Elecraft

Re: KPA1500 PIN diode T/R, fans

Classic

List

Threaded

4 messages Options

wayne burdick

Re: KPA1500 PIN diode T/R, fans

Administrator

Hi Paul,

To protect the amp and T/R switch, we’re using heavy-duty PIN diodes, very high reverse voltage, and virtually instantaneous detection of high SWR. All possible catastrophic load scenarios have been extensively tested.

On fans:

We started with a humongous custom heat sink extrusion and thick copper spreader, optimized for our packaging. We also use two LDMOS devices rather than one, allowing heat to be distributed across all that heavy metal much more effectively. This slows fan onset time. (Some competing compact amps use inadequate heat sinking, with predictable results.)

Next, we added three large, deep fans. The center fan is controlled independently so it can turn on first, at low speed. In many cases that's all you'll ever hear. Only during high duty-cycle operation are the other two fans turned on. We then carefully manage the speed of all three.

Ultimately, you have to get rid of the heat. But our goal is always to minimize noise.

73,
Wayne
N6KR

>
> *From: *"Paul Christensen"
>
> Wayne,
>
> Congrats on what looks like a very well-designed amp. I've been
> waiting on
> an amp with these features for a very long time. Of particular
> interest to
> me is your continued use of PIN diode T/R switching. Can you describe SWR
> protection to the Rx PIN diodes at the 1.5KW level? I suspect that a
> fast-detecting SWR switch will be the main focus of protection, as well as
> HV back-biasing of the Rx diodes. An open or short RF termination
> requires
> over 900V DC to keep Rx PIN diodes from going into conduction. Can you
> describe this area of circuit protection just a bit?
>
> Secondly, I know that fan noise is difficult to quantify in words.
> Anything
> particularly innovative you're going to minimize cooling noise? Thanks!
>
> Paul, W9AC
>
>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> ______________________________________________________________
> 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]

Clay Autery

Re: KPA1500 PIN diode T/R, fans

Yep!!! Thermal Design.... you can bend the rules of physics, but one
cannot break them.

Yet another reason beyond packaging to put the power supply in a
separate package.

Sounds like an excellent engineering approach/trade-off.

And the three fully exposed/unobstructed fans on the back panel are
almost begging for custom ductwork to deliver nice 76 F (24.4 C) air
supply (lightly pressurized via HVAC). Less fan "on" time and
mitigation for fan noise...

Lot of flexibility to supplement thermal control if you're obsessive
like me.... or not.... if you're normal like most folks. :-)

73,

______________________
Clay Autery, KY5G

On 4/21/2017 2:25 PM, Wayne Burdick wrote:

> Hi Paul,
>
> To protect the amp and T/R switch, we’re using heavy-duty PIN diodes, very high reverse voltage, and virtually instantaneous detection of high SWR. All possible catastrophic load scenarios have been extensively tested.
>
> On fans:
>
> We started with a humongous custom heat sink extrusion and thick copper spreader, optimized for our packaging. We also use two LDMOS devices rather than one, allowing heat to be distributed across all that heavy metal much more effectively. This slows fan onset time. (Some competing compact amps use inadequate heat sinking, with predictable results.)
>
> Next, we added three large, deep fans. The center fan is controlled independently so it can turn on first, at low speed. In many cases that's all you'll ever hear. Only during high duty-cycle operation are the other two fans turned on. We then carefully manage the speed of all three.
>
> Ultimately, you have to get rid of the heat. But our goal is always to minimize noise.
>
> 73,
> Wayne
> N6KR

Bill K9YEQ

Re: KPA1500 PIN diode T/R, fans

In reply to this post by wayne burdick

This is impossible to resist buying. Sell the car, the house, the Wife... nope on the last.

73,
Bill
K9YEQ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Wayne Burdick
Sent: Friday, April 21, 2017 2:25 PM
To: Elecraft <[hidden email]>
Subject: Re: [Elecraft] KPA1500 PIN diode T/R, fans

Hi Paul,

To protect the amp and T/R switch, we’re using heavy-duty PIN diodes, very high reverse voltage, and virtually instantaneous detection of high SWR. All possible catastrophic load scenarios have been extensively tested.

On fans:

We started with a humongous custom heat sink extrusion and thick copper spreader, optimized for our packaging. We also use two LDMOS devices rather than one, allowing heat to be distributed across all that heavy metal much more effectively. This slows fan onset time. (Some competing compact amps use inadequate heat sinking, with predictable results.)

Next, we added three large, deep fans. The center fan is controlled independently so it can turn on first, at low speed. In many cases that's all you'll ever hear. Only during high duty-cycle operation are the other two fans turned on. We then carefully manage the speed of all three.

Ultimately, you have to get rid of the heat. But our goal is always to minimize noise.

73,
Wayne
N6KR

>
> *From: *"Paul Christensen"
>
> Wayne,
>
> Congrats on what looks like a very well-designed amp. I've been
> waiting on an amp with these features for a very long time. Of
> particular interest to me is your continued use of PIN diode T/R
> switching. Can you describe SWR protection to the Rx PIN diodes at
> the 1.5KW level? I suspect that a fast-detecting SWR switch will be
> the main focus of protection, as well as HV back-biasing of the Rx
> diodes. An open or short RF termination requires over 900V DC to keep
> Rx PIN diodes from going into conduction. Can you describe this area
> of circuit protection just a bit?
>
> Secondly, I know that fan noise is difficult to quantify in words.
> Anything
> particularly innovative you're going to minimize cooling noise? Thanks!
>
> Paul, W9AC
>
>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> ______________________________________________________________
> 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]

Nr4c

Re: KPA1500 PIN diode T/R, fans

You should be able to one of those items. You pick!

Sent from my iPhone
...nr4c. bill

> On Apr 21, 2017, at 6:15 PM, Bill Johnson <[hidden email]> wrote:
>
> This is impossible to resist buying. Sell the car, the house, the Wife... nope on the last.
>
> 73,
> Bill
> K9YEQ
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Wayne Burdick
> Sent: Friday, April 21, 2017 2:25 PM
> To: Elecraft <[hidden email]>
> Subject: Re: [Elecraft] KPA1500 PIN diode T/R, fans
>
> Hi Paul,
>
> To protect the amp and T/R switch, we’re using heavy-duty PIN diodes, very high reverse voltage, and virtually instantaneous detection of high SWR. All possible catastrophic load scenarios have been extensively tested.
>
> On fans:
>
> We started with a humongous custom heat sink extrusion and thick copper spreader, optimized for our packaging. We also use two LDMOS devices rather than one, allowing heat to be distributed across all that heavy metal much more effectively. This slows fan onset time. (Some competing compact amps use inadequate heat sinking, with predictable results.)
>
> Next, we added three large, deep fans. The center fan is controlled independently so it can turn on first, at low speed. In many cases that's all you'll ever hear. Only during high duty-cycle operation are the other two fans turned on. We then carefully manage the speed of all three.
>
> Ultimately, you have to get rid of the heat. But our goal is always to minimize noise.
>
> 73,
> Wayne
> N6KR
>
>
>>
>> *From: *"Paul Christensen"
>>
>> Wayne,
>>
>> Congrats on what looks like a very well-designed amp. I've been
>> waiting on an amp with these features for a very long time. Of
>> particular interest to me is your continued use of PIN diode T/R
>> switching. Can you describe SWR protection to the Rx PIN diodes at
>> the 1.5KW level? I suspect that a fast-detecting SWR switch will be
>> the main focus of protection, as well as HV back-biasing of the Rx
>> diodes. An open or short RF termination requires over 900V DC to keep
>> Rx PIN diodes from going into conduction. Can you describe this area
>> of circuit protection just a bit?
>>
>> Secondly, I know that fan noise is difficult to quantify in words.
>> Anything
>> particularly innovative you're going to minimize cooling noise? Thanks!
>>
>> Paul, W9AC
>>
>>
>>
>>
>> ---
>> This email has been checked for viruses by Av