R Cole]

From: Gerald Wilson <[hidden email]>
To: [hidden email]
Subject: [Elecraft] Some "Cool" heat sink info.
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=utf-8

It is a little long but has some good info and surprising results in it.

https://www.youtube.com/watch?feature=player_embedded&v=8ML1tRnUIZo

73,
KF5JNU
----------------

Pretty basic side-by-side test.

What it tells me is the thermal mass of the heat sink is more
significant  than the  interface between radio and heat sink.  Both
are aluminum, I assume, so thermal conductivity is probably the same.

I would have expected a uncoated smooth surface interface would work
better, but in this example apparently no difference is detectable.

I have one of the "Coo!er KX" heat sinks installed on my KX3.
http://www.ve7fmn.ca/

I was an early buyer so Fred has done quite a bit of development
since I bought mine.  I opted for the unpainted bare aluminum,
thinking it might conduct a bit better.

The you-tube demo would suggest it may not have any significant
difference from the powder-coated heat sink which looks nicer.

I performed the Elecraft Thermal Compensation Procedure on my KX3 and
then ran some heat vs frequency tests using 5w RF output on 6m:
http://www.kl7uw.com/KX3.htm
http://www.kl7uw.com/KX3_FREQ_DRIFT_TABLE.pdf

Note the first ten curves were done before performing Temp
Compensation. Frequency drift is up to 30-Hz in one minute
key-down.  After the Compensation drift is most noticeable in the
first couple minutes and tames to 5-Hz after 15-minutes running.  The
frequency "bump" at 20-seconds running is probably due to a bad data
point in the Temp. Comp. curve so I plan to repeat the Temp. Comp. Procedure.

I do not have curves published after installing the heat sink but
drift drops to about 2-Hz, after the first three sequences from a
cold-start.  I will repeat these tests for the 2M module.  Regarding
drift at HF I would expect it to be proportionately less as Frequency is lower.


73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

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[Johnny Siu]

Hello Howard,

Thanks for useful information in your web site www.proaudioeng.com which is interesting (the portable power supply for KX3 looks cool)

I must admit that English is my second language and sometimes I may not choose the right words.  I have no intention to bad mouth any specific design / R&D on KX3 heat sinks available in the commercial market.  In fact, I eventually bought a KB8UHN heat sink, which is a commercial product, for my KX3.  The heat sink suits my purpose of prolong operation in FM mode in 10/6m under full power.

As a ham, I trust some of them may like to do their own experiment in building their own heat sinks (since it is not a rocket science).  Doing experiment at a fraction of the cost could give some satisfaction to the investigating minds.

In my case, I did some experiment on fitting different 'amateur' heat sinks.  Clearly, the result was not that successful and I eventually settled down on a heat sink available from the commercial market.

I have been adopting that kind of 'experimenting' attitude for ham radio for years,  Sometimes, I succeed but there were many times when I completely failed.

The most successful experiment in my case is that I found a Panasonic boom headset at US$25 which gave me excellent audio reports so that I eventually sold all my Heils (no disgrace to Heil products).

73

Johnny VR2XMC

 
 寄件人︰ Howard Hoyt <[hidden email]>
收件人︰ [hidden email]
傳送日期︰ 2014年08月14日 (週四) 1:55 AM
主題︰ [Elecraft] Some "Cool" heat sink info.
 

Hi all,

Johnny, VR2XMC wrote:

>>It should not?be any rocket science, all you need is a piece of thick metal plate
>>to suck the heat from the PA transistors and with fins to facilitate air circulation.


You are right: a thick piece of metal will sink the heat from the PA
transistors.  But how thick?  Too thin and there is little benefit. Too
thick and the stored heat in the metal mass actually inhibits recovery
time after a heating event.

How many fins?  How tall? How far apart?  And what combination of all of
these gives the most benefit at a targeted small size?

You are right: it is not rocket science, but a dismissive attitude
towards the importance of learning the interaction between the variables
leads to some of the poorly-performing (not to mention ugly) designs I
have seen hung off of several KX3s.  I also happen to agree with
Elecraft's design criteria which is the same as just about all
amateur-radio gear made:  100% power on CW and SSB, 50% power on digital
modes.  To upgrade this to commercial broadcast equipment performance of
100% duty cycle in all modes would greatly increase the price and size. 
If someone wants more power and xmit time in digital they can always buy
a heatsink, and the cost of doing so is not added to the KX3 for 90% of
the purchasers who do not need it.

More info on my website www.proaudioeng.com if you are interested,

Howie - WA4PSC

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[g8kbvdave]

You can also of course, use a minature 12V fan (CPU cooler type for example) to
waft some extra air over either the back of an unmodified KX3, or any of the
after market heatsinks if you need extra cooling, or the environment is
somewhat warm.

Even a low speed (audiably quiet) fan will have a marked effect for the better,
for minimal extra 12V current load.   Remember to decouple the motor, else you
might hear fan related rumble or buzzing sounds in headphones etc.  (I've not
tried this by the way, just sayin'.)

73.

Dave G0WBX.

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