I have my K3 driving an I0JXX 500W solid state 144Mhz amplifier. With this i use an LPF from an old ARRL manual http://g4fre.com/2mlpf.pdf using doorstop capacitor which has 0.1dB insertion loss and works well
Dave ww2r > > Message: 48 > Date: Wed, 12 May 2010 07:01:05 -0700 > From: Lew Phelps K6LMP <[email protected]> > Subject: [Elecraft] Semi-OT: seeking circuit designs for 2 meter LPF > To: Elecraft <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=us-ascii > > I'm building a 300 watt external amplifier for use on 6 meters and 2 meters, > a specialized "VHF Contesting" amp that I will use with my K3-10 (with > internal 2 meter transverter). > > There's a good design for a kilowatt-capable 6 meter low pass filter in the > ARRL Handbook (2007), but I haven't found a design for a 2 meter LPF filter > that I really like. The best I've found so far is at: > > http://rf-transmitter.blogspot.com/2008/09/200w-lowpass-filter-for-150-mhz-2-meter.html > > > which seems fine except it's only rated for 200 watts. My amplifier > (Communications Concepts AR313) is rated to deliver about 250 watts at 144 > mHz when driven with 10 watts, and running off of 28vdc power supply. Given > that I will be transmitting on SSB at somewhat less than 50% duty cycle, a > rated power capacity of 200 watts is probably sufficient, but I'd like to > know what alternatives, if any, are available. Surely the EME crowd has good > designs for legal limit LPF projects for 2 meters? I haven't found any > online. > > It should be noted that the amplifier itself (due to push pull design) > suppresses even order harmonics very deeply, and at 144 mHz suppresses 3rd > order harmonics -40dB or more, so it doesn't really need a low pass filter, > except that (my understanding) the FCC require a LPF on any amplifier. > > Any thoughts appreciated on whether the cited 200 watt LPF will do even > though it's slightly under-rated for power capacity, and also any pointers to > other filters, would be appreciated. > > Thanks in advance. Please reply off list unless you think the group as a > whole would benefit from your reply. > > > Lew K6LMP > > ______________________________________________________________ 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
