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1. [Amps] Moto MRF-150's out of Hong Kong on eBay (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Mon, 27 Sep 2010 11:50:29 -0700; I've noticed a bunch of auctions for MRF-150 power transistors recently on eBay. The ads depict parts made by Motorola, claim that the parts are new, and are all coming out of Hong Kong. The sellers; /archives//html/Amps/2010-09/msg00330.html (6,877 bytes)
2. [Amps] Holes vs. screen for chassis ventilation? (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Tue, 5 Oct 2010 20:24:51 -0700; Am building an HF amp, and will need several large (~3" diameter) openings in the chassis for ventilation. I would like the chassis to be as RF tight as is reasonably possible, so trying to figure ou; /archives//html/Amps/2010-10/msg00038.html (7,284 bytes)
3. Re: [Amps] New 2 PA design (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Fri, 15 Oct 2010 17:43:19 -0700; The big issue with parts like the ARF-1500 is managing the heat. For high duty cycle use, like contesting or RTTY (or worse yet, contest RTTY :-) ), you are dealing with dissipating something like 15; /archives//html/Amps/2010-10/msg00252.html (8,701 bytes)
4. Re: [Amps] Building a Mock Up (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Wed, 17 Nov 2010 13:49:23 -0800; NB: I am in the middle of doing this for the first time! I started out with a cardboard box and blocks of foam - moving the pieces around until I had things the way that I wanted them. Then I designe; /archives//html/Amps/2010-11/msg00316.html (8,091 bytes)
5. Re: [Amps] 'heat spreader' sizing ?? (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Fri, 4 Feb 2011 21:16:06 -0800; Dan, to answer these questions, you have to do some math. The answer depends on a variety of factors, including the thermal resistance of the junction between the transistors and the heat spreader, t; /archives//html/Amps/2011-02/msg00025.html (8,915 bytes)
6. [Amps] 50v power supply options for SS amps (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Sun, 3 Feb 2013 13:57:19 -0800; Paul, My sense is that you are better of buying a used 50v supply from the telco equipment industry than you are trying to build one. I especially like the Valere rectifiers, like this one: http://ww; /archives//html/Amps/2013-02/msg00022.html (7,641 bytes)
7. Re: [Amps] LDMOS PAs and high power low pass filters/diplexers (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Tue, 5 Feb 2013 09:22:39 -0800; To do the cooling right, you have to do some math. You start with the max allowed junction temp and the junction-to-case thermal resistance (both specified on the data sheet of the device), and work; /archives//html/Amps/2013-02/msg00044.html (8,173 bytes)
8. [Amps] On the subject of chassis... (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Sat, 4 May 2013 11:21:13 -0700; Obviously, a key issue when it comes to this type of question is cost. If you are looking for an absolutely professional "look", and aren't too cost sensitive, I recommend Protocase: www.protocase.co; /archives//html/Amps/2013-05/msg00079.html (7,658 bytes)
9. Re: [Amps] Advice needed for SS amp (score: 1): Author: Dan Levin <dan@andlev.com>; Date: Wed, 5 Jun 2013 21:24:25 -0700; FWIW, cooling 750 watt parts is going to be a PITA. All the more so if you use two of them push-pull on the same amplifier module / board. Water will help, but only somewhat, and has been mentioned i; /archives//html/Amps/2013-06/msg00069.html (9,435 bytes)

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