Re: [AMRadio] Re: [AM Radio] 360 Watt class E transmitter - modified design for new MOSFETs
At 11:21 AM 8/22/2002 -0700, you wrote: Does anyone have an audio file (.mp3 or .wav etc) of one of these transmitters? Being VERY new to AM and having a burning desire to build something that keeps the smoke inside the parts, I would like to venture out on this project! Hi! These babies sound REALLY good. I've built LOTS of transmitters - PDM, series modulation, phase-to-amplitude - you name it, I've probably built it over the past 30 years or so :-) I have *never* before built any transmitter which is as good as the current class E setup, with the class H modulator. And, it is reproducable. Bob, K1KBW is operating this setup, and it sounds just fantastic. The reason these things can sound so good is that there is nothing whatsoever to limit the frequency response or linearity. There are no transformers, no high resistance devices, and in the case of class H, no switching (aliasing) products. So, it's just about as good as it gets :-) On the microphone (VERY important and a good question!), I use a condenser mic from Radio Shack - just the element (which costs a couple of bucks or so) mounted in an old microphone case. I've been using this microphone for YEARS :-). GREAT frequency response (down to a few cycles per second!) and real clean. Any MP3 or similar file you might hear will be subject to the restrictions and limitations of the receiver in use at the time. The detectors of most receivers leave much to be desired in the distortion department (this can spark a whole discussion just about receiver detector circuits - an art unto itself - with real experts to tell all (I am FAR from an expert in this area, although I did build a nice low distortion detector for my homebrew receiver). So, just something to think about, that's all... With transmitters, I tend to like to use real measurements - waveforms, etc. to first prove audio designs. Then add the equalization, etc. which is quite important to the overall "sound". So, if a transmitter will modulate a triangle wave correctly, a square wave without tilt, and a sine wave, it's generally going to sound very good. Very few transmitters are able to successfully (and without distortion) modulate a 400 cycle triangle wave, a 50 cycle square wave, and a sine wave from 20 to 10kHz with a more or less flat response. The class E transmitter using the class H modulator described at the class E web site can do all of this. It's not because my particular designs are so wonderful, it's just due to the fact that all of the limiting factors, by the very nature of class H, are eliminated. It's just easier to get good sound. Anyway, there's some info to chew on :-) Regards, and talk later. Steve
[AMRadio] Re: [AM Radio] 360 Watt class E transmitter - modified design for new MOSFETs
Does anyone have an audio file (.mp3 or .wav etc) of one of these transmitters? Being VERY new to AM and having a burning desire to build something that keeps the smoke inside the parts, I would like to venture out on this project! Going WAY back (and yes this even includes my CB days back in the 70s) it was VERY important for my station to sound CLEAN! I really like the D-104 but not too fond of the sound quality. I suspect that the D-104 was not matched to the radio correctly. So if you have a recording of one of these transmitters, what mic are you using? What mic is recommended? I own a Shure 444-D, 526T, D-104SE, D-104 unamplified with the 10-DA head, various Yaesu Mics, and Heil. I was even thinking of putting a HC-5 element in a D-104 (which sits nice on my belly!) and scraping the internal amp. But then again, the HC-5 was designed for SSB. Garbage in, garbage out. I think an audio circuit should be designed with all the intended parts in mind. But then again, I really don't know what I'm talking about yet. Building this transmitter will teach me...and I want to learn! How do you put a 2000 ohm mic on a circuit designed for a 600 ohm mic? I have a lot of reading to do and maybe some of this is covered in the text. But I would sure like to hear one! My other hobby is High End Audio. I like tubes! I've owned Mark Levinson and it sounds great! But I like tubes better! I'm hoping this Class E transmitter "sounds" good! KFI here is Southern CA does not have the same romance that it did when it had tube transmitters. What about a hybrid design? Tube audio circuit into a mosfet final amplifier? Some High End Audio companies use tube pre amps and solid state amplifiers with their integrated amps. Its just a thought. OK, teach me! I want to learn! Nobody is going to call me an appliance operator! Dino...K6RIX At 01:23 PM 08/22/2002 -0500, Steve Cloutier, 978-597-3311 wrote: Hi! For anyone who is planning on building the 360 watt, 6 FET transmitter which I have documented on the class E web site, I have changed the design to reflect changes needed for the new Fairchild MOSFETs. Anywon who is planning on using the Fairchild FETs in this design should get the updated information and look at the new pictures of the transmitter. The transmitter is somewhat more efficient with the new Fairchild MOSFETs, and the new design uses a simpler driver than the previous design. I will have MOSFETs available at Boxboro for those who want them. Bob, K1KBW and I will also have an operating class E transmitter. I am doing a presentation about class E at the AM Forum on Saturday at Boxboro. See you there is you can make it! The class E site is at: http://www.netway.com/~stevec/ham/classe.htm Regards, Steve WA1QIX
