Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
I'm always a little wary about changing a design. I ask myself: what was in the designer's mind when he did this? What characteristic was he trying to achieve and what information did he have that I do not? Consult the fan design and see how its rating varies with pressure on one side or the other. The air flow rate drops dramatically from its headline advertised value as soon as it encounters any back pressure in front of it and with restriction on the inlet side. The manufacturer should know which is best for his product. There are lots of fan types about and some are better at sucking than blowing. David G3UNA From: Darwin, Keith [EMAIL PROTECTED] Date: 2006/12/06 Wed PM 03:08:22 GMT To: elecraft@mailman.qth.net Subject: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100? Very key point. If you want to take heat out of a box, you're far better to point the fans out and let them draw in cool air from the other side than to point the fan in and blow cool air in. Here's why. When you blow a fan into a box (K2, PC, or your house in the summer) you're blowing into a confined space and the pressure goes up. That increase in pressure fights against the fan and reduces the amount of air that flows. Mechanical efficiency and air transfer go down. Turn the fan around and blow it out of the box into the universe. The outside world cannot be pressurized by the fan so the fan moves air more effectively. And I believe the air being blown into the box helps to set up dead zones where hot air can pool up. The flow through the box is better in the exhaust case. I've tested the theory both with my computer and with using fans to cool my house in the summer. In both cases, better cooling is achieved with fans blowing out than in. Makes me wonder about reversing the fan in the K2. It just might make it more effective and allow it to say on low longer. I have to open it up to tighten the HW and insert one more shield spring so I'll get another chance to give it a good lookin' over. - Keith N1AS - - K2 5411.ssb.100 - -Original Message- From: Don Wilhelm The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 - Email sent from www.ntlworld.com Virus-checked using McAfee(R) Software Visit www.ntlworld.com/security for more information ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
[Elecraft] Re: Elecraft Thermal control for Q1 / Q2 in KPA100
Keith, I have never had the fan in my KPA100 activate, it never gets warm enough here in Southern Ontario. I doubt that your New England temperatures are much different than here. Forget about the fan operation and use your K2/100. 73, Bob VE3XM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
At 10:08 AM 12/6/2006, Darwin, Keith wrote... Very key point. If you want to take heat out of a box, you're far better to point the fans out and let them draw in cool air from the other side than to point the fan in and blow cool air in. Here's why. When you blow a fan into a box (K2, PC, or your house in the summer) you're blowing into a confined space and the pressure goes up. That increase in pressure fights against the fan and reduces the amount of air that flows. It's not that simple. How does the fan know which side is confined? It's not a matter of pressure fights the fan in only one case - it's equally valid to say that vacuum fights in the other. A fan is a pump, which creates a pressure differential. At the extreme, one can only achieve a suction equal to atmospheric pressure, while the amount of pressure can be virtually unlimited. So, in the extreme case, more flow can be achieved by blowing than by sucking. For the application at hand, it doesn't make much difference to total airflow whether the fan is sucking or blowing - the fan is limited by the pressure differential it can create. Whether that differential is between atmospheric and a (very) slight vacuum, or atmospheric and a (very) slight pressure simply doesn't make any practical difference. For electronics, airflow direction may be determined by the available fan location(s), and a desire to have the most heat sensitive components receive the coolest airflow. Another consideration is that by having the fan blow into the device, all airflow through the device travels through a well defined area - so it can be easily filtered. Pressurizing the enclosure is the preferred method, since incoming air can be readily filtered. In addition, a pressurized enclosure will prevent dust entering through cracks or crevices. The fan is also handling cooler, denser air, and it will therefore have a slightly higher pressure capability (this may be a very slight advantage for low heat dissipating systems). An important feature of a pressurized system is that the fan life and reliability are increased due to the fan ambient temperature being lower. The disadvantage of pressurization is that heat generated by the fan is dissipated into the enclosure. - Mike Turner, Comar Rotron (a major fan manufacturer) - http://www.electronics-cooling.com/Resources/EC_Articles/MAY96/may96_01.htm ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
David G3UNA wrote: Consult the fan design and see how its rating varies with pressure on one side or the other. The air flow rate drops dramatically from its headline advertised value as soon as it encounters any back pressure in front of it and with restriction on the inlet side. - The restriction on the inlet side that David mentions would include the effect of any air filter. This might appear to be obvious, but it does mean that the filter has has to be cleaned when necessary to maintain proper air flow, a task often forgotten. I believe that air cooling systems should include air filters whenever possible. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Also finger grills and panel slots create turbulence which can drastically reduce flow. For a common or garden 'computer' type of fan, a dust filter can practically stop air flow all together, so, choose with care. David G3UNA - Original Message - From: Geoffrey Mackenzie-Kennedy [EMAIL PROTECTED] To: Elecraft Discussion List elecraft@mailman.qth.net Sent: Thursday, December 07, 2006 1:05 PM Subject: Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100? David G3UNA wrote: Consult the fan design and see how its rating varies with pressure on one side or the other. The air flow rate drops dramatically from its headline advertised value as soon as it encounters any back pressure in front of it and with restriction on the inlet side. - The restriction on the inlet side that David mentions would include the effect of any air filter. This might appear to be obvious, but it does mean that the filter has has to be cleaned when necessary to maintain proper air flow, a task often forgotten. I believe that air cooling systems should include air filters whenever possible. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Indeed, turbulence can reduce flow. I must confess that I have no experience with using a 'computer' type of fan to cool rigs. 73, Geoff GM4ESD - Original Message - From: David Cutter [EMAIL PROTECTED] To: Geoffrey Mackenzie-Kennedy [EMAIL PROTECTED]; Elecraft Discussion List elecraft@mailman.qth.net Sent: Thursday, December 07, 2006 1:43 PM Subject: Re: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100? Also finger grills and panel slots create turbulence which can drastically reduce flow. For a common or garden 'computer' type of fan, a dust filter can practically stop air flow all together, so, choose with care. David G3UNA ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
A designer will take into account which parts he wants to cool first. For instance, if a sensitive component (vfo?) is on the cool side of the draught then it will not be affected by a hot component down stream. However, if the direction is reversed you could be creating a problem that wasn't there before. David G3UNA - Original Message - From: Darwin, Keith [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Wednesday, December 06, 2006 3:08 PM Subject: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100? Very key point. If you want to take heat out of a box, you're far better to point the fans out and let them draw in cool air from the other side than to point the fan in and blow cool air in. Here's why. When you blow a fan into a box (K2, PC, or your house in the summer) you're blowing into a confined space and the pressure goes up. That increase in pressure fights against the fan and reduces the amount of air that flows. Mechanical efficiency and air transfer go down. Turn the fan around and blow it out of the box into the universe. The outside world cannot be pressurized by the fan so the fan moves air more effectively. And I believe the air being blown into the box helps to set up dead zones where hot air can pool up. The flow through the box is better in the exhaust case. I've tested the theory both with my computer and with using fans to cool my house in the summer. In both cases, better cooling is achieved with fans blowing out than in. Makes me wonder about reversing the fan in the K2. It just might make it more effective and allow it to say on low longer. I have to open it up to tighten the HW and insert one more shield spring so I'll get another chance to give it a good lookin' over. - Keith N1AS - - K2 5411.ssb.100 - -Original Message- From: Don Wilhelm The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
-Original Message- From: Stan Rife From the description of the noise that the fan on your KPA-100 is making, I'd guess you have a defective fan. I never hear the fan on my KPA-100. I have a pretty quiet shack, and operate with the volume fairly low on the K2 and I have only noticed the fan running a few times. -- On low speed I don't hear the fan at all. On high it is definitely heard. It is louder than some but not all computer muffin fans I've had. As a musician I love a noisy fan. As a ham, I don't. One of my gripes about the IC-735 was the fan noise. One of the things I love about TenTec stuff is that they need no fan. Well, the one's I've owned didn't. Of course the K2 is a small package with a small heat sink. Ya gotta get rid of the heat somehow and a fan is the way to do it given the size constraints of the system. I'm wondering about using a larger (quieter) fan with some sort of duct system to get the airflow from the fan to the fan-port on the back of the rig. It could be run off the same fan wires that run the mini-whizzer and would probably move more air. The first step with be to run a bit reduced power and see what that gives me. If it continues to be a annoyance, I'll plop a muffin fan on top to keep 'er cool quiet. - Keith N1AS - - K2 5411.ssb.100 - ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Hi Dave: You wrote, regarding the KPA100 cooling fan... I note it blows air INTO the KPA, but there doesn't appear to be much by way of provision for the warmed air to get out, so I guess oscillators are going to move around quite a bit when the warm air circulates around and around. The 'cooling' air exits out the top of the KPA100 assembly, at the front of the heatsink fins AND out the bottom of the K2 case. Pretty LOW VOLUME. Maybe a nice, quiet ex-computer muffin fan sitting on top of the heatsink might be a better way of cooling the PA? I've made a cooling 'plenum' for my K2, using a very lo-profile cover and a tiny muffin fan from a CPU cooler. It pulls cool air in from outside across most of the heatsink fins and exhausts straight up. I can supply illustrations and some info on the design if you, or anyone else might be interested. Cheers, Tom N0SS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Tom, Yes, we should all see what you have created. How about a photo and a short note on your website (no need for a .pdf file IMHO). Such an addition is great for those running digital modes and is nice to have when operating hot and heavy during a contest. As you have pointed out, it is important that the fan moves air upward so it aids the flow from the internal fan rather than blowing air onto the heat sink. Just laying a muffin fan on top of the heat sink is effective as a 'quick and dirty' solution, your plenum sounds like a great permanent addition for those instances where there is not a lot of free-air space above the K2/100. The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. 73, Don W3FPR -Original Message- I've made a cooling 'plenum' for my K2, using a very lo-profile cover and a tiny muffin fan from a CPU cooler. It pulls cool air in from outside across most of the heatsink fins and exhausts straight up. I can supply illustrations and some info on the design if you, or anyone else might be interested. Cheers, Tom N0SS -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.9/571 - Release Date: 12/5/2006 11:50 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Very key point. If you want to take heat out of a box, you're far better to point the fans out and let them draw in cool air from the other side than to point the fan in and blow cool air in. Here's why. When you blow a fan into a box (K2, PC, or your house in the summer) you're blowing into a confined space and the pressure goes up. That increase in pressure fights against the fan and reduces the amount of air that flows. Mechanical efficiency and air transfer go down. Turn the fan around and blow it out of the box into the universe. The outside world cannot be pressurized by the fan so the fan moves air more effectively. And I believe the air being blown into the box helps to set up dead zones where hot air can pool up. The flow through the box is better in the exhaust case. I've tested the theory both with my computer and with using fans to cool my house in the summer. In both cases, better cooling is achieved with fans blowing out than in. Makes me wonder about reversing the fan in the K2. It just might make it more effective and allow it to say on low longer. I have to open it up to tighten the HW and insert one more shield spring so I'll get another chance to give it a good lookin' over. - Keith N1AS - - K2 5411.ssb.100 - -Original Message- From: Don Wilhelm The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
G'day, | The fact that an exhaust fan flow cools objects better than blowing air onto | a surface is a bit counter-intuitive because standing in the downstream side | of a fan feels cooler to the skin - but that is only because of evaporation. | Careful measurement will show that the cooling effectiveness for an object | like a heat sink is more effective by moving the heated air away from the | object. Getting the heat away is the objective, and blowing on it is less | effective than exhausting the heated air. Never seen a suction cooled external anode HPA, from single 4CX250's to 10kW Klystrons. I've used a small PC fan blowing onto the right hand side of the heatsink, front to rear, inclined about 45 degrees. During 10-12 hour QRSS beacon runs at 40W o/p the little fan never came on and the heatsink was room temperature. A bladed fan is easy to stall if there is any restriction to throughput. Regards, Mike VP8NO ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Don, et al: I've now placed the PDF of my KPA100 Cooling Fan Enclosure on my web site (www.n0ss.net). The PDF is located in the K2 Specific Files section of the page, about 3/4 of the way down the page. The fan shown in the illustrations came from a CPU cooler.. It's much smaller than most PC cooling fans, but just about anything will work pretty well is seems. The PDF contains hole cutting and drilling info for both 92mm and 80mm square muffin fans. I originally had an 80mm square fan installed, but when I scavenged the tiny CPU cooler fan, I installed it using a cover plate which mounted in the 80mm fan mounting holes. I have two fan speeds... The low speed suffices for about 90% of my operation and the higher speed is used when I'm contesting and want a bit more cooling. The KPA100's fan seldom comes on, and when it does, it's on for a very short length of time... and everything(!) stays nice 'n cool. The cooling enclosure is low profile and extends all the way to the back of the KPA100 heatsink, so cool air is drawn over a large area of the fins. Additionally, the enclosure extends just ahead of the front of the heatsink, so it draws air OUT of the K2 case via the vents in front of the heatsink (vents actually 'made' by the heatsink and the cover plate just ahead of it). 73, Tom N0SS At 08:38 AM 12/6/2006, Don Wilhelm wrote: Tom, Yes, we should all see what you have created. How about a photo and a short note on your website (no need for a .pdf file IMHO). Such an addition is great for those running digital modes and is nice to have when operating hot and heavy during a contest. As you have pointed out, it is important that the fan moves air upward so it aids the flow from the internal fan rather than blowing air onto the heat sink. Just laying a muffin fan on top of the heat sink is effective as a 'quick and dirty' solution, your plenum sounds like a great permanent addition for those instances where there is not a lot of free-air space above the K2/100. The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. 73, Don W3FPR -Original Message- I've made a cooling 'plenum' for my K2, using a very lo-profile cover and a tiny muffin fan from a CPU cooler. It pulls cool air in from outside across most of the heatsink fins and exhausts straight up. I can supply illustrations and some info on the design if you, or anyone else might be interested. Cheers, Tom N0SS -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.9/571 - Release Date: 12/5/2006 11:50 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
The question of grease vs. pads came up before and Eric answered it as follows: We officially recommend that you use the thermal pads supplied with the KPA100 kit instead of grease. They consist of a very efficient thermally conductive compound coated on both sides a a very thin aluminum sheet. The compound reflows when the transistors get hot the first time and fills all of the small air gaps between the devices and the heatsink. It is very effective and provides a better thermal bond in most cases than manual application of thermal grease. 73, Eric WA6HHQ Elecraft = You aren't the only one to be bothered by what I call the whizzer on the back of the K2, although I confess I'm getting used to it. Sort of... The fan doesn't just blow air into the box, it forces air into the space between the KPA100 shield and the KPA100 heat sink, which includes the KPA100 PCB of course. The air exits at the end of the heat sink nearest the front panel, flowing out through the spaces between the heat sink fins. One thing some builders have done is to put a large muffin fan on top of the heat sink. A larger, slower speed fan should be a lot quieter. Of course, how quickly the fan comes on depends upon the ambient temperature in the shack and the duty cycle as well as the power level and efficiency of the finals. I don't know if anyone has run tests to see what the minimum fan action has to be, but I know that I've run tests with my K2/100 that involved keying it so much I couldn't leave my hand on the heat sink. No harm was done to the KPA100 in those tests. Ron AC7AC -Original Message- As I'm thinking about trying to operate the K2/100 so the fan doesn't run (or doesn't make noise) I wonder some things. First, blowing air out of a box cools the box better than blowing air into it. I'm half surprised the fan blows in. I suppose it is to direct the stream of air on the finals. Still, I wonder about doing it differently. What about thermal grease? There is only a non-grease pad between the transistors and the heat sink. Would a dab of grease conduct more heat away from the transistor? I have some fancy silver stuff left over from my computer assembly activities. What power level should I run if I don't want the fan to come on? 75 Watts? 50, 30, 12? - Keith N1AS - - K2 5411.ssb.100 - ___ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Hi Keith, The thermal pads actually conduct more heat away than thermal grease. The pads used these days are quite impressive. A couple of years ago an engineer Friend of mine and I had this discussion and he then went out and dug up enough data to have me buried for a week. Tom W8AMZ Darwin, Keith [EMAIL PROTECTED] wrote: As I'm thinking about trying to operate the K2/100 so the fan doesn't run (or doesn't make noise) I wonder some things. First, blowing air out of a box cools the box better than blowing air into it. I'm half surprised the fan blows in. I suppose it is to direct the stream of air on the finals. Still, I wonder about doing it differently. What about thermal grease? There is only a non-grease pad between the transistors and the heat sink. Would a dab of grease conduct more heat away from the transistor? I have some fancy silver stuff left over from my computer assembly activities. What power level should I run if I don't want the fan to come on? 75 Watts? 50, 30, 12? - Keith N1AS - - K2 5411.ssb.100 - ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Whizzer - what a good name. It actually startled me when it came on and the noise interfered a bit with copy of the weak station I was working. I may have to go to closed headphones. The MEs here at work tell me similar things. Some of the pads are better than grease. Good, grease is a PITN (neck) to work with. I'm also glad to hear the pad reflows when it gets hot the first time. That answers a concern I had that maybe things just aren't tight enough yet. I have a few muffin fans left over from a PC build-up. I think I'll set something up. The 60 deg air in my basement plus some fan-action should keep the whizzer under control ... Thanks Ron others. 73! - Keith N1AS - - K2 5411.ssb.100 - -Original Message- From: Ron D'Eau Claire [mailto:[EMAIL PROTECTED] You aren't the only one to be bothered by what I call the whizzer on the back of the K2, although I confess I'm getting used to it. Sort of... ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
I was playing around with the KAT100 a couple of nights ago and was leaving the K2/100 on tune for periods of 15 - 20 seconds at a time (20W) at intervals through several bands. After a few minutes, the whizzer fired up its engine, so if your average Tx power is 20W then you have maybe 5 mins before the little hovercraft starts up. I note it blows air INTO the KPA, but there doesn't appear to be much by way of provision for the warmed air to get out, so I guess oscillators are going to move around quite a bit when the warm air circulates around and around. Maybe a nice, quiet ex-computer muffin fan sitting on top of the heatsink might be a better way of cooling the PA? 73 Dave L G3TJP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
Dave, In heat removal, the name of the game is air circulation, which is different than just 'blowing air' - there must be an escape path for the heated air. In the KPA100 that path is from the back to the front of the unit, the air escapes through the heatsink fins just behind the top of the front panel. If you have something (even a piece of paper) on top of the KPA100, it will block this air flow and reduce the cooling capacity - which in turn will cause the fan to come on earlier than expected. If you have the KAT100 stacked on top of the KPA100 I suggest changing things to place the KAT100 below the K2/100. An easy way to add an auxiliary fan to the KPA100 is to place a muffin fan on top of the heat sink - pulling air away from the heat sink. Even a slow moving fan will help, a DC fan salvaged from a computer will do nicely and you can slow it down with a series resistor. 73, Don W3FPR -Original Message- I was playing around with the KAT100 a couple of nights ago and was leaving the K2/100 on tune for periods of 15 - 20 seconds at a time (20W) at intervals through several bands. After a few minutes, the whizzer fired up its engine, so if your average Tx power is 20W then you have maybe 5 mins before the little hovercraft starts up. I note it blows air INTO the KPA, but there doesn't appear to be much by way of provision for the warmed air to get out, so I guess oscillators are going to move around quite a bit when the warm air circulates around and around. Maybe a nice, quiet ex-computer muffin fan sitting on top of the heatsink might be a better way of cooling the PA? 73 Dave L G3TJP -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.15.9/571 - Release Date: 12/5/2006 11:50 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
David Lankshear wrote: I note it blows air INTO the KPA, but there doesn't appear to be much by way of provision for the warmed air to get out, so I guess oscillators are going to move around quite a bit when the warm air circulates around and around. Maybe a nice, quiet ex-computer muffin fan sitting on top of the heatsink might be a better way of cooling the PA? The air gets out at the front of the heatsink, and blows across the fins a bit. I like mine to run extra cool, so I attached a muffin fan to the right side of the heatsink, sucking air up through the fins. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100?
From the description of the noise that the fan on your KPA-100 is making, I'd guess you have a defective fan. I never hear the fan on my KPA-100. I have a pretty quiet shack, and operate with the volume fairly low on the K2 and I have only noticed the fan running a few times. Stan Rife W5EWA Houston, TX K2 S/N 4216 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Darwin, Keith Sent: Tuesday, December 05, 2006 12:52 PM To: elecraft@mailman.qth.net Subject: RE: [Elecraft] Thermal control for Q1 / Q2 in KPA100? Whizzer - what a good name. It actually startled me when it came on and the noise interfered a bit with copy of the weak station I was working. I may have to go to closed headphones. The MEs here at work tell me similar things. Some of the pads are better than grease. Good, grease is a PITN (neck) to work with. I'm also glad to hear the pad reflows when it gets hot the first time. That answers a concern I had that maybe things just aren't tight enough yet. I have a few muffin fans left over from a PC build-up. I think I'll set something up. The 60 deg air in my basement plus some fan-action should keep the whizzer under control ... Thanks Ron others. 73! - Keith N1AS - - K2 5411.ssb.100 - -Original Message- From: Ron D'Eau Claire [mailto:[EMAIL PROTECTED] You aren't the only one to be bothered by what I call the whizzer on the back of the K2, although I confess I'm getting used to it. Sort of... ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
