Hi Mike, Agreed. The ART1K6 looks like the best choice. It is in fact one hell of an all around part! I am curious if the pictures I attached in my last reply came thru as the Elecraft list administrator sent a message says my post had been rejected due to size? If they did not show up, my water cooled amp using a pair of BLF189XR devices can be seen at: https://www.youtube.com/channel/UCfPLagy3tyL164PjCmWUaqg 73, Hal W7YNC From: M Cresap [mailto:[email protected]] Sent: Wednesday, November 02, 2022 9:40 AM To: Dynolab; [email protected] Subject: Re: [Elecraft] KPA1500 replacement devices Hi Hal I like the water cooling! I debated about using water cooling on a W6PQL 2 meter amp I built several years ago, ended up with an oversize heat sink instead. Since the KPA1500 power supply probably can't safely be adjusted to 65 volts to best accommodate the ART2K0, the ART1K6 is likely the better choice since it is expecting 50 volt on the drain. An interesting experiment. Thanks for your perspective 73, Mike, W3IP On Wednesday, November 2, 2022 at 01:13:46 AM EDT, Dynolab <[email protected]> wrote: Hi Mike, Agreed, the ART series does have lower Rth but I would still worry that it may not be low enough to make up for the increased saturation voltage and loss of efficiency due to a drain to drain impedance that has been optimized for a Vdd of 50Vdc. However, I may be overly timid as I have a graveyard of LDMOS devices that did not survive air-cooled amplifiers. I have since gone to water-cooling and don’t have to deal with the heat problems anymore. (See Attached) 73, Hal W7YNC From: M Cresap [mailto:[email protected]] Sent: Tuesday, November 01, 2022 3:21 PM To: Dynolab; [email protected] Subject: Re: [Elecraft] KPA1500 replacement devices Hi Hal I see the Rds difference. Wouldn't the higher Rds be compensated by the better Rth (thermal resistance from junction to case) spec in the ART devices? 73, Mike, W3IP On Tuesday, November 1, 2022 at 03:15:09 PM EDT, Dynolab <[email protected]> wrote: While the higher voltage ratings of the ART1K6 or ART2K0 series looks very attractive, it is extremely important to remember that heat is the number one killer of LDMOS RF power FETs! That being said, take a look at the specifications of the ART1K6 and ART2K0 and note that the Rds(on) drain-source on-state resistance of these devices is significantly higher than that of the devices presently being used in the KPA1500. And this higher Rds(on) would result in higher drain-source saturation voltage when the amplifier is running near its limits which would in turn result in higher heat dissipation. It is therefore possible that the ART1K6 or ART2K0 devices may be less reliable than the devices currently being used in the KPA1500. 73, Hal W7YNC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of M Cresap via Elecraft Sent: Tuesday, November 01, 2022 10:21 AM To: [email protected] Subject: [Elecraft] KPA1500 replacement devices Anyone have an educated guess whether the ART1K6xx or ART2K0xx devices would be a drop in replacement for the currently used device in the KPA1500? Most of the interesting specs are within 10% of the current device, the open loop gain may be a dB or two higher (if the data sheets are really comparing apples to apples). The main attraction of the ART1K6 and ART2K0 devices is the higher peak voltage handling capability - 177 or 200 volts vice 135 volts for the current device. Maybe a higher peak voltage capability will keep the amplifier out of the repair shop due to external events like arcing baluns or antennas flexing in the wind. The package styles are identical, the ART devices are in stock from a few of your favorite distributors, similar price to the current device, maybe the quiescent bias voltage would have to be tweaked a bit... 73, Mike, W3IP - ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html <http://www.qsl.net/donate.html%20> Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected]
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