Re: [Elecraft] LDMOS for QRO [OT]
Thanks for showing us that, Gerry, be nice to see more of the water works. Do you have any pics of the build? David G3UNA - Original Message - From: Gerry Hull To: David Cutter Cc: Reflector Elecraft Sent: Tuesday, December 16, 2014 3:19 AM Subject: Re: [Elecraft] LDMOS for QRO [OT] Here's a 144MHz 1.5Kw water-cooled LDMOS amplifier putting out full power in a June VHF contest, with me operating at W2SZ/1. It was a cloudy day, and the amp was so cool, in fact, we were worried about condensation. Look at the size! The power supply is a 50v/50a surplus PC supply off of ebay. The amp was built by Brian Justin, WA1ZMS. I have found cold plates on the surplus market. Every once in a while, Electronic Surplus Sales in Manchester, NH has em. Amp in Action: https://www.youtube.com/watch?v=vegBv6ddAUA 73 Gerry Hull, W1VE | Hancock, NH USA On Sun, Dec 14, 2014 at 6:32 PM, David Cutter d.cut...@ntlworld.com wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
Hopefully the manufacturers will produce GAN devices that operate that low in frequency. Currently available ones do 3GHz and above. I have one producing 50W at 10Ghz and another 70W at 3.4GHz neither will even go down to 1.2GHz Dave G4FRE Date: Sun, 14 Dec 2014 08:53:24 -0700 From: Myron WV?H myronschaf...@gmail.com To: Kevin Stover kevin.sto...@mediacombb.net Cc: elecraft@mailman.qth.net elecraft@mailman.qth.net Subject: Re: [Elecraft] LDMOS for QRO Message-ID: 5524275a-b2d7-4a9d-86bf-d0e9f1bc0...@gmail.com Content-Type: text/plain; charset=utf-8 Soon GaN will hold possibilities. Myron WV?H Printed on Recycled Data __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
If one wanted to use one of these to cool an LDMOS VHF KW, where would one find the design info to calculate which cold plate would provide sufficient cooling ? I envision a stack something like this: LDMOS PC Board Copper Heatsink (thickness need be determined) Cold Plate Aluminum Heat Sink (is this really necessary ?). 73 es HH, Dick, W1KSZ On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to w1...@earthlink.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
Unless you want to run fresh water down the drain (in Arizona we don't do this) you have to get the heat into the air someplace. I'm not sure that running water lines to outside air is much easier than getting coax through a concrete wall. Speaking of difficult, the U.S. Navy AIM-54A Phoenix Missile which with I was intimately familiar, used oil (Coolanol) cooling. Chassis were mounted on cold plates and the vacuum tube modulator and pulse transformer were immersed in oil and it also circulated through the PA klystron. Lines ran from the missile umbilical to the wing or belly mounted launchers then to the F4 aircraft where a conditioning unit resided. The stuff was insidious to work with. I ruined lots of clothes, And it was hygroscopic, just the thing to use on a ship-borne system. Wes N7WS On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
Hi Dick Start from the LDMOS data sheet and work out the temperature you wish to keep within at the junction. Because water cooling is so good, you can choose either to run the device cooler than you would with air cooling to improve reliability, or stick to the same temperature and get more power / use a smaller cooling plate / use less water. There's a direct relationship between reliability and temperature, but it's not linear. Then use the temperature rise per W rating of the device to get to the surface temperature. In work I did 10 years ago all devices were directly bolted to the liquid-cooled plate without an intermediate spreader, however, these LDMOS devices are so small (ie very high heat density) there is a good reason to spread the heat out first before cooling proper takes place, I'm somewhat hazy what thickness, but you must achieve good flatness of contact against the plate. Some very large devices eg IGBTs and rectifiers the size of your open hand are supplied curved and the bolting-down process achieves the flatness with the correct torque setting on the bolts. Then you do the same sums as you do with air cooling ie temperature rise v watts dissipated from the heat sink data. Say you want to dissipate 1kW of heat continuously (eg in a data contest) then a small 2 pass model would give you around 90 to 100K rise at the surface of the plate with 1 US gallon per minute, whereas a 4 pass model would give you around 20K rise on a 152mm length plate. This of course assumes that the heat is being delivered into the plate evenly over the whole surface, ie using a spreader. Heat sink paste adds a little to the thermal gradient and is needed in very small amounts, evenly spread. Do the sums several times with different criteria until you get to the one you feel comfortable with. If you live in a cold climate you can dump the heat into a small central heating radiator to keep the shack warm and no fans required just an aquarian pump to run it; if you live in a hot place, then put the radiator on the shade side of the house or even bury it. If water is abundant, eg river water or a pond, you can re-cycle it back to the source. You can make your own water cooling plate, see here a small example cooling a dozen TO-220 devices: https://www.youtube.com/watch?v=WGpau-raMho Somebody here will check my sums I'm sure. 73 David G3UNA - Original Message - From: Richard Solomon w1...@earthlink.net To: elecraft@mailman.qth.net Sent: Tuesday, December 16, 2014 4:44 PM Subject: Re: [Elecraft] LDMOS for QRO [OT] If one wanted to use one of these to cool an LDMOS VHF KW, where would one find the design info to calculate which cold plate would provide sufficient cooling ? I envision a stack something like this: LDMOS PC Board Copper Heatsink (thickness need be determined) Cold Plate Aluminum Heat Sink (is this really necessary ?). 73 es HH, Dick, W1KSZ On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
This is really a fascinating idea. I have noticed that there are water cooling kits made for computer CPU's. Some of the bigger CPU's run over 225 watts of power. I wonder how applicable one those CPU kits might be. They include a heat sink, pump and radiator. 73, Doug -- K0DXV On 12/16/2014 11:10 AM, David Cutter wrote: Hi Dick Start from the LDMOS data sheet and work out the temperature you wish to keep within at the junction. Because water cooling is so good, you can choose either to run the device cooler than you would with air cooling to improve reliability, or stick to the same temperature and get more power / use a smaller cooling plate / use less water. There's a direct relationship between reliability and temperature, but it's not linear. Then use the temperature rise per W rating of the device to get to the surface temperature. In work I did 10 years ago all devices were directly bolted to the liquid-cooled plate without an intermediate spreader, however, these LDMOS devices are so small (ie very high heat density) there is a good reason to spread the heat out first before cooling proper takes place, I'm somewhat hazy what thickness, but you must achieve good flatness of contact against the plate. Some very large devices eg IGBTs and rectifiers the size of your open hand are supplied curved and the bolting-down process achieves the flatness with the correct torque setting on the bolts. Then you do the same sums as you do with air cooling ie temperature rise v watts dissipated from the heat sink data. Say you want to dissipate 1kW of heat continuously (eg in a data contest) then a small 2 pass model would give you around 90 to 100K rise at the surface of the plate with 1 US gallon per minute, whereas a 4 pass model would give you around 20K rise on a 152mm length plate. This of course assumes that the heat is being delivered into the plate evenly over the whole surface, ie using a spreader. Heat sink paste adds a little to the thermal gradient and is needed in very small amounts, evenly spread. Do the sums several times with different criteria until you get to the one you feel comfortable with. If you live in a cold climate you can dump the heat into a small central heating radiator to keep the shack warm and no fans required just an aquarian pump to run it; if you live in a hot place, then put the radiator on the shade side of the house or even bury it. If water is abundant, eg river water or a pond, you can re-cycle it back to the source. You can make your own water cooling plate, see here a small example cooling a dozen TO-220 devices: https://www.youtube.com/watch?v=WGpau-raMho Somebody here will check my sums I'm sure. 73 David G3UNA - Original Message - From: Richard Solomon w1...@earthlink.net To: elecraft@mailman.qth.net Sent: Tuesday, December 16, 2014 4:44 PM Subject: Re: [Elecraft] LDMOS for QRO [OT] If one wanted to use one of these to cool an LDMOS VHF KW, where would one find the design info to calculate which cold plate would provide sufficient cooling ? I envision a stack something like this: LDMOS PC Board Copper Heatsink (thickness need be determined) Cold Plate Aluminum Heat Sink (is this really necessary ?). 73 es HH, Dick, W1KSZ On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to k0...@aol.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
What might be even more interesting is mineral oil immersion cooling. You would still need a heatsink to conduct heat away from the PA device(s) but the advantage to oil immersion cooling is that it can also efficiently cool all the other parts such as Low pass filter coils, Voltage regulators, power supply etc. It's becoming a thing in High performance computing for servers http://www.datacenterknowledge.com/archives/2012/09/04/intel-explores-mineral-oil-cooling/ I guess one of the questions at RF is how much the dielectric constant of the oil will change things and if it's enough that it needs to be taken into account at the design phase. For our application the thermal mass of the oil combined with our duty cycles would also help keep the radiator requirements reasonable I love the idea of having a silent High power Amplifier. On Tue, 2014-12-16 at 12:06 -0700, Doug Person via Elecraft wrote: This is really a fascinating idea. I have noticed that there are water cooling kits made for computer CPU's. Some of the bigger CPU's run over 225 watts of power. I wonder how applicable one those CPU kits might be. They include a heat sink, pump and radiator. 73, Doug -- K0DXV On 12/16/2014 11:10 AM, David Cutter wrote: Hi Dick Start from the LDMOS data sheet and work out the temperature you wish to keep within at the junction. Because water cooling is so good, you can choose either to run the device cooler than you would with air cooling to improve reliability, or stick to the same temperature and get more power / use a smaller cooling plate / use less water. There's a direct relationship between reliability and temperature, but it's not linear. Then use the temperature rise per W rating of the device to get to the surface temperature. In work I did 10 years ago all devices were directly bolted to the liquid-cooled plate without an intermediate spreader, however, these LDMOS devices are so small (ie very high heat density) there is a good reason to spread the heat out first before cooling proper takes place, I'm somewhat hazy what thickness, but you must achieve good flatness of contact against the plate. Some very large devices eg IGBTs and rectifiers the size of your open hand are supplied curved and the bolting-down process achieves the flatness with the correct torque setting on the bolts. Then you do the same sums as you do with air cooling ie temperature rise v watts dissipated from the heat sink data. Say you want to dissipate 1kW of heat continuously (eg in a data contest) then a small 2 pass model would give you around 90 to 100K rise at the surface of the plate with 1 US gallon per minute, whereas a 4 pass model would give you around 20K rise on a 152mm length plate. This of course assumes that the heat is being delivered into the plate evenly over the whole surface, ie using a spreader. Heat sink paste adds a little to the thermal gradient and is needed in very small amounts, evenly spread. Do the sums several times with different criteria until you get to the one you feel comfortable with. If you live in a cold climate you can dump the heat into a small central heating radiator to keep the shack warm and no fans required just an aquarian pump to run it; if you live in a hot place, then put the radiator on the shade side of the house or even bury it. If water is abundant, eg river water or a pond, you can re-cycle it back to the source. You can make your own water cooling plate, see here a small example cooling a dozen TO-220 devices: https://www.youtube.com/watch?v=WGpau-raMho Somebody here will check my sums I'm sure. 73 David G3UNA - Original Message - From: Richard Solomon w1...@earthlink.net To: elecraft@mailman.qth.net Sent: Tuesday, December 16, 2014 4:44 PM Subject: Re: [Elecraft] LDMOS for QRO [OT] If one wanted to use one of these to cool an LDMOS VHF KW, where would one find the design info to calculate which cold plate would provide sufficient cooling ? I envision a stack something like this: LDMOS PC Board Copper Heatsink (thickness need be determined) Cold Plate Aluminum Heat Sink (is this really necessary ?). 73 es HH, Dick, W1KSZ On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you
Re: [Elecraft] LDMOS for QRO [OT]
Oops typo. F-14 aircraft On 12/16/2014 10:27 AM, Wes (N7WS) wrote: Unless you want to run fresh water down the drain (in Arizona we don't do this) you have to get the heat into the air someplace. I'm not sure that running water lines to outside air is much easier than getting coax through a concrete wall. Speaking of difficult, the U.S. Navy AIM-54A Phoenix Missile which with I was intimately familiar, used oil (Coolanol) cooling. Chassis were mounted on cold plates and the vacuum tube modulator and pulse transformer were immersed in oil and it also circulated through the PA klystron. Lines ran from the missile umbilical to the wing or belly mounted launchers then to the F4 aircraft where a conditioning unit resided. The stuff was insidious to work with. I ruined lots of clothes, And it was hygroscopic, just the thing to use on a ship-borne system. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
OK. My reason for mentioning these amps was to answer some of the negative points being made in regard to a fictitious KPA1500. These days one does not have to combine a lot of lower power FETs to reach QRO. I gave you a link to the device which is made by Freescale. There are comparable devices made by NXP. I replied to the argument that one can not run them linear at 1200w. To quote myself: So combining two running 750w each gets you 1500w in linear operation with 2400w dissipation. Most RF transistors will not be linear if driven into saturation so one backs off on the drive and resultant output to improve linearity. Heat dissipation is taken care of by using copper heat spreaders under the transistors coming from all these suppliers unless you buy the LDMOS directly (W6PQL uses a 3x5x1/2 inch copper spreader). I would suggest either the amp kits or buying assembled amp pallets to build with. Price: two LDMOS would run roughly $500. I new 8877 from RFParts is $1450 (Eimac) or $665 (Taylor). Of course you can purchase a used 8877 in the $350-450 range. The HVPS will run about $500 and you probably would have another $400 in materials to complete a basic HF amp with manual tuning (total= $2350 (Eimac) to $1250 (used 8877)). W6PQL is offering an assembled single LDMOS amp for $825 so two would run $1650 and probably another $400 to make a complete 1500w SSB HF amp. Surplus HP Blade 50v -50A PS run $30-50 on e-bay. To run two LDMOS you just have two 50vv PS supplying each separately. Total= $2150. If you build your own you can save a little off this total - W6PQL kit is $563 which includes the NXP BLF-188XR. http://www.w6pql.com/parts_i_can_provide.htm est. total 2x$563+$400+$100 = $1625 No point belaboring this as there are going to be some amps showing up this coming year using these LDMOS devices. - From: Kevin Stover kevin.sto...@mediacombb.net To: elecraft@mailman.qth.net Subject: Re: [Elecraft] LDMOS for QRO Message-ID: 548dafbd.7000...@mediacombb.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed W6PQL has designed and built a 1KW SSPA for 1.8-54MHz using an LDMOS device. Freescale I think. he has also designed a pretty stout Low Pass filter designed for 1.5KW 1.8-54 MHz. He can get 1.2KW out of it at saturation with 2-3 W drive. A pair of these devices @ 750W could do 1500W all day any mode. but then the power supply becomes the limiting factor.. 50V at 70amps? http://www.w6pql.com/1_kw_sspa_for_1_8-54_mhz.htm 73, Ed - KL7UW http://www.kl7uw.com Kits made by KL7UW Dubus Mag business: dubus...@gmail.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
Neither morse (loosely called CW), nor JT65, are pure sine waves, so they will have IMD, although it may well be less than the key clicks (as conventionally understood for morse, and because of the abrupt frequency changes in JT65). True CW cannot convey any more information than its existence. Measured in a 1Hz bandwidth, the JT65 IMD would be very low, and measured in the total bandwidth, it would be concentrated, in time, around signalling unit boundaries. Similarly for the clicks. As to the mobile powers, I would have thought that it would be unsafe to operate at some of the power levels mentioned, both in terms of the risk to other people (e.g. someone in an open, or soft, top vehicle, or even pedestrians in slow moving traffic), and the risk of causing an accident as as result of EMC failures in passing vehicles. -- David Woolley Owner K2 06123 On 14/12/14 09:10, Edward R Cole wrote: You are correct that the specs are for pulse and one can run CW/JT65 at this level since there is no IMD produced by a single sine wave. So combining two running 750w each gets you 1500w in linear operation with 2400w dissipation. 1500w mobile!!! Are you serious? I'd guess 200-250w would be adequate for mobile. But I do not do serious HF'ing. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
I did a random selection of 3 of their alleged distributors and found nothing on their sites. Too bad, they look like they could be useful. Guess I'll ping them directly and see what I get. 73 es HH, Dick, W1KSZ On 12/14/2014 4:32 PM, David Cutter wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to w1...@earthlink.net __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
Here's a 144MHz 1.5Kw water-cooled LDMOS amplifier putting out full power in a June VHF contest, with me operating at W2SZ/1. It was a cloudy day, and the amp was so cool, in fact, we were worried about condensation. Look at the size! The power supply is a 50v/50a surplus PC supply off of ebay. The amp was built by Brian Justin, WA1ZMS. I have found cold plates on the surplus market. Every once in a while, Electronic Surplus Sales in Manchester, NH has em. Amp in Action: https://www.youtube.com/watch?v=vegBv6ddAUA 73 Gerry Hull, W1VE | Hancock, NH USA AKA: VE1RM | VY2CDX | VO1CDX | 6Y6C | 8P9RM http://www.yccc.org http://www.yccc.org/ http://www.facebook.com/gerryhull https://plus.google.com/+GerryHull/posts http://www.twitter.com/w1ve On Sun, Dec 14, 2014 at 6:32 PM, David Cutter d.cut...@ntlworld.com wrote: I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/ pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to ge...@w1ve.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
On 12/14/2014 2:10 AM, Edward R Cole wrote: 1500w mobile!!! Are you serious? I'd guess 200-250w would be adequate for mobile. But I do not do serious HF'ing. When you get serious, here's how to do it. My Elmer, W7UVR, ran a high level modulated 4-1000A mobile in the 1950s. Later went to SSB and a 15KW generator in a bigger trailer. The one in the photo (trailer) was only 5KW. The whip antennas had motor-tuned matching networks with vacuum variables and edge-wound inductors. The beam was later replaced with a tribander, diced up with machined tubular hinges built by a tool-maker ham friend. http://www.k0bg.com/gallery2/main.php?g2_itemId=1039 http://www.k0bg.com/gallery2/main.php?g2_itemId=1042 http://www.k0bg.com/gallery2/main.php?g2_itemId=1045 Wes N7WS __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
Your issue with heat sinks and copper spreaders is already solved and one can run simple fans instead of blowers. And combining two devices is more complicated than combining 8 or 16? Huh? I'm not saying it isn't possible - nor that is hasn't been solved. Only that is it not less expensive than an 8877 and that those who say a single 1.25 KW LDMOS is a suitable replacement for an 8877 are not considering other performance issues like IMD, etc. The multiple module with combiner configurations have been around for a long time. The LDMOS modules were designed for television broadcast service in addition to ISM purposes. The broadcaster transmitters use a large number of combined modules to reach quite high power levels but each module is running less than 1 KW and the transmitters have significant amounts of adaptive precorrection to maintain linearity. If you want to step back and design precorrection capability into the transceiver DSP (e.g., an input for a directional coupler/RF tap at the output of the *system*) and can maintain linearity of multiple modules close enough to use a single composite correction, be my guest. However, the cost and complexity are an order of magnitude greater than a good cathode driven triode - but then if you add phase modulation to the precorrection, perhaps you can get away saturated (pulse) amplifiers. 73, ... Joe, W4TV On 2014-12-14 4:10 AM, Edward R Cole wrote: Joe, You are correct that the specs are for pulse and one can run CW/JT65 at this level since there is no IMD produced by a single sine wave. So combining two running 750w each gets you 1500w in linear operation with 2400w dissipation. 1500w mobile!!! Are you serious? I'd guess 200-250w would be adequate for mobile. But I do not do serious HF'ing. Your issue with heat sinks and copper spreaders is already solved and one can run simple fans instead of blowers. And combining two devices is more complicated than combining 8 or 16? Huh? If you think this is all theoretical you are mistaken as these are out there as kits and assembled amps on VHF to 1296. Several companies have them for sale (M2 is one). The kits come with the LDMOS already installed on a copper spreader designed for the needed heat conduction. They haven't hit the HF market as yet but no reason why not (be interesting to re-examine this topic in dec. 2015). I sure would consider a 50v PS a lot simpler and safer than a 4kV PS. In fact I have one that I bought on e-bay for $31 made by HP (it will run my 1100w 6m PA). I also have a HB 4kV - 1.5A PS for my 8877...cost me a lot more than $31. Once I use up my current 8877, I will likely sell my amp with the final 8877 pull that I have in hand and replace it with a LDMOS amp since I can install it next to the base off my tower instead of having it inside with all the noise and HV. Then I can haul the 1-5/8 inch Hardline to the metal recycle'r as I will only need to run RG213 to the amp with 4w. Yes, 240vac will be needed but running that is not rocket science as every home well pump is wired with buried 240vac. 73, Ed - KL7UW From: Joe Subich, W4TV li...@subich.com To: elecraft@mailman.qth.net Subject: Re: [Elecraft] (no subject) Message-ID: 548cee2e.7050...@subich.com Content-Type: text/plain; charset=utf-8; format=flowed But no longer do you need to run a dozen pills (man I hate that term). Here is all you need for 1250w 1.8-600 MHz: Unfortunately, the LDMOS device data sheets provide *no* IMD spec's for linear operation. The only data is for CW and pulse service. If one is to extrapolate from similar LDMOS devices (single FET vs. two FETs on a common die), one would need to derate to 800-900 W PEP in order to achieve reasonable IMD levels. That conclusion is further corroborated by the compression spec's (actual vs. ideal output power) which show the onset of output compression above 59 to 60 dBm (59 dBm = ~800W). The devices work at 1200 W CW (or JT65) because those modes are single tone and work with saturated operation (class C amplifiers) where IMD performance is not tested. At full output these devices would be as dirty in SSB operation as the old FM brick amplifiers were when run in SSB service - perhaps like the RMA Italia solid state amps G. BTW, since these are 50V parts they are not suited for mobile use at 12V (13.8 V nominal) service. $241.50 compared with the new price of a 8877 is pretty cheap! To even approach the IMD performance and reliability of an 8877 you would need two devices and the cooling problems (cost of heat sinks, heat spreaders, etc.) are much more difficult with two of these devices than with a single 8877. Any cost advantage for even two of the LDMOS devices over an 8877 will be more than offset by cooling system (in addition to splitter/combiner and protection system) costs. 73, ... Joe, W4TV 73, Ed - KL7UW http://www.kl7uw.com Kits made by KL7UW Dubus Mag business: dubus...@gmail.com
Re: [Elecraft] LDMOS for QRO
W6PQL has designed and built a 1KW SSPA for 1.8-54MHz using an LDMOS device. Freescale I think. he has also designed a pretty stout Low Pass filter designed for 1.5KW 1.8-54 MHz. He can get 1.2KW out of it at saturation with 2-3 W drive. A pair of these devices @ 750W could do 1500W all day any mode. but then the power supply becomes the limiting factor.. 50V at 70amps? http://www.w6pql.com/1_kw_sspa_for_1_8-54_mhz.htm -- R. Kevin Stover AC0H ARRL FISTS #11993 SKCC #215 NAQCC #3441 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
Soon GaN will hold possibilities. Myron WVØH Printed on Recycled Data On Dec 14, 2014, at 8:41 AM, Kevin Stover kevin.sto...@mediacombb.net wrote: W6PQL has designed and built a 1KW SSPA for 1.8-54MHz using an LDMOS device. Freescale I think. he has also designed a pretty stout Low Pass filter designed for 1.5KW 1.8-54 MHz. He can get 1.2KW out of it at saturation with 2-3 W drive. A pair of these devices @ 750W could do 1500W all day any mode. but then the power supply becomes the limiting factor.. 50V at 70amps? http://www.w6pql.com/1_kw_sspa_for_1_8-54_mhz.htm -- R. Kevin Stover AC0H ARRL FISTS #11993 SKCC #215 NAQCC #3441 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to myronschaf...@gmail.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO
Kevin Stover wrote W6PQL A pair of these devices @ 750W could do 1500W all day any mode. but then the power supply becomes the limiting factor.. 50V at 70amps? Expert 2k-fa uses a commercial 50v 60A (more peak) PS that weights perhaps 5 lb and is pretty small. Costs $500 in single quantities. Running 1.5KW in contests, the Expert heats the room much less than TT Centurion. For 2m SSB the Freescale device has decent IMD at 900W (and 50% efficiency) and indecent IMD but some 70% efficiency at 1.3 KW. With pre distortion (which every SDR will have soon) perhaps one can get IMD of -50 db at 1.3 KW. At HF the issue is of multi band efficient matching. Ignacy, NO9E -- View this message in context: http://elecraft.365791.n2.nabble.com/LDMOS-for-QRO-tp7595956p7595970.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
Good point David, I have seen an industrial RF amplifier heat sink made out of a 1/4 copper plate married to a aluminum water cooled plate. Ran on a simple 120 VAC pump to a 5 gal tank, like my 5KW Bird water cooled dummy load that uses a total water waste system does the same dissipation. As I remember, many years ago, it was rated at removing 5KW of heat. I know should have the BTU but I don't remember. Mel, K6KBE From: David Cutter d.cut...@ntlworld.com To: elecraft@mailman.qth.net Sent: Sunday, December 14, 2014 3:32 PM Subject: Re: [Elecraft] LDMOS for QRO [OT] I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to farrerfo...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
There are 3,413 btu per KW HR consumed. Mel Farrer via Elecraft wrote...I know should have the BTU but I don't remember. Nick N1KMP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] LDMOS for QRO [OT]
Water cooling is OK for QRP. A friend of mine was building a special contest amplifier. He was working out the cooling which presented a problem because of the heat involved. I suggested using an upright type freezer and put amp in the freezer, It worked great!! George, fritkin On Sunday, December 14, 2014 3:55 PM, Mel Farrer via Elecraft elecraft@mailman.qth.net wrote: Good point David, I have seen an industrial RF amplifier heat sink made out of a 1/4 copper plate married to a aluminum water cooled plate. Ran on a simple 120 VAC pump to a 5 gal tank, like my 5KW Bird water cooled dummy load that uses a total water waste system does the same dissipation. As I remember, many years ago, it was rated at removing 5KW of heat. I know should have the BTU but I don't remember. Mel, K6KBE From: David Cutter d.cut...@ntlworld.com To: elecraft@mailman.qth.net Sent: Sunday, December 14, 2014 3:32 PM Subject: Re: [Elecraft] LDMOS for QRO [OT] I'm a little surprised that folks in this group haven't suggested liquid cooling for this modest application. Semiconductor cold plates have been around for a long time, are economical to use and in my view a much better solution than forced air cooling. They are compact, quiet, require far less cabinet space, keep junctions cooler and more stable than air could ever and enable higher reliability. Look at Aavid for instance, whose devices I used on many occasions: http://www.aavid.com/sites/default/files/products/liquid/pdf/liquid-cold-plate-datasheet-hicontact.pdf If you play your cards right, you can cool the amplifier and the power supply on a short 4-pass plate. Put the heat somewhere convenient, not in your shack. 73 David G3UNA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to farrerfo...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to georgefrit...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
