Steve, You probably have my information, but I am currently using the 350 watt 75 M transmitter with the Class H modulator. I found the Class H modulator to be much easier to get working than the old series modulator. I originally used FQA15N70 MOSFETs, but had trouble with them blowing whenever I hit the modulation too hard. I replaced them with FQA11N90s and have had no more problems. I built an op amp stage of amplification and a two band equalizer for the transmitter. I just completed a compressor and will add that to the audio chain shortly. I originally used the prototype transmitter that you published and found it to work well too. The AM group out here pretty much uses commercial tube type equipment and some home brew tube type equipment.
I sent you some pictures a while back and can send some more if you would like. Externally everything looks pretty much the same, but I designed a different heat sink arrangement out of copper (0.10") for the RF MOSFETs that lets me reduce the bus lengths. I mount the drain bus on two door knob caps and the gate bus on two insulators. My original transmitter had the MOSFET leads soldered to the buses, but the current one uses small (2-56) brass screws, washers and nuts. I did this so I could replace blown MOSFETs more easily, but now find that that should not be a problem. I may solder them to the buses, but clamping the leads with the screws is a pretty good connection also. I have tried the transmitter at 350 watts of carrier out and it seems to work very well. There is no significant heating, except for the carrier MOSFETs in the modulator (not really that much, just enough to notice that the heat sink gets warm). Normally I run 250 watts of carrier output and the transmitter and modulator run close to room temperature. I haven't measured the efficiency recently, but was previously getting better than 90 % (typically 93 %) at 250 watts of carrier out. I use small boxer fans on both the modulator and RF heat sinks. It's a great idea to write an article. ARRL needs to recognize the growing popularity of AM and that it involves new technology, as well as the old. Most of the areas of ham radio no longer lend themselves to home brewing, so the use of Class E and solid state makes the jump from the old to the new. I'd like to try your PDM, but will have to wait until I get a bit more time. Let me know if you need any other information. I look forward to reading the article. Regards, Fred WA0GMH "Steve Cloutier, 978-597-3311" wrote: > Hi! > > If you've built a class E rig, or are actively building one at the moment, > please send me email with the particulars. I am writing a QST article > about class E AM transmitters. There is more than a suggestion from > various people at ARRL H.Q. that such an article, if well presented, will > be published. > > For evidence that this class E thing is not just a novelty, I would like to > include a list of everyone who has or is actively building a class E > transmitter. It would be good to include what design you're using, how > much power, what band, etc. etc. > > Of course, I already know about many people who have built rigs, or are > building them, but my memory is not perfect, and I probably don't have all > the details. So, this is the "official" call :-) I'll collect all of the > information in one place, and distill it all down into an organized, clear > descriptive list. > > If you happen to be using the class H modulator design, or the 6 FET RF > amplifier design (or any of my other designs), specifically let me know, as > this is further evidence that the design can be reproduced, and does work. > > Another thing I will need are *good*, close-up pictures of neatly built > (which lets my stuff out) class E transmitters, modulators, etc. These may > be published, so don't send me anything that you wouldn't want shared with > the world :-) I will, of course, give specific credit to everyone who > contributes or whose transmitter picture is published. > > This is a good chance to show those who think AM is just old dinosaurs > playing around with antique equipment what's happening in modern world with > AM today. > > This could be really great! > > Thanks and Regards, > > Steve WA1QIX (send email to: [EMAIL PROTECTED]) > mailto://[EMAIL PROTECTED] > > At 12:14 PM 2/7/2003 -0500, you wrote: > >Ron, > > You can also look at this http://www.amwindow.org/tech/htm/813/813.htm for > >ideas on a pair of 813s modulated by a pair of 813s. The class e rig is more > >efficient, however if it's glowing like the 813s do, something is wrong! > > > > Bill > > KA8WTK > > > > > >----- Original Message ----- > >From: "Ron Samchuk" <[EMAIL PROTECTED]> > >To: <[email protected]> > >Sent: Friday, February 07, 2003 1:03 AM > >Subject: [AMRadio] re: 4-1000 or 813 AM transmitter information needed > > > > > > > Hi everyone. I need information on building a good AM kilowatt rig using > >either two 4-1000A tubes or two 813's as finals. I have several parts > >(including those tubes), but I need some advise, plans, schematics, etc. on > >such a project. I am considering using 813's or 810's as modulators. Links > >to a good website would help. > > > Thanks in advance for your assistance. from Ron VE4SR > > > > > > --- StripMime Report -- processed MIME parts --- > > > multipart/alternative > > > text/plain (text body -- kept) > > > text/html > > > The reason this message is shown is because the post was in HTML > > > or had an attachment. Attachments are not allowed. To learn how > > > to post in Plain-Text go to: http://www.expita.com/nomime.html --- > > > _______________________________________________ > > > AMRadio mailing list > > > [email protected] > > > http://mailman.qth.net/mailman/listinfo/amradio > > > > > > > > > >_______________________________________________ > >AMRadio mailing list > >[email protected] > >http://mailman.qth.net/mailman/listinfo/amradio > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
