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In case you haven't seen this yet.

Postby Phil G4ZOW » Mon May 16, 2005 11:20 am

It'll no doubt be at Dayton:

http://www.sgcworld.com/500watt.html

Enjoy

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Postby Tom WA3KLR » Mon May 16, 2005 1:48 pm

I'm curious to know what FETs they are using.

Perhaps someone going to Dayton can find out for us.
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yep

Postby N9NEO » Tue May 17, 2005 9:03 pm

SWEET!
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SGC class E PA

Postby John K5PRO » Wed May 18, 2005 12:25 pm

Must be using Envelope Elimination and Recovery technique with their class E?
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SGC MINI LINI

Postby Todd WD4NGG » Sat Jul 02, 2005 2:45 pm

I just looked at the SGC website and they have updated details on their 500 watt output MINI LINI amplifier. It does indeed use Envelope Elimination and Restoration along with a Class-E Power Amplifier to be able to amplify an SSB signal with 90% efficiency. It looks like SGC is the first to bring a working Class-E / EER amplifier to the Amateur market. They must be using a switching power supply also as they advertise the total weight of the amplifier and power supply as less than 5 lbs. Probably would have to be derated quite a bit for AM operation but still a marvelous achievement for an SSB linear amplifier! 73 Todd WD4NGG
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Interesting . . . Equiv. AM Power Level = 80 watts

Postby steve_qix » Mon Jul 04, 2005 12:13 am

Interesting product! That's a good accomplishment at 20 meters, for sure.

As a note of interest, if I figure an equiv. AM power level for this amplifier, using the designs presented in this forum and elsewhere - designs that will do a minimum of 150% positive modulation - it comes out to 80 watts carrier output, on AM == 500 watts PEP (AM) modulated to 150 % positive.

Carrier:
40 volts * 2.3 amperes = 92 watts input = (about) 80 watts output.

Using the usual rule of thumb for 150% positive modulation, the modulator output would be 100 volts at the full positive peak for our 40 volts of carrier voltage. In this example, the DC resistance of the RF amplifier is about 17.39 ohms (40 / 2.3), so for the full 100 volt output (150% modulation) of the modulator, the current would be about 5.75 amperes and the power will be 575 watts input, or about 500 watts output.

The documentation for the mini linear suggests, an RF rated, high voltage MOSFET is used. There are a number of these on the market; IXYS and APT make these, among others. If one chose the right MOSFET and the right driver, it COULD be done with one device. Whether they did it that way is unknown. I would probably use two devices.

Someone needs to buy one and take it apart :-)

Regards,

Steve
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http://www.classeradio.com
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an idea

Postby kd0ar » Thu Jul 14, 2005 5:59 pm

question:

If one were to add a hard limiter to the input to Steve's design and an envelope detector (detecting the envelope of the input RF) feeding the PDM modulator, would you not have a linear Class E amplifier?

I have been playing with some class E stuff (not necessarily on AM) for the past couple years. When I saw the SGC amplifier, I wanted to investigate how they were doing it. Turns out that the broadcast guys are using this same technology for IBOC. I scanned thru some of the papers by the big Broadcast transmitter companies and came to this conclusion. We have a 6KW AM Class E broadcast transmitter at one site, and the way I understand it, you can order a "kit" to make it IBOC ready. Perhaps this consists of the envelope detector/ limiter combination needed to do a linear amplification modification.

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please attach links.

Postby N9NEO » Sat Jul 16, 2005 7:27 pm

Can you please post links to the papers that you have been reading.

Also I am interested in very large transmitter that is IBOC ready. 200kW, 500kW, and 1MW transmitting powers I am interested in if you have this information. My interests are for broadcast and also for some other power supply issues like EV charging some interesting applications heating crucibles potentialy using class e or similar magic that should be looked into.

73
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