Guys,
I just looked up the MRF150. For the moment look at the characteristics below with a big AM final amplifier in mind. With a 300 watt Pd rating, this thing might do well as a efficiency amplifier (modulate the gate bias) to make 100 watts AM, and do so with room to spare. So with say 33% efficiency (SWAG), 300 watts DC input, you get 100 watts RF output with 200 watts Pd. With modulation the efficiency improves (doubles @100% modulation from sine wave tone input). If you do a conventional Class C high level modulated amplifier with say 150 watts Pd, and 75% efficiency (SWAG), that gives you 600 watts DC input X .75 = 450 watts RF output! There are tons of hi power solid state audio amplifiers around, so there is your modulator too! Sure, the application notes dwell on SSB linear usage, but heck if it works on SSB, you can make it work on AM! Regards, Jim So how much do these things cost? :-) MRF150 MAXIMUM RATINGS DrainSource Voltage VDSS 125 Vdc DrainGate Voltage VDGO 125 Vdc GateSource Voltage VGS ±40 Vdc Drain Current Continuous ID 16 Adc Total Device Dissipation @ TC = 25°C Derate above 25°C PD 300 1.71 W/°C Storage Temperature Range Tstg 65 to +150 °C Operating Junction Temperature TJ 200 °C MOTOROLA RF DEVICE DATA ELECTRICAL CHARACTERISTICS (TC = 25°C unless otherwise noted.) Characteristic Symbol Min Typ Max Unit OFF CHARACTERISTICS DrainSource Breakdown Voltage (VGS = 0, ID = 100 mA) V(BR)DSS 125 Vdc Zero Gate Voltage Drain Current (VDS = 50 V, VGS = 0) IDSS 5.0 mAdc GateBody Leakage Current (VGS = 20 V, VDS = 0) IGSS 1.0 mAdc ON CHARACTERISTICS Gate Threshold Voltage (VDS = 10 V, ID = 100 mA) VGS(th) 1.0 3.0 5.0 Vdc DrainSource OnVoltage (VGS = 10 V, ID = 10 A) VDS(on) 1.0 3.0 5.0 Vdc Forward Transconductance (VDS = 10 V, ID = 5.0 A) gfs 4.0 7.0 mhos DYNAMIC CHARACTERISTICS Input Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Ciss 400 pF Output Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Coss 240 pF Reverse Transfer Capacitance (VDS = 50 V, VGS = 0, f = 1.0 MHz) Crss 40 pF FUNCTIONAL TESTS (SSB) Common Source Amplifier Power Gain f = 30 MHz (VDD = 50 V, Pout = 150 W (PEP), IDQ = 250 mA) f = 150 MHz Full data sheet: http://www.twhrf.net/mkic/mrf150.pdf -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Jim candela Sent: Monday, January 30, 2006 6:54 PM To: Discussion of AM Radio Subject: RE: [AMRadio] AM Transmitter Advice?? Larry, I am interested in what your friend Jim, KR1S has in mind for that 100 watt AM solid state exciter for 75 meters. Is that carrier output, or PEP? In thinking about it, this could vary from a "scaled up CB" rig with a tuned class C final with high level modulation, or maybe a small AM exciter with a solid state push pull linear, or maybe a class E setup. We seemed to get side tracked on the 813 amp idea, and glossed over the exciter concept you laid out. How about a nice juicy MRF-150 with high level drain modulation, or low level gate bias modulation? I bet no one has ever tried it either way.. Regards, Jim WD5JKO [mailto:[EMAIL PROTECTED] Behalf Of Larry Keith My friend, KR1S (Jim Kearman) is designing an AM transceiver, for me. We plan for this to be a solid-state unit that will deliver about 100 watts out. It will be single band (75 meters) and I have been considering using that to feed a homebrew linear. I have the makings of a 2 x 813 amp thanks to my and Jim's hamfesting efforts. Larry KQBY Larry Keith -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.375 / Virus Database: 267.14.23/243 - Release Date: 1/27/2006
